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Literatura académica sobre el tema "Austenite-Ferrite phase transformation"

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Publicado: 1 de febrero de 2025

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Artículos de revistas sobre el tema "Austenite-Ferrite phase transformation"

Padilha, Angelo Fernando, D. J. M. Aguiar y R. L. Plaut. "Duplex Stainless Steels: A Dozen of Significant Phase Transformations". Defect and Diffusion Forum 322 (marzo de 2012): 163–74. http://dx.doi.org/10.4028/www.scientific.net/ddf.322.163.

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During processing or use, duplex stainless steels are subject to a great number of significant phase transformations, such as solidification, partial ferrite transformation to austenite, ferrite eutectoid decomposition to sigma phase plus austenite, chi phase precipitation, chromium carbide precipitation, chromium nitride precipitation, ferrite spinodal decomposition, phase dissolution during solution annealing, forming of two types (epsilon and alpha prime) of strain induced martensite, martensite reversion to austenite, ferrite and austenite recrystallization. This paper summarizes the phase transformations that occur (individually or combined) in duplex stainless steels and presents some new results.

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Villalobos Vera, Doris Ivette y Ivan Mendoza Bravo. "Effect of annealing temperature on the microstructure of hyperduplex stainless steels". Ingeniería Investigación y Tecnología 20, n.º 2 (1 de marzo de 2019): 1–6. http://dx.doi.org/10.22201/fi.25940732e.2019.20n2.024.

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Samples of hyperduplex stainless steels were produced experimentally and exposed to different conventional annealing heat treatments in order to obtain the microstructural balance of 50% ferrite and 50% austenite. To differentiate the ferrite and austenite from any secondary phase, selective etching was used and quantitative metallography was performed to measure the percentage of phases. Results showed that conventional annealing heat treatments promote the transformation from ferrite to sigma phase and secondary austenite, suggesting a higher occurrence of sigma phase in the experimental hyperduplex alloys compared to other duplex alloys due to the superior content of chromium and molybdenum. On the other hand, a balanced microstructure free of secondary phases was accomplished increasing the temperature of the annealing heat treatment, which allowed the transformation of ferrite into austenite during cooling.

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Bräutigam–Matus, Krishna, Gerardo Altamirano, Armando Salinas, Alfredo Flores y Frank Goodwin. "Experimental Determination of Continuous Cooling Transformation (CCT) Diagrams for Dual-Phase Steels from the Intercritical Temperature Range". Metals 8, n.º 9 (28 de agosto de 2018): 674. http://dx.doi.org/10.3390/met8090674.

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The phase transformation kinetics under continuous cooling conditions for intercritical austenite in a cold rolled low carbon steel were investigated over a wide range of cooling rates (0.1–200 ∘ C/s). The start and finish temperatures of the intercritical austenite transformation were determined by quenching dilatometry and a continuous cooling transformation (CCT) diagram was constructed. The resulting experimental CCT diagram was compared with that calculated via JMatPro software, and verified using electron microscopy and hardness tests. In general, the results reveal that the experimental CCT diagram can be helpful in the design of thermal cycles for the production of different grades of dual-phase–advanced high-strengh steels (DP-AHSS) in continuous processing lines. The results suggest that C enrichment of intercritical austenite as a result of heating in the two phases (ferrite–austenite) region and C partitioning during the formation of pro-eutectoid ferrite on cooling significantly alters the character of subsequent austenite phase transformations.

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Wang, Qihui, Kun Chen, Kejia Liu, Lianbo Wang, Yu Chu y Bichen Xie. "Study on Characterization of Phase Transition in Continuous Cooling of Carbon Steel Using In Situ Thermovoltage Measurement". Coatings 14, n.º 8 (3 de agosto de 2024): 980. http://dx.doi.org/10.3390/coatings14080980.

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In this paper, a self-designed and enhanced thermovoltage measuring device was built to capture thermovoltage curves of 45 steel during continuous cooling. The phase zones of the thermovoltage curve were interpreted based on the Engel–Brewer electron theory and Fe-Fe3C phase diagram. The results show that the curve was stratified into three homogeneous phase zones and two-phase transition zones as follows: Zone Ι: single-phase austenite (A) zone; Zone III: austenite and ferrite (A+F) homogeneous phase zone; Zone V: ferrite and pearlite (P+F) homogeneous phase zone; Zone II: austenite to ferrite (A-F) phase transition zone; and Zone IV: austenite to pearlite (A-P) phase transition zone. Notably, the deflection point marked the transition temperature, which indicates that the thermovoltage curve can quantitatively characterize phase formation and transformation, as well as the phase transformation process. Furthermore, the sample was quenched at the measured ferrite phase transition temperature. Microstructure observations, electron probe microanalyzer (EPMA) and microhardness measurements corroborated our findings. Specifically, our experiments reveal ferrite precipitation first from the cold end at the phase transition temperature, leading to increased carbon content in adjacent austenite. The results of this study achieved the in situ characterization of bulk transformations during the materials heat treatment process, which expands the author’s research work conducted previously.

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Cheng, Wei Chun, Kun Hsien Lee, Shu Mao Lin y Shao Yu Chien. "The Observation of Austenite to Ferrite Martensitic Transformation in an Fe-Mn-Al Austenitic Steel after Cooling from High Temperature". Materials Science Forum 879 (noviembre de 2016): 335–38. http://dx.doi.org/10.4028/www.scientific.net/msf.879.335.

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Fe-Mn-Al steels with low density have the potential to substitute for TRIP (transformation induced plasticity) steels. For the development of Fe-Mn-Al TRIP steels, phase transformations play an important role. Our methods of studying the phase transformations of the Fe-16.7 Mn-3.4 Al (wt%) austenitic steel include heating and cooling. We have studied the martensitic transformation of the ternary Fe-Mn-Al steel. Single austenite phase is the equilibrium phase at 1373 K, and dual phases of ferrite and austenite are stable at low temperatures. It is noteworthy that lath martensite forms in the prior austenite grains after cooling from 1373 K via quenching, air-cooling, and/or furnace-cooling. The crystal structure of the martensite belongs to body-centered cubic. The formation mechanism of the ferritic martensite is different from the traditional martensite in steels. Ferrite is the stable phase at low temperature.

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Yu, Dunji, Yan Chen, Lu Huang y Ke An. "Tracing Phase Transformation and Lattice Evolution in a TRIP Sheet Steel under High-Temperature Annealing by Real-Time In Situ Neutron Diffraction". Crystals 8, n.º 9 (11 de septiembre de 2018): 360. http://dx.doi.org/10.3390/cryst8090360.

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Real-time in situ neutron diffraction was used to characterize the crystal structure evolution in a transformation-induced plasticity (TRIP) sheet steel during annealing up to 1000 °C and then cooling to 60 °C. Based on the results of full-pattern Rietveld refinement, critical temperature regions were determined in which the transformations of retained austenite to ferrite and ferrite to high-temperature austenite during heating and the transformation of austenite to ferrite during cooling occurred, respectively. The phase-specific lattice variation with temperature was further analyzed to comprehensively understand the role of carbon diffusion in accordance with phase transformation, which also shed light on the determination of internal stress in retained austenite. These results prove the technique of real-time in situ neutron diffraction as a powerful tool for heat treatment design of novel metallic materials.

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Sun, Fei, Yoshihisa Mino, Toshio Ogawa, Ta-Te Chen, Yukinobu Natsume y Yoshitaka Adachi. "Evaluation of Austenite–Ferrite Phase Transformation in Carbon Steel Using Bayesian Optimized Cellular Automaton Simulation". Materials 16, n.º 21 (28 de octubre de 2023): 6922. http://dx.doi.org/10.3390/ma16216922.

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Austenite–ferrite phase transformation is a crucial metallurgical tool to tailor the properties of steels required for particular applications. Extensive simulation and modeling studies have been conducted to evaluate the phase transformation behaviors; however, some fundamental physical parameters still need to be optimized for better understanding. In this study, the austenite–ferrite phase transformation was evaluated in carbon steels with three carbon concentrations during isothermal annealing at various temperatures using a developed cellular automaton simulation model combined with Bayesian optimization. The simulation results show that the incubation period for nucleation is an essential factor that needs to be considered during austenite–ferrite phase transformation simulation. The incubation period constant is mainly affected by carbon concentration and the optimized values have been obtained as 10−24, 10−19, and 10−21 corresponding to carbon concentrations of 0.2 wt%, 0.35 wt%, and 0.5 wt%, respectively. The average ferrite grain size after phase transformation completion could decrease with the decreasing initial austenite grain size. Some other parameters were also analyzed in detail. The developed cellular automaton simulation model combined with Bayesian optimization in this study could conduct an in-depth exploration of critical and optimal parameters and provide deeper insights into understanding the fundamental physical characteristics during austenite–ferrite phase transformation.

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Hu, Feng y Kai Ming Wu. "Isothermal Transformation of Low Temperature Super Bainite". Advanced Materials Research 146-147 (octubre de 2010): 1843–48. http://dx.doi.org/10.4028/www.scientific.net/amr.146-147.1843.

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Fine-scale bainitic microstructure with excellent mechanical properties has been achieved by transforming austenite to bainite at low temperature ranging from 200oC to 300oC. Microstructural observations and hardness measurements show that transformed microstructures consist of bainitic ferrite and carbon-enriched retained austenite. The thickness of bainitic ferrite plates is less than 50 nm. The hardness reaches approximately 640 HV1. Strong austenite and/or large driving force at the low transformation temperature leads to ultra fine bainitic ferrite plates. X-ray diffraction analysis indicates that low-temperature bainite transformation is an incomplete reaction. The carbon content in carbon-enriched retained austenite is below the para-equilibrium (Ae3′) phase boundary predicted. The carbon content in bainitic ferrite is less than that T0′ phase boundary predicted.

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Zrník, Jozef, O. Muránsky, Petr Lukáš, Petr Šittner y Z. Nový. "In Situ Neutron Diffraction Analysis of Phase Transformation Kinetics in TRIP Steel". Materials Science Forum 502 (diciembre de 2005): 339–44. http://dx.doi.org/10.4028/www.scientific.net/msf.502.339.

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The precise characterization of the multiphase microstructure of low alloyed TRIP steels is of great importance for the interpretation and optimisation of their mechanical properties. In-situ neutron diffraction experiment was employed for monitoring of conditioned austenite transformation to ferrite, and also for retained austenite stability evaluation during subsequent mechanical loading. The progress in austenite decomposition to ferrite is monitored at different transformation temperatures. The relevant information on the course of transformation is extracted from neutron diffraction spectra. The integrated intensities of austenite and ferrite neutron diffraction profiles over the time of transformation are then assumed as a measure of the volume fractions of both phases in dependence on transformation temperature. Useful information was also obtained on retained austenite stability in TRIP steel during mechanical testing. The in-situ neutron diffraction experiments were conducted at two different diffractometers to assess the reliability of neutron diffraction technique in monitoring the transformation of retained austenite during room temperature tensile test. In both experiments the neutron investigation was focused on the volume fraction quantification of retained austenite as well as on internal stresses rising in structure phases due to retained austenite transformation.

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Lee, Sang Hwan, Jong Min Choi, Yeol Rae Cho y Kyung Jong Lee. "The Effects of Si and Deformation on the Phase Transformation in Dual Phase Steels". Solid State Phenomena 124-126 (junio de 2007): 1617–20. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.1617.

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The effect of Si on phase transformation was well known in dual phase steels. Si promoted the ferrite transformation and the enriched C in untransformed austenite prohibited the transformation at intermediate temperature range resulting in the formation of lower bainite and martensite at low temperature range. In addition, during continuous cooling with fast cooling rate, it was very hard to differentiate one phase from the others. In order to clarify the effects of Si on the austenite-to-ferrite transformation quantitatively, the start temperatures of bainite(BS) and martensite(MS) as well as ferrite(Ae3) and pearlite(Ae1) were calculated by thermodynamic analysis. LVDT measured by dilatometer and 1st differentiation peaks of LVDT were examined with microstructures, which gives a possibility of the phase separation. In CCT diagrams, it was also found that large austenite grain size(AGS) widened the gap between the transformation start(Ts) and end(Tf) when Si was added.

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Tesis sobre el tema "Austenite-Ferrite phase transformation"

Perevoshchikova, Nataliya. "Modeling of austenite to ferrite transformation in steels". Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0342/document.

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La thèse porte sur la modélisation de la transformation de l'austénite en ferrite dans les aciers en mettant l'accent sur les conditions thermodynamiques et cinétiques aux interfaces alpha/gamma en cours de croissance de la ferrite. Dans une première partie, la thèse se concentre sur la description des équilibres thermodynamiques entre alpha et gamma à l'aide de la méthode CalPhad. Nous avons développé un nouvel algorithme hybride combinant la construction d'une enveloppe convexe avec la méthode classique de Newton-Raphson. Nous montrons ses possibilités pour des aciers ternaire Fe-C-Cr et quaternaire Fe-C-Cr-Mo dans des cas particulièrement difficiles. Dans un second chapitre, un modèle à interface épaisse a été développé. Il permet de prédire l'ensemble du spectre des conditions à l'interface alpha/gamma au cours de la croissance de la ferrite, de l'équilibre complet au paraéquilibre avec des cas intermédiaires des plus intéressants. Nous montrons que de nombreux régimes cinétiques particuliers dans les systèmes Fe-C-X peuvent être prévus avec un minimum de paramètres d'ajustement, principalement le rapport entre les diffusivités de l'élément substitutionnel dans l'interface épaisse et dans le volume d'austénite. Le troisième chapitre porte sur l'étude d'un modèle de champ de phase. Une analyse approfondie des conditions à l'interface données par le modèle est réalisée en utilisant la technique des développements asymptotiques. En utilisant les connaissances fournies par cette analyse, le rôle de la mobilité intrinsèque d'interface sur la cinétique et les régimes de croissance est étudié, à la fois dans le cas simple d'alliages binaires Fe-C et dans le cas plus complexe d'alliages Fe-C-Mn
Transformation in steels focusing on the thermodynamic and kinetics conditions at the alpha/gamma interfaces during the ferrite growth. The first chapter deals with the determination of thermodynamic equilibria between alpha and gamma with CalPhad thermodynamic description. We have developed a new hybrid algorithm combining the construction of a convex hull to the more classical Newton-Raphson method to compute two phase equilibria in multicomponent alloys with two sublattices. Its capabilities are demonstrated on ternary Fe-C-Cr and quaternary Fe-C-Cr-Mo steels. In the second chapter, we present a thick interface model aiming to predict the whole spectrum of conditions at an alpha/gamma interface during ferrite growth, from full equilibrium to paraequilibrium with intermediate cases as the most interesting feature. The model, despite its numerous simplifying assumptions to facilitate its numerical implementation, allows to predict some peculiar kinetics in Fe-C-X systems with a minimum of fitting parameters, mainly the ratio between the diffusivities of the substitutional element inside the thick interface and in bulk austenite. The third chapter deals with the phase field model of austenite to ferrite transformation in steels. A thorough analysis on the conditions at the interface has been performed using the technique of matched asymptotic expansions. Special attention is given to clarify the role of the interface mobility on the growth regimes both in simple Fe-C alloys and in more complex Fe-C-Mn alloys

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Pariser, Gerhard Carolus. "Modeling the austenite to ferrite phase transformation for steel development /". Aachen : Shaker, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014913109&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.

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Pariser, Gerhard C. [Verfasser]. "Modeling the Austenite to Ferrite Phase Transformation for Steel Development / Gerhard C Pariser". Aachen : Shaker, 2006. http://d-nb.info/1170529216/34.

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Liebaut, Christophe. "Rhéologie de la déformation plastique d'un acier Fe-C durant sa transformation de phase "austenite-->ferrite + perlite"". Vandoeuvre-les-Nancy, INPL, 1988. http://www.theses.fr/1988NAN10451.

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Borges, Gomes Lima Yuri. "Μοdélisatiοn atοmistique de la transfοrmatiοn de phase austénite-ferrite dans les aciers". Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMR086.

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Cette thèse applique l'approche des Quasiparticles (QA) pour étudier les mécanismes à l'échelle atomique qui conduisent à la transformation de phase CFC à CC dans le fer. Dans un premier temps, cette étude se concentre sur le fer pur, fournissant des résulats détaillés sur la nature et le rôle des dislocations à l'interface CFC-CC. Il a été montré que l'interface CFC-CC est semi-cohérente, avec des marches, et contient deux réseaux de dislocations de transformations. L'approche des Quasiparticles a permis de révéler l'influence de la relation d'orientation sur les caractéristiques de l'interface. Bien que les relations d'orientation étudiées ont montré diférentes structures d'interface, il a été démontré que toutes suivent le même chemin de transformation atomique, dû au glissement des dislocations de transformation à l'interface. Il a été conclu que la transformation complète de CFC à CC implique le mécanisme de transformation de Kurdjumov-Sachs (KS) en deux variantes le long des lignes de dislocations, avec le mécanisme de transformation de Kurdjumov-Sachs-Nishiyama (KSN) qui émerge comme la moyenne de l'action des deux mécanismes KS. Cette description détaillée a servi de base pour l'étude des systèmes Fe-C, où la ségrégation du carbone à l'interface a été observée. De plus, il a été montré que les profils de concentration de carbone sont cohérents avec des conditions d'équilibre local à l'interface
This thesis applies the Quasiparticle Approach (QA) to investigate the atomic scale mechanisms driving the phase transformation from FCC to BCC structures in iron. Initially, the study focuses on pure iron, providing detailed results into the nature and role of dislocations, at the FCC-BCC interface. It was shown that the FCC-BCC interface is semi-coherent and stepped, with two sets of transformations dislocations at the interface. The QA framework reveals how each orientation relationship (OR) influences the interface characteristics. Although the ORs displayed different interface structures, all were ultimately found to follow the same atomic transformation path, driven by the glide of transformation dislocations at the interface. It was concluded that the complete FCC to BCC phase transformation involves the action of the Kurdjumov-Sachs (KS) transformation mechanism in two variants along the two sets of dislocations, with the Kurdjumov-Sachs-Nishiyama (KSN) mechanism emerging as the average of the two KS mechanisms. This detailed description served as a basis for the study of Fe-C systems, where carbon segregation at the interface was observed. Moreover, it was shown that the carbon concentration profiles were consistent with local equilibrium conditions at the interface

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Wang, Li. "Effects of niobium on phase transformations from austenite to ferrite in low carbon steels". Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12012.

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Niobium is a widely used microalloying element in many steel products, e.g. plates, strip, sections and linepipe. Niobium has important effects on transformation behaviour, grain size refinement and precipitation strengthening during hot rolling and subsequent cooling, with even a low content of niobium having a strong effect on the transformation rate from austenite to ferrite. The purpose of this research was to accurately characterise and quantify the effects of solute niobium atoms and niobium carbo-nitride precipitates on phase transformations from austenite and ferrite, and to incorporate these effects into metallurgical models to predict the transformation behaviour and microstructure of niobium containing steels, which can benefit industry through their use of the models to optimise processing conditions.

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Kim, Yoon-Jun. "Phase Transformations in Cast Duplex Stainless Steels". Ames, Iowa : Oak Ridge, Tenn. : Ames Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/837274-V0QAJQ/webviewable/.

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Thesis (Ph.D.); Submitted to Iowa State Univ., Ames, IA (US); 19 Dec 2004.
Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 2322" Yoon-Jun Kim. US Department of Energy 12/19/2004. Report is also available in paper and microfiche from NTIS.

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Dalton, John Christian. "Surface Hardening of Duplex Stainless Steel 2205". Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1480696856644048.

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Capítulos de libros sobre el tema "Austenite-Ferrite phase transformation"

An, Dong, Shiyan Pan, Qing Yu, Chen Lin, Ting Dai, Bruce Krakauer y Mingfang Zhu. "Modeling of Ferrite-Austenite Phase Transformation". En TMS2015 Supplemental Proceedings, 791–98. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2015. http://dx.doi.org/10.1002/9781119093466.ch96.

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An, Dong, Shiyan Pan, Qing Yu, Chen Lin, Ting Dai, Bruce Krakauer y Mingfang Zhu. "Modeling of Ferrite-Austenite Phase Transformation". En TMS 2015 144th Annual Meeting & Exhibition, 791–98. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-48127-2_96.

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López-Baltazar, Alejandro, Armando Salinas-Rodríguez y Enrique Nava-Vázquez. "Austenite-Ferrite Transformation in Hot Rolled Mn-Cr-Mo Dual Phase Steels". En Advanced Structural Materials III, 79–84. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-446-4.79.

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Gamsjäger, Ernst. "Kinetics of the Austenite-to-Ferrite Phase Transformation - From the Intrinsic to an Effective Interface Mobility". En THERMEC 2006, 2570–75. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-428-6.2570.

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"Isothermal and Continuous Cooling Transformation Diagrams". En Steels, 197–211. 2^a ed. ASM International, 2015. http://dx.doi.org/10.31399/asm.tb.spsp2.t54410197.

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Isothermal and continuous cooling transformation (CT) diagrams help users map out diffusion-controlled phase transformations of austenite to various mixtures of ferrite and cementite. This chapter discusses the application as well as limitations of these engineering tools in the context of heat treating eutectoid, hypoeutectoid, and proeutectoid steels. It also provides references to large collections of transformation diagrams and includes several diagrams that plot quenching and hardening transformations as a function of bar diameter.

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Sietsma, J. "Nucleation and growth during the austenite-to-ferrite phase transformation in steels after plastic deformation". En Phase Transformations in Steels, 505–26. Elsevier, 2012. http://dx.doi.org/10.1533/9780857096104.4.505.

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Tabiyeva, Yerkezhan, Bauyrzhan Rakhadilov, Gulzhaz Uazyrkhanova y Waqar Ahmed. "Surface Hardening on Wheel Steel Using Electrolytic Plasma". En Innovations in Materials Chemistry, Physics, and Engineering Research, 197–210. IGI Global, 2023. http://dx.doi.org/10.4018/978-1-6684-6830-2.ch005.

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Transmission electron microscopy (TEM) investigations of the structure and phase composition of ferritic-pearlitic wheel steel mark two surface after electrolyte-plasma surface hardening are presented. Initially the morphology of the steel matrix consists of lamellar perlite and non-fragmented and fragmented ferrite. Electrolytic plasma quenching of the steel surface results in the martensite transformation, steel self-tempering, and the formation of cementite particles in all martensite crystals. This treatment also leads to the diffusion transformation of gamma to alpha phases, the release of residual austenite along the low-temperature martensite laths and lamellas and in all crystals of lamellar martensite, the formation of М23С6 special carbides and, finally, to the enhancement of all parameters of the steel fine structure.

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"Pearlite, Ferrite, and Cementite". En Steels, 39–62. 2^a ed. ASM International, 2015. http://dx.doi.org/10.31399/asm.tb.spsp2.t54410039.

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The microstructure of carbon steel is largely determined by the transformation of austenite to ferrite, cementite, and pearlite. This chapter focuses on the microstructures produced by diffusion-controlled transformations that occur at relatively low cooling rates. It describes the conditions that promote such transformations and, in turn, how they affect the structure of various phases and the rate at which they form. The chapter also discusses the concepts of transformation kinetics, minimum free energy, and nucleation and growth, and provides information on alloying, interphase precipitation, and various types of transformations.

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Liu, Y., P. R. China, F. Sommer y E. J. Mittemeijer. "Nature and kinetics of the massive austenite-ferrite phase transformations in steels". En Phase Transformations in Steels, 311–81. Elsevier, 2012. http://dx.doi.org/10.1533/9780857096104.2.311.

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Actas de conferencias sobre el tema "Austenite-Ferrite phase transformation"

Hatakeyama, Tomotaka, Kota Sawada, Masaru Suzuki y Makoto Watanabe. "Microstructure of Modified 9Cr-1Mo Steel Manufactured via Laser Powder Bed Fusion". En AM-EPRI 2024, 365–72. ASM International, 2024. http://dx.doi.org/10.31399/asm.cp.am-epri-2024p0365.

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Abstract Modified 9Cr-1Mo steel was manufactured via laser powder bed fusion (LPBF) using gas atomized powders under various building conditions. Dense samples were obtained at an energy density of 111-125 J/mm3. As-built samples were subjected to a normalization and tempering heat treatments. The microstructure of the as-built sample exhibits a duplex structure, comprising coarse columnar δ-ferrite grains and fine martensite grains. In addition, a small amount of retained austenite phase was observed at the interface between δ-ferrite and martensite. The formation of δ-ferrite is attributed to the extremely rapid solidification that occurs during the LPBF process, while martensite is obtained through the phase transformation because of the thermal cycles experienced during the process. The area fraction of δ-ferrite and martensite can be controlled by adjusting the LPBF parameters. Typical as-built microstructure morphology characterized by the columnar δ- ferrite was eliminated after the heat treatments, resulting in a tempered martensitic microstructure that is identical with that obtained through the conventional process. However, an increase in prior austenite grain size was observed when the area fraction of δ-ferrite in the as-built condition was high, due to faster phase transformation kinetics of martensite than that of δ-ferrite during the normalization. This suggests that the prior austenite grain size can be controlled by optimizing the area fraction of δ-ferrite and martensite in the as-built microstructure.

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Li, Zhichao (Charlie), B. Lynn Ferguson, Edward Lee, Stefan Habean y Jason Meyer. "Sources of Heat Treatment Distortion and Approaches for Distortion Reduction during Quench Hardening Process". En IFHTSE 2024, 132–38. ASM International, 2024. http://dx.doi.org/10.31399/asm.cp.ifhtse2024p0132.

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Abstract Heat treatment of steels is a process of modifying the mechanical properties by solid-state phase transformations or microstructural changes through heating and cooling. The material volume changes with phase transformations, which is one of the main sources of distortion. The thermal stress also contributes to the distortion, and its effect increases with solidstate phase transformations, as the material stays in the plastic deformation field due to the TRIP effect. With the basic understanding described above, the sources of distortion from a quench hardening process can be categorized as: 1) nonuniform austenitizing transformation during heating, 2) nonuniform austenite decomposing transformations to ferrite, pearlite, bainite or martensite during quenching, 3) adding of carbon or nitrogen to the material, and forming carbides or nitrides during carburizing or nitriding, 4) coarsening of carbide in tempered martensite during tempering, 5) stress relaxation from the initial state, 6) thermal stress caused by temperature gradient, and 7) nonhomogeneous material conditions, etc. With the help of computer modeling, the causes of distortion by these sources are analyzed and quantified independently. In this article, a series of modeling case studies are used to simulate the specific heat treatment process steps. Solutions for controlling and reducing distortion are proposed and validated from the modeling aspect. A thinwalled part with various wall section thickness is used to demonstrate the effectiveness of stepped heating on distortion caused by austenitizing. A patented gas quenching process is used to demonstrate the controlling of distortion with martensitic transformation for high temperature tempering steels. The effect of adding carbon to austenite on size change during carburizing is quantified by modeling, and the distortion can be compensated by adjusting the heat treat part size.

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Toloui, Morteza y Matthias Militzer. "Phase Field Modelling of Microstructure Evolution in the HAZ of X80 Linepipe Steel". En 2012 9th International Pipeline Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ipc2012-90378.

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The heat affected zone (HAZ) during welding experiences a very steep temperature gradient which results in significant microstructure gradients. Thus, model approaches on the length scale of the microstructure, i.e. the so-called mesoscale, are useful to accurately simulate microstructure evolution in the HAZ. In this study, a phase field model (PFM) is employed to simulate austenite grain growth and austenite decomposition in the HAZ of an X80 linepipe steel microalloyed with Nb and Ti. The interfacial mobilities and nucleation conditions are obtained by benchmarking the PFM with experimental data from austenite grain growth and continuous cooling transformation tests. An effective grain boundary mobility is introduced for austenite grain growth to implicitly account for dissolution of NbC. Subsequently, austenite decomposition into polygonal ferrite and bainite is considered. For this purpose the PFM is coupled with a carbon diffusion model. Ferrite nuclei are introduced at austenite grain boundaries and suitable interfacial mobilities are selected to reproduce experimental ferrite formation kinetics. Bainite nucleation occurs for a sufficiently high undercooling at available interface sites (i.e. austenite grain boundaries and/or austenite-ferrite interfaces). For simplicity, the formation of carbide-free bainite is considered and a suitable anisotropy approach is proposed for the austenite-bainite interface mobility. The model is then used to predict austenite grain growth and phase transformation in the HAZ.

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Liu, Dehao, Gang Wang, Zhenguo Nie y Yiming (Kevin) Rong. "Numerical Simulation of the Austenitizing Process in Hypoeutectoid Fe-C Steels". En ASME 2014 International Manufacturing Science and Engineering Conference collocated with the JSME 2014 International Conference on Materials and Processing and the 42nd North American Manufacturing Research Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/msec2014-3948.

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For predicting of diffusive phase transformations during the austenitizing process in hypoeutectoid Fe-C steels, a two-dimensional model has been developed. The diffusion equations are solved within each phase (α and γ) using an explicit finite volume technique formulated using a square grid. The discrete α/γ interface is represented by special volume elements α/γ. The result showing the dissolution of ferrite particles in the austenite matrix are presented at different stages of the phase transformation. Specifically, the influence of the microstructure scale and heating rate on the transformation kinetics has been investigated. Final austenitization temperature calculated with this 2D model is compared with predictions of a simpler one dimensional (1D) front-tracking calculation.

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Ghosh, Suhash y Chittaranjan Sahay. "Modeling Phase Transformation Kinetics and Their Effect on Hardness and Hardness Depth in Laser Hardening of Hypoeutectoid Steel". En ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-50175.

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Much research has been done to model laser hardening phase transformation kinetics. In that research, assumptions are made about the austenization of the steel that does not translate into accurate hardness depth calculations. The purpose of this paper is to develop an analytical method to accurately model laser hardening phase transformation kinetics of hypoeutectoid steel, accounting for non-homogeneous austenization. The modeling is split into two sections. The first models the transient thermal analysis to obtain temperature time-histories for each point in the workpiece. The second models non-homogeneous austenization and utilizes continuous cooling curves to predict microstructure and hardness. Non-homogeneous austenization plays a significant role in the hardness and hardness depth in the steel. A finite element based three-dimensional thermal analysis in ANSYS is performed to obtain the temperature history on three steel workpieces for laser hardening process with no melting; AISI 1030, 1040 and 1045 steels. This is followed by the determination of microstructural changes due to ferrite and pearlite transformation to austenite during heating and the subsequent austenite to martensite and other diffusional transformations during cooling. Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation is used to track the phase transformations during heating, including the effects of non-homogenous austenitization. The solid state nodal phase transformations during cooling are monitored on the material’s digitized Continuous Cooling Transformation (CCT) curve through a user defined input file in ANSYS for all cooling rates within the Heat Affected Zone (HAZ). Material non-linearity is included in the model by including temperature dependent thermal properties for the material. The model predictions for hardness underneath the laser and the HAZ match well with the experimental results published in literature.

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Yuan, Zhetao, Satoru Kobayashi y Masao Takeyama. "Microstructure Control Using the Formation of Laves Phase through Interphase Precipitation in Ferritic Heat Resistant Steels". En AM-EPRI 2019, editado por J. Shingledecker y M. Takeyama. ASM International, 2019. http://dx.doi.org/10.31399/asm.cp.am-epri-2019p0090.

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Abstract The formation of periodically arrayed rows of very fine Fe2Hf Laves phase particles was recently found in 9 wt. % chromium ferritic matrix through interphase precipitation along a reaction path of δ-ferrite → γ-austenite + Fe2Hf with a subsequent phase transformation of the γ phase into the α-ferrite phase. One of the problems on the formation of the fine Laves phase dispersion is a poor heat treatability; the interphase precipitation (δ-Fe→γ-Fe+Fe2Hf) is competitive with the precipitation of Laves phase from the δ phase in the eutectoid-type reaction pathway (δ→δ+Fe2Hf). In the present work, the effect of supersaturation on the precipitation of Laves phase from δ phase (δ→δ+Fe2Hf) and the δ→γ transformation in the reaction pathway was investigated by changing the Hf and Cr contents. The results obtained suggest that it is effective to have a high supersaturation for the precipitation of Laves phase and an adequately high supersaturation for the δ→γ transformation at the same time in order to widen the window of the interphase precipitation

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Silwal, Bishal y Michael Santangelo. "Vibration Assisted Hot-Wire Gas-Tungsten Arc Welding of Duplex Stainless Steel 2205". En ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-67665.

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Duplex stainless steel are excellent corrosion resistance two-phase alloy as compared to stainless steel. The corrosion resistance of duplex stainless steel depends upon the balance phase of ferrite and austenite. During non-equilibrium processes such as welding, the fast cooling rate (as compared to the controlled environment where it is produced) suppresses the austenite to ferrite transformation. A low frequency vibration assisted hot-wire Gas-Tungsten Arc Welding (GTAW) has been used to weld commercial duplex stainless steel alloy 2205. The results are compared with cold-wire GTAW weldments. The micro-hardness and microstructure of the weldments and heat-affected zones are characterized. A pitting corrosion test was performed on the weldments to measure the weight loss. A lower weight loss was achieved by using the low frequency vibration assisted hot-wire GTAW, however small pit was observed on the weld cap.

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Kim, Jeong-Tae, Yeong-Soo Lee, Byeong-Ook Kong y Seog-Hyeon Ryu. "Thermal Histories Causing Low Hardness and the Minimum Hardness Requirement in a MOD.9Cr1Mo Steel for Boiler". En ASME 2005 Pressure Vessels and Piping Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/pvp2005-71255.

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In a Mod.9Cr1Mo steel applied widely to boiler components, low hardness problem related with manufacturing and fabrication processes has become a critical issue recently. In this study, hardness, microstructure, tensile and creep rupture tests have been performed using specimens given various thermal cycles to investigate the detailed mechanism causing low hardness values of 150 to 170 Hv and the minimum hardness requirement from a standpoint of the tensile properties and the maximum allowable stresses. Low hardness values were mainly attributed to the formation of ferrite phase on cooling after heating at intercritical temperatures just above the Ac1, about 850°C. Ferrite transformation on cooling after intercritical heating occurred even at a relatively faster cooling rate of 3.5 °C/sec since the nose of ferrite transformation in the continuous cooling transformation (CCT) curve moved to the left due to the very low carbon content in austenite phase formed at intercritical region. Low hardness value of 160’s Hv occurred occasionally in practical applications was observed at a cooling rate of below 0.167 °C/sec after intercritical heating. At least 190 Hv of hardness values or more were needed to satisfy tensile properties and maximum allowable stresses specified in ASME Boiler & Pressure Vessel (B&PV) code.

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Polishetty, Ashwin, Guy Littlefair, Thomas Musselwhite y Chinmay Sonavane. "A Preliminary Study on Machinability Assessment of Nanobainite Steel". En ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-64004.

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The demand for high strength materials and improvements in heat treatment techniques has given rise to this new form of high strength steel known as nanobainite steel. The production of nanobainite steel involves slow isothermal holding of austenitic steel around 200°C for 10 days, in order to obtain a carbon enriched austenite and cooling to room temperature using austempering. The microstructure of nanobainite steel is dual phase consisting of alternate layers of bainitic ferrite and austenite. The experimental design consists of face milling under 12 combination of Depth of Cut (DoC)-1, 2 and 3mm; cutting speed-100 and 150m/min; constant feed- 0.15mm/rev and coolant on/off. The machinability of the material is assessed by means of analysis such as metallography and cutting force analysis. The results obtained are used to assess the most favorable condition to machine this new variety of steel. Future work involves study on phase transformation by quantifying the microstructural phase before and after milling using XRD.

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Musonda, Vincent y Esther T. Akinlabi. "Quantitative Characterisation of Pearlite Morphology in Hot-Rolled Carbon Steel". En ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10690.

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Abstract During the hot rolling of carbon steel, austenite phase transforms into a pearlitic morphology, which essentially is a matrix of ferrite lamellae (α-Fe) and cementite (Fe3C). This transformation occurs at the cooling bed after an equalisation temperature of around 600 °C. Pearlitic steels find their use in ropes for bridges and elevators, rails, and tyre cords among others. Characterisation of microstructure has not been broadly applied to pearlitic steels because of their complex microstructures. Therefore, the characterisation of this morphology becomes inevitable, in order to identify potential weaknesses in the matrix. In this study, hot-rolled reinforcement bars (rebars) produced from recycled steel and direct reduced iron (DRI), were used for microstructural examination using standard metallurgical procedures. Although the optical microscope (OM) and scanning electron microscope (SEM) were used to obtain qualitative microstructure, they could not characterise the pearlite morphology quantitatively because of their three-dimensional (3D) limitation. Hence, the image analyser - Gwyddion Software, was used to quantify the pearlite morphology of these Y16 rebars. The results indicate that the pearlite colony is characterised by 3D single interpenetrating crystals of ferrite and cementite running parallel to each other due to their common growth during the transformation process of austenite. It was further observed that, the dimensional properties of the phases in the morphology in terms of their width and Interlamellar spacing (S), including the roughness of the pearlite colony can vary significantly. These results could be used to enhance the processing methodology of the industrial production processes.

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