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1
James, Jocelyn S. "The microstructural modelling of austempered ductile iron camshafts". Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/14359.
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Austempered ductile iron (AD!) is a material which is receiving increasing interest from the manufacturers of automotive components such as camshafts due to its superior mechanical properties, and in particular excellent wear resistance, compared with other grades of cast iron. ADI is produced from a spheroidal graphite casting using a two-stage heattreatment process. During the first stage of the heat-treatment the matrix is transformed to austenite, and then in the second austempering stage, some of the austenite is transformed to bainitic ferrite. The final microstructure is therefore complex, consisting of graphite, bainitic ferrite, austenite, carbides and possibly martensite. The major focus of this work has been to develop a novel method of predicting the effect of composition and heat-treatment parameters on the major constituents of the microstructure. This has resulted in a single model which can predict a 'microstructural map' of ADI and will assist the foundry industry in reducing lead times for component manufacture. The high temperature equilibrium between graphite and austenite was investigated using Gibbs free energy minimisation in conjunction with critically assessed thermodynamic data. Having established the carbon concentration in austenite at the start of the austempering process, the volume fraction of bainitic ferrite was established from prediction of the limiting carbon content for the diffusionless transformation. The kinetics of the bainite transformation were determined by making modifications to a model which was originally developed for low alloy steels. The predictions were compared with experimental data obtained, both during the course of this research and available in the literature, using dilatometric and X-ray diffraction techniques. The kinetics of the austenitisation were investigated through consideration of a diffusion couple between graphite and austenite. The degree of segregation and formation of primary carbides, in the original ductile iron casting, was calculated using a Scheil approach to solidification. The effect of this segregation was subsequently accounted for by making microstructural predictions on a number of individual 'shells' of material between two graphite nodules. Finally, complete microstructure predictions were compared with reported mechanical properties for a range of compositions and heat treatments of austempered ductile irons.
2
Putman, Duncan Colin. "Modelling of microstructural evolution in austempered ductile iron". Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/36092.
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Austempered ductile iron (ADI) has a microstructure consisting mainly of high carbon austenite, bainitic ferrite and graphite nodules, produced by a two stage austenitisation and austempering heat treatment. The resulting microstructure gives these materials a combination of high strength and toughness, making them attractive for a wide range of applications. To increase surface hardness, ductile iron alloys can also be cast into chilled moulds to induce carbide formation in the required areas of components. These chilled ductile iron alloys can also be subjected to austenitisation and austempering heat treatments, therefore further improving the mechanical properties of the components core, whilst retaining the hard carbides present in the surface layers. This work encompasses three main areas: two are concerned with the production of generic microstructure models, which work in conjunction with thermodynamic modelling software MTDATA; and one relates to high temperature X-ray diffraction experiments.
3
Fordyce, E. P. "The unlubricated sliding wear behaviour of austempered ductile irons". Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/21955.
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Bibliography: pages 85-89.A study has been made of the unlubricated sliding wear behaviour of austempered ductile irons under conditions of sliding velocity and load. The load was varied between 0.9 and 2.8 MPa, whilst the sliding velocity range was between 0.5 and 2.0 ms⁻¹. Two commercial grades of spheroidal graphite irons, SG42 and SG60 were austempered between 250⁰C and 400⁰C. A distinction in the wear behaviour was found with metallic type wear dominating at the lower sliding velocities and an oxidative type wear being evident at the higher sliding velocities. It was however found that an increase in the load resulted in an earlier onset of the oxidative type wear regime, for a specific sliding velocity. On austempering these spheroidal graphite irons the mechanical properties as well as the sliding wear resistance increased dramatically. Furthermore, the austempered irons' outperformed a series of steels of much higher hardness by factors between 2 and 28 times under the same conditions. At the lower velocity of testing the outstanding wear resistance is attributed to the austempered iron's unique microstructure of acicular ferrite and retained austenite and a partial transformation of austenite to martensite. However, at the higher sliding velocity the exceptional wear resistance is derived from a development of an tribologically protective oxide film together with the formation of a hardened white layer. The development of the work hardened layer is linked to the high carbon in the matrix of these irons. The work hardened layer leads to a similar wear rate prevailing for all irons austempered from a specific parent iron. The synergism of variation in load, sliding velocity and wear counterface together with the effect of initial microstructure has been explain in terms of simple wear models.
4
Zahiri, Saden H. (Saden Heshmatollah) 1966. "Prediction of the processing window and austemperability for austempered ductile iron". Monash University, School of Physics and Materials Engineering, 2002. http://arrow.monash.edu.au/hdl/1959.1/8408.
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Stokes, Ben. "Fatigue analysis of austempered ductile iron suitable for automotive camshaft applications". Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288156.
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Sa, Andre Ricardo de Souza e. "Influência do alumínio nas propriedades mecânicas do ADI (Austempered Ductile Iron)". Universidade Federal de Minas Gerais, 2004. http://hdl.handle.net/1843/BUOS-8DQE8A.
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The ADI (Austempered Ductile Iron), a cast iron obtained after the proper heat treatment of regular sheroidal graphite iron, has been intensely studied in the last years. Silicon is the standard element added for graphitization of the alloy. In this study it was replaced by aluminium, an element know as presenting a similar chemical behavior in the alloy. Themelting procedure was the same as the used in the production of the standard ADI-Si. The aluminium content, replacing part of the silicon, were 0,75; 2,26 and 2,99% Al. The austempering temperatures were 270, 320, 370°C. The testing specimens were obtained according ASTM A 897 and regular tensile and hardness tests were used to determine the mechanical properties of the alloy with non-reacted austenite and carbide precipitation. The mechanical properties degenerated, accordingly, establishing the need of the use of a special melting procedure when dealing with this Al-bearing alloy.O ADI (Austempered Ductile Iron), produzido pelo tratamento de austêmpera de um ferro fundido nodular, vem sendo desenvolvido e estudado nos últimos anos tendo o silício como elemento grafitizante e portanto, como o segundo principal elemento de liga, definidor da liga. Este trabalho, no entanto, contemplou estudar as propriedades mecânicas do ADI (L.R., L.E., dureza e alongamento) utilizando o alumínio em substituição ao silício como elemento grafitizante. Foram realizados experimentos com adições de 0,75; 2,26 e 2,99% Al. A fusão foi realizada segundo os procedimentos usuais para obtenção do ADI-Si. Os tratamentos térmicos foram feitos em três temperaturas: 270, 320, 370°C. Os corpos de prova foram obtidos segundo norma ASTM A 897. Verificou-se que o alumínio causou a deterioração progressiva da grafita, o aumento da quantidade de austenita não reagida e a precipitação de carbonetos. Consequentemente, as propriedades mecânicas, de resistência e ductilidade, se deterioraram, indicando a necessidade de cuidados especiais na fusão do material.
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Yescas-Gonzáles, Miguel Angel. "Modelling the microstructure and mechanical properties of austempered ductile irons". Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/221871.
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Ozcan, Alper. "The Effect Of Sn Content And Isothermal Transformation Temperature On The Mechanical Properties Of Austempered Ductile Cast Iron". Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1055359/index.pdf.
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In this study the effects of Sn content and isothermal transformation temperature on the ultimate tensile strength (UTS), elongation and hardness of austempered ductile cast iron (ADI) was investigated. To determine the possible effect of Sn on these properties the Sn content of standard GGG30, GGG40 and GGG50 materials were taken as reference, whose chemical compositions vary from 0,016 to 0,050% in terms of Sn. However the Sn content was increased to a maximum of 0,26% for investigating the effect of Sn on mechanical properties. The test specimens were obtained from standard 1-in Y-blocks and austenitized at 925oC for 1 hour and austempered at 350oC,375oC, 400oC and 420oC for 60 minutes in a salt bath.
Microstructural examination of the specimens were also done. To determine the amount of retained austenite of the specimens X-Ray analyses were used. As a result of the study The UTS increases up to 0,1% Sn and then levels off. A similar behavior is observed in the variation of hardness. Percent elongation decreases and falls to a minimum around 0,1% Sn, from this point on, a slight increase is observed. Strength and hardness increase while percent elongation decreases with decreasing temperatures.
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Goldberg, Moshe. "Machinability research into the mechanics and surface integrity characteristics of austempered ductile iron". Thesis, Southampton Solent University, 2002. http://ssudl.solent.ac.uk/621/.
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Montenegro, Davi Melo. "An analysis of the machinability of ASTM grades 2 and 3 austempered ductile iron". Instituto Tecnológico de Aeronáutica, 2011. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=1943.
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Austempered Ductile Iron (ADI) is a ferrous material that was first fabricated in the second half of last century, therefore a relatively new material compared to steel, which has been used for different applications by mankind for some millennia now. ADI';s mechanical properties, such as its strength-to-weight ratio, which has proven to outperform that of forged steel by up to 10%, are very suitable for structural applications, such as connecting rods, crankshafts, and heavy farm machinery among others. The main goal of this work is to perform an analysis of the machinability of two ASTM grades of ADI, namely 2 and 3. The samples used in this work were cast and austempered according to ASTM standards for the production of grade 2 (G2) and grade 3 (G3) ADI. Characterization was accomplished through tensile and hardness tests, metallography and X-ray diffraction. Machinability was evaluated by analyzing tool life, cutting forces, surface finish and chip characteristics in turning operations. A quick-stop test was also performed. Tool life when machining G2 was 33% lower than G3, although the latter is a harder material. Abrasion and adhesion were the wear mechanisms observed through SEM images, whereas in other cast irons mainly abrasion is observed. Cutting forces measurements showed that the value of Kc1,1 decreased 19%, from 1448 to 1175N/mm2, for G2 as the depth of cut increased from 2 to 5mm at a cutting speed of 80m/min and 18%, from 1501 to 1236N/mm2, for G3. Surface roughness measurements proved that a smoother surface is obtained for both alloys at f = 0.10mm/rev when using an insert with nose radius 1.6mm instead of smaller radii. Both alloys presented similar surface quality. All chips observed were segmented.
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Banerjee, Sayanti. "Effect of Chemistry on the Transformation of Austenite to Martensite for Intercritically Austempered Ductile Iron". Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/19258.
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Intercritically austempered ductile iron (IADI) with a matrix microstructure of ferrite plus metastable austenite has an excellent combination of strength and toughness. The high strength and good ductility of this material is due to the transformation of metastable austenite to martensite during deformation. In the present study, the transformation of austenite to martensite for intercritically austempered ductile irons of varying alloy chemistry (varying amounts of nickel and/or manganese) were examined using in-situ neutron diffraction under strain-controlled loading at VULCAN at the Spallation Neutron Source at Oak Ridge National Laboratory (ORNL). Both diffraction and tensile data were collected and synced using the VDRIVE software (a proprietary ORNL software package). The single peak fit method was employed in the analysis of the diffraction data. In this thesis, the stress and strain for the start of the transformation of metastable austenite to martensite were determined. The development of residual stresses during deformation and the elastic diffraction constants for both the ferrite and austenite phases were also determined. The material was characterized using optical microscopy, backscattered imaging in the scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy.
Master of Science
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Azevedo, Cesar Roberto de Farias. "Efeito do tamanho do grão austenítico na cinética e na morfologia do produto da reação bainítica de um ferro fundido nodular austemperado". Universidade de São Paulo, 1991. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-11102007-165928/.
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Investigou-se o efeito do tamanho de grão austenítico na cinética e na morfologia do produto da reação bainítica de um ferro fundido nodular austemperado (FFNA). Foram estudados 3 tamanhos de grão austeníticos, a saber: GG (grão grosseiro), GM (grao mediano); e GR (grao refinado). A condição GR foi obtida pela austenitização rápida de microestruturas martensíticas. A condição GG foi obtida por tratamento de austenitização em duas etapas, de modo a, respectivamente, provocar o crescimento de grão e manter o teor de carbono igual aos das demais condições. Na segunda etapa do tratamento da condição GG ocorreu precipitação de grafita secundária, que acelerou significativamente a taxa de reação bainítica, possibilitando estudar o efeito da.variação na quantidade de interfaces austenita/grafita e austenita/ austenita sobre a cinética e a morfologia da reação bainítica. O refino do grão austenítico acelerou a cinética de reação, aumentou a proporção de ferrita alotriomorfa de contorno de grão, refinou a microestrutura bainítica (ferrita + austenita retida) e melhorou em 14% o limite de escoamento dos FFNA. Finalmente, a predominância de ferrira alotriomorfa na condição mais fina indica que a formação de interfaces incoerentes (mecanismo difusional ao inves de reação displaciva) durante a austenitização rápida da martensita (aquecimento de 100°C/ s).The effect of austenite grain size on the kinetics and the morphology of the bainitic reaction in an austempered ductile iron (ADI) has been investigated, Three austenite grain sizes were produced: GG (coarse grain), GH (medium grain) and GR (fine grain), The GR condition was obtained by the rapid austenitization of martensitic microstructures The secondary graphite precipitation observed in GG condition strongly accelerated the rate of bainite formation and made possible the study of the effect of austenite/graphite interface on the kinetics of this reaction, The austenite grain refinement also accelerated the bainite precipitation, increased the proportion of grain boundary alotriomorphs ferrite, refined the bainitic microstructure and improved by 14% the yield stress of ADI, The predominance of grain boundary alotriomorphs in GR was associated to the structure of austenite/austenite interface formed during the rapid austenitization of the studied ductile iron at heating rates of 100oC/s. It is suggested that the dominant mechanism of austenitization in this condition is a thermally activated one (not a displacive transformation). The different morphologies of the austenite decomposition used the Duhê\'s morphological system.
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Junior, Aristides Rodrigues Mattar. "Influência dos elementos de liga Cu-Ni-Mo nas propriedades mecânicas e na austemperabilidade do ADI". Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-04062009-145511/.
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O ADI constitui-se no desenvolvimento mais recente na família dos ferros fundidos nodulares. Com o tratamento de austêmpera, consegue-se produzir uma microestrutura única, constituída de ferrita acicular e austenita estável rica em carbono, a ausferrita, proporcionando alta resistência mecânica aliada à ductilidade e tenacidade, além de boa resistência à fadiga e ao desgaste. Neste trabalho estudou-se o efeito dos elementos de liga Cu, Ni e Mo nas propriedades mecânicas e austemperabilidade do ADI. Foram produzidas barras cilíndricas de ferros fundidos nodulares nos diâmetros de Ø2, Ø3 e Ø4 ligadas com Cu, Cu-Ni, Cu-Ni- Mo respectivamente. Os corpos de prova utilizados nos ensaios de tração, impacto e microdesgaste foram retirados a meio-raio das barras. Posteriormente, cada conjunto de corpo de prova foi austenitizado a 890°C durante 2 horas, sendo em seguida submetido a uma condição de tratamento de austêmpera específica, combinando temperaturas de austêmpera de 300 e 360°C e tempos de 1, 2, 3 e 4 horas. Realizou-se análises microestruturais ópticas e por microscopia eletrônica de varredura para correlacionar propriedades mecânicas com a microestrutura. Na análise de austemperabilidade, as barras cilíndricas foram austemperadas para verificar a variação de microestrutura em função do raio da barra. Verificou-se que a temperatura de austêmpera exerce forte influência na microestrutura do ADI e consequentemente nas propriedades de tração, ductilidade, tenacidade e resistência ao desgaste. Nos tratamentos a 300°C obteve-se uma microestrutura mais refinada, com maior quantidade de ferrita acicular, responsável pela maior resistência mecânica e resistência ao desgaste; enquanto que no tratamento realizado a 360°C obteve-se uma microestrutura mais grosseira, com maior quantidade de austenita estável, responsável pela melhor ductilidade e tenacidade. Nos tempos de austêmpera analisados, não ocorreram variações significativas nas microestruturas e propriedades mecânicas. A resistência mecânica e a tenacidade decresceram com a adição de Mo, provavelmente devido à segregação deste elemento, mas a resistência ao desgaste a seco e a austemperabilidade foram mais efetivas em comparação com ligas contendo Cu e Cu-Ni. No ensaio de desgaste usando-se lubrificante, o ADI ligado com Cu-Ni austemperado a 360°C apresentou uma resistência ao desgaste um pouco inferior a de um aço 17CrNiMo6 cementado.The ADI is the most recent development in the nodular iron family. With the austempering treatment, a unique microstructure, consisting of acicular bainite ferrite and stable austenite rich in carbon, named ausferrite is produced. This microstructure provides high mechanical strength combined with ductility, toughness and good fatigue and wear resistances. In this work, the effect of alloying elements Cu, Ni and Mo on the mechanical properties and austemperability of the ADI were studied. To conduct these studies, cylindrical bars with diameters of Ø2\", Ø3\" and Ø4\" were cast with Cu, Cu-Ni and Cu-Ni-Mo alloying, respectively. The samples were then manufactured by removing specimens from the bar midradius position. Subsequently, each set of the samples was austenitized at 890°C for 2 hours, and then subjected different conditions of austempering treatment. These treatments were developed by combining austempering temperatures of 300 and 360°C with austempering times of 1, 2, 3 and 4 hours. Microstructural analysis was carried out using optical and scanning electron microscopy to correlate mechanical properties with the microstructure. In the austemperability analysis, cylindrical bars were austempered (at 360°C for 3 hours) to correlate microstructure and radius. The experimental results showed that the austempering temperature exerts strong influence on the ADI´s microstructure and consequently on the mechanical properties. The austempering temperature of 300°C produced the best results, a refined microstructure, with a greater amount of acicular ferrite, responsible for greater strength and wear resistance. The austempering temperature of 360°C produced a coarse microstructure, with larger amount of austenite and responsible for better ductility and toughness. The austempering times used in this work did not produce significant variations in the properties and microstructures. Regarding alloying elements, the mechanical strength and toughness decreased with the addition of Mo, probably due to the segregation of this element, but the wear resistance and austemperability were more effective when compared with the alloys containing Cu and Cu-Ni. In the lubricated wear test, the ADI alloyed with Cu-Ni and austempered at 360°C presented a wear resistance only a fraction lower than a cemented 17CrNiMo6 steel.
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Boneti, Ludiere Lucas Toldo. "INFLUÊNCIA DAS TEMPERATURAS DE AUSTENITIZAÇÃO E AUSTÊMPERA NA MICROESTRUTURA E PROPRIEDADES DE TRAÇÃO DE UM FERRO FUNDIDO NODULAR". UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2014. http://tede2.uepg.br/jspui/handle/prefix/1471.
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Previous issue date: 2014-08-29The present study aimed to evaluate the influence of the austempering heat treatment parameters on microstructure and mechanical properties of a ductile cast iron produced in industrial conditions, containing 3.59% carbon, 2.68% silicon, 0.46% copper (in wt%) and a carbon equivalent of 4.50%. The material was produced in a foundry located in the southwest region of Parana state, Brazil. The specimens were obtained by casting the alloy into Y-block molds. The austempering heat treatments consisted of pre-heating at 500°C, followed by austenitizing step at 870°C, 900°C and 930°C during 60 minutes. Austempering was carried out in molten metal baths at temperatures of 300°C and 370°C for 30 minutes. Microstructural characterization was carried out by light optical microscopy (LOM) with image analysis, scanning electron microscopy (SEM-FEG) and X-ray diffraction with Rietveld refinement. The mechanical properties were evaluated by tensile and Vickers hardness tests. The as-cast microstructure displayed a very heterogeneous microstructure, characterized by the presence of regions with graphite flotation and carbide containing intercellular regions. The graphite nodules showed low nodularity, of 85%, which was attributed to the fading effect of magnesium alloy. Austempered samples were characterized by the presence of bainitic ferrite, interspersed with retained austenite in films and blocks. The austempering at 300°C resulted in a finer microstructure containing smaller volume fractions of retained austenite. All heat treated samples displayed transformation gradients between graphite flotation and intercellular regions. These gradients affected the mechanical properties, as well as the fracture characteristics. The best results of mechanical properties were obtained in the specimen austenitized at 900°C followed by austempering at 300°C, allowing the ADI produced to fit into a high strength class, according to ASTM A897. The study of fracture surfaces showed a sharp transition between graphite flotation and intercellular regions. The fracture at the vicinity of graphite nodules have occurred by a ductile mechanism, characterized by dimples. It was observed a rapid transition to the cleavage mode at intercellular regions, containing solidification carbides.
O presente trabalho teve como objetivo avaliar a influência dos parâmetros de tratamento térmico de austêmpera na microestrutura e nas propriedades mecânicas de tração e dureza, em uma liga de ferro fundido nodular produzida em condições industriais. A liga em estudo possui de teor de carbono de 3,59%, silício de 2,68% e adições de 0,46% de cobre, possuindo ainda um carbono equivalente de 4,50%. O material foi produzido em condições industriais, em uma fundição localizada no sudoeste do estado do Paraná. Os corpos de prova para retirada de amostras foram obtidos pelo vazamento da liga em moldes de blocos Y. Os tratamentos térmicos de austêmpera consistiram de pré-aquecimento a 500°C, seguido da etapa de austenitização a 870°C, 900°C e 930°C, por um tempo fixo de 60 minutos. A etapa de austêmpera foi realizada em banhos de metais fundidos, em temperaturas de 300°C e 370°C, durante 30 minutos. A caracterização microestrutural de amostras foi realizada pelas técnicas de microscopia ótica, com análise de imagens, microscopia eletrônica de varredura e difração de raios X, com refinamento pelo método de Rietveld. As propriedades mecânicas foram avaliadas por meio de ensaios de tração e dureza Vickers. A liga no estado bruto de fundição apresentou microestrutura bastante heterogênea, caracterizada pela presença de regiões com flotação de grafita e regiões intercelulares contendo carbetos de solidificação. Os nódulos de grafita apresentaram baixo grau de nodularização, de 85%, resultado que foi atribuído ao efeito de fadiga térmica da liga nodularizante. A microestrutura de amostras austemperadas foi caracterizada pela presença de agrupamentos de feixes de ripas de ferrita bainítica, entremeadas por austenita retida, na forma de filmes e blocos. A austêmpera a 300°C produziu microestruturas mais refinadas e com menores frações volumétricas de austenita retida. Em todas as amostras tratadas termicamente, foi observado um gradiente de transformação entre as regiões de flotação de grafita e regiões intercelulares. Estes gradientes afetaram tanto os resultados de propriedades mecânicas, como as características de fratura dos corpos de prova. Os melhores resultados de propriedades mecânicas foram obtidos para a condição de austenitização a 900°C seguida de austêmpera, permitindo enquadrar o ADI em uma classe de alta resistência, segundo a norma ASTM A897. As análises das superfícies de fratura dos corpos de prova de tração mostraram uma mudança nas características de fratura entre as regiões de flotação de grafita e as regiões intercelulares. Nas proximidades dos nódulos de grafita houve predominância do mecanismo de fratura dúctil, caracterizada pela presença de cavidades alveolares (“dimples”), com rápida transição para o modo de fratura por clivagem nas regiões com baixos números de nódulos de grafita, contendo carbetos de solidificação.
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Ferreira, Eduardo Prudente. "Estudo do comportamento tribológico em ferros fundidos nodulares austemperados para aplicações em eixo comando de válvulas". Universidade do Estado de Santa Catarina, 2012. http://tede.udesc.br/handle/handle/1630.
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Previous issue date: 2012-08-23Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
In this present conducted in wear resistance nodular cast iron subjected to heat treatment at different temperatures isothermal austempering treatment (340 ° C and 320 °), corresponding to the materials of Classes 3 and 4 of ASTM A897, compared with nodular quenched and tempered with same level hardness. The objective was to develop alternatives for future studies on new materials applied camshaft valve internal combustion engines. For this wear tests were conducted pin-on-disc, using as alumina ball against the body, thus considering zero wear on the counter-body. All cast irons tested under the conditions of this work had hardness in the range 40-46 HRc. It was found in analyzes by scanning electron microscopy the effect of graphite nodules and the matrix material, the wear mechanisms, thus observing the effect that stress concentrator nodes imposes the metallic matrix. The damage to the material surface was initially with crack of the matrix surrounding graphite nodules, they generally located subsurface, moreover, it can be seen that the nodules torn metal matrix acted as a lubricant for testing, and the sites left by lumps were previously coated particles detached from the matrix. It was found with the results of wear tests the performance of austempered ductile iron in comparison with the quenched and tempered for distances exceeding 1000 m slip, thereby qualifying the ADI as an alternative material for future studies in manufacturing valve camshafts.
Apresenta-se neste trabalho um estudo de resistência ao desgaste realizado em ferros fundidos nodulares submetidos ao tratamento térmico de austêmpera em duas temperaturas isotérmicas de tratamento (340°C e 320°), correspondendo aos materiais das classes 3 e 4 da norma ASTM A897, comparativamente com o nodular temperado e revenido de nível de dureza similar. Objetivou-se desenvolver alternativas para estudos futuros em novos materiais aplicados a eixo comando de válvula de motores a combustão interna. Para isto foram realizados ensaios de desgaste pino-sobre-disco, utilizando como contra corpo esfera de alumina, considerando assim desgaste zero no contra-corpo. Todos os ferros fundidos ensaiados nas condições deste trabalho tiveram dureza na faixa de 40 46 HRc. Constatou-se em análises por microscopia eletrônica de varredura o efeito dos nódulos de grafita e da matriz do material, sobre os mecanismos de desgaste, observando assim o efeito concentrador de tensão que os nódulos impõe a matriz metálica. O dano à superfície do material ocorreu inicialmente com o tricamento da matriz em torno dos nódulos de grafita, estes geralmente localizados subsuperficialmente, além disto, pode se observar que os nódulos arrancados da matriz metálica atuaram como lubrificantes ao ensaio, e os sítios deixados pelos nódulos foram recobertos por partículas anteriormente desprendidas da matriz. Constatou-se com os resultados dos ensaios de desgaste o bom desempenho do ferro nodular austemperado em comparação com o temperado e revenido para distâncias de deslizamento superiores a 1000 m, qualificando assim o ADI como material alternativo para futuros estudos na fabricação de eixos comando de válvula.
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Dragan, Rajnović. "Uticaj mikrostrukture na prelaznu temperaturu ADI materijala". Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2015. http://www.cris.uns.ac.rs/record.jsf?recordId=94932&source=NDLTD&language=en.
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U disertaciji je izvršena karakterizacija mikrostrukture i mehaničkih osobinanelegiranog austemperovanogi nodularnog liva (ADI materijala), kao i uticajamikrostrukture na prelaznu temperaturu u intervalu od -196 do +100°C.Utvrđeno je da mehaničke osobine ADI-ja zavise od morfologije ausferitnemikrostrukture i količine zadržanog austenita, tj. parametara austemperovanja.Na osnovu mehaničkih osobina utvrđen je i opseg procesiranja u skladu sastandardima ASTM, ISO i EN. Zaključeno je da prelazna temperatura ADImaterijala zavisi od količine i stabilnosti zadržanog austenita. U višemtemperaturnom opsegu (iznad cca. -25°C) dominantna je količina zadržanogaustenita, dok na nižim temperaturama, stabilnost. Visoka obogaćenostugljenikom, stabilnog zadržanog austenita sprečava stvaranje martenzita naniskim temperaturama, a time i pojavu krtosti kod ADI-ja.The object of this thesis was to characterize microstructure and mechanical propertiesof the unalloyed ADI material (Austempered Ductile Iron). In addition, the influence ofmicrostructure on the ductile to brittle transition temperature (DBTT) by Charpy impacttest in temperature interval from 196 to +100°C has been studied. The all propertiesobtained depend on the morphology of microstructure and the amount of retainedaustenite, i.e. on the austempering parameters. According to the mechanical propertiesand standard requirements (ASTM, ISO and EN) the processing window has beenproposed, also. It was found that DBTT is influenced by amount and stability of retainedaustenite. In upper temperature range (above cca. 25°C) the most influence factor onDBTT is amount of retained austenite, while at the lower temperatures the stability ismore prominent. Stability of high carbon retained austenite at lower temperaturesprevents transformation to martensite and thus the embrittlement of ADI.
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Mariani, Fábio Edson. "Tratamentos térmicos e termoquímicos de boroaustêmpera em ferros fundidos nodulares e caracterização dos produtos resultantes". Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-05092014-082721/.
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Amostras de ferros fundidos nodulares ligados com Cu, Cu-Ni ou Cu-Ni-Mo foram austemperadas, boretadas e boroaustemperadas e caracterizadas quanto à dureza e o comportamento ao desgaste microadesivo, tendo sido também estudada a cinética de formação da camada. O método de boretação utilizado foi via líquida em banho de bórax fundido, com tempos de permanência de 2 e 4 horas nas temperaturas de 850, 900 e 950ºC. Procedeu-se o tratamento direto de austêmpera, a partir dessa temperatura, em banhos de sal fundidos nas temperaturas de 240, 300 e 360ºC com tempos de permanência de 4 horas (boroaustêmpera). Realizou-se também, para fins de comparação, tratamento convencional de austêmpera. Microscopias óptica e eletrônica de varredura, EDS por raios-X, testes de dureza Brinell (substrato) e Vickers (revestimento) foram realizados, bem como ensaios de desgaste microadesivo do tipo esfera presa. A boretação resultou na formação de camadas de elevadas durezas, na faixa de 1300 a 1700 HV, e elevadas resistências ao desgaste. As resistências ao desgaste das amostras boretadas ou boroaustemperadas foram aumentadas em até 40x em relação às amostras brutas de fundição ou apenas austemperadas, indicando a grande eficácia do tratamento neste tipo de propriedade.Samples of ductile cast iron alloyed with Cu, Cu-Ni or Cu-Ni-Mo were austempered, borided and boroaustempered and afterwards characterized for hardness and micro-adhesive wear behavior. The kinetics of layer formation were also studied. The boriding method used was liquid molten borax bath, in periods of 2 and 4 hours at temperatures of 850, 900 and 950°C. The direct austempering treatment was performed from the borax bath temperature using molten salt baths at temperatures of 240, 300 and 360°C for 4 hours (boroaustempered). For comparative purposes, the conventional austempering treatment was also conducted. Optical microscopy, scanning electron microscopy, EDX, Brinell hardness measurements (substrate) and Vickers (coating) were performed, as were the tests for micro-adhesive wear. The boriding treatment resulted in the formation of layers with high hardness, in the range of 1300 to 1700 HV and high wear resistance. The wear resistance of borided or boroaustempered samples were increased by 40 times when compared to cast irons or austempered samples, indicating the high efficiency of this type of treatment in increasing the wear resistance of this material.
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Jacumasso, Tiago. "INFLUÊNCIA DOS PARÂMETROS DE AUSTÊMPERA EM FERRO FUNDIDO NODULAR: MICROESTRUTURA, PROPRIEDADES MECÂNICAS E ASPECTOS DA GEOMETRIA FRACTAL NA FRATURA". Universidade Estadual de Ponta Grossa, 2018. http://tede2.uepg.br/jspui/handle/prefix/2684.
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A mecânica da fratura foi desenvolvida, utilizando-se uma descrição geométrica euclidiana que pressupõem uma trinca lisa sem irregularidades. Por esta razão, a modelagem matemática de uma trinca rugosa, usando a geometria fractal, tem sido a preocupação de vários autores nas últimas décadas. O intuito destes pesquisadores é descrever o fenômeno da fratura de forma mais autentica e precisa. Uma das formas de se avaliar as propriedades mecânicas de um material fraturado é usando o conceito de integral-J. Este conceito aplicado ao fenômeno da fratura define uma curva de resistência ao crescimento de trinca chamado de curva J-R. Sendo assim, vários modelos fractais de curva J-R têm sido propostos. Um dos modelos que vem ganhando destaque na literatura científica foi proposto por ALVES (2010, 2011). Por esta razão investigou-se, neste trabalho, a aplicação desse modelo no estudo da fratura do ferro fundido nodular e ferro fundido nodular austemperado (ADI). O objetivo foi avaliar os efeitos dos tratamentos térmicos de austêmpera na microestrutura e nas propriedades mecânicas de uma liga de ferro fundido nodular. Para tanto foi empregado duas rotas de tratamentos térmicos: austêmpera convencional, consistindo de austenitização a 900ºC por 60min, seguida de austêmpera até 250ºC e à 300ºC, com permanência por 60min e 120min para cada temperatura, totalizando quatro condições, com resfriamento ao ar. As amostras tratadas termicamente foram caracterizadas com auxílio de microscopia óptica, microscopia eletrônica de varredura (FEG) e difração de raios X (DRX), com objetivo de determinar suas fases e microconstituintes. O efeito das condições de tratamento nas propriedades mecânicas foi verificado por ensaios de dureza Vickers e de impacto instrumentado Charpy. Por meio de ensaios de impacto instrumentado e solicitação mecânica de tração e com o auxílio de microscopia eletrônica por emissão de campo (FEG) foi possível estudar o crescimento de trincas rugosas na fratura do ferro fundido nodular austemperado, comparando os resultados entre as quatro condições de tratamento térmico de austêmpera. Deste modo, foi possível fornecer dados experimentais para comprovar a validade da equação da curva J-R na presença de uma trinca rugosa proposta por ALVES (2010, 2011) com base na geometria fractal e na mecânica da fratura. Os resultados obtidos permitiram comparar e discutir o efeito das rotas de tratamento térmico, no sentido de desenvolver as propriedades mecânicas do ferro fundido nodular para aplicações diversas. As curvas D J ajustadas pelo modelo fractal mostraram-se em boa concordância com aquelas obtidas pelo método descrito na ASTM E1820-17a (2017). O ADI tratado a 300ºC por 60 minutos foi o material que apresentou as melhores condições de resistência mecânica a tração e ao impacto, superando o material bruto de fundição na tenacidade a fratura, calculada pelos parâmetros fractais da curva. Este ferro fundido nodular austemperado é comparado ao da classe de alta resistência de ADI.
The mechanics of the fracture were developed using a geometric Euclidean description that assumes a smooth crack without irregularities. For this reason, the mathematical modeling of a rough crack, using fractal geometry, has been the concern of several authors in the last decades. The aim of these researchers is to describe the fracture phenomenon more authentically and accurately. One of the ways to evaluate the mechanical properties of a fractured material is by using the concept of integral-J. This concept applied to the fracture phenomenon defines a crack growth resistance curve called the J-R curve. Thus, several fractal J-R curve models have been proposed. One of the models that have gained prominence in the scientific literature was proposed by ALVES (2010, 2011). For this reason we investigated the application of this model in the study of nodular cast iron and austempered nodular cast iron (ADI). The objective was to evaluate the effects of thermal treatments of austempering in the microstructure and mechanical properties of a ductile cast iron alloy. Two routes of thermal treatments were used: conventional austenitic, consisting of austenitization at 900ºC for 60min, followed by tempering up to 250ºC and at 300ºC, with permanence for 60min and 120min for each temperature, totaling four conditions, with air cooling. The thermally treated samples were characterized by optical microscopy, scanning electron microscopy (FEG) and X - ray diffraction (XRD), in order to determine their phases and microconstituents. The effect of the treatment conditions on the mechanical properties was verified by tests of Vickers hardness and instrumented impact Charpy. By means of instrumented impact and mechanical tensile stress tests and with the aid of field emission electron microscopy (FEG), it was possible to study the growth of rough cracks in austempered nodular cast iron fracture, comparing the results between the four conditions of heat treatment. Thus, it was possible to provide experimental data to prove the validity of the J-R curve equation in the presence of a rough crack proposed by ALVES (2010, 2011) based on fractal geometry and fracture mechanics. The results obtained allowed to compare and discuss the effect of heat treatment routes in order to develop the mechanical properties of nodular cast iron for different applications. The D J curves fitting by the fractal model show in agreement with the curves obtained by the method described in the ASTM E1820-17a (2017). The ADI treated at 300ºC for 60 minutes was the material that presented the best conditions of tensile and impact mechanical strength, surpassing the crude casting material in the fracture toughness, calculated by the fractal parameters of the curve. This austempered nodular cast iron is compared to that of the ADI high strength class.
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Li, Xiaohu [Verfasser], Winfried [Akademischer Betreuer] Petry, Winfried [Gutachter] Petry y Wolfram [Gutachter] Volk. "Investigation of strain induced martensite transformations kinetic in Austempered Ductile Iron (ADI) using neutron and synchrotron diffraction / Xiaohu Li ; Gutachter: Winfried Petry, Wolfram Volk ; Betreuer: Winfried Petry". München : Universitätsbibliothek der TU München, 2018. http://d-nb.info/115493179X/34.
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Santos, Hugo dos. "Mecanismos de fratura de ferro fundido nodular austemperado a partir da zona crítica". Universidade do Estado de Santa Catarina, 2010. http://tede.udesc.br/handle/handle/1764.
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This work is part of a research project at UDESC, which aims to understand and compare the process of fracture of ADI with dual matrix structure, such as sites of plastic deformation concentration and crack nucleation, and paths of crack propagation. The fracture mechanisms of two types of duals ADI with different ausferrite volume fraction were compared to those of conventional ADI. Intercritical austenitising temperatures chosen were 790°C and 820°C, and resulted in dual ADI with 17% and 85% of ausferrite respectively. The full ADI, which was austenitised at 900°C, was used to serve as reference material. The three materials were austempered at 360°C for 2h. Results showed that in dual ADI with predominantly ferrite, the nucleation of cracks occurred along the interface graphite/matrix. Increasing the ausferrite volume fraction, the nucleation of cracks tended to occur along the inclusions and intercellular boundaries. Moreover, in dual ADI, the crack propagation and concentration of plastic deformation occurred preferentially in the ferrite. With respect to the fracture´s analysis, all materials showed that the quantities of fracture ductile/fragile were equivalent. The fractures had an aspect predominantly ductile, being formed mostly by dimples with some regions of quasi-cleavage.
Este trabalho faz parte de uma linha de pesquisa executada na UDESC, que visa entender e comparar o processo de fratura dos ADI duais, tais como, locais de concentração de deformação plástica e de nucleação de trincas, e caminhos de propagação de trinca. Os mecanismos de fratura de dois tipos de ADI duais com diferente fração volumétrica de ausferrita foram comparados com o ADI pleno. As temperaturas de austenitização intercrítica escolhidas foram 790°C e 820°C, e resultaram em ADI duais com 17 e 85% de ausferrita respectivamente. O ADI pleno, no qual foi austenitizado a 900°C, foi utilizado para servir de material de referência. Os três materiais foram austemperados a 360°C por 2h. Verificou-se que para o ADI dual com predominância de ferrita, a nucleação da trinca ocorreu junto à interface grafita/matriz. Conforme aumentou a fração volumétrica de ausferrita na matriz, a nucleação da trinca tendeu a ocorrer junto à inclusão intercelular e em contornos de célula. Além disso, nos ADI duais, a propagação da trinca e a concentração de deformação plástica ocorreu preferencialmente na ferrita. Vale ressaltar que os três materiais apresentaram quantidades de fratura dúctil/frágil equivalentes. As fraturas tinham uma característica predominantemente dúctil, sendo formadas na maioria por alvéolos com algumas regiões de quase-clivagem.
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Lopes, Clarissa Lussoli. "Estudo da influência das temperaturas de austenitização nas propriedades mecânicas do ferro nodular austemperado a partir da zona crítica". Universidade do Estado de Santa Catarina, 2009. http://tede.udesc.br/handle/handle/1748.
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In the present work the influence of austenitizing temperature on mechanical properties Austempered Ductile Iron from intercritical austenitizing temperature ranges was investigated. A heat treatment for development of material with improved mechanical properties for application in suspension parts is shown. Samples of alloyed ductile iron with a fully ferritic matrix was austenitized within intercritical range between 775°C and 820°C for 5h and then austempered at 360°C for 2h to produce ductile iron with dual matrix; with different percentages of free ferrite. After the heat treatment, the samples were sends for mechanical testing (tensile, impact and hardness tests) and for metallographic analysis. The percentages of free ferrite ranged from 9,5 to 21%, new ferrite of 7 to 10%; the observation of new ferrite was made through special reagents. The austenite (ausferrite at room temperature) nucleates firstly in the eutectic cell. The intercritical austenitizing can be interpreted in two stages: 1) short times the austenite is found only in the eutectic cell or grain boundaries and 2) long times the austenitizing also occur inside of grain. Due long times of austenitizing, it is probably that this work has arrived to the equilibrium of phases in austenitizing, which explain fewer ferrite, when compared with other literature. Samples exhibited good combination mechanical properties, with high strength and excellent amount of elongation. The study presents fracture s microstructure from scan electron microscopy of tension s specimen, has noticed large dimples near graphite; quantities of cleavage s area increase with decrease ferrite in the microstructure. The materials show few secondary cracks, characteristic in tension tests of high strength irons. Quality index (IQ) were calculated for samples this work, specimen austenitized to 805°C has shown better result to tensile test. However, it is important to add that specimen austenitized to 790°C has shown better result to components that require impact strength. The result of mechanical properties achieved in this study follow an extrapolation of the values of international standard (ex. ASTM), which facilitates the normalizing this group of materials, including it in present standard of austempered ductile iron.
Estuda-se no presente trabalho a influência das temperaturas de austenitização nas propriedades mecânicas do ferro fundido nodular austemperado a partir da zona crítica. Apresenta-se um tratamento térmico para o desenvolvimento de materiais com propriedades mecânicas otimizadas para aplicação em componentes de suspensão. Amostras de ferro fundido nodular ligado com matriz inicialmente ferrítica foram austenitizadas dentro da zona crítica entre 775 e 820°C por 5h e então transferidos para austêmpera a 360°C por 2h para produzir ferros fundidos nodulares com matriz dual; com diferentes percentagens de ferrita proeutetóide. Após o tratamento térmico, as amostras foram encaminhadas para ensaios mecânicos de tração, impacto e dureza, seguindo então para análise metalográfica. As percentagens de ferrita proeutetóide variaram de 9,5 a 21%, e as quantidades de ferrita nova foram de 7 a 10%; a observação da ferrita nova foi através do uso de reagentes especiais. Os locais preferenciais para o início da transformação de ferrita para austenita (ausferrita a temperatura ambiente) foram os contornos de células eutéticas. A austenitização intercrítica pode ser interpretada em dois estágios: 1) curtos tempos - a austenita encontra-se apenas em contornos de célula eutética e de grão e 2) longos tempos a austenitização ocorre também dentro do grão. Devido aos longos tempos de austenitização empregados, é provável que neste trabalho se esteja próximo ao equilíbrio de fases na austenitização, o que explica as menores quantidades de ferrita obtidas, quando comparado com vários trabalhos da literatura. As amostras apresentaram boas combinações de propriedades mecânicas, com elevadas resistências e ótimos valores de alongamento. Apresentaram-se fractografias obtidas via microscopia eletrônica de varredura dos corpos de prova de tração, onde se observaram grandes quantidades de alvéolos próximos dos nódulos; a quantidade de áreas com clivagem cresce com a diminuição de ferrita na microestrutura. Além disso, os materiais apresentaram poucas trincas secundárias, característica típica em ensaios de tração de ferros fundidos de alta resistência. Foram calculados os índices de qualidade (IQ) para as amostras do trabalho, sendo que a amostra austenitizada a 805°C foi a que apresentou melhor resultado em ensaios de tração. Porém, vale ressaltar que a amostra austenitizada a 790°C apresentou melhores resultados para componentes que exigem resistência ao impacto. Os valores de propriedades mecânicas obtidos seguem uma extrapolação dos valores das normas internacionais (por ex, da ASTM), o que facilita a normalização deste grupo de materiais, incluindo-o nas normas atuais de nodulares austemperados.
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Tesařová, Hana. "Strukturní a mechanické charakteristiky niklových litin s kuličkovým grafitem". Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-233891.
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The aim of this dissertation work is the evaluation of the influence of nickel alloying on the structure and mechanical properties, both monotonic and dynamic, of nodular cast iron with ferritic and bainitic matrix. Two chock melts with 0.5 and 2.7 % Ni were used to study the nickel influence. The quantitative evaluation of structure of these melts using image analysis was done and basic tensile mechanical properties were determined. Subsequently, the time optimization of two-stage ferritic annealing and isothermal austempered heat treatment at 375 °C was performed with the aim to obtain optimal ferritic and bainitic structures with best static and dynamic mechanical properties. After ferritic annealing the nickel alloying contributes to substitution hardening of ferritic matrix which positively affects its strength and other mechanical properties. The higher nickel content in the bainitic structure causes the shift of phase transformation times to longer times which results in restricted production of small carbides and in bigger volume of retained austenite. These features were confirmed by observation in transmission electron microscope. Precise tensile and low cycle fatigue tests at temperatures 23 and – 45 °C were performed on the optimized structures of both nodular cast irons. As a result of the notch effect of graphite nodules, microplastic deformation of both nodular cast irons was observed at stresses which were lower than the yield stress. The Hollomon's equation very well describes the individual parts of tensile curves for both nodular cast irons including their mutual comparison. From the low cycle fatigue tests, the cyclic hardening/softening curves, the evolution of elastic modulus and hysteresis loop shape parameters, cyclic stress-strain curves and fatigue life curves were obtained for both temperatures and materials. Moreover, the decrease of retained austenite volume was measured by neutron diffraction and the evolution of surface relief was characterized during cyclic straining for both austempered nodular cast irons at both temperatures. On the basis of these results both cyclic plasticity and fatigue degradation mechanisms in relation to the cyclic strain localization were described for both nodular cast irons.
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Franco, Eliana. "Estudo da influência dos parâmetros de austenitização sobre a microestrutura do ferro fundido nodular austemperado a partir da zona crítica". Universidade do Estado de Santa Catarina, 2008. http://tede.udesc.br/handle/handle/1617.
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This work examines the influence of austenitizing parameters on the microstructure of ductile cast iron austempered from the critical zone, called in this work as NAZC Nodular Austemperado a partir da Zona Crítica (ductile iron austempered from the critical zone). Initially a differential thermal analysis was performed to determinate the critical temperatures range, according to this analysis the critical zone is placed between 750 e 850o C. Alloyed ductile iron specimens were austenitized within the critical zone and water quenched to evaluate the amount of phases present in the final microstructure, proeutectoid ferrite and martensite. This preliminary study was conducted in order to quantify the amount of austenite (martensite at room temperature) which would become ausferrite later in the study of austempering. The treatment of austempering results in a dual microstructure of ausferrite and proeutectoid ferrite. The microstructural and quantitative analysis allowed the evaluation of the amount of phases formed, as well the evolution of microstructural transformation. This study was the basis to determine the parameters of austenitizing to austempering. Austempering treatments were performed under several conditions of austenitizing, until a microetruture related to a high mechanical strength and ductility were obtained. It s possible control the microetruture and consequently the properties from the control of the austenitizing temperature and time and austempering conditions. The microstructural analyses of austempered specimens showed that the austenitizing temperature within the critical zone of 790 °C and times of 3 and 4 hours led to a final microstructure formed by approximately 49 and 64% of ausferrite. An austempered material in these conditions of austenitizing should present an interesting set of mechanical properties, a mechanical strength next to the pearlitic grades associated with a considerable elongation, near the ferritic grades. The austempered materials from the critical zone of this study also present a good distribution between the phases proeutectoid ferrite and ausferrite, even near eutectic cell boundary and around graphite nodules, what must produce good properties of fatigue.
Este trabalho avalia a influência dos parâmetros de austenitização sobre a microestrutura do ferro fundido nodular austemperado a partir da zona crítica, denominado neste trabalho como NAZC - Nodular Austemperado a partir da Zona Crítica. Inicialmente foi realizada uma análise térmica diferencial para determinação da faixa de temperaturas crítica, conforme essa análise a zona crítica se situa entre 750 e 850o C. Amostras de ferro nodular com adição de elementos de liga foram austenitizadas dentro da zona crítica e temperadas em água para avaliação da quantidade de fases presentes na microestrutura final, ferrita pró-eutetóide e martensita. Esse estudo preliminar foi realizado a fim de quantificar a quantidade de austenita (martensita na temperatura ambiente), a qual se transformaria em ausferrita no estudo posterior de austêmpera. O tratamento de austêmpera resulta em uma microestrutura bifásica composta por ausferrita e ferrita pró-eutetóide. As análises microestruturais e quantitativa permitiram avaliar a quantidade de fases formadas, bem como a evolução da transformação microestrutural. Esse estudo foi a base para a determinação dos parâmetros de austenitização para austêmpera. Foram realizados tratamentos de austêmpera em diversas condições de austenitização, até que fosse obtida uma microestrutura relacionada à elevada resistência mecânica e ductilidade. É possível controlar a microestrutura e consequentemente as propriedades a partir do controle da temperatura e tempo de austenitização e das condições de austêmpera. As análises microestruturais de amostras austemperadas mostraram que a temperatura de austenitização dentro da zona crítica de 790o C e tempos de 3 e 4 horas levaram a uma microestrutura final formada por aproximadamente 49 e 64% de ausferrita. Um material austemperado nessas condições de austenitização deve apresentar um interessante conjunto de propriedades mecânicas, ou seja, uma resistência mecânica próxima a de classes perlíticas associada a um considerável alongamento, próximo ao de classes ferríticas. Os materiais austemperados a partir da zona crítica deste estudo também apresentam uma boa distribuição entre as fases ferrita pró-eutetóide e ausferrita, mesmo próxima aos contornos de célula e nódulos de grafita, o que deve conferir boas propriedades de fadiga.
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Ceccon, Lorenzo. "Effetto dell'esposizione ad alta temperatura su microstruttura e proprietà meccaniche di ghise sferoidali". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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Lo scopo della presente ricerca è stato valutare l’effetto dell’esposizione ad alta temperatura su microstruttura e proprietà meccaniche di quattro ghise sferoidali prodotte dalle Fonderie Zanardi: ADI 1050 (ghisa duttile austemperata), IDI 800 (ghisa perlitica isotermica), GJS/800-2 (ghisa sferoidale perlitica) e GJS/400-18 (ghisa sferoidale ferritica).
Lo studio ha previsto il degrado in temperatura dei quattro materiali, l’analisi delle proprietà meccaniche statiche dopo degrado termico mediante prove di durezza Brinell, analisi microstrutturali, XRD, prove di trazione sia a freddo che alla temperatura di degrado.
Per quanto concerne le prove di durezza, è emerso che superata la temperatura di 500 °C la durezza dei materiali ADI 1050 e IDI 800 cala significativamente, la durezza della GJS/800-2 risulta stabile fino a 550 °C, mentre per la GJS/400-18 la durezza rimane pressoché costante fino a 600 °C.
Le analisi microstrutturali hanno mostrato che nell’ADI 1050, IDI 800 e GJS/800-2 la matrice si trasforma sino a diventare quasi completamente ferritica a temperatura di degrado di 600 °C mantenuta per 120 ore. Nella ghisa sferoidale ferritica invece non vi sono mutamenti significativi nella microstruttura dopo degrado.
Le prove di trazione svolte sulla lega ADI 1050 hanno evidenziato una diminuzione di circa 50-60 % della tensione di rottura e quella di snervamento nei provini degradati e trazionati a 500°C rispetto ai provini degradati trazionati a temperatura ambiente, ed una diminuzione di circa 20 % della tensione di rottura e quella di snervamento nei provini degradati rispetto ai provini non degradati trazionati a temperatura ambiente. Le prove di trazione a temperatura ambiente su ghisa sferoidale perlitica degradata hanno mostrato un calo delle proprietà resistenziali di circa il 6% nei provini degradati a 240 ore mentre nella ghisa IDI 800 degradata si è notato un calo di circa il 10% delle proprietà resistenziali già nei provini degradati a 72 ore
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Megna, Gianluca. "Application of austempered ductile irons to structural components of railway vehicles". Doctoral thesis, 2020. http://hdl.handle.net/2158/1188742.
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In this thesis, a state of the art of the structural components of railway vehicles and the material used for their manufacturing is analyzed in order to find possible new applications for ADI (Austemperd Ductile Iron). The main scope of the research is therefore to demonstrate that high stressed steel components of railway vehicles can be replaced by casted ADI components. After a survey of the possible components to be produce in ADI, three possible applications were found: wheel centre for tyred wheels, bogie frame, couplers for heavy haul operation. A feasibility analysis was performed and after a preliminary design the project has been focused in the development of an optimized tyred wheel as replacement of the current wheel for an existing Diesel Multiple Unit (DMU). Prototypes of this wheel have been finally manufactured and tested in order to demonstrate the feasibility of the application of ADI to the structural components of railway vehicles.
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Chen, Bi-Ting y 陳碧亭. "Microstructure of Intercritical Austempered Ductile Iron". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/4tsmrw.
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碩士國立臺北科技大學
材料科學與工程研究所
99
The current study investigates the influences of intercritical austenitizing temperatures on microstructures and mechanical properties of austempered ductile irons. A series of intercritical austenitizing temperatures ranging from 775 to 900°C are used and austempering is performed at 400°C on a conventional FCD700 ductile iron. Experimental results show that mechanical properties, including strength, ductility, and the toughness, all increase with intercritical austenitizing temperatures till an optimum austenitizing temperature of 830°C. At this optimum processing condition, strength of 974 MPa, impact energy of 166 J, and 16.4% ductility is achieved. These properties are much higher than non-treated ductile iron with 790 MPa strength, 42 J impact energy, and 8.2% ductility. The 830°C austenitized and 400°C austempered microstructure consists of 8% proeutectoid ferrite and 27% retained austenite. The uniform distribution of refined ausferrite grains is responsible for the increase of overall strength. Furthermore, nano-size martensitic transformation induced by plastic strain can be observed via TEM inside the blocky type retained austenite. The increased carbon content, adequate size and distribution of retained austenite combine to increase toughness through martensitic transformation giving rise to transformation induced plasticity (TRIP) effect.
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Chang, M. C. y 張明哲. "Cutting Properties of Austempered Ductile Iron". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/13488315145063896767.
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TSAI, FENG-CHING y 蔡豐慶. "Study on Aluminization of Austempered Ductile Iron". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/14586714244297276209.
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碩士國立高雄應用科技大學
模具工程系
105
In this paper, the austempered ductile iron(ADI) was used as a substrate and aluminized at 900 ℃ to aluminized layer on the ADI for increasing hardness, corrosion resistance, and antioxidant at high temperature. Since the aluminized treatment make the ADI restore to tradiction dutile iron, the austempered treatment was applied. It was not only possessed the property of ADI but also improved the oxidation at high temperature.
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Chang, Chao-hsu y 鄭朝旭. "Ausferrite Transformation in Austempered Ductile Irons". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/49983796060878989031.
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博士國立中央大學
機械工程研究所
82
A modified thermal analysis was presented in this study to discuss the effect of alloy elements and surface areas of nodular graphite on ausferrite reaction and used to observe the transformation kinetics of ferrite in austenite matrix of ductile irons during isothermal holding (250℃∼400℃). The transformed ferrite fractions analyzed by the modified thermal analysis are close to those measured by metallographic observations of specimens austempered for different time. Latent heats released from phase transformation were in relation to the amounts of ferrite transformed. Addition of alloy elements, surface areas of nodular graphite and isothermal holding temperatures resulted in a marked influence on the rate of volumetric heat evolution during the period of recalescence. Synergistic effect of higher alloying elements, which delayed substantially the carbon diffusion, shifted the maximum rate of heat evolution to a higher temperature. The morphologies of ferrite plates transformed during the period of recalescence were also observed metallographically. Silicon and suface area of nodular graphite were found to have accelerated nucleation and early growth of ferrite in the matrix of ductile irons during isothermal holding. Manganese retarded the early growth of ferrite plate. Synergistic effect of Cu ,Mo, or Ni effectively suppressed the growth of ferrite during the period of recalescence. A model was proposed to simulate the average rate of volumetric heat evolution in the period of recalescence, another model was proposed to predict the time of τe for ADIs in the austempering temperatures 250℃ ∼400℃. The time for the termination of heat evolution occurs at time for terminating the ferrite plate growth and is close to (but less than) the time for developing the optimum toughening properties of austempering ductile irons (ADIs).
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Gao, Ming-Shiung y 高銘祥. "The Repeat Heat Treatment of Austempered Ductile Iron". Thesis, 1998. http://ndltd.ncl.edu.tw/handle/77461628721543139363.
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Feng, Hui-Ping y 馮慧平. "Study on Fracture Toughness of Austempered Ductile Iron". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/29598386444377039351.
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博士大同工學院
材料工程研究所
87
In this study, applied ductile iron castings in different section size and with/ without Bi alloying addition, we evaluate the effects of mass variation and graphite refinement (with Bi alloying addition) in castings on the fracture toughness of ADI. And applied the compact tensile (CT) specimens of fracture toughness via single-step or two-step austempering heat treatment and testing at the different environmental temperatures (150℃, 25℃, or -150℃), this research is also to investigate the variation of the fracture toughness of ADI. We made three types of ductile iron casting materials, named as material A, B, and C in this experiment. The casting forms of material A (without Bi alloying addition) and material B are the same Y-block of 30, 60, and 115mm section size, which were added alloying elements Cu, Ni, and Mo to enhance their harden-ability to avoid the pearlite formation during austempering heat treatment process. The form of ductile iron material C casting, in T-block with two ends of 35mm and 65mm in thickness, is designed to meet the practical machine parts generally containing different section sizes. The results show the effect of graphite nodule refinement by Bi alloying addition on the plane stain fracture toughness (KIC) is significant, the highest toughness value of 56.0 MPa√m obtained in this study, and only at the very high nodules count of 400 nodules/ mm2 compounded with high ferrite content in the as-cast matrix. Otherwise, the as-cast ferritic-pearlitic ductile iron of thickness from 30 mm to 115 mm possess KIC fracture toughness only within 40~ 46 MPa√m. For KIC fracture toughness and retained austenite of the austempered materials A and B within 30 mm to 115 mm thick casting size, it appeared that because of the homogenization effect from high temperature austenitization (900℃), the specimens after 1~3 hours subsequent austempering did not seem to change the properties too greatly. Conventional single-step austempering of material A, B, and C ductile iron, can obtain a marked increase in the plane strain fracture toughness KIC from 42.7/46.7/38.2 MPa√m of the as-cast material A, B, and C to 64.3/71.3/57.4 MPa√m of the austempered, an improvement over 40%. Two-step austempering of the ductile iron material C yielded the good KIC 77.8 MPa√m , which is close to the KIC 77.3 MPa√m of the ductile iron subjected by a single-step austempered at higher temperature 360℃ and better than the KIC 57.4 MPa√m at lower temperature 300℃. At room temperature the fracture toughness of the mixed ausferrite of two-step austempering is close to that of the upper ausferrite of austempering temperature 360℃, however mixed ausferrite has a higher strength and hardness than those of the upper ausferrite. Therefore, we can conclude that ADI of two-step austempering is a suitable material for machine parts with good strength and fracture toughness. At medium (150℃) and low (-150℃) temperature in this experiment, the microstructures of ADI seem no significant change. However, the KIC of ADI markedly decrease at temperature of -150℃, which might be related to the martensite transformation of the retained austenite in the matrix under lower environmental temperature. Another observation, the fractography of ADI at low temperature generally shows large cleavage facets, which are typical brittle fracture.
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陳正中. "The study of austempered ductile iron fatigue characteritic". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/55029565223490715411.
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SUN, ZHENG-YU y 孫政郁. "Research and Development of Improved Austempered Ductile Iron". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/um4322.
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Ren, Hwang Jiunn y 黃俊仁. "A Study on the Processing Windows of Austempered Ductile Iron". Thesis, 1996. http://ndltd.ncl.edu.tw/handle/73585223020616247585.
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碩士國立臺灣科技大學
機械工程研究所
84
Mechanical properties, including ultimate tensile strength, 0.2% offset stress, elongation, impact energy and hardness, were used to study the suitability on processing window of austempered ductile iron alloyed with 0.77%Cu and 0.5%Ni at high austempering temperature. The ranges of processing windows were derived from the electrical resistivity variations during austempering of the ductile iron. If austempered within the range of processing windows, results of higher strength and hardness but lower ductility and impact toughness will be obtained at either higher austenitizing temperature or lower austempering temperature. Optimum mechanical properties are obtained when heat treating periods are within the processing window. Both mechanical properties and microstructures show that the processing windows defined from the electrical resistivity are feasible. This thesis also discusses the improvement of segregation by homogenizing heat treatment; and the influence of the size and amount of specimen, related to the quench bath, on the hardness during austempering; also the assocaited fractography of mechanical testing.
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Chen, Chan Tung y 陳建同. "The Study on the Transformation Kinetics of Austempered Ductile Iron". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/39813908367660353579.
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博士國立臺灣科技大學
機械工程系
87
The resistivity of alloyed ductile iron during austempering was measured to investigate the influence of austenitising temperature﹐austempering temperature and content of alloys on the kinetics of phase transformation. The specimens were heat-treated in a vacuum furnace by passing through direct current monitored and controlled with a personal computer to follow the heating and cooling scheme. Austenitising temperature from 850 to 950oC was used to bring the matrix of ductile iron into austenite phase. After a holding period at austenitising temperature, the specimens were quenched, with a liquid nitrogen spray, to desired austempering temperature to conduct the isothermal transformation. During the isothermal transformation process, the resistivity varied with time and showed three sequences of transformation: stage1﹔the processing window﹔and stage 2; clearly. The changes of resistivity around the process window were related to the volume fraction of retained austenite which was measured by X-ray diffraction technique. A model is then proposed to predict the volume fraction of retained austenite from the change of resistivity for austempering. During the progress of isothermal transformation, the resistivity of austempered ductile iron vs. time was recorded and then analyzed to determine the processing window. X-ray diffraction, heat tinting technique, and microstructural examination were conducted to examine the suitability of this processing window in terms of microstructural changes. The data of mechanical properties of the ductile iron from the same casting batch and same austempering were extracted from a concurrent work to discuss the suitability of this processing window. Both the evaluation of microstructures and mechanical properties confirmed the suitability of this processing window. A slow rate transformation during the time interval of processing window was observed, which was associated with the continuous decomposition of blocky austenite and resulted in a slight variation of the mechanical properties. A further kinetics analysis demonstrates that the reaction of all three stages mainly obey the Johnson-Mehl equation with an average value of exponent n equal to 1.20, 1.09, and 1.57, except for the final portion of stage 1 reaction for alloyed ductile iron at lower austempering temperature. The empirical activation energy of three-stage reactions calculated from the rate constant k are 19, 127, and 240 kJ/mole respectively. Increasing the austenitising temperature results in reducing the austempering reaction rate and the amount of retained austenite and in suppressing the onset of stage1 reaction. Decreasing the austempering temperature has the same influence on austempering reaction as increasing austenitising temperature. Alloyed ductile irons are shown to shift the heat treatment processing window to a longer time. The segregation of alloy elements produces the reducing of the stage 1 reaction rate but slightly accelerated the stage 2 reaction and then causes the shrinkage of the processing window.
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Cheng, S. J. y 鄭石釧. "The Effect of Low Temperature Austenitizing on Austempered Ductile Iron". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/01413017580081159436.
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碩士國立臺灣科技大學
機械工程系
92
Abstract This research is aimed to investigate the effect of low temperature austenitizing on austempered ductile irons. Use a self designed vacuum heat treating system to measure electrical resistivity during the heat treating. The austenitizing have two stages: the first stage kept in 900℃and the second stage adopt a lower temperature and then followed by an austempering. The temperature profile, microstructures and hardness from the austempered ductile irons were used to antithesis the temperature zones of phase transformation. The experimental results show that : (1) in all tests, only the ductile iron FCD 700 with austenitizing at 747℃, specimen C3, have its hardness at center portion meet the MADI standard; (2) through the temperature profiles of FCD 450、550 and 700 specimens, the critical transformation temperature range of pro-eutectoid ferrite are 784~730、750~697 and 753~689℃ respectively; (3)assisted with the micro- structures, the zone with a great quantity of pro-eutectoid ferrite would associated with a rapidly drops along the hardness profile; (4) through the micro structural observation of FE-SEM, the growth of ausferrite be hindered by the existed pro-eutectoid ferrite and resulted to a shape like short wicker. In the ferrite region of the matrix, there exists a two-layer structure. The reason is explained as that the carbon content of the pro-eutectoid ferrite are less then that of austempered ferrite.
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Fang, Ying-chan y 房瑛展. "Effect of Compressive Strain on Characteristics of Austempered Ductile Iron". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/x5bb99.
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碩士大同大學
材料工程學系(所)
102
In this study, ductile iron was selected as the experimental material. The processing conditions of the austenitizing of 910℃-1.5hrs and austempering of 360℃-2hrs were adopted to further treat the iron as austempered ductile iron (ADI). First, the stress of 950MPa was used to compress ADI with duration time to get different compressive strain by MTS machine. Then microstructural observation, mechanical tests (such as hardness, wear, and erosion), and polarization corrosion tests in 3.5wt%NaCl, were performed to understand the effects of compressive strain on the microstructure, mechanical and corrosion behaviors of the iron. OM, SEM, XRD, HV hardness tests, wet and dry erosion tests ,and polarization tests were all performed. The experimental results showed that the increase of compressive strain could increase HV hardness, but the surrounding of graphite generated some cracks. The reason should be that the stress concentration occurred in surrounding graphite after compressive process. The increase of compressive strain lowered corrosion resistance to show the type of crevice corrosion. In terms of wear, the friction coefficient decreased from 0.45 to 0.38 with increasing compressive strain. In terms of erosion, after the solid erosion and wet erosion tests, all the compressed specimens had the same erosion morphology. When compressive strain was up to 4%, the surrounding of graphite would form the TRIP zone avoid erosion attack and increase ADI’s erosion resistance. In terms of wet erosion with 3.5wt% NaCl, The experimental results showed that the increase of compressive strain changed the corrosion morphology from crevice corrosion to uniform corrosion. The reason was that the graphite nodules were deformed by compressive strain, and the gap between graphite and base could keep dense structure to inhibit the permeation of NaCl solution. The results showed compressive strain could increase wet erosion resistance in NaCl solution.
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Tsai, Jui-Shen y 蔡睿紳. "Study of Austempered Ductile Iron Process in the Intercritical Region". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/9c2ftm.
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碩士國立臺北科技大學
材料科學與工程研究所
97
The purpose of this thesis is to investigate the influences of intercritical austenitizing temperutures on the microstructures and mechanical properties of austempered ductile irons.Intercritical austenitization is used to control the austenitizing temperature in the region where ferrite, austensite, and graphite coexist. In this study, 775℃, 790℃, and 805℃ are used as intercritical austenitizing temperatures and austempering is performed at 300℃or 400℃. The results of these treatments are compared with conventionally austempered ductile iron. The experimental results show that the optimum combination of strength and ductlity is achieved when austenitizing temperature approaches the upper critical temperature and tempering using higher tempertures.The increased carbon content of retained austenite and austenite volume fraction are beneficial to the increase of strain hardening coefficients. TRIP effects are observed to aid the improved toughness.
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Liao, Chi-Meng y 廖繼盟. "Study on The Wear Performance of The Austempered Ductile Iron". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/9z8ex8.
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碩士國立虎尾科技大學
機械設計工程研究所
103
Austempered Ductile Iron (ADI) is a material with combined matrix of acicular ferrite and carbon-rich austenite, which is transformed during austemper process of ductile iron. The material possesses properties of high strength, hardness, good toughness, high strength-to-weight ratio, low cost, and less density, which has great potential value in application and is widely used in automotive, construction and agricultural industry. This study aims to investigate the tribological properties of ADI under various test methods and lubricants. A plan of experiment is generated through Taguchi’s technique and is conducted by multi-purpose friction and wear tester. The testing parameters include contact load, sliding speed, slide-roll ratio, surface roughness, and temperature. Experiment was designed using Taguchi’s method and by combining with Grey Relation Analysis, a mathematical model is built by friction coefficient, contact temperature, and wear. Then, build a database of ideal combination of parameters systematically based on the mathematical model, and verify the effectiveness of this combination of parameters. The wear surface morphology were investigated using optical microscope and SEM.
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Wu, Chang-Zhin y 吳滄欽. "Phase Transformation and mechanical Properties of Austempered Ductile Irons". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/11222809030384309910.
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博士國立中央大學
機械工程研究所
91
ABSTRACT This doctoral thesis aims to make a thorough investigation on the matrix microstructure of ADI, hoping to understand the relations between phase transformation and mechanical performance via different approaches. The whole thesis is composed of three parts. In Part I, the discussion focuses on the effects of austempered temperatures and alloy addition on the phase transformation and mechanical properties of alloyed (0.9%Ni-0.6%Cu) and unalloyed ADI. When treated at the low temperatureat (320℃), slim acicular ferrite plates were densely distributed in matrix, so the volume fraction of string-type austenite was higher. By contrast, at the high temperature (360℃), ferrite plates were coarse and loosely distributed in matrix, resulting in the increase of more blocky austenite. Also, the stubbed ferrite plates were coarse and dense in unalloyed ADI. Ausferrite transformed with a great nucleation rate and/or a pronounced sidewise growth, so more apparent branches of ferrite plates and large amounts of string-type austenite emerged in unalloyed ADI. String-type austenite tended to generate carbide precipitation. So the specimens at 320℃ or unalloyed ADI exhibited higher strength and hardness, but lower impact energy and elongation. But there were less long slim ferrite plates with more blocky austenite evenly distributed in the matrix of alloyed ADI. More blocky austenite implies more austenite content. During plastic deformation, blocky austenite was prone to absorb energy accompanied with the formation of stress-induced martensite transformation, i.e. the TRIP effect. So the elongation and impact energy were higher in the specimens at 360℃ or alloyed ADI. Fatigue properties are also significantly affected by the austenite content. Specimens at 360℃ or alloyed ADI developed excellent high-cycle fatigue strength attributed to large amounts of retained austenite. After painting and baking, the fatigue strength, however, decreased because of (1) the precipitation of coarse carbides and/or (2) the micro-cracks caused by the uneven diffusion of hydrogen along the interface of ferrite and austenite. In short, the alloyed ADI treated at 360℃ developed an optimum strength and elongation as well as superior impact toughness and high-cycle fatigue strength due to large amounts of dispersed blocky austenite. In Part II, an ultrasonic vibration treatment was adopted to investigate the effect of cavitation erosion (combining the effects of micro-jet impact and shock waves) on the phase transformation and micro-hardness changes in the matrix of alloyed/unalloyed ADI at 320℃/360℃ for 2hr. Results show that the matrix temperature would gradually increase along with the ultrasonic treatment and fostered the carbon diffusion to undergo the Stage II reaction. Specimens after subjected to the ultrasonic vibration treatment might develop phase transformation induced by plastic deformation. Some string-type austenite was found to precipitate carbides, while some island-like/blocky austenite was transformed into martensite. With increased cumulative ultrasonic time, carbide particles became coarser, and martensite might further precipitate to ferrite and carbides. However, the stress-induced martenite transformation in the austenite of alloyed ADI was obviously retarded due to the addition of Ni and Cu. The stabilized austenite behaved good work hardening. Detecting the stress-induced martensite areas after ultrasonic vibration by EPMA, we found that micro-cracks were rarely seen in the blocky austenite area with higher Mn content, but they appeared in the area with lower Mn content. After the treatment, the micro-hardness values increased with the increasing treating time, while the retained austenite content revealed a declination tested by X-ray diffraction. The occasional declination of micro-hardness in unalloyed ADI might be resulted from the decomposition of martensite into ferrite and carbides. The aim of Part III is to elucidate the influence of inclusion particles on the microstructure and mechanical properties of high strength unalloyed ADI with different contents of Mn and Si. For a given C and Si content, the total particle count decreased with the increasing Mn content (0.25-0.48%). But under a given Mn content, increasing Si content from 2.45% to 3.10% contrarily enhanced the total particle count. In addition, within the colony of eutectic cell, a Mg-deficient inclusion tended to be surrounded by ferrite ring, while the vicinity of a Mg-enriched inclusion formed acicular ferrite or ferrite lath. Inclusion particles, especially when its size is less than 5µm, were mostly found in intercellular regions. Whether an inclusion particle can induce the formation of acicular ferrite lies in Mn segregation. In intercellular region, acicular ferrite was hard to form in the vicinity of inclusion particles due to (1) serious Mn segregation, and/or (2) the Mg-enriched inclusions here in halo-like. Consequently martensite tended to form in the blocky austenite that was unevenly distributed in intercellular region after austempering treatment. Under the plastic deformation, cracks would form and accelerated their speed along the inclusions, so more fine inclusions (＜5mm) accompanied with Mn segregation caused the deterioration of fatigue strength and ductility.
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Tai, Hsin-Liang y 戴信良. "Modeling Processing Window of Austempered Ductile Iron by Support Vector Machine". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/66840064286845979532.
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碩士北台灣科學技術學院
機電整合研究所
96
Characterized by a large margin learning machine, support vector machine is shown to exhibit a high generalization performance, which is employed here to model the austempering heat treatment for austempered ductile irons. Four most critical parameters of austempered ductile irons are addressed to assess the possibility of the present approach and further to establish austempering heat treatment model models, including the carbon content of ductile iron at the completion of austenization, volume fraction of retained austenite after austempering heat treatment, and the processing window of austempering heat treatment, the optimum austempering time (corresponding to the time for the maximum retained austenite volume fraction). Relevant data are first collected, including the initial carbon content in austempering heat treatment and the volume fraction of retained austenite after austempering heat treatment. For processing window, the time corresponding to 10% and 90% of retained austenite are taken to represent the start and end of process window. With cross validations, the support vector machine-based models are selected to achieving a high generalization accuracy according to the principles of Bayesian framework and Resubstitution. Hence, the study considers not only minimizing the training errors but also minimizing the model complexity to prevent the models from over-fitting. The results show that the regression models obtained exhibit favorable generalization capability. The promising results also indicate the practical use of support vector machine in modeling the heat treatment of austempered ductile irons is feasible.
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Lai, Ping-Kun y 賴炳坤. "Study on High-Cycle Fatigue Properties of Austempered Ductule Iron". Thesis, 1995. http://ndltd.ncl.edu.tw/handle/09817976628068692513.
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Su, Heng-Chie y 蘇恒至. "The Effect of Repetitive Heat Treatments on the Unalloyed Austempered Ductile Iron". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/34719194153717701726.
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碩士義守大學
材料科學與工程學系
91
During the austempering process, some unpredictable conditions such as power failure or wrong heat treatment parameters setting may take place to stop the austempering procedure. The ductile iron was used containing 3.6wt.%C and 2.5wt.%Si. The austempering process is interrupted at different austenitizing time (1~50min.), austempering temperature (320,370,420℃), and austempering time (1~90min.). After interrupted the austempering treatment in each condition and water quench down to the room temperature, the complete austempeering treatment is then carried out. In the meantime, the effects of the number of interrupted and repeated austempering treatment (1,3,5times) on the change of dimensions, microstructures, and mechanical properties will be investigated. The results showed that the amounts of retained austenite(from20.2% to 16.9%), ductility(from 12.1% to 9.0%), and toughness(from 130J to 101J) increase with increasing the number of reaustenitizing heat treatment. The tensile strength, yield strength and toughness have no changes in the pocess. The dimensional change was increaseing with the number of reaustenitizing heat treatment from 0.3% to 0.5%. There are three process parameters(420℃, 370℃ and 320℃) in reaustempering heat treatment. The parameter of retained austenite, ductility and toughness decrease with number of interrupted and repeated austempering treatment. The dimensional change increases with the number of repeated times. The amounts of retained austensite(from 31.3% to 25.5%), ductility(from 17.6% to 14.4%) and toughness(from 122J to 91J) decrease followed on the number of repeated heat treatment in 420℃.When the reaustempering temperature was down to 370℃, the amount of retained austensite(from 21.7% to 17.2%), ductility(from 10.5% to 8.6%) and toughness(from 124J to 100J) decrease with the number of repeated heat treatment increasing. And the retained austensite(from 9.4% to 5.1%), ductility(from 6.3% to 5.7%) and toughness(from 69J to 58J) increase with the number of repeated heat treatment decreased in 320℃. The tensile strength and yield strength keeps constant with the number of times of repeated heat treatment but the retained austenite, ductility and toughness decreased. The variation of dimension after interrupting at different stages showed to increase with the number of times of repeated heat treatment.
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Lin, Kuan-Ting y 林冠廷. "Study on Microstructure and Characteristics of Copper and Molybedium Alloyed Austempered Ductile Iron". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/02720530610893138761.
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碩士大同大學
材料工程學系(所)
97
In this study, there kinds of ductile irons (DI), 1 wt.% Mo alloyed Alloyed ductile iron (FCD450), were selected as the experimental materials. Both the austempering conditions consisting of 300℃-3hrs and 360℃-2hrs were respectively adopted to further treat these irons as austempered ductile iron (ADI). Then microstructural observation, mechanical tests (such as hardness, tensile, impact toughness, and KIC), and corrosion tests (such as polarization tests in 3.5wt.% NaCl, immersion tests in 10 Vol.% H2SO4 and 10 Vol.% HCl) were all performed to understand the correlation of microstructure, mechanical and corrosion behaviors of these iron. The experimental results showed that ADI added 1 wt.% Mo could increase the hardness, tensile strength, erosion resistance, and wear resistance due to the less retained austenite content, while the addition of 1 wt.% Cu could increase the ductility, impact toughness, KIC value of ADI due to the more retained austenite content. In corrosion behavior, 1 wt.% Cu alloyed DI has the best corrosion resistance among the three as-casts. For ADI, ADI is superior to DI in corrosion resistance reganrdless of alloying addition. In particular, 1wt.% Cu-ADI treated with 360℃-2hrs has the best corrosion resistance among all the irons due to the most retained austenite in its microstructure.
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Lee, Chun-ying y 李俊穎. "Effects of Cobalt, Nickel Addition on Microstructureand Mechanical Characteristics of Austempered Ductile iron". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/40178180873633951611.
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碩士大同大學
材料工程學系(所)
92
The study focus on the influence of alloying elements with cobalt and nickel added on mechanical properties, constant temperature transformation of ADI. Comparing them with the original situation that added nothing with alloying element. The article in this study among three ingredients（without alloying element）,（4﹪cobalt）,（4﹪nickel）. By doing the difference of graphite numbers to compare the influence of mechanical properties. The material first austenization at 900℃ and holds time for 1.5hrs,then austempering processing at300℃∼360℃ and holds time for 1∼3hrs. The mechanical properties of discussion including tensile strength, elongation, hardness, impact values, fracture toughness and amount of retained austenite. The experimental results showed when austempering in lower temperature, the microstructure of A,B,C alloying elements almost unchanged during 1∼3hrs. In the portion of mechanical characteristics, the ductile iron through heat treatment will promote whether add alloying element or not. For the testing of all kinds of mechanical properties, all have the optimum existence. By the observation of ingredient analysis, cobalt and nickel are almost no segregation phenomenon. The graphite numbers and base organization really affect the mechanical properties in some level.
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kai, Chang chih y 張智凱. "A Study of Mechanical and Microstructure with Austempered Ductile Iron by Cold Treatment". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/36114428134773962781.
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碩士中州科技大學
機械與自動化工程系
103
The mechanical properties and microstructures of various Cold treatment austempered ductile iron (ADI) were investigated in this study. Y-block castings (25 mm) with inoculation for different austempering heat treatments of ductile irons (ADI and its subzero cooling), were prepared and test the mechanical properties of heat treated ADI. The developed mechanical properties were in relation with subzero temperature, distribution of residual austenite and the types of ausferrite in the martrix of ADI. The specimens were taken from Y-block castings for austempered ductile iron. Then they treated with subzero cooling procedure in different subzero temperatures (ice water, CO2, N2). Mechanical properties included UTS, YS, elongation, hardness and impact toughness. Therefore observed microstructures of SEM used to describe the difference of mechanical properties for ADI and its subzero cooling. To improve the mechanical properties and stability of microstructure were fully development in this study and application in the future of industry.
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(9875183), D. Prayitno. "The effect of holding time on the mechanical properties of Austempered Ductile Iron". Thesis, 1996. https://figshare.com/articles/thesis/The_effect_of_holding_time_on_the_mechanical_properties_of_Austempered_Ductile_Iron/13425251.
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Project describes experiments done to study the effects of some variants in the austempering process on mechanical properties, especially fatigue of ADI. The calculation of the stress intensity factor is also looked into.. Some factories in Indonesia plan to produce Austempered Ductile Iron (ADI), because this material offers some advantages over other cast irons, such as having excellent fatigue properties and also being cheaper than steel. This thesis describes some experiments done to study the effect of some variants in the austempering process on mechanical properties, especially fatigue of ADI. In particular the effect of holding time on fatigue properties of ADI were studied, and an attempt was made to answer the question "Can the stress concentration factor theory proposed by Kubicki be applied to ductile cast iron and ADI?" This stress concentration model enables quantification of the influence of both matrix yield strength and size ofinclusions on the endurance limit of inhomogeneous material. Initially some laboratory experiments were done such as tensile tests, hardness tests and fatigue tests. The tensile and hardness data are plotted on a histogram diagram while the fatigue results are plotted on an S-N curve. The results of the calculations were compared withthe fatigue test results. The conclusions are: Increasing holding time can decrease the mechanical properties of ADI; Comparing Kubicki's theoretical result with the fatigue test result shows quite strong agreement.
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Hung, Tun-Pu y 洪敦浦. "Low-cycle Fatigue Behavior of As-cast and Austempered Ductile Irons". Thesis, 1995. http://ndltd.ncl.edu.tw/handle/68645710482459076460.
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Yang, Chang Hao y 楊章豪. "Influence of Environment Factors on High-Cycle Fatigue Behavior of Austempered Ductile Cast Iron". Thesis, 2001. http://ndltd.ncl.edu.tw/handle/23549400552049009906.
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碩士國立中央大學
機械工程研究所
89
The purpose of this study is to investigate the influence of various aqueous solutions and ambient air temperatures on the high-cycle fatigue (HCF) behavior of austempered ductile iron (ADI) . The effects of presence of chloride, pH value and temperature in aqueous solution on the HCF resistance were characterized. HCF results obtained in air at temperature ranging from room temperature to 250oC were made a comparison to characterize the temperature effect on HCF strength of ADI. Fractography and microstructural analyses with scanning electron microscopy (SEM) were conducted to determine the fatigue crack initiation and propagation modes. Experimental results show the HCF lives in room-temperature water, 3.5% NaCl, 80oC 3.5% NaCl, and sulfuric acid solutions were shorter than those in room-temperature air for the given ADI. In addition, increasing solution temperature, adding chloride, and decreasing pH value would further decrease the HCF life as compared to room-temperature water. Among these factors, the decrease of pH value generated the most detrimental effect on HCF resistance. The SAE 10W40 lubrication oil provided an inert environment to increase the HCF life of ADI as compared to atmospheric environment. The synergism between corrosive environment and cyclic stresses was primarily responsible for the reduction of HCF life as the effect of prior corrosion did not significantly change the fatigue life when tested in air. At temperatures from room temperature to 300oC, the tensile strength of ADI was invariant with temperature. The fatigue life of ADI would decrease with increasing temperature at high stress levels. However, the fatigue lives in 220oC and 250oC at low stress levels were comparable with those in 180oC. This is due to the fact that a higher temperature would cause more carbide precipitation and increase the temperature of Ms for martensitic transformation. Therefore, the unstable retained austenite could transform to martensite more easily under cyclic loading at higher temperatures. The volume expansion resulting from this transformation would produce residual compressive stress at crack tip to retard fatigue crack growth and extend fatigue life.
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王世衛. "The Effect of Heat Treatment Conditions on Austempered Ductive Iron Wear Resistance Performance". Thesis, 1998. http://ndltd.ncl.edu.tw/handle/64478009308704875671.
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碩士國立臺灣科技大學
機械工程技術研究所
86
Austempered ductile iron (ADI) had the excellent mechanical properties that have been applied to various engineering structures widely. However, The study on wear resistance of ADI is not well established. In this thesis experiments are conducted with a TE77 frictional test machine in a reciprocating sliding mode. The test specimens with roller on flat will be be used to evaluate the wear resistance performance of ADI under high temperature and extreme pressure in lubrication states. The ADI flat specimen had been treated in various heat treatments conditions. However, the surface hardened malleable cast iron (FCMP) will e used to compare the wear resistance performance of the ADI. The optical microscope and X-Ray diffraction were be used to analysis the microstructures and retatined austinite of the ADI In the testing process is evaluated with the contact (electrical) resistance to monitor the chemical film reaction rate. Then, it is confirmed by the EDS analysis on the worn surface. SEM will identify the wear mechanism of the worn surface. It is expected that the experiment results can be used to determine the wear mechanism and optimal heat treatment conditions. The results show that austempered ductile iron (ADI) has the excellent wear resistance performance than surface hardened malleable cast iron (FCMP). From the tested data we could confirm the austempered at 270℃ in salt-bath 30 min had the best wear resistance performance. Therefore, under high sliding speed and low contact stress is the best working condition for ADI. The results show that the chemical reaction film of ZDDP within rubbing surface of ADI can avoid the wear behavior from severe adhesion. Fiinally, we can make sure that ZDDP can reduce wear behavior very effectively for ADI in extreme pressure lubrication states. SEM results show that the mainly wear mechanism in this experimental caused by surface fatigue, abrasive wear and tribochemical wear.