Дисертації з теми "Zr-Cu"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Zr-Cu.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Zr-Cu".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Carrasco, Valenzuela Wilson Rodrigo. "Cristalización de Aleaciones Amorfas Cu – Zr – Al." Tesis, Universidad de Chile, 2009. http://www.repositorio.uchile.cl/handle/2250/103378.
Анотація:
El estudio de las aleaciones amorfas ha cobrado importancia en la actualidad debido a las singulares propiedades físicas y mecánicas que éstas presentan, como una alta resistencia a la corrosión y buena resistencia mecánica. Recientes estudios efectuados a aleaciones metálicas amorfas de CuZr muestran que éstas poseen ductilidades superiores a otras aleaciones amorfas.
El mecanismo de deformación plástica en vidrios metálicos involucra la formación de bandas de corte, y la presencia de nanocristales juega un papel importante en dicho proceso. En el presente trabajo se estudió la cristalización y formación de nanocristales en las aleaciones amorfas Cu-Zr-Al con diferentes porcentajes de aluminio (0, 2.5, 5, 7.5 y 10 % en peso). Las aleaciones producidas mediante atomización en la Universidad de California sede Davis, fueron caracterizadas mediante Difracción de Rayos X (DRX), Calorimetría diferencial de barrido (DSC), nanoindentación y Microscopía electrónica de alta resolución (HR-TEM).
Los polvos con las aleaciones para los análisis fueron divididos en 2 tipos: polvos sin recocer, tal como fueron recibidos desde UC Davis, y polvos recocidos, que son los polvos posterior al análisis DSC, en que éstos fueron calentados desde temperatura ambiente hasta 550ºC.
A partir de los difractogramas de polvos sin tratamiento térmico, se observó el estado inicialmente vítreo de las aleaciones. Un nuevo análisis DRX a los polvos recocidos reveló la formación de estructuras cristalinas y la presencia del compuesto Cu10Zr7 en todas las aleaciones.
De las curvas calorimétricas se observó que las temperaturas de transición vítrea y de cristalización aumentan con el incremento del contenido de aluminio en la aleación. La aleación que presentó el mayor tramo de líquido subenfriado y, por lo tanto, una mayor estabilidad frente a la cristalización fue aquella con un 2.5 % de aluminio. Además esta aleación fue la que liberó una mayor energía entálpica durante la reacción de cristalización, siendo la con mejor habilidad para formar una estructura vítrea. Del análisis energético se obtuvo que la energía de activación para el comienzo de la cristalización aumenta con el contenido de aluminio.
Se observó que al aumentar el contenido de aluminio en las aleaciones amorfas, la dureza aumenta. Así es como las aleaciones con 5 y 10% en peso de aluminio presentaron durezas elevadas: 520 y 608 [HV] respectivamente. Estos valores resultan ser muy superiores a los presentados por otras aleaciones metálicas de base cobre.
De las observaciones de HR-TEM, se pudo comprobar el estado predominantemente amorfo de los polvos sin recocer a escala atómica. Sin embargo, en estas aleaciones se encontró la presencia de pequeños nanocristales de unos 5 [nm] insertos en la matriz amorfa. Los análisis de espectroscopía de rayos X confirmaron diferencias en la composición química de las zonas amorfas y las zonas cristalinas, siendo estas últimas más ricas en cobre que las zonas amorfas.
Las observaciones de los polvos recocidos con 0 y 7.5 % de Al mostraron la desaparición de la estructura amorfa y la formación de cristales de Cu10Zr7 en ambas aleaciones, además de la posible formación del compuesto Al3Zr4 en la aleación con 7.5 % en peso de Al.
2
Xu, Min. "Crystallization of Zr₂Pd(subscript x)Cu(₁₋(subscript x)) and Zr₂Ni(subscript x)Cu(₁₋(subscript x)) metallic glass." [Ames, Iowa : Iowa State University], 2008.
3
Абдулов, А. Р. "Термодинамические свойства расплавов Cu-Ti-Zr, Cu-Ni-Ti, Cu-Fe-Ti и моделирование их склонности к аморфизации". Дис. канд. хім. наук, Донбасская государственная машиностроительная академия, 2008.
4
Ismail, Nahla. "Electrochemical Hydrogen Absorption by Zr-Cu-Al-Ni Metallic Glasses." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2002. http://nbn-resolving.de/urn:nbn:de:swb:14-1037185293084-48289.
Анотація:
Effect of electrochemical absorption of hydrogen has been studied on the Zr-based amorphous alloys. The influence of hydrogen absorption on the stability of the amorphous phase and its crystallisation was investigated. Additionally, the cathodic hydrogen reaction mechanism on the surface of the alloy, the reversibility of the absorbed hydrogen and the hydrogen diffusion in the alloy were studied. These alloys are able to absorb large amounts of hydrogen (>1:1 hydrogen to metal ratio) but a rearrangement of the amorphous matrix takes place so that Cu rich areas are detected on the surface and Zr-hydride may precipitate. The thermal stability and crystallisation behaviour depends on the hydrogen concentration in the alloy. At low hydrogen concentration, the thermal stability deteriorates and primary crystallisation of Cu and/or Cu-rich phases is observed. At high hydrogen concentration, primary crystallisation of Zr-hydride takes place. The cathodic polarisation behaviour of amorphous Zr-based alloys as derived from Tafel plots reveals three characteristic potential regions reflecting the different mechanisms of hydrogen on the surface. In the Tafel region, hydrogen discharge and adsorption takes place on the alloy surface as fast steps reactions followed by the rate determining electrodic desorption reaction step in competition with hydrogen absorption as a fast step. In the further negative potential region, the current density is independent on the potential as both the Volmer and the Heyrowsky reactions take place at the same rate and the hydrogen mass transfer from the solution to the electrode surface is the rate-determining step. In the high polarisation region, all the partial hydrogen reactions take place intensively. The reversibility of the absorbed hydrogen tests reflects the possibility of hydrogen desorption from different energy sites in the amorphous alloy. The diffusion of hydrogen in the Zr-based alloys is comparable with that in the crystalline Pd and it is reduced in the pre-hydrogenated samples.
5
Casas, Gómez Camilo Andrés. "Simulación Dinámica Molecular de Aleaciones Amorfas de Cu-Zr-Al." Tesis, Universidad de Chile, 2010. http://www.repositorio.uchile.cl/handle/2250/102475.
6
Kosiba, Konrad. "Flash-Annealing of Cu-Zr-Al-based Bulk Metallic Glasses." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-222874.
Анотація:
(Bulk) metallic glasses ((B)MGs) are known to exhibit the highest yield strength of any metallic material (up to 5GPa), and show an elastic strain at ambient conditions, which is about ten times larger than that of crystalline materials. Despite these intriguing mechanical properties, BMGs are not used as structural materials in service, so far. The major obstacle is their inherent brittleness, which results from severe strain localization in so-called shear bands. MGs fail due to formation and propagation of shear bands. A very effective way to attenuate the brittle behaviour is to incorporate crystals into the glass. The resulting BMG composites exhibit high strength as well as plasticity. Cu-Zr-Al-based BMG composites are special to that effect, since they combine high strength, plasticity and work-hardening.
They are comprised of the glass and shape-memory B2 CuZr crystals, which can undergo a deformation-induced martensitic transformation. The work-hardening originates from the martensitic transformation and overcompensates the work-softening of the glass. The extent of the plasticity of BMG composites depends on the volume fraction, size and particularly on the distribution of the B2 CuZr crystals. Nowadays, it is very difficult, if not impossible to prepare BMG composites with uniformly distributed crystals in a reproducible manner by melt-quenching, which is the standard preparation method. Flash-annealing of BMGs represents a new approach to overcome this deficiency in the preparation of BMG composites and is the topic of the current thesis. Cu46Zr46Al8 and Cu44Zr44Al8Hf2Co2 BMGs were flash-annealed and afterwards investigated in terms of phase formation, crystallization kinetics and mechanical properties. Flash-annealing is a process, which is characterized by the rapid heating of BMGs to predefined temperatures followed by instantaneous quenching. A temperature-controlled device was succesfully developed and built. The Cu-Zr-Al-based BMGs can be heated at rates ranging between 16 K/s and about 200 K/s to temperatues above their melting point. Rapid heating is followed by immediate quenching where cooling rates of the order of 1000 K/s are achieved.
As a BMG is flash-annealed, it passes the glass-transition temperature, Tg, and transforms to a supercooled liquid. Further heating leads to its crystallization and the respective temperature, the crystallization temperature, Tx, divides the flash-annealing of BMGs into two regimes:
(1) sub-Tx-annealing and (2) crystallization.
The structure of the glass exhibits free volume enhanced regions (FERs) and quenched-in nuclei. Flash-annealing affects both heterogeneities and hence the structural state of the glass. FERs appear to be small nanoscale regions and they can serve as initiation sites for shear bands. Flash-annealing of Cu-Zr-Al-based BMGs to temperatures below Tg leads to structural relaxation, the annihilation of FERs and the BMG embrittles. In contrast, the BMG rejuvenates, when flash-annealed to temperatures of the supercooled liquid region (SLR). Rejuvenation is associated with the creation of FERs. Compared to the as-cast state, rejuvenated BMGs show an improved plasticity, due to a proliferation of shear bands, which are the carrier of plasticity in MGs. Flash-annealing enables to probe the influence of the free volume in bulk samples on their mechanical properties, which could not be studied, yet.
In addition, B2 CuZr nanocrystals precipitate during the deformation of flash-annealed Cu44Zr44Al8Hf2Co2 BMGs. Deformation-induced nanocrystallization does not occur for the present as-cast BMGs. Flash-annealing appears to stimulate the growth of quenched-in nuclei, which are subcritical in size and can also dissolve, once the BMG is heated to temperatures in the SLR. Rejuvenation represents a disordering process, whereas the growth of quenched-in nuclei is associated with ordering. There is a competition between both processes during flash-annealing. The ordering seems to lead to a “B2-like” clustering of the medium range of Cu44Zr44Al8Hf2Co2 BMGs with increasing heating duration. So far, there does not exist another method to manipulate the MRO of BMGs. If Cu44Zr44Al8Hf2Co2 BMGs are flash-annealed to temperatures near Tx, most likely compressive resiudal stresses develop near the surface, which is cooled faster than the interior of the BMG specimen. They hinder the propagation of shear bands and increase the plasticity of flash-annealed BMGs in addition to rejuvenation and deformation-induced nanocrystallization.
If BMGs are heated to temperatures above Tx, they start to crystallize. Depending on the exact temperature to which the BMG is flash-annealed and subsequently quenched, one can induce controlled partial crystallization. Consequently, BMG composites can be prepared. Both Cu-Zr-Al-based BMGs are flash-annealed at various heating rates to study the phase formation as a function of the heating rate. In addition, Tg and Tx are identified for each heating rate, so that a continuous heating transformation diagram is constructed for both glass-forming compositions. An increasing heating rate kinetically constrains the crystallization process, which changes from eutectic (Cu10Zr7 and CuZr2) to polymorphic (B2 CuZr). If the Cu-Zr-Al-based BMGs are heated above a critical heating rate, exclusively B2CuZr crystals precipitate, which are metastable at these temperatures. Thus, flash-annealing of Cu46Zr46Al8 and Cu44Zr44Al8Hf2Co2 BMGs followed by quenching enables the preparation of B2 CuZr BMG composites. The B2 precipitates are small, high in number and uniformly distributed when compared to conventional BMG composites prepared by melt-quenching. Such composite microstructures allow the direct observation of crystal sizes and numbers, so that crystallization kinetics of deeply supercooled liquids can be studied as they are flash-annealed. The nucleation kinetics of devitrified metallic glass significantly diverge from the steady-state and at high heating rates above 90 K/s transient nucleation effects become evident. This transient nucleation phenomenon is studied experimentally for the first time in the current thesis. Once supercritical nuclei are present, they begin to grow. The crystallization temperature, which depends on the heating rate, determines the crystal growth rate. At a later stage of crystallization a thermal front traverses the BMG specimen. In levitation experiments, this thermal front is taken as the solid-liquid interface and its velocity as the steady-state crystal growth rate. However, the thermal front observed during flash-annealing, propagates through the specimen about a magnitude faster than is known from solidification experiments of levitated supercooled liquids. As microstructural investigations show, crystals are present in the whole specimen, that means far ahead of the thermal front. Therefore, it does not represent the solid-liquid interface and results from the collective growth of crystals in confined volumes. This phenomenon originates from the high density of crystals and becomes evident during the heating of metallic glass. It could be only observed for the first time in the current thesis due to the high temporal resolution of the high-speed camera used.
The heating rate and temperature to which the BMG is flash-annealed determine the nucleation rate and the time for growth, respectively. The size and number of B2 CuZr crystals can be deliberately varied. Thus mechanical properties of B2 CuZr BMG composites can be studied as a function of the volume fraction and average distance of B2 particles. Cu44Zr44Al8Hf2Co2 BMG specimens were flash-annealed at a lower and higher heating rate (35 K/s and 180 K/s) to different temperatures above Tx and subsequently subjected to uniaxial compression. BMG composites prepared at higher temperatures show a lower yield strength and larger plastic strain due to the higher crystalline volume fraction. They not only exhibit plasticity in uniaxial compression, but also ductility in tension as a preliminary experiment demonstrates. Furthermore, nanocrystals precipitate in the amorphous matrix of BMG composites during deformation. They grow deformation-induced from quenched-in nuclei, which are stimulated during flash-annealing.
In essence, flash-annealing of BMGs is capable of giving insight into most fundamental scientific questions. It provides a deeper understanding of how annealing affects the structural state of metallic glasses. The number and size of structural heterogeneities can be adjusted to prepare BMGs with improved plasticity. Furthermore, crystallization kinetics of liquids can be studied as they are rapidly heated. Transient nucleation effects arise during rapid heating of BMGs and they cannot be described using the steady-state nucleation rate. Therefore, an effective nucleation rate was introduced. Besides, the flash-annealing process rises the application potential of BMGs. The microstructure of BMG composites comprised of uniformly distributed crystals and the glass, can be reliably tailored. Thus, flash-annealing constitutes a novel method to design the mechanical properties of BMG composites in a reproducible manner for the first time. BMG composites, which exhibit high strength, large plasticitiy and as in the case of B2 CuZr BMG composites as well work-hardening behaviour, can be prepared, so that the intrinsic brittleness of monolithic BMGs is effectively overcome.
7
Nekouie, Vahid. "Deformation behaviour of a Zr-Cu-based bulk metallic glass." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/25246.
Анотація:
While inelastic mechanical behaviour of crystalline materials is well-understood in terms of lattice defects, bulk metallic glasses (BMGs) pose significant challenges in this respect due to their disordered structure. They can be produced by rapid cooling from the liquid state (among other technique) and, thus can be frozen as vitreous solids. Due to the absence of a long-range order in atomic structure and a lack of defects such as dislocations, BMGs generally show unique mechanical properties such as high strength and elastic limit, as well as good fracture toughness and corrosion resistance. Typically, inorganic glasses are brittle at room temperature, showing a smooth fracture surface as a results of mode-I brittle fracture. At small scale, it was well documented that inelastic deformation of bulk metallic glasses is localised in thin shear bands. So, in order to understand deformation mechanisms of BMGs comprehensively, it is necessary to investigate formation of shear bands and related deformation process. In this thesis, a history of development of BMGs is presented, followed by a review of fundamental mechanisms of their deformation.
8
Frigerio, Jean-Marc. "Densités d'états électroniques d'alliages métalliques amorphes Cu-y, Cu-Zr déterminées par spectroscopie optique et d'électrons." Paris 6, 1986. http://www.theses.fr/1986PA066184.
Анотація:
Alliages constitués d'un métal à bande d remplie Cu et d'un métal de début de transition y ou Zr. Etude de l'influence du remplissage de la bande 4d sur la stabilité et la structure électronique des alliages amorphes. Comparaison de la relaxation structurale des deux types d'échantillons par calorimétrie différentielle à balayage et par diffusion centrale de rayons x. Etude de l'absorption optique et de la contribution des transitions interbandes. Les mesures de photoémission et de photoémission inverse confirment les résultats optiques.
9
Maria, Felipe Henrique Santa. "Análise térmica da influência do oxigênio na amorfização de ligas baseadas em Cu-Zr." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-23052018-105250/.
Анотація:
Os vidros metálicos baseados em Cu-Zr representam uma classe bastante promissora para a categoria de materiais estruturais, tendo em vista suas interessantes propriedades resultantes da natureza amorfa. Sabe-se que o oxigênio tem grande influência na formação da estrutura amorfa e consequentemente nas propriedades dessa classe de materiais. No presente trabalho, ligas amorfas baseadas em Cu-Zr foram analisadas termicamente a fim de se observar o comportamento das mesmas frente à contaminação com oxigênio. As análises térmicas foram realizadas em um equipamento de calorimetria exploratória diferencial (DSC), e as temperaturas características como de transição vítrea, cristalização, fusão e líquidus foram determinadas. Concluiu-se que conforme a literatura apresenta, o processo de cristalização é favorecido pela presença de oxigênio, causando uma queda na energia de ativação dos processos de cristalização das ligas trabalhadas. Através de ensaios que simularam tratamentos térmicos, cristalizou-se controladamente as amostras amorfas baseadas em Cu-Zr a fim de formar compósitos entre cristais e vidros metálicos buscando diminuir a fragilidade das ligas.Cu-Zr-based bulk metallic glasses represent a very promising class of structural materials with interesting properties resulting from the amorphous nature. It is known that oxygen has a great influence on the formation of the amorphous structure and consequently on the properties of these materials. In the present work, Cu-Zr-based amorphous alloys were thermally analyzed in order to observe their behavior against oxygen contamination. Thermal analyzis were performed on a differential scanning calorimetry (DSC) equipment, and characteristic temperatures as glass transition, crystallization, melting and liquidus were determined. It was concluded that, according to the literature, the crystallization process is favored by the presence of oxygen, causing a decrease in the activation energy of the crystallization processes of the worked alloys. Through tests that simulated heat treatments, the amorphous samples were crystallized in order to form composites between crystals and metallic glasses in order to reduce the brittleness of the alloys.
10
Pauly, Simon. "Phase formation and mechanical properties of metastable Cu-Zr-based alloys." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-39545.
Анотація:
In the course of this PhD thesis metastable Cu50Zr50-xTix (0≤ x ≤ 10) and (Cu0.5Zr0.5)100-xAlx (5 ≤ x ≤ 8) alloys were prepared and characterised in terms of phase formation, thermal behaviour, crystallisation kinetics and most importantly in terms of mechanical properties.
The addition of Al clearly enhances the glass-forming ability although it does not affect the phase formation. This means that the Cu-Zr-Al system follows the characteristics of the binary Cu-Zr phase diagram, at least for Al additions up to 8 at.%. Conversely, the presence of at least 6 at.% Ti changes the crystallisation sequence of Cu50Zr50-xTix metallic glasses and a metastable C15 CuZrTi Laves phase (Fd-3m) precipitates prior to the equilibrium phases, Cu10Zr7 and CuZr2. A structurally related phase, i.e. the “big cube” phase (Cu4(Zr,Ti)2O, Fd-3m), crystallises in a first step when a significant amount of oxygen, on the order of several thousands of mass-ppm (parts per million), is added. Both phases, the C15 Laves as well as the big cube phase, contain pronounced icosahedral coordination and their formation might be related to an icosahedral-like short-range order of the as-cast glass. However, when the metallic glasses obey the phase formation as established in the binary Cu-Zr phase diagram, the short-range order seems to more closely resemble the coordination of the high-temperature equilibrium phase, B2 CuZr.
During the tensile deformation of (Cu0.5Zr0.5)100-xAlx bulk metallic glasses where B2 CuZr nanocrystals precipitate polymorphically in the bulk and some of them undergo twinning, which is due to the shape memory effect inherent in B2 CuZr. Qualitatively, this unique deformation process can be understood in the framework of the potential energy landscape (PEL) model. The shear stress, applied by mechanically loading the material, softens the shear modulus, thus biasing structural rearrangements towards the more stable, crystalline state. One major prerequisite in this process is believed to be a B2-like short-range order of the glass in the as-cast state, which could account for the polymorphic precipitation of the B2 nanocrystals at a comparatively small amount of shear. Diffraction experiments using high-energy X-rays suggest that there might be a correlation between the B2 phase and the glass structure on a length-scale less than 4 Å. Additional corroboration for this finding comes from the fact that the interatomic distances of a Cu50Zr47.5Ti2.5 metallic glass are reduced by cold-rolling. Instead of experiencing shear-induced dilation, the atoms become more closely packed, indicating that the metallic glass is driven towards the more densely packed state associated with the more stable, crystalline state.
It is noteworthy, that two Cu-Zr intermetallic compounds were identified to be plastically deformable. Cubic B2 CuZr undergoes a deformation-induced martensitic phase transformation to monoclinic B19’and B33 structures, resulting in transformation-induced plasticity (TRIP effect). On the other hand, tetragonal CuZr2 can also be deformed in compression up to a strain of 15%, yet, exhibiting a dislocation-borne deformation mechanism.
The shear-induced nanocrystallisation and twinning seem to be competitive phenomena regarding shear band generation and propagation, which is why very few shear offsets, due to shear banding, can be observed at the surface of the bulk metallic glasses tested in quasistatic tension. The average distance between the crystalline precipitates is on the order of the typical shear band thickness (10 - 50 nm) meaning that an efficient interaction between nanocrystals and shear bands becomes feasible. Macroscopically, these microscopic processes reflect as an appreciable plastic strain combined with work hardening.
When the same CuZr-based BMGs are tested in tension at room temperature and at high strain rate (10-2 s-1) there seems to be a “strain rate sensitivity”, which could be related to a crossover of the experimental time-scale and the time-scale of the intrinsic deformation processes (nanocrystallisation, twinning, shear band generation and propagation). However, further work is required to investigate the reasons for the varying slope in the elastic regime.
As B2 CuZr is the phase, that competes with vitrification, it precipitates in a glassy matrix if the cooling rate is not sufficient to freeze the structure of the liquid completely. The pronounced work hardening and the plasticity of the B2 phase, which are a result of the deformation-induced martensitic transformation, leave their footprints in the stress-strain curves of these bulk metallic glass matrix composites. The behaviour of the yield strength as a function of the crystalline volume fraction can be captured by the rule of mixtures at low crystalline volume fractions and by the load bearing model at high crystalline volume fractions. In between both of these regions there is a transition caused by percolation (impingement) of the B2 crystals. Furthermore, the fracture strain can be modelled as a function of the crystalline volume fraction by a three-microstructural-element body and the results imply that the interface between B2 crystals and glassy matrix determines the plastic strain of the composites. The combination of shape memory crystals and a glassy matrix leads to a material with a markedly high yield strength and an enhanced plastic strain.
In the CuZr-based metastable alloys investigated, there is an intimate relationship between the microstructure and the mechanical properties. The insights gained here should prove useful regarding the optimisation of the mechanical properties of bulk metallic glasses and bulk metallic glass composites.
11
Khorashadizadeh, Anahita [Verfasser]. "Microstructure characterization of ultra-fine grained Cu-0.17wt%Zr / Anahita Khorashadizadeh." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/1029489432/34.
12
Aleman, Omar Jimenez. "Deposition and characterization of magnetron sputtered coatings in the Zr-Cu-JN and Zr-li-JN(B) ternary systems." Thesis, University of Sheffield, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521963.
13
Asgharzadeh, Javid Fatemeh. "Phase formation, martensitic transformation and mechanical properties of Cu-Zr-based alloys." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-210276.
Анотація:
Die Motivation zur Untersuchung ternärer und quaternären CuZr-Legierungen bestand in der Annahme, dass die Zugabe von Kobalt den Stabilitätsbereich von B2 CuZr bis zur Raumtemperatur erweitert und Aluminium einen signifikanten Effekt auf die Glasbildungsfähigkeit des CuZr-Systems hat. Die vorliegende Dissertation befasst sich mit der Herstellung und Charakterisierung von Cu50-xCoxZr50 (0 ≤ x ≤ 20) und Cu50-xCoxZr45Al5- (x = 2, 5, 10 und 20) Legierungen. Hierbei wurden die Phasenbildung, die thermische Stabilität, die Mikrostruktur, die Martensitbildung und die mechanischen Eigenschaften der Legierungen untersucht. Die Abhängigkeit der Phasenbildung von der Erstarrungsrate und der thermodynamischen Stabilität von Cu-Co-Zr-Legierungen zeigte, dass die Zugabe von Kobalt die Glasbildungsfähigkeit von Cu-Co-Zr-Legierungen absenkt und die stabilen kristallinen Produkte des Systems von Cu10Zr7 + CuZr2 zu (Cu,Co)Zr Phase mit einer B2 Struktur verändert. Die Ergebnisse weisen darauf hin, dass bei den schmelzgesponnene Bänder mit wenigstens 5 Atom-% Co das Glas direkt in B2 (Cu,Co)Zr kristallisiert, während Massivproben mit Co-Gehalten zwischen 0 ≤ x < 5 die monokline (Cu,Co)Zr Phase und Cu10Zr7 sowie CuZr2 beinhalten, wobei für x ≥ 10 die B2 (Cu,Co)Zr Phase bei Raumtemperatur im Gleichgewicht ist. Des Weiteren werden mit steigendem Co-Gehalt die Martensitumwandlungstemperaturen zu niedrigeren Werten verschoben. Die Phasenbildung im ternären System wird im pseudo-binären (Cu,Co)Zr-Phasendiagramm zusammengefasst, welches die Entwicklung neuer Formgedächtnislegierungen sowie metallischer Glas-Komposite bei Zugabe des Glasbildungselementes Aluminium vereinfacht. In den Vierstofflegierungen erhöht Al die Glasübergangs- und Kristallisationstemperaturen und verbessert dadurch die Glasbildungsfähigkeit des Systems. Die röntgenographische Analyse zeigte, dass die Kristallisationsprodukte der schmelzgesponnenen Bänder variieren: von Cu10Zr7 + CuZr2 + AlCu2Zr zu (Cu,Co)Zr + AlCu2Zr, wenn Co ≤ 5 und Co ≥ 10. Die Herstellung von Massivproben mit unterschiedlichen Durchmessern führte zu einem vollständig amorphen Gefüge, einem metallischen Glas-Komposit oder einem vollständig kristallinen Gefüge. Für Co ≤ 5 tritt neben (Cu,Co)Zr und AlCu2Zr ebenfalls Cu10Zr7 auf. Mittels Rasterelektronen (REM)- und Transmissionselektronenmikroskopie (TEM) erfolgte die Analyse des Einflusses von Al- und Co-Zugaben auf die Mikrostruktur von CuZr-Legierungen. Für die Cu-Co-Zr-Al-Legierungen sowie Cu30Co20Zr45Al5 (ø = 4 mm) und Cu45Co5Zr45Al5 (ø = 2 mm) wurden mikrostrukturelle Untersuchungen mittels TEM durchgeführt. Nachfolgend wurde die Heterogenität der Mikrostruktur in der Cu40Co10Zr45Al5 (ø = 2 mm) untersucht. Der Einfluss von Co auf die mechanischen Eigenschaften von rascherstarrten Cu50-xCoxZr50 (x = 2, 5, 10 und 20 Atom-%) Legierungen zeigt, dass das Verformungsverhalten der Stäbe unter Druckbeanspruchung stark von der Mikrostruktur der (Cu,Co)Zr Phase und somit von der Legierungszusammensetzung abhängt. Kobalt beeinflusst die Bruchfestigkeit der Gussproben. Weiterhin zeigen Proben mit martensitischem Gefüge eine Kaltverfestigung. Neben der Kaltverfestigung zeigen die Legierungen mit hohem Co-Gehalt eine verformungsinduzierte Martensitumwandlung und weisen zwei Streckgrenzen auf. Für die Vierstofflegierungen wurde der Einfluss der Kühlrate und der chemischen Zusammensetzung auf die mechanischen Eigenschaften untersucht. Für Cu48Co2Zr45Al5 (ø = 1.5, 2, 3 und 4 mm) und Cu45Co5Zr45Al5 (ø = 3 mm) wurde der Einfluss der Kühlrate und der Heterogenität diskutiert. Die Ergebnisse zeigen, dass die mechanischen Eigenschaften der Cu50-xCoxZr45Al5-Legierungen stark von der Makrostruktur und dem Volumenanteil der amorphen und kristallinen Phase abhängen. Die verformungsinduzierte Martensitumwandlung in Cu40Co10Zr50- und Cu40Co10Zr45Al5-Gussstäben wurde mittels hochenergetischer Röntgenstrahlung durchgeführt. Die In-situ- Druckversuche erfolgten weg- und kraftkontrolliert. Das makroskopische und mikroskopische Spannung-Dehnungs-Verhalten sowie die Phasenumwandlungskinetik wurden dabei betrachtet. Die relativen Veränderungen der vollständig integrierten Intensität der ausgewählten B2- und Martensitreflexe, die auf die Veränderungen der Volumenanteile der entsprechenden Phasen unter Verformung hinweisen, wurden als Phasenumwandlungsvolumen M/M+B2 beschriebenThe fact that the presence of Co extends the stability range of B2 CuZr to room temperature, together with the significant effect of Al on improving the glass forming ability of the CuZr system was the motivation to investigate the ternary and quaternary CuZr alloys with the aim of synthesizing BMG composites containing B2 (Cu,Co)Zr crystals. This PhD thesis deals with preparation and characterization of Cu50-xCoxZr50 (0 ≤ x ≤ 20) and Cu50-xCoxZr45Al5 (x = 2, 5, 10 and 20) alloys. The phase formation, thermal stability, microstructure, martensitic transformation and mechanical properties of these alloys were investigated. The dependence of phase formation on solidification rate and the thermodynamically stability of Cu-Co-Zr alloys reveals that the addition of Co decreases the glass forming ability (GFA) of the Cu-Co-Zr alloys and changes the stable crystalline products of the system from Cu10Zr7 + CuZr2 to (Cu,Co)Zr phase with a B2 structure. The results indicate that for the melt-spun ribbons with at least 5 % Co, the glass crystallizes directly into B2 (Cu,Co)Zr, while in the case of bulk specimens, compositions with 0 ≤ x < 5 of Co contain the monoclinic (Cu,Co)Zr phase and Cu10Zr7 and CuZr2, whereas, for x ≥ 10, the B2 (Cu,Co)Zr phase is the equilibrium phase at room temperature. Furthermore, increasing the cobalt content decreases the martensitic transformation temperatures to lower temperatures. The phase formation in the ternary system is summarized in a pseudo-binary (Cu,Co)Zr phase diagram, that helps for designing new shape memory alloys, as well as bulk metallic glass composites with the addition of glass former elements. In the quaternary alloys, Al increases the glass transition and crystallization temperatures and hence improves the GFA of the system. The X-ray analysis illustrates that for the melt-spun ribbons, the crystallization products vary from Cu10Zr7 + CuZr2 + AlCu2Zr to (Cu,Co)Zr + AlCu2Zr when Co ≤ 5 and Co ≥ 10, respectively. Depending on the cooling rates, the bulk samples represent a fully amorphous structure or BMG composites or a fully crystalline structure. For Co ≤ 5, beside (Cu,Co)Zr and AlCu2Zr, Cu10Zr7 exists as well. Scanning (SEM) and transmission (TEM) electron microscopy investigations were done to investigate the effect of Al and Co addition to the microstructure of CuZr alloys. In the case of Cu-Co-Zr-Al alloys, Cu30Co20Zr45Al5 (ɸ = 4 mm) and Cu45Co5Zr45Al5 (ɸ = 2 mm) compositions were selected for the microstructure verification using TEM. Later, the heterogeneity of the microstructure in Cu40Co10Zr45Al5 (ɸ = 2 mm) alloy was considered. The effect of Co on the mechanical properties of rapidly solidified Cu50-xCoxZr50 (x = 2, 5, 10 and 20 at.%) alloys depict that the deformation behavior of the rods under compressive loading strongly depends on the microstructure, and as a results, on the alloy composition. Cobalt affects the fracture strength of the as-cast samples; and deformation is accompanied with two yield stresses for high Co-content alloys, which undergo deformation-induced martensitic transformation. Instead samples with a martensitic structure show a work-hardening behavior. For quaternary alloys, the effects of cooling rate and chemical composition on mechanical properties of the alloys were investigated. Cu48Co2Zr45Al5 (ɸ= 1.5, 2, 3 and 4 mm) and Cu45Co5Zr45Al5 (ɸ = 3 mm) compositions were selected to discuss the effect of cooling rate and heterogeneity, respectively. The results depict that the mechanical properties of Cu50-xCoxZr45Al5 alloys strongly depend on the microstructure and the volume fraction of the amorphous and crystalline phases. The deformation-induced martensitic transformation of Cu40Co10Zr50 and Cu40Co10Zr45Al5 as-cast rods, was studied by means of high-energy X-rays. The in situ compression measurements were performed in track control and load control modes. The macroscopic and microscopic stress-strain behavior, as well as the phase transformation kinetics were considered. The relative changes in the fully integrated intensity of the selected B2 and martensite peaks, which indicate the changes in volume fraction of the corresponding phases under deformation, was described as phase transformation volume, M/M+B2
14
Fernández, Urrutia Rubén Marcos. "Recubrimientos de Cu-Zr-Al Amorfos Producidos Mediante Técnicas de Aspersión Dinámica." Tesis, Universidad de Chile, 2010. http://www.repositorio.uchile.cl/handle/2250/102309.
15
Hendrichs-Troeglen, Nicolas Jorge. "Consolidation structures and properties of rapidly soldified Cu-Cr-Zr alloy powders." Thesis, University of Sheffield, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319440.
16
Gomiero, Philippe. "Microstructure et propriétés mécaniques de l'alliage Al-Li-Cu-Mg(Zr) (2091)." Grenoble INPG, 1990. http://www.theses.fr/1990INPG0129.
Анотація:
L'objectif de ce travail est de correler l'evolution de la microstructure a l'evolution des proprietes mecaniques d'un alliage al-li-cu-mg (zr), type 2091, a l'etat sous revenu, en les comparant aux alliages modeles al li et al cu mg. Une etude fine de la microstructure de l'alliage a ete effectuee par microanalyse x, diffusion centrale en rayon x, microcalorimetrie et microscopie electronique en transmission. Elle a mis en evidence: i) une phase grossiere r en quantite non negligeable, qui diminue la teneur en solutes par rapport a la composition initiale; ii) une phase al#3li spherique de structure l1#2, et des zones gpb (plaquettes riches en cuivre et magnesium); iii) des lattes s semi-coherentes sur une structure dense et orientee de defauts de trempe. A partir de l'etude de l'evolution de la microstructure le durcissement structural mesure a pu etre correctement interprete a partir de modeles existants, en tenant compte entre autres d'un effet d'ordre pour la precipitation al#3li et d'un effet de module pour les zones gpb. Le durcissement d'ecrouissage est decrit par le modele d'ashby, en tenant compte de la localisation de la deformation. L'evolution des caracteristiques de l'effet portevin le chatelier en fonction du revenu est invoquee pour rendre compte de la chute de tenacite, en termes de dissipation plastique en tete de fissure
17
Déo, Leonardo Pratavieira. "Verificação da precisão de um critério para a seleção de composições formadoras de vidro em ligas metálicas do ternário Zr-Ni-Cu." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-14122011-142544/.
Анотація:
No presente trabalho verificou-se a precisão de um critério que prevê composições de ligas vítreas aplicado ao sistema Zr-Ni-Cu. Este critério combina o parâmetro de instabilidade topológica (\'lâmbda\'), e o parâmetro termodinâmico (\'delta\' h) entre os elementos de liga. Os dois parâmetros correlacionam quantitativamente à composição química a tendência à formação de vidros metálicos. Este critério é uma ferramenta promissora e simples para guiar e reduzir o trabalho tedioso e intensivo de encontrar composições altas tendências a vitrificação em sistemas metálicos. Para comprovar a eficiência desta ferramenta, a metodologia foi calcular o parâmetro para o sistema de interesse e preparar ligas de acordo com algumas composições fornecidas. A metodologia de preparação das ligas seguiu a fusão a arco elétrico e subsequentemente o emprego das técnicas de resfriamento rápido, melt-spinning e splat-cooling, para a produção de fitas e discos metálicos respectivamente, e o coquilhamento para a produção de amostras maciças em forma de cunha. Para as amostras confeccionadas por melt-spinning e splat-cooling, verificou-se a precisão do critério de seleção através da quantificação das porcentagens de fases vítreas a partir de análises de difratogramas de raios-X e seus comportamentos térmicos a partir dos termogramas de análises por calorimetria exploratória diferencial (DSC). Já para as ligas coquilhadas em cunha, obtiveram-se alguns resultados com indícios de estruturas vítreas que foram caracterizadas por difração de raios-X e metalografia. Desta forma chegou-se à conclusão que o critério de seleção aplicado ao sistema Zr-Ni-Cu pode ser utilizado para o desenvolvimento de composições favoráveis à formação de vidro antes da produção das ligas. Conclui-se que o critério que combina o parâmetro de instabilidade topológica (\'lâmbda\' min) e o parâmetro termodinâmico (\'delta\' h) é uma ferramenta que pode ser utilizada como guia para encontrar as composições mais fáceis de formar vidro, reduzindo assim o trabalho experimental de tentativa e erro.In the present work it was verified the accuracy of a proposed criterion to predict compositions of glassy alloys applied in the Zr-Ni-Cu system. This criterion combines the topological instability parameter (\'lâmbda\') and a thermodynamic parameter (\'delta\' h) among the alloying elements. The two parameters correlate quantitatively the chemical composition with the glass forming ability. This criterion is a promising and simple tool to guide and reduce the tedious and intensive work of finding good compositions of glasses in metallic systems. In an attempt to prove the efficiency of such tool, the methodology was to calculate the parameter for the system of interest and prepare alloys in accordance with the compositions provided by the tool. The methodology of preparation of the alloys followed the electric arc- melting and subsequent use of fast cooling techniques, melt-spinning and splat-cooling for the production of metallic ribbons and discs, respectively, and a wedge-shaped chiller mold to produce bulk metallic samples. For samples prepared from the melt-spinning and splat-cooling, it was verified the accuracy of the selection criteria by quantifying the percentage of glassy phases from X-ray diffractograms and their thermal behaviors from thermograms produced by differential scanning calorimetry (DSC). For alloys produced from the wedge-shaped mold, some results were obtained with evidence of vitreous structures that were characterized by X-ray diffraction and metallography. Therefore the conclusion is that the selection criteria applied to the system Zr-Ni-Cu can be used to develop favorable compositions for the formation of glasses before the production of the alloys. It is concluded that the selection criterion is a good tool and can be used as a guide to find the best glass forming alloys, thus reducing the experimental procedures of trial and error.
18
Poblano-Salas, Carlos A. "The microstructure and properties of consolidated water atomised Cu-Cr-Zr alloy powders." Thesis, University of Sheffield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425174.
19
Berezina, A. L., N. N. Budarina, A. V. Kotko, O. A. Molebny, A. A. Chayka, and A. Y. Ischenko. "Structural changes in friction-stir welded Al-Li-Cu-Sc-Zr (1460) alloy." Thesis, Sumy State University, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20580.
Анотація:
Structure and properties of Al-2.3%Li-3%Cu-0.1%Sc-0.1%Zr (1460) were studied
after FSW on thin cold-rolled sheets with the thickness of 2mm. Sheets were aged in the
T8mode. During FSW, severe plastic deformation and material flow occurs at the temperature
lower than melting temperature. Welding was performed at the tool rotation
speed 2880 rps. The tool was moved along the weld joint at the constant speed 16m/h.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20580
20
MAIS, LAURA. "Electrodeposition of Nb, Ta, Zr and Cu from Ionic Liquid for Nanocomposites Preparation." Doctoral thesis, Università degli Studi di Cagliari, 2015. http://hdl.handle.net/11584/266571.
Анотація:
Multilayer metal materials with nanometric scale are important in modern engineering applications. Composite materials based on metals with different characteristics give rise to new materials with unique properties. Among the others, nanostructured composites constituted by immiscible metals can present interfaces able to control defects produced by high doses of radiation, stress and temperature: their properties can be exploited in nuclear power reactor. Immiscible systems constituted by Cu/Nb or Cu/Ta multilayers exhibit higher thermal stability and improved mechanical properties with respect to bulk Nb, bulk Ta and bulk Cu. Refractory metals present high melting point, high hardness and high resistance against strong acids and bases. The electrodeposition of these metals presents several limitations: the most important is the very negative deposition potential that makes difficult the deposition of metals such as niobium, tantalum and zirconium. Since both oxygen reduction and hydrogen evolution from water splitting occur at potential values much less cathodic than the metals reduction, at the low potential requested to obtain niobium, tantalum and zirconium in metal form it is necessary the use of electrolytes free of water and oxygen and characterized by high stability in large potential windows. To overcome this limitation, the electrodeposition from molten salts or ionic liquids as solvents have been proposed.
In the present project the electrochemical coating of niobium, tantalum zirconium and copper has been investigated in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide([BMP][TFSA]) on both boron doped diamond (BDD) and metal substrates in order to determine the reduction path for both single metal and nanometric composites electrodeposition.
Electrochemical experiments have been performed at different temperatures in a glove box, under nitrogen atmosphere. Galvanostatic runs and cyclic voltammograms performed at different scan rates and different potential windows have been carried out in order to determine the behaviour of the systems employed. Potentiostatic experiments were performed at the potential values corresponding to the voltammetric peaks and the samples obtained were analysed by SEM-EDX analyses.
Regarding the electrodeposition of refractory metals nanometric crystallites have been obtained at 125 °C.
Cu/Nb and Cu/Ta composites have been prepared by a dual bath deposition technique; the deposits were constituted by fine crystallites with average sizes in the range 50-100 nm. The elemental maps indicate a different distribution of Cu/Nb and Cu/Ta in the composites obtained with the different substrates.
21
Gaganov, Alexander. "Hochfeste und hochleitfähige Cu-Ag-Leitermaterialien." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-62066.
Анотація:
Die Cu – Ag - Mikroverbund – Werkstoffe besitzen das Potenzial die gegensätzlichen Anforderungen an das Leitermaterial für den Einsatz in einem Hochfeldmagneten, wie hohe Festigkeit bei gleichzeitig hoher elektrischen Leitfähigkeit und ausreichender Verformbarkeit, zu erfüllen. Außerdem bieten diese Werkstoffe gegenüber den anderen, die dafür in Frage kommen können, den großen technologischen Vorteil einer konventionellen schmelzmetallurgischen Herstellung. Jedoch wurde bisher dafür eine sehr aufwändige Technologie verwendet, die die Herstellung des Leitermaterials nur im Labormaßstab ermöglicht. Die vorliegende Arbeit befasst sich mit einer Technologie der Herstellung von Leitern, die den Anforderungen für den Einsatz in einem Hochfeldmagneten genügen können und in einem großtechnischen Maßstab verfügbar sind. Der Schwerpunkt der Leiterherstellung aus Cu – Ag - Legierung lag in der Einstellung der geeigneten Mikrostruktur über metallkundliche Mechanismen vor der Drahterzeugung. Hierfür wurden während der einzelnen Prozessschritten die Gefügeentwicklung und für die Anwendung relevante Eigenschaften der Legierungen in binären Cu – Ag – Legierungen und in ternären Cu – Ag -X –Legierungen untersucht. Darüber hinaus wurde der Einfluss der Mikrostruktur und der Zusammensetzung auf die mechanischen und elektrischen Eigenschaften der Drähte ermittelt sowie eine Korrelation zwischen Mikrostruktur und elektrischen Eigenschaften aufgestellt.
22
Laffont, Paul. "Comportement à la rayure de verres métalliques massifs base CuZr." Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALI018.
Анотація:
La structure amorphe des verres métalliques (VM) leur confère des résistances mécaniques hors du commun. Elle est également à l'origine des mécanismes de déformations plastiques qui leur sont spécifiques et qui se traduit par la localisation spatiale de la déformation menant à la création et la propagation de bandes de cisaillement. L'impact de ces mécanismes de déformation reste néanmoins encore mal connu concernant les sollicitions mécaniques complexes, il est par exemple très difficile de prédire les évolutions de l'usure d'un VM dans un système complexe et donc sa durée de vie qui est intimement liée à la perte de matière. Ces travaux ont ainsi pour but de comprendre la réponse mécanique des VM vis à vis des mécanismes de déformation qui leurs sont propres, lors d'essais de rayure, sur trois verres métalliques différents base Zr et Cu.La comparaison des essais de rayure à ceux d'indentation a révélé l'importance de la résistance au cisaillement dans les VM dès que l'indenteur exerce une force latérale, entraînant la création de bandes de cisaillement à l'avant du passage de l'indenteur. L'activation du mécanisme d'adoucissement propre aux VM a ainsi été mise en lumière. Ce dernier favorise alors l'enfoncement de l'indenteur lors de la rayure. Des modifications de la structure des VM étudiés, et donc des propriétés mécaniques, ont ensuite été réalisées à l'aide de traitements thermiques de relaxation et de cristallisation partielle permettant de discuter le rôle de la dureté mais aussi de l'importance de la ténacité. Ainsi le VM le plus dur n'est pas forcement, comme généralement admis dans la communauté scientifique, le verre possédant la plus grande résistance à la rayure. Grâces aux résultats obtenus, des stratégies ciblées pour les différents types de VM existants sont proposées afin de limiter leur usure lors de la rayureMetallic glasses (MGs) exhibit incredible mechanical properties arising from their particular amorphous structure. This structure is also responsible for the specific deformation mechanisms of MG leading to the nucleation and propagation of shear bands (SBs). Nevertheless, under complex loading, the deformation mechanisms remain to be understood, for example, it isnearly impossible to predict the wear behaviour and so, the lifetime which isdirectly linked to the wear loss of a metallic glass sample. This work aims to understand the mechanical behaviour of MGs, in light of their specific deformation mechanisms, under scratch test for three differents Zr- and Cu-based MGs.The analogy of indentation and scratch tests revealed the importance of the shear strength for MGs. Indeed, the introduction of a lateral force in the case of a scratch test induces the creation of SBs ahead of the tip of the indenter. The activation of the softening mechanism has also been pointed out, which leads to the sink in of the indenter during a scratch test. The study of thermally treated MGs (relaxed and partially crystalized) helps us revealing the impact of the hardness along with the fracture toughness on the wear resitance of a MG. Thereby, the MG showing the best wear resistance is not necessarily the hardest MG, as admitted by the scientific community. Eventually, different strategies in agreements with the results shown in this work, are discussed in order to minimize the wear during the scratch of a MG
23
Bicker, Matthias. "Strukturelle Änderungen in dünnen amorphen Zr-Al-Ni-Cu- und Ta-Si-N-Schichten." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=960137440.
24
Sun, Kou María del Rosario, and Sagrario Mendioroz. "Preparación y propiedades de montmorillonitas pilaradas con Zr y su interacción con Cu(II)." Revista de Química, 2013. http://repositorio.pucp.edu.pe/index/handle/123456789/100753.
25
Cataldo, Laurent. "Contribution à l'élaboration et à l'optimisation d'alliages magnétiques permanents Sm-Co-Cu-Fe-Zr." Lyon 1, 1996. http://www.theses.fr/1996LYO10206.
Анотація:
L'etude concerne l'elaboration d'alliages sm-co-fe-cu-zr utilises pour la fabrication d'aimants permanents. L'objectif poursuivi a ete une optimisation des proprietes magnetiques a travers la mise au point des conditions d'elaboration. Les aimants permanents a base de co-sm-cu-fe et zr sont encore actuellement les seuls materiaux susceptibles de travailler a haute temperature (300\c) sans alteration notable de leurs proprietes magnetiques (temperature de curie, coercitivite elevee, produit energetique 28mgoe). Le processus d'elaboration de ces alliages est complexe et comporte trois etapes : une etape d'homogeneisation a haute temperature destinee a obtenir un materiau monophase, un recuit a basse temperature au cours duquel se forme la microstructure cellulaire responsable des bonnes proprietes magnetiques de ces alliages, un durcissement magnetique produit par un refroidissement lent. L'objectif du travail a ete de definir les limites des domaines monophases des phases constitutives de ces aimants. Ces deux phases derivent des composes sm 2co 1 7 et smco 5. La substitution par cu, fe et zr conduit a des composes de type 2:17 rhomboedriques ou hexagonaux suivant que la phase est issue de sm 2co 1 7 ou smco 5. En raison du manque de donnees coherentes de la litterature, une etude systematique des sous systemes limites du systeme quinaire co-sm-cu-fe-zr a ete entreprise. Systeme binaire co-sm dans le domaine riche en cobalt : il a ete mis en evidence que dans ce systeme il existe une solubilite importante vers 1370\c du samarium dans le cobalt. Les differentes phases existant dans le domaine riche en cobalt (sm 2co 1 7, smco 5, sm 5co 1 9, sm 2co 7) ont ete etudiees du point de vue de leur proprietes physicochimiques (fusion, reaction de formation, spectre de diffraction de rx, stoechiometrie). Systemes ternaire co-sm-cu et quaternaire co-sm-cu-fe : les domaines monophases des phases 2:17 rhomboedrique et 1:5 ont ete determines en composition et en temperature. Systeme quinaire co-sm-cu-fe-zr : a la stoechiometrie 2:17 correspondent deux formes cristallines, l'une rhomboedrique, l'autre hexagonale issue de la phase 1:5 a travers une phase desordonnee 1:7. Des echantillons quinaires ont ete elabores a 1150\c, le domaine monophase 1:5/1:7/2:17h a ete delimite pour une teneur en cuivre egale a 4 at%, et les phases adjacentes susceptibles d'etre observees dans des materiaux en fonction d'une modification de composition ont ete definies. L'etude a ete completee par la recherche de l'evolution des materiaux lors de l'etape de recuit basse temperature. Dans cette etude, les materiaux ont ete elabores par fusion au four a arc et recuits sous atmosphere d'argon purifie. La composition nominale des echantillons a ete determinee par spectrometrie d'emission plasma. Les phases ont ete caracterisees par diffraction de rx, examen metallographique et leur composition a ete analysee par microsonde. Une analyse par mossbauer a permis de situer les sites substitues par le fer dans les phases 2:17r et 1:5.
26
Rahioui, Ahmed. "Contribution à l’Étude microstructurale des effets d'implantation d’espèces métalliques (Cu,Zr,Fe) dans l'alumine." Lyon, INSA, 1993. http://www.theses.fr/1993ISAL0046.
Анотація:
L'implantation ionique est un traitement envisagé pour l'amélioration des propriétés de surface des matériaux, notamment les céramiques. Elle permet de modifier fondamentalement les microstructures superficielles. Notre travail a porté sur l'implantation à forte concentration d'espèces métalliques (Cu, Zr, Fe) dans une alumine polycristalline. Les espèces ont été choisies en raison de la diversité de leur valence et de la stabilité de leurs oxydes avec l'alumine. Plusieurs techniques complémentaires ont permis la caractérisation microstructurale de la couche implantée en fonction des paramètres d'implantation (énergie, fluence,. . . ),de la nature de l'ion, et de traitements thermiques réalisés après l'implantation. Ces techniques sont la microscopie électronique conventionnelle et à haute résolution, la microanalyse d'émission photonique X (EDS) et la technique d'absorption X (XANES). La couche superficielle formée lors de 1'implantation est constituée de grains finement morcelés d'alumine en association avec une précipitation fine des espèces métalliques. La présence en surface de la variété spinelle fortement maclée est également observée dans le cas du fer. Une amorphisation est seulement observée dans le cas d'implantation du zirconium alors que systématiquement, une sous-couche très fautée est décelée au delà de la zone implantée. La composition de la couche superficielle évolue avec les traitements thermiques vers un système constitué d'alumine et d'oxyde(s) des espèces métalliques qui, globalement, est en accord avec les prévisions thermodynamiquesIon implantation is being investigated as a method to alter near-surface properties of materials, particularly ceramics. It allows, in non-equilibrium conditions, a thin layer to be created, the composition and structure have beneficial effects of surface properties. This study was related to the high doses implantation of metallic ions into polycrystalline alumina. The species (Cu, Zr, Fe) has been chosen from the gap between their valences and the formation free enthalpies of their oxides. In order to understand the microstructural evolution of the as-imp- planted and the implanted-annealed samples, various techniques have been used, suer as transmission electron microscopies (conventional and high resolution), X-ray emission spectroscopy (EDS) and X-ray absorption spectroscopy (XANES) The observed microstructure in the as-implanted material is composed of several regions. The first of these consists in of highly divided alumina grains including a fine precipitation of the metallic species. In the case of iron, the spinel phase is also observed near the implanted surface. Beyond the implanted zone, a high density M crystalline defects is seen in the alumina lattice. Moreover, an amorphous-like layer is produced by implantation of zirconium. In most cases, the evolution of the implanted zone composition after annealing is consistent with the expected equilibrium phase diagrams
27
Mechler, Stefan. "Die Rolle der ikosaedrischen Nahordnung bei Glasbildung und Kristallisation im System Zr-Ti-Ni-Cu-Be." [S.l.] : [s.n.], 2007. http://opus.kobv.de/tuberlin/volltexte/2007/1539.
28
Pavlenyi, Marc. "Effects of short range order on structural and transport properties of Cu-Ni-Zr amorphous alloys." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59379.
Анотація:
The effects of short range order on the structural and transport properties of the $ rm Cu sb{1-x}Ni sb{x}Zr sb2$ amorphous metallic alloy system are studied. Depending on composition, these amorphous alloys crystallize into different structures. CuZr$ sb2$ has the I4/mmm (C11) structure and NiZr$ sb2$ has the I4/mcm (C16) structure. It is believed that the short range order in the amorphous phase is related to the final crystalline phase. A careful study (using differential scanning calorimetry, X-ray diffraction on as made and crystallized states, room temperature magnetic susceptibility and resistivity, and a determination of the superconducting transition temperature of as-made and annealed states) has been done to see what transport properties are affected.It is observed that there is a linear increase in the values of the susceptibility, resistivity, and superconducting transition temperature of the system from CuZr$ sb2$ to NiZr$ sb2.$ This is attributed to an increase of the electronic density of states as the concentration of Ni increases. There is little or no influence on transport properties due to topological short range order.
29
Davin, Laury F. "Ultra-fine characterisation of nanostructures in Al-(Li)-Cu-Mg-(Zr) alloys by three-dimensional atom probe." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408822.
30
Verdu, Catherine. "Origines microstructurales et modélisation de l’Amorçage des fissures inter granulaires d'un alliage Al-Li-Cu-Mg-(Zr)." Lyon, INSA, 1991. http://www.theses.fr/1991ISAL0012.
Анотація:
Le travail réalisé porte sur l'analyse des mécanismes microscopiques de la rupture inter granulaire des alliages Al. Li. Cu. Mg. (Zr). Par une méthodologie expérimentale originale, nous avons montré que la rupture dans ces alliages est liée à leur mode de déformation plastique particulier. En effet, on observe qu'une seule famille de plans. De glissement est principalement activée, en raison d'une texture cristallographique marquée, et du cisaillement des précipités Al Li. Il s'en suit des incompatibilités de déformation entre les grains qui entraînent une localisation de la déformation près des joints de grains et l'apparition d'un glissement sinueux très grossier. Les ruptures inter granulaires sont dues principalement à l'effet de l'interaction avec les joints de grains, des glissements rectilignes et sinueux. D'autre part la précipitation inter granulaire de la phase quasi-crystalline T et de la présence d'une zone dénudée en précipités Al Li, favorisent l'amorçage inter granulaire des fissures en raison des incompatibilités de déformation plastique entre la phase T2 et la matrice. Dans la dernière partie, nous développons un modèle d'amorçage pour les fissures inter granulaires à partir d'un empilement de dislocations contre les joints de grains. Ce modèle appliqué au cas des états revenus conduit à une vision assez claire de la rupture inter granulaire dans les alliages Al. Li. Cu. Mg. (Zr)This work is concerned with the microscopic mechanisms of inter granular fracture in an Al. Li. Cu. Mg. (Zr) alloy. By means of an original approach, it has been shown that the fracture of this alloy is due to his specific plastic deformation mode. Indeed, only a one single slip system is mainly activated due to a very pronounced crystallographic texture and the shearing of Al Li precipitates. Therefore incompatible deformation occurs between contiguous grains. It induces a localisation of the plastic deformation near the grain boundaries and the initiation of a very coarsened and sinuous slip. Inter granular granular cracks are mainly due to the interaction of slips with grain boundaries. The crack initiation is also enhanced because of the plastically interaction stress field induced by incompatibility problems between: the T2 phase and the precipitate free zone. In the last part of this work an inter granular crack initiation model is proposed from the formation of dislocations pile ups against the grain boundaries. This model leads to à clear understanding of the inter granular fracture in the againg Al. Li. Cu. Mg. (Zr) alloys
31
Bolam, Vivienne Jane. "The influence of surface treatments on the fatigue properties of an AL-LI-CU-MG-ZR (8090) alloy." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315087.
32
Xiaofeng, Gu. "Preparation, glass forming ability, crystallization and deformation of (Zr, HF)-CU-NI-AL-TI based bulk metallic glasses." Available to US Hopkins community, 2003. http://wwwlib.umi.com/dissertations/dlnow/3080671.
33
Ritter, Yvonne [Verfasser], Karsten [Akademischer Betreuer] Albe, and Gerhard [Akademischer Betreuer] Wilde. "Molecular Dynamics Simulations of Structure-Property Relationships in Cu-Zr Metallic Glasses / Yvonne Ritter. Betreuer: Karsten Albe ; Gerhard Wilde." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2012. http://d-nb.info/1106256514/34.
34
Marques, Paulo Wilmar Barbosa. "Relaxação estrutural em ligas vítreas e parcialmente cristalizadas do sistema Cu-Zr-Al através da técnica de espectroscopia mecânica." Universidade Federal de São Carlos, 2013. https://repositorio.ufscar.br/handle/ufscar/4965.
Анотація:
Made available in DSpace on 2016-06-02T20:15:29Z (GMT). No. of bitstreams: 1
5591.pdf: 65197476 bytes, checksum: 0562626136c2cda8c961be66e989832e (MD5)
Previous issue date: 2013-11-08Universidade Federal de Sao Carlos
In recent years the study of bulk metallic glasses (BMG) is being of great scientific and technological interest due to their unique properties (the lack of long range atomic order in the structure and compositional homogeneity similar to the liquid state). These alloys show better mechanical properties, superior corrosion resistance, high yield stress and fracture toughness, if compared to their crystalline counterparts. However, a physical understanding of disordered structure and how it affects the properties of metallic glasses is still considered one of the great challenges in Condensed Matter Physics and Materials Science. Since the Mechanical Spectroscopy technique is sensitive to phase transitions and dynamical processes, it provides the anelastic spectra (internal friction and oscillation frequency) as function of temperature, through which relevant informations to the understanding of structural and vibrational changes of metallic glasses are obtained. In this study, the mechanical spectroscopy technique was used to investigate dynamic processes related to elastic and electronic contributions of atomic motions and clusters, as well as other changes in the atomic bonds on the glassy and partially crystallized alloys of the ternary system Cu-Zr-Al. The samples were obtained combining criteria of the minimum topological instability and the average electronegativity (λmin∙Δē), and were investigated at temperatures above and below room temperature (300 K) with applied frequencies in Hz, kHz and MHz magnitude order. Above room temperature, the application of alternated stresses in the order of Hz and KHz allowed us to observe structural changes involving atomic rearrangements due to anelastic, viscoelastic and thermoelastic aspects present in the relaxation process. In this temperature range, the viscoelastic and thermoelastic character overlaps the anelastic relaxation mechanisms that could be observed in metallic glasses. Analysis of samples with nominal composition Cu54Zr40Al6 - nanocrystalline and vitreous - show that the anelastic relaxation processes begin below room temperature, and are dependent of the applied frequency. When the applied frequencies are in the Hz magnitude order, some clusters have their shell affected by the alternate elastic stresses. When the samples are excited with kHz order of magnitude frequencies, two well-defined relaxation centers will appear. This phenomenon is caused by the movement of clusters which are created and annihilated at the same time the stress is applied. When the applied stresses are of MHz magnitude order, the clusters are rearranged in a more efficient way, in which the less stable clusters involving Zr are annihilated and clusters with Al or Cu at their centers are reordered in order to promote the stability of the icosahedral structure embedded in the amorphous matrix. Under applied mechanical energy corresponding to the MHz frequencies, more stable structures are created and the clusters approach, interact and interpenetrate each other, giving rise to the free bond planes where the superclusters rearrange leading to the formation of medium range chains. Under persistent mechanical stimulation in MHz, the structures begin to form long-range order that lead to formation of the first crystalline precipitates. Those purely anelastic relaxation mechanisms are initiated at low temperatures, and in most cases, it´s not possible to observe them at higher temperatures due to the viscoelastic and thermoelastic character, which generally occur simultaneously in metallic glasses.
Nos últimos anos, o estudo e o processamento dos vidros metálicos de grande volume (BMG Bulk Metallic Glasses), em sistemas multicomponentes, tem sido de grande interesse científico e tecnológico devido as suas propriedades únicas: como a falta de regularidade atômica de longo alcance e a sua homogeneidade composicional semelhante ao estado líquido. Estas ligas apresentam melhores propriedades mecânicas, resistência à corrosão e alta resistência à fratura quando comparado a sua contraparte cristalina. No entanto, um compreensivo entendimento físico da estrutura desordenada e de como a mesma afeta as propriedades dos vidros metálicos, ainda é considerado um dos grandes desafios na Física da Matéria Condensada e na Ciência dos Materiais. A Espectroscopia Mecânica que fornece o espectro anelástico (atrito interno e frequência de oscilação) em função da temperatura é considerada uma técnica sensível a transições de fase e a processos dinâmicos, através da qual são obtidas informações relevantes para a compreensão das alterações estruturais e vibracionais dos vidros metálicos. Neste estudo, foi utilizada a técnica de Espectroscopia Mecânica para investigar os processos dinâmicos relacionados a contribuições elásticas e eletrônicas devido aos movimentos atômicos e de cluster, bem como, as demais mudanças nas ligações atômicas nas ligas vítreas e parcialmente cristalizadas do sistema ternário Cu-Zr-Al. As amostras obtidas com base no diagrama topológico combinado λmin∙Δē foram investigadas em temperaturas acima e abaixo da temperatura ambiente (300 K) com frequências da ordem de Hz, kHz e MHz. Acima da temperatura ambiente, aplicando tensões alternadas em Hz e kHz, foi possível observar as mudanças estruturais que envolvem rearranjos atômicos devidos aos aspectos anelástico, viscoelástico e termoelástico presentes no processo de relaxação. Nesta faixa de temperatura, o caráter viscoelástico e termoelástico sobrepõe os mecanismos de relaxação anelástica que poderiam ser observados nos vidros metálicos. Em temperaturas abaixo da ambiente, as amostras de composição nominal Cu54Zr40Al6 - vítreas e nanocristalinas - mostram que os processos de relaxação anelástica se iniciam abaixo da temperatura ambiente e são dependentes da frequência aplicada. Nas frequências aplicadas em escala Hz, alguns clusters tem sua blindagem afetada pelas tensões elásticas alternadas. Quando as amostras são excitadas com uma frequência da escala de kHz surgem dois centros de relaxação bem definidos que envolvem a movimentação de clusters que tendem a ser criados e aniquilados ao mesmo tempo em que a tensão é aplicada. Em tensões aplicadas na ordem de MHz, os clusters passam a se reordenar de forma mais eficiente, de modo que, os clusters menos estáveis que envolvem o Zr são aniquilados e os clusters que possuem Al ou Cu em seu centro são reordenados de forma a promover a estabilidade da estrutura icosaédrica dentro da matriz amorfa. Conforme as energias mecânicas em MHz são aplicadas, mais estruturas estáveis são criadas de forma que os clusters tendem a aproximar, interagir e se interpenetrar dando origem aos planos de ligações livres por onde os superclusters passam a se reordenar originando cadeias de médio alcance. Com indefinidos estímulos mecânicos em MHz, as estruturas tendem a formar os primeiros precipitados cristalinos. Estes mecanismos de relaxação puramente anelástica se iniciam em baixas temperaturas, e na maioria das vezes, não são possíveis de serem observados em altas temperaturas devido ao caráter viscoelástico e termoelástico que, em geral, ocorrem simultaneamente nos vidros metálicos.
35
Mackie, Alexander J. "Spark Plasma Sintering as a powder processing route for pre-alloyed Sm2(Co, Fe, Cu, Zr)17 permanent magnets." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/21654/.
Анотація:
The ’rare earth crisis’ that occurred in 2011 ignited research into mitigating and replacing the dependence on these elements in Rare Earth Permanent Magnets (REPM) and their applications. It is the former that this body of work is based upon. A method of increasing the bulk resistivity of a REPM, Sm(Co, Fe, Cu, Zr)8.2 (henceforth referred to as Sm2(Co, Fe, Cu, Zr)17), through the addition of an electrically insulating material, CaF2, to form a rare earth composite permanent magnet is studied. The aim of increasing the bulk resistivity is to minimise the irreversible demagnetisation and performance losses that occur within REPMs due to circulating eddy currents during operation of high frequency applications, such as electric motors and drives. The project utilises an emerging sintering technology platform, Spark Plasma Sintering (SPS), to rapidly consolidate powders. The processing methodology for Sm2(Co, Fe, Cu, Zr)17 powders by the SPS technique has therefore been studied with the optimal processing parameters found for producing full dense specimens for study: 1050°C to 1100°C hold temperature, 100°C= min to 200°C= min heating rate, 51MPa hold pressure and 5 minute hold time. Sm2(Co, Fe, Cu, Zr)17 permanent magnets require a characteristic multi-stage heat treatment to precipitate a cellular nanostructure which enhances the coercivity of the permanent magnets. The optimal heat treatment for the full density SPS processed Sm2(Co, Fe, Cu, Zr)17 magnets has also been studied, with the following achieving the largest coercivities and energy products: 1. Homogenisation - 1170°C for 2 hours in an argon atmosphere. Cooled slowly in air to room temperature. 2. Ageing - 850°C for 8 hours (for largest coercivity) or 16 hours (for largest (BH)max) in argon atmosphere. 3. Slow cool (1°C=min) from 850°C to 400°C in argon atmosphere. Quench in oil to room temperature. This established processing route was then used to prototype isotropic Sm2(Co, Fe, Cu, Zr)17 and CaF2 composite magnets and study the effect of the electrically insulating phase on the microstructure, and material and magnetic properties before and after heat treatment.
36
Vilela, Marcio Maia. "Medidas de poder de freamento de Si, Ti, V, Cu, Zn, Zr e Pd utilizando ions 14N e 16O." Universidade de São Paulo, 1986. http://www.teses.usp.br/teses/disponiveis/43/43131/tde-08112013-145930/.
Анотація:
Foram medidas as perdas de ernergia de íons 14N e 16O em sólidos (Si,Ti,V,Cu,Zn, Zr e Pd) na faixa de energias de 1 MeV/uma. A técnica utilizada constitui-se na medida de energia de projéteis espalhados a 25° por um alvo delgado de Au, antes e depois de atravessar a folha do element freador. Os resultados experimentais são comparados com as previsões semi-empíricas de Northcliffe & Schilling (N&S), Ziegler e uma nova versão de N&S feita por Hubert e colaboradores, sendo observada uma razoável concordância entre os valores medidos e as curvas semi-empíricas.Energy loss has been measured 14N and 16O at energies of 1 MeV/amu to 4 MeV/amu in Si, Ti, V, Cu, Zn, Zr and Pd foils. The technique consists in the measurement of the energies of ions scattered through 25 ° by a goldfoil before and after passing through the stopping foil. Our data compared to the semiempirical tabulations of Northcliffe and Schilling (N&S), Ziegler and new version of N&S by Hubert et al.. The predictions of these semiempirical compilations are in reasonable agreement with our experimental data.
37
Krzelowski, Mirosław. "Analiza struktury faz Laves'a Nb (Cu, Al, X) 2 (X = Ni, Co, Cr, Ti i Zr) metodą krystalografii elektronowej." Doctoral thesis, Katowice : Uniwersytet Śląski, 2008. http://hdl.handle.net/20.500.12128/5130.
Анотація:
Aktualnie prowadzone badania w różnych ośrodkach naukowych związane z poszukiwaniem coraz to bardziej wytrzymałych i odpornych na degradację termiczną materiałów wskazują jednoznacznie, że jednym z właściwych kierunków badań jest zainteresowanie się materiałami, których struktura zawiera fazy międzymetaliczne. Fazami takimi są ponad wszelką wątpliwość fazy Laves’a, które stwarzają dodatkowe możliwości znacznej poprawy różnych charakterystyk tych materiałów, nie powodując jednocześnie
pogorszenia innych pożądanych właściwości. Przykładem są tu stopy typu Cu-Al-Nb wykazujące pamięć kształtu w podwyższonych temperaturach. Obecność w tych stopach wydzieleń fazy Laves’a typu Nb(Cu,Al)2 powoduje równoczesny wzrost właściwości wytrzymałościowych i plastycznych. Wprowadzenie do tych stopów czwartego pierwiastka stopowego prowadzi do dalszych zmian, jednakże nie zawsze korzystnych.
Spowodowane to jest pojawieniem niewielkiej ilości innych faz międzymetalicznych jak również zmianami w składzie chemicznym, strukturze i właściwościach samej fazy Laves’a (Nb(Cu,Al,X)2, gdzie X - czwarty pierwiastek stopowy). Ze względu na rozmiary tych wydzieleń, badanie zmian ich struktury prowadzone jest głównie przy pomocy transmisyjnej mikroskopii elektronowej. Celem pracy jest zbadanie wpływu składu chemicznego na strukturę fazy Laves’a typu Nb(Cu,Al,X)2, gdzie (X = Ni, Co, Cr, Ti lub Zr), wykorzystując głównie metodę krystalografii elektronowej.
38
Lin, Pin-Chen, and 林品辰. "High-Temperature Oxidation Behavior of Cu-Zr Binary and Zr-Cu-Al Ternary Bulk Metallic Glasses." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/94418180036321475320.
Анотація:
碩士國立臺灣海洋大學
材料工程研究所
98
The oxidation behabior of three Cu-Zr based bulk metallic glasses, containing Cu64.5Zr35.5 (CZ2), Zr50Cu43Al7 (CZA7) and Zr50Cu40Al10 (CZA10) and their crystalline counterparts was studied over the temperature range of 400oC ~ 500oC in dry air. In general, the oxidation kinetics of three glassy alloys followed the two- to three-stage parabolic-rate law, indicating that diffusion is the rate-determining step during oxidation. The oxidation rate constants (kp values) gradually increasing with temperature for CZ2, but fluctuating with temperature for both CZA7 and CZA10. The scales formed on these BMGs consisted mostly of monoclinic-ZrO2 (m-ZrO2) and CuO, and minor amounts of tetragonal- and orthornombic-ZrO2 (t- and o- ZrO2). However α-Al2O3 was also detected at 500oC for CZA7 and CZA10, whose formation is responsible for the reduction of oxidation rates, as compared to those at lower temperatures. It was found that small amounts of Al addition increased glass forming ability (GFA), however, there is no reduction of the oxidation rates with respect to the binary BMG. The amorphous substrates retained unchanged at the temperature below the glass-transition temperature (Tg), however they underwent a pre-oxidation process and followed by the crystallization after oxidation at the temperature above Tg , consisting of both Cu10Zr7 and Cu51Zr14 for the CZ2 substrate, and of both Zr2Cu and Cu2ZrAl for the Al-containing ternary alloys.
39
Liu, Chih-Hua, and 柳智華. "Zr-Cu-Ni Phase Diagram at 800℃." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/35921417714601195951.
Анотація:
碩士國立中山大學
材料科學研究所
92
Zirconium base alloys have very good metallic glass forming ability. In this study,the Zr-Cu-Ni ternary isotherm at 800℃ were determined by using metallography,electron-probe microanalysis and X-ray diffraction.The main objective is to provide the necessary information for alloy design to form new Zr-base with better glass forming ability.
40
Chen, Chih-jung, and 陳致榮. "Preparation and Characterization of Sputtered Zr-Ti and Zr-Cu Thin Film Metallic Glasses." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/2sepbs.
41
Chen, Bo-Jyun, and 陳柏均. "Determination of the amorphous regions of the Cu-Zr-Ag ternary system and the phase equilibria of Cu-Zr-Ag, Cu-Al-Ag ternary systems at 500oC." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/23320511711154954591.
Анотація:
碩士國立臺灣科技大學
材料科學與工程系
100
Bulk metallic glasses (BMGs) have attracted many interests in recent years because their strong mechanical properties, excellent corrosion resistance and good permeability. Zr-Cu based systems have high glass-forming ability (GFA)while Ag is easy to obtain. In this study, Cu-Zr-Ag alloys with different compositions were prepared, and the BMGs were produced by arc melting and copper mold. For comparison, the phase equilibria of Cu-Zr-Ag and Cu-Al-Ag ternary systems was investigated at 500oC. As the result, the best glass-forming ability (GFA) was obtained by the Cu45Zr45Ag10 alloy. In general, the amorphous region of Cu-Zr-Ag ternary system is Cu35-50Zr40-55Ag10-20. While amorphous and crystalline structures existed simultaneously in the region of Cu30-50Zr30-55Ag0-30. According to the results of phase equilibria, there were 9 single-phase regions, 15 two-phase regions and 7 three-phase regions in Cu-Zr-Ag ternary system at 500oC, and no ternary compound was found. On the other hand, in the Cu-Al-Ag ternary system, there were 8 single-phase regions, 13 two-phase regions and 6 three-phase regions but there was no ternary compound at 500oC.
42
"Estudo da degradação dos eletrodos Cu/Zr e Cu/Cr/Zr utilizados na soldagem de aços revestidos com Zn e liga Zn-Fe." Tese, Biblioteca Digital de Tese e Dissertação da UFF, 1998. http://www.bdtd.ndc.uff.br/tde_busca/arquivo.php?codArquivo=1397.
43
Kosiba, Konrad. "Flash-Annealing of Cu-Zr-Al-based Bulk Metallic Glasses." Doctoral thesis, 2016. https://tud.qucosa.de/id/qucosa%3A30262.
Анотація:
(Bulk) metallic glasses ((B)MGs) are known to exhibit the highest yield strength of any metallic material (up to 5GPa), and show an elastic strain at ambient conditions, which is about ten times larger than that of crystalline materials. Despite these intriguing mechanical properties, BMGs are not used as structural materials in service, so far. The major obstacle is their inherent brittleness, which results from severe strain localization in so-called shear bands. MGs fail due to formation and propagation of shear bands. A very effective way to attenuate the brittle behaviour is to incorporate crystals into the glass. The resulting BMG composites exhibit high strength as well as plasticity. Cu-Zr-Al-based BMG composites are special to that effect, since they combine high strength, plasticity and work-hardening.
They are comprised of the glass and shape-memory B2 CuZr crystals, which can undergo a deformation-induced martensitic transformation. The work-hardening originates from the martensitic transformation and overcompensates the work-softening of the glass. The extent of the plasticity of BMG composites depends on the volume fraction, size and particularly on the distribution of the B2 CuZr crystals. Nowadays, it is very difficult, if not impossible to prepare BMG composites with uniformly distributed crystals in a reproducible manner by melt-quenching, which is the standard preparation method. Flash-annealing of BMGs represents a new approach to overcome this deficiency in the preparation of BMG composites and is the topic of the current thesis. Cu46Zr46Al8 and Cu44Zr44Al8Hf2Co2 BMGs were flash-annealed and afterwards investigated in terms of phase formation, crystallization kinetics and mechanical properties. Flash-annealing is a process, which is characterized by the rapid heating of BMGs to predefined temperatures followed by instantaneous quenching. A temperature-controlled device was succesfully developed and built. The Cu-Zr-Al-based BMGs can be heated at rates ranging between 16 K/s and about 200 K/s to temperatues above their melting point. Rapid heating is followed by immediate quenching where cooling rates of the order of 1000 K/s are achieved.
As a BMG is flash-annealed, it passes the glass-transition temperature, Tg, and transforms to a supercooled liquid. Further heating leads to its crystallization and the respective temperature, the crystallization temperature, Tx, divides the flash-annealing of BMGs into two regimes:
(1) sub-Tx-annealing and (2) crystallization.
The structure of the glass exhibits free volume enhanced regions (FERs) and quenched-in nuclei. Flash-annealing affects both heterogeneities and hence the structural state of the glass. FERs appear to be small nanoscale regions and they can serve as initiation sites for shear bands. Flash-annealing of Cu-Zr-Al-based BMGs to temperatures below Tg leads to structural relaxation, the annihilation of FERs and the BMG embrittles. In contrast, the BMG rejuvenates, when flash-annealed to temperatures of the supercooled liquid region (SLR). Rejuvenation is associated with the creation of FERs. Compared to the as-cast state, rejuvenated BMGs show an improved plasticity, due to a proliferation of shear bands, which are the carrier of plasticity in MGs. Flash-annealing enables to probe the influence of the free volume in bulk samples on their mechanical properties, which could not be studied, yet.
In addition, B2 CuZr nanocrystals precipitate during the deformation of flash-annealed Cu44Zr44Al8Hf2Co2 BMGs. Deformation-induced nanocrystallization does not occur for the present as-cast BMGs. Flash-annealing appears to stimulate the growth of quenched-in nuclei, which are subcritical in size and can also dissolve, once the BMG is heated to temperatures in the SLR. Rejuvenation represents a disordering process, whereas the growth of quenched-in nuclei is associated with ordering. There is a competition between both processes during flash-annealing. The ordering seems to lead to a “B2-like” clustering of the medium range of Cu44Zr44Al8Hf2Co2 BMGs with increasing heating duration. So far, there does not exist another method to manipulate the MRO of BMGs. If Cu44Zr44Al8Hf2Co2 BMGs are flash-annealed to temperatures near Tx, most likely compressive resiudal stresses develop near the surface, which is cooled faster than the interior of the BMG specimen. They hinder the propagation of shear bands and increase the plasticity of flash-annealed BMGs in addition to rejuvenation and deformation-induced nanocrystallization.
If BMGs are heated to temperatures above Tx, they start to crystallize. Depending on the exact temperature to which the BMG is flash-annealed and subsequently quenched, one can induce controlled partial crystallization. Consequently, BMG composites can be prepared. Both Cu-Zr-Al-based BMGs are flash-annealed at various heating rates to study the phase formation as a function of the heating rate. In addition, Tg and Tx are identified for each heating rate, so that a continuous heating transformation diagram is constructed for both glass-forming compositions. An increasing heating rate kinetically constrains the crystallization process, which changes from eutectic (Cu10Zr7 and CuZr2) to polymorphic (B2 CuZr). If the Cu-Zr-Al-based BMGs are heated above a critical heating rate, exclusively B2CuZr crystals precipitate, which are metastable at these temperatures. Thus, flash-annealing of Cu46Zr46Al8 and Cu44Zr44Al8Hf2Co2 BMGs followed by quenching enables the preparation of B2 CuZr BMG composites. The B2 precipitates are small, high in number and uniformly distributed when compared to conventional BMG composites prepared by melt-quenching. Such composite microstructures allow the direct observation of crystal sizes and numbers, so that crystallization kinetics of deeply supercooled liquids can be studied as they are flash-annealed. The nucleation kinetics of devitrified metallic glass significantly diverge from the steady-state and at high heating rates above 90 K/s transient nucleation effects become evident. This transient nucleation phenomenon is studied experimentally for the first time in the current thesis. Once supercritical nuclei are present, they begin to grow. The crystallization temperature, which depends on the heating rate, determines the crystal growth rate. At a later stage of crystallization a thermal front traverses the BMG specimen. In levitation experiments, this thermal front is taken as the solid-liquid interface and its velocity as the steady-state crystal growth rate. However, the thermal front observed during flash-annealing, propagates through the specimen about a magnitude faster than is known from solidification experiments of levitated supercooled liquids. As microstructural investigations show, crystals are present in the whole specimen, that means far ahead of the thermal front. Therefore, it does not represent the solid-liquid interface and results from the collective growth of crystals in confined volumes. This phenomenon originates from the high density of crystals and becomes evident during the heating of metallic glass. It could be only observed for the first time in the current thesis due to the high temporal resolution of the high-speed camera used.
The heating rate and temperature to which the BMG is flash-annealed determine the nucleation rate and the time for growth, respectively. The size and number of B2 CuZr crystals can be deliberately varied. Thus mechanical properties of B2 CuZr BMG composites can be studied as a function of the volume fraction and average distance of B2 particles. Cu44Zr44Al8Hf2Co2 BMG specimens were flash-annealed at a lower and higher heating rate (35 K/s and 180 K/s) to different temperatures above Tx and subsequently subjected to uniaxial compression. BMG composites prepared at higher temperatures show a lower yield strength and larger plastic strain due to the higher crystalline volume fraction. They not only exhibit plasticity in uniaxial compression, but also ductility in tension as a preliminary experiment demonstrates. Furthermore, nanocrystals precipitate in the amorphous matrix of BMG composites during deformation. They grow deformation-induced from quenched-in nuclei, which are stimulated during flash-annealing.
In essence, flash-annealing of BMGs is capable of giving insight into most fundamental scientific questions. It provides a deeper understanding of how annealing affects the structural state of metallic glasses. The number and size of structural heterogeneities can be adjusted to prepare BMGs with improved plasticity. Furthermore, crystallization kinetics of liquids can be studied as they are rapidly heated. Transient nucleation effects arise during rapid heating of BMGs and they cannot be described using the steady-state nucleation rate. Therefore, an effective nucleation rate was introduced. Besides, the flash-annealing process rises the application potential of BMGs. The microstructure of BMG composites comprised of uniformly distributed crystals and the glass, can be reliably tailored. Thus, flash-annealing constitutes a novel method to design the mechanical properties of BMG composites in a reproducible manner for the first time. BMG composites, which exhibit high strength, large plasticitiy and as in the case of B2 CuZr BMG composites as well work-hardening behaviour, can be prepared, so that the intrinsic brittleness of monolithic BMGs is effectively overcome.
44
Zhang, Yi-zong, and 張益綜. "Zr-based and Zr-Cu based Glass-forming Films for Fatigue-property Improvements of 7075-T6 Aluminum Alloy." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/98008095198122246510.
Анотація:
碩士國立中央大學
機械工程研究所
99
We proposed with the Zr-based and Zr-Cu based metallic glass thin film (MGTF) as promising coating for aluminum alloy fatigue property enhancement. According to the four-point-bending fatigue results, 7075-T6 aluminum alloy with a 200-nm-thick Zr-based MGTF improved its fatigue life cycle 22 times at a stress level of 250 MPa than the bare one. And the other fatigue life cycle of Zr-Cu based MGTF is further improved 44 times which ups to 107 cycles. The improvements of MGTF coating samples in fatigue limit were 235 MPa (56.7 % increase) and 250 MPa (66.7 % increase) for Zr-based and Zr-Cu based glass-forming film, respectively, and 150 MPa for uncoated sample. The films actually restrict the surface offsets and cracks propagating during the fatigue test. Zr-Cu based glass-forming film have better fatigue resistance than Zr-based MGTF, the fatigue life had improved by more than 2 times under a stress of 250 MPa, due to higher hardness and strength, better plasticity, thus it exhibits better improvement in fatigue property. A 50-nm-thick Titanium buffer layer between the film and the substrate was reported adhesion enhancement. The superior mechanical properties of MGTF, such as high strength and good bending ductility, coupled with good adhesion between the film and the substrate as well as the reduced surface roughness, and high compressive residual stress of the metallic film yield the fatigue property improvement of aluminum alloy. Thus demonstrating MGTF as promising coating materials for improving the fatigue properties of materials, and further applied to aerospace, automobile industry and bicycle manufacturing etc.
45
Shih, Chih-Hsiung, and 施志雄. "The measurement of Ti-Zr-Cu-Ni phase diagram at 800℃." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/76998752147969416797.
46
Yang, Ta-Kai, and 楊達凱. "Effect of Sn addition on the Cu-Zr-Ti amorphous alloys." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/a2863n.
Анотація:
碩士大同大學
材料工程學系(所)
93
This study examined the effect of Sn element addition on the Cu-Zr-Ti amorphous alloys by mechanical alloying technique. The microstructural evolution during mechanical alloying of the mixed powders was investigated by both X-ray diffraction and scanning electron microscopy (SEM).The phase stabilities of the as-milled powders were studied by DSC measurement. According to the result, after 5 hours of milling, the composition of Cu-Zr-Ti-Sn alloys were all amorphization. The thermal stability of the Cu-Zr-Ti-Sn amorphous powder was also investigated by differential scanning calorimeter (DSC). As the results demonstrated, the amorphous powder were found to exhibit a wide supercooled liquid region before crystallization. The temperature interval of the supercooled liquid region was defined by the difference between Tg and Tx. The highest value of △T was found to exhibit at Cu46Zr30Ti20Sn4 alloys system (93K). Finally, the small addition of Sn element significantly improved the glass forming ability (GFA) of Cu-Zr-Ti amorphous alloys.
47
Kao, Pei-Chin, and 高佩琴. "The Oxidation Behavior of Cu-Zr-Al-Ag Bulk Metallic Glasses." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/97446194829799000309.
Анотація:
碩士國立臺灣海洋大學
材料工程研究所
97
The oxidation behavior of three Cu-Zr based bulk metallic glasses, containing Cu45Zr45Al5Ag5 (CZ45-BMG), Cu43Zr43Al7Ag7 (CZ43-BMG), and (Cu43Zr43Al7Ag7)99.5Si0.5(CZ43S-BMG) was studied over the temperature range of 375 – 500oC in dry air. The oxidation kinetics of the three glassy alloys generally followed a multi-stage parabolic-rate law, and the steady-state parabolic-rate constants (kp values) fluctuated with temperature. It was found that kp values increased with increasing temperature, when it was below the supercooled region, however, those values decreased with increasing temperature at T > 450oC. The scales formed these BMGs consisted mostly of tetragonal-ZrO2 (t-ZrO2), CuO, minor amounts of monoclinic- and orthorhombic-ZrO2, (m- and o-ZrO2), and α-Al2O3 (only detected at 500oC). The formation of α-Al2O3 was responsible for the reduction of oxidation rates of these BMGs at 500oC. ZrO2 of different structures was depended strongly on temperature and duration of time. In addition, small amounts of Ag and Si addition increased glass forming ability (GFA) and provided a better oxidation resistance at T < 425oC. However, no improvement was obtained at higher temperatures. In addition, three amorphous substrates retained unchanged at the temperature below the glass-transition temperature (Tg), however they underwent a pre-oxidation process and followed by the phase transformation after the oxidation at T > 400oC, having a dual-phase structure of Cu10Zr7 and ZrAl for both CZ45- and CZ43-BMG. On the other hand, CZ43S-BMG substrate transformed from the fully amorphous to the mostly Cu10Zr7 and minor Si2Zr crystallines. In summary, CZ45-BMG exhibited a better thermal stability among these BMGs studied.
48
Yang, Man-Ning, and 楊曼寧. "Fabrication and Thermal Properties of Diamond/Cu-Zr Electronic Packaging Composites." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/55661231363056225199.
49
Tsai, Jian-Cheng, and 蔡建丞. "Sutdy on Zr-based amorphous alloys roll bonding with Cu sheet." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/k4p8z9.
Анотація:
碩士義守大學
材料科學與工程學系
106
Amorphous alloys have excellent mechanical properties, but it lack of ability of plastic deformation and dutility at room temperature. In order to improve these disadvantage, there are many methods that can improve the properties have been developed. For example, thermal treatments, adding of elements, rolling and so on. Zr53Cu30Ni9Al8, this bulk metallic glasses has good glass forming ability, its γm is about 0.739 and wide supercooled liquid region, its ΔTx is about 80K. In this study, for research the working ability of bulk metallic glasses at room temperature, the Cu sheets have been chosen to place at the upside and downside of Zr53Cu30Ni9Al8 bulk metallic glasses to carry out the roll bonding to disperse stress distribution and achieve the goal of average deformation, make bulk metallic glasses and Cu sheet become a composite material. The thin metal coating slows down shear band dynamics and retards its attainment to a critical unstable state. It not only is beneficial to working of bulk metallic glasses but also can keep the thermal properties of bulk metallic glasses, that is different from warm rolling. This study also through Zr53Cu30Ni9Al8 bulk metallic glasses roll bonding with Cu sheet to investigate how the process of roll bonding influence the effet of roll bonding, like surface treatments, the rolling direct of roll bonding, the reduction rate of roll bonding and the thickness of bulk metallic glasses.
50
Xie, Sujing. "Plastic Deformation and Annealing of Zr- and Cu- Based Bulk Metallic Glasses." 2007. http://etd.utk.edu/2007/XieSujing.pdf.