Tesis sobre el tema "Cu-based alloy"
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Howard, P. "Precipitation and creep in an Al-Zn-Mg-Cu based alloy". Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356709.
Texto completoVargas, Ignacio Alejandro Figueroa. "Processing, structures and properties of some bulk cu-based alloy glasses". Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489379.
Texto completoSzablinski, Eric (Eric Allen). "Systematic study of the Taylor method for production of cu-based shape memory alloy microwires : a master's thesis". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/79564.
Texto completoCataloged from PDF version of thesis.
Includes bibliographical references (p. 39-40).
The Taylor method is a proven way to produce Cu-based shape memory microwires that aren't plagued by problems typical in polycrystalline copper SMAs produced by other methods. Here we set out to expand and refine this processing method to take the first critical steps toward large-scale continuous production. Using a semi-automated processing route, we draw continuous, uniform fibers up to 5 meters in length with diameters in the range 10 - 35 microns. Particular attention is paid to microwires made from a Cu-Sn shape memory alloy. In addition, because the properties of shape memory microwires depend on their diameter, processing parameters were varied to understand their impact on the diameters of the resulting wires.
by Eric Szablinski.
S.M.
Arslan, Hulya. "Synthesis And Characterization Of Nickel Based Bulk Amorphous Alloys". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/12605099/index.pdf.
Texto completoAbid, Fatma. "Contribution à la robustesse et à l'optimisation fiabiliste des structures Uncertainty of shape memory alloy micro-actuator using generalized polynomial chaos methodUncertainty of shape memory alloy micro-actuator using generalized polynomial chaos method Numerical modeling of shape memory alloy problem in presence of perturbation : application to Cu-Al-Zn-Mn specimen An approach for the reliability-based design optimization of shape memory alloy structure Surrogate models for uncertainty analysis of micro-actuator". Thesis, Normandie, 2019. http://www.theses.fr/2019NORMIR24.
Texto completoThe design of economic system leads to many advances in the fields of modeling and optimization, allowing the analysis of structures more and more complex. However, optimized designs can suffer from uncertain parameters that may not meet certain reliability criteria. To ensure the proper functioning of the structure, it is important to consider uncertainty study is called the reliability analysis. The integration of reliability analysis in optimization problems is a new discipline introducing reliability criteria in the search for the optimal configuration of structures, this is the domain of reliability optimization (RBDO). This RBDO methodology aims to consider the propagation of uncertainties in the mechanical performance by relying on a probabilistic modeling of input parameter fluctuations. In this context, this thesis focuses on a robust analysis and a reliability optimization of complex mechanical problems. It is important to consider the uncertain parameters of the system to ensure a robust design. The objective of the RBDO method is to design a structure in order to establish a good compromise between the cost and the reliability assurance. As a result, several methods, such as the hybrid method and the optimum safety factor method, have been developed to achieve this goal. To address the complexity of complex mechanical problems with uncertain parameters, methodologies specific to this issue, such as meta-modeling methods, have been developed to build a mechanical substitution model, which at the same time satisfies the efficiency and the precision of the model
Xie, Chenyang. "Corrosion studies on Cu-based alloys". Doctoral thesis, Universitat Politècnica de Catalunya, 2021. http://hdl.handle.net/10803/671526.
Texto completoEls aliatges de coure es fan servir freqüentment en entorns corrosius. La millora de la resistència a la corrosió reduiria notablement el consum d’energia i la sobreexplotació de recursos naturals. Nou derivats de l’imidazol amb diferents grups funcionals ha estat analitzats com a potencials inhibidors de la corrosió, per tal d’augmentar la resistència a la corrosió del Cu. S’escolliren derivats de l’imidazol a la vista de la seva resposta diferent com a inhibidors de la corrosió en Cu pur. Aquest inhibidors han estat aplicats sobre els metalls purs i sobre aliatges CuZn i CuZr cristal·lines i amorfes, per tal d’explorar les correlacions entre inhibició, estructura i espècies atòmiques. La determinació de l’eficiència d’inhibició en metalls és un problema complex a causa de la influència creuada entre les condicions a la superfície, la interacció inhibidor-superfície i les condicions ambientals. En aliatges CuZn s'han estudiat les composicions Cu70Zn30 (fase a-Cu) i Cu30Zn70 (fase no-a-Cu). Els aliatges CuZr són la base d'una família de vidres metàl·lics amb gran capacitat d’amortització i excel·lents propietats mecàniques. S'ha determinat la resistència a la corrosió d'aliatges cristal·lins i amorfs de composició CuxZr (100-x) (x = 40, 50, 64 at.%). Tots els aliatges van ser analitzades en dissolució aquosa contenint un 3% de NaCl en pes, sense i amb una concentració de 1mM de l'inhibidor. S'han efectuat mesures dinàmiques de polarització, espectroscòpia d'impedància electroquímica i immersió durant períodes prolongats seguida de microscòpia i espectroscòpia Raman. L'anàlisi comparativa mostra que els inhibidors efectius en Cu pur ho són també en Cu70Zn30. Un comportament similar apareix entre Zn i Cu30Zn70. No obstant això, el poder d'inhibició mostra un valor molt diferent, que s'atribueix a l'efecte de "cicatrització". Els defectes presents en la majoria de les mostres acceleren la corrosió localitzada (pitting) en aquests punts. L'efecte de cicatrització produeix "pegats" en les mateixes posicions, el que redueix la velocitat de l'atac localment. Els aliatges CuZr cristal·lins mostren una resistència a la corrosió molt més alta que els aliatges cristal·lins amb la mateixa composició, originalment i en presència d'inhibidors. El principal factor que controla la resistència a la corrosió dels aliatges és l'alta concentració de Zr (al menys equiatòmica) en l'estructura amorfa; l'efecte dels inhibidors resulta ser secundari. Els resultats mostren una relació complexa entre l'eficiència de l'inhibidor, la microestructura i la composició dels aliatges CuZr. SH-ImiH-4Ph mostra potencial per inhibir la corrosió en aliatges on la fase dominant és a-Cu, mentre que SH-BimH-5NH2 mostra potencial com a inhibidor en aliatges on el Zn és majoritari i en aliatges CuZr. Les mesures electroquímiques, especialment de llarga durada, mostren una bona correlació amb les anàlisis d'immersió. La recerca realitzada ofereix elements de comprensió del mecanisme de corrosió en presència d'inhibidors. L'oxidació pre-existent de la superfície, els defectes en la superfície i el grup funcional de l'inhibidor són els factors dominants en l'efectivitat dels inhibidors. L'efecte de cicatrització afecta també notablement el rendiment d'alguns inhibidors.
Heil, Joseph Patrick. "Damping and microstructures in aged Cu-Mn based alloys". Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23000.
Texto completoHolsten, Guy Victor. "Phase transformations and microstructural evolution in aged Mn-Cu-based alloys". Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA232473.
Texto completoThesis Advisor(s): Perkins, Jeff. "June 1990." Description based on title screen as viewed on March 22, 2010. DTIC Identifier(s): Alloys, Spinodal Decomposition, Flickering, Damping. Author(s) subject terms: High Damping Alloys, Spinodal Decomposition, Cu-Mn alloys, Flickering. Includes bibliographical references (p. 85-92). Also available in print.
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.
Texto completoLiu, Dan. "Thixoforming of high performance alloys mainly based on the Al-Cu system". Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401159.
Texto completoAsgharzadeh, 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.
Texto completoThe 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
Peng, Lu. "Metal Nanoparticles Wrapped on Defective Nitrogen-doped Graphitic Carbons as Highly Selective Catalysts for C02 Hydrogenation". Doctoral thesis, Universitat Politècnica de València, 2021. http://hdl.handle.net/10251/172329.
Texto completo[CA] Tenint en compte l'esgotament dels combustibles fòssils i la creixent concentració de CO2 en l'atmosfera, la hidrogenació de CO2 és una forma prometedora de convertir el CO2 en productes químics i combustibles de carboni d'alt valor afegit. Considerant la gran influència de la grandària de partícula, la composició química, la naturalesa del suport i les condicions d'operació sobre el comportament catalític dels catalitzadors, s'han desenvolupat una sèrie de catalitzadors per a la hidrogenació de CO2 basats en metalls abundants no nobles i polisacàrids naturals com a precursors del grafé. En la present tesi doctoral, les espècies metàl·liques suportades sobre una matriu de carboni grafític defectuosa, amb diferents grandàries de partícules, mostren diferent activitat catalítica i selectivitat per a la hidrogenació de CO2. Es van preparar, de manera controlada, nanopartícules d'aliatges de Co i Co-Fe suportades en grafens dopats amb N defectuosos, amb una àmplia distribució de grandària de nanopartícules, per a la reacció de Sabatier, presentant una selectivitat a metà superior al 90% amb valors de conversió de CO2 superiors al 85%. En el cas d'un sol metall, Co o Fe, i els seus aliatges en forma de "clústers" i xicotetes nanopartícules suportades en el mateix material, la selectivitat de la hidrogenació de CO2 canvia a CO, en lloc de metà, obtenint-se un valor del 98% i aconseguint una conversió de CO2 del 56%. Convé ressaltar que, els catalitzadors basats en "clústers" d'aliatges de metall amb una càrrega de metall fins i tot per davall del 0.2% en pes, exhibeixen una major selectivitat i rendiment que els que tenen nanopartícules d'aliatges de Co-Fe més grans que varien d'1 a 4 nm i una càrrega de metall més alta en una composició similar. Seguint la línia d'investigació d'hidrogenació de CO2, es van desenvolupar una sèrie de nanopartícules d'aliatges de Co-Fe suportades sobre grafens dopats amb N defectuosos amb distribució de grandària de nanopartícules controlada en el rang de 7-17 nm, obtenint una selectivitat cap a hidrocarburs C2+ al voltant del 45% i una conversió del CO2 pròxima al 60%. A més, es va realitzar un estudi comparatiu de l'activitat catalítica de catalitzadors similars basats en Co-Fe amb promotors i inhibidors per a la hidrogenació de CO2, observant la seua influència en la conversió i selectivitat de CO2. Finalment, a més dels catalitzadors basats en Co-Fe, també s'han preparat catalitzadors basats en Cu-ZnO mitjançant un mètode de dos passos. Aquestes nanopartícules de Cu-ZnO suportades sobre grafé defectuós dopat amb N exhibeixen una alta selectivitat cap a la conversió de CO2 a metanol.
[EN] Considering the depletion of fossil fuels and the increasing atmospheric CO2 concentration, CO2 hydrogenation is a promising way to convert CO2 into value-added carbon-containing chemicals and fuels. Taking into account the significant influences of the particle size, chemical composition, nature of the support, and operation conditions on the catalytic performance of catalysts, a series of catalysts for CO2 hydrogenation have been developed based on the use of abundant non-noble metals and natural polysaccharides as graphene precursors. In the present PhD Thesis, metal species supported on defective graphitic carbon matrix with different particle sizes show different catalytic activity and selectivity for CO2 hydrogenation. Under effective control, Co and Co-Fe alloy nanoparticles wrapped on defective N-doped graphenes with a broad nanoparticle size distribution were prepared and performed for the Sabatier reaction, exhibiting a selectivity to methane over 90 % at CO2 conversion values over 85 %. In the case of single Co or Fe metal and their alloys in the form of clusters and small nanoparticles wrapped on the same support, the selectivity for CO2 hydrogenation shifts to CO, rather than methane, reaching a conversion of 56 % with 98 % CO selectivity. It is worth noting that the metal alloy clusters-based catalysts with the metal loading even below 0.2 wt.% exhibit a higher selectivity and better performance than the ones with larger Co-Fe alloy nanoparticles ranging from 1-4 nm and higher metal loading in a similar composition. Following the research line for CO2 hydrogenation, a series of Co-Fe alloy nanoparticles supported on defective N-doped graphenes with controlled nanoparticle size distribution in the range of 7-17 nm are developed, obtaining a selectivity towards C2+ hydrocarbons about 45% with a CO2 conversion close to 60%. In addition, a comparative catalytic activity of similar Co-Fe-based catalysts with promoters and poison has been studied for CO2 hydrogenation to observe their influence on CO2 conversion and selectivity. Finally, besides Co-Fe-based catalysts, Cu-ZnO-based catalysts have also been prepared by a two-step method. These Cu-ZnO nanoparticles supported on N-doped defective graphene exhibit a high selectivity for CO2 conversion to methanol.
Peng, L. (2021). Metal Nanoparticles Wrapped on Defective Nitrogen-doped Graphitic Carbons as Highly Selective Catalysts for C02 Hydrogenation [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/172329
TESIS
Javidani, Mousa. "Effect of Cu, Mg and Fe on solidification processing and microstructure evolution of Al-7Si based foundry alloys". Doctoral thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/26146.
Texto completoOver the past decade, Al-Si based foundry alloys have increasingly been used as a suitable alternative for cast iron in the fabrication of engine components. This project was aimed to study the effect of Cu, Mg and Fe elements on solidification defects (hot rearing tendency and microporosity), and on evolution of post eutectic phases in the Al-7Si (wt.-%) based alloys. Initially, the previous works and the most pertinent literatures were thoroughly reviewed to elaborate the thermo-mechanical fatigue loads, characteristics, requirements and materials applicable in engine components (mainly cylinder-head). Subsequently, the solidification defects of the Al-Si based alloys were evaluated. By increasing Cu and Fe content of the alloys, the hot tearing sensitivity and the microporosity content of the alloys were both enhanced. Multiphase back diffusion model was utilized to simulate the theoretical hot tearing indices. A very good correlation was obtained between the experimental and the theoretical hot tearing indices. Effect of the chemistry (Cu, Mg and Fe content) on microstructure evolution of the Al-Si foundry alloys was consequently studied. As-cast and solution heat treated (SHT) microstructures of the alloys were evaluated by optical- and electron-microscopy. Two etchants were developed to discriminate the Mg-bearing intermetallics (Q-Al5Cu2Mg8Si6, π- Al8FeMg3Si6) under optical microscope. Differential scanning calorimetry (DSC) was utilized to examine the phase transformations occurring during heating/cooling process. Thermodynamic computations were carried out to assess the phase formation in the equilibrium/non-equilibrium conditions. According to the predicted/experimental results, the solidification sequence and the stability of Cu/Mg bearing intermetallics are strongly influenced by the chemistry of the alloys. Q-Al5Cu2Mg8Si6 phase was solidified either at the same temperature or earlier than θ-Al2Cu phase depending the Cu content of the alloy. Moreover, Q-Al5Cu2Mg8Si6 and π- Al8FeMg3Si6 which were soluble at 505℃ in the alloy Al-7Si-1.5Cu-0.4Mg, remained almost intact in the alloy Al-7Si-1.5Cu-0.8Mg wt.-%. Tough the AlCuFe- intermetallic was barely observed in the as-cast microstructure, the reaction of α-Al with the β-Al5FeSi phase caused the formation of the N-Al7Cu2Fe phase during SHT. The solid state phase transformation (precipitation temperature and mechanism) of β-Al5FeSi to the N-Al7Cu2Fe phase was also investigated.
Rakhmonov, Jovid. "Development and characterization of a new generation of transition elements based secondary Al-Si-Cu-Mg foundry alloys". Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3425241.
Texto completoSecondary Al-Si-Cu-Mg based foundry alloys are widely used in automotive industry to particularly produce powertrain cast components mainly due to their good ratio between weight and mechanical properties, and excellent casting characteristics. Presence of impurity elements, such as Fe, Mn, Cr, Ti, V and Zr, in secondary Al-Si alloys is one of the critical issues since these elements tend to reduce alloy mechanical properties. There is an ongoing effort to control the formation of intermetallic phases containing transition metals, during alloy solidification. Although phases formation involving these transition metal impurities in non-grain-refined Al-Si alloys is well documented in the literature, the role of grain refinement in microstructural evolution of secondary Al-Si-Cu-Mg alloys needs further experimental investigations since chemical grain refinement is one of the critical melt treatment operations in foundries. The primary aim of this PhD work is thus defined to characterize the formation of intermetallic phases containing transition metals in secondary Al-7Si-3Cu-0.3Mg alloy before and after grain refinement by different master alloys and contribute to the understanding of the mechanisms underlying the microstructural changes occurring with the addition of grain refiner. Another critical issue related to Al-Si-Cu-Mg alloys is their limited thermal stability at temperatures above 200 oC. The operating temperature in engine combustion chamber is reported to often exceed 200 oC during service. Moreover, a further increase of operating temperature is anticipated due to the expected engine power enhancement in near future, which indicates the necessity for the development of a new creep-resistant Al alloys. Deliberate addition of transition metals is believed to yield a new heat-resistant alloy by promoting the formation of thermally stable dispersoids inside α-Al grains. This study thus also attempted to investigate the effect of adding transition metals Zr, V and Ni on the solidification processing, microstructural evolution and room/high-temperature tensile properties of secondary Al-7Si-3Cu-0.3Mg alloy, one of the most used alloys in automotive engine manufacturing. The influence of transition metal impurities on microstructural evolution of secondary Al-7Si-3Cu-0.3Mg alloy was investigated before and after chemical treatment with different master alloys: Al-10Sr, Al-5Ti-1B, Al-10Ti and Al-5B. The Al-10Zr, Al-10V and Al-25Ni master alloys were used for the experimental investigations of the effects of deliberate additions of transition metals on the solidification path, microstructure and mechanical properties of secondary Al-7Si-3Cu-0.3Mg alloy. Solidification path of the alloys was characterized by the traditional thermal analysis technique and differential scanning calorimetry (DSC). Optical microscope (OM), scanning electron microscope (SEM) equipped with energy-dispersive (EDS), wavelength-dispersive spectrometers (WDS) and electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) equipped with EDS were used to characterize the type, morphology and distribution of the phases precipitated during solidification and heat treatment of the studied alloys. The static tensile properties of the alloys were characterized at room (20 oC) and high temperatures (200 and 300 ºC). Experimental findings indicate that the Sr-modification and grain refinement of secondary Al-7Si-3Cu-0.3Mg alloy with Al-Ti-B can be enough effective despite the presence of transition metal impurities in the material and the variation of pouring temperature. However, the V and Zr (~100 ppm each) available in secondary Al-7Si-3Cu-0.3Mg alloy tended to promote the precipitation of harmful, primary AlSiTi intermetallics during solidification of grain-refined alloy. This implies that more effective optimization of grain refiner addition level in secondary Al foundry alloys can be achieved by considering the role of transition metal impurities, Ti, V and Zr, since the formation of primary AlSiTi particles causes (1) the depletion of Ti needed for effective α-Al grains growth restriction and (2) the formation of casting defects, such as shrinkage, due to their flaky morphology. Iron available in secondary Al-7Si-3Cu-0.3Mg alloy as impurity only formed more desirable α-Al15(FeMn)3Si2 phase in non-grain refined state. After grain refinement by Al-5Ti-1B, Fe was also involved in the formation of more deleterious β-Al5FeSi phase. The TiB2 particles acted as nucleation site for β-Al5FeSi phase. Both higher cooling rate and higher Al-5Ti-1B addition levels tended to promote the formation of deleterious β-Al5FeSi at the expense of α-Al15(FeMn)3Si2 in the alloy refined by Al-5Ti-1B. This implies that rather than the ratio between Mn and Fe, the nucleation kinetics of Fe-rich intermetallics play a decisive role in the selection of competing α-Al15(FeMn)3Si2 and β-Al5FeSi intermetallic phases for the precipitation during alloy solidification. Moreover, grain refinement of secondary Al-7Si-3Cu-0.3Mg alloy by Al-5B showed comparable performance to that of Al-5Ti-1B master alloy, however, without any deleterious influence on the precipitation sequence of Fe-rich phases, i.e. deleterious β-Al5FeSi reaction remained unfavourable during alloy solidification. Experimental findings from the investigations of the effect of deliberate Zr and V addition revealed that Zr and V addition can induce the grain refinement of secondary Al-7Si-3Cu-0.3Mg alloy. While Zr addition yielded the formation of pro-peritectic Zr-rich particles, which are found to nucleate primary α-Al at low undercooling, the effect of adding V can be characterized by the enhancement of the degree of constitutional undercooling. Combined Zr and V addition showed more effective grain refinement level than their individual additions. Majority of both Zr and V added to the alloy were retained inside α-Al matrix during solidification. As a result, limited amounts of Zr and V were rejected to the interdendritic liquid by the growing α-Al dendrites, then forming small-sized and rarely distributed intermetallics. Owing to its low solid solubility in α-Al, nickel available as impurity (~ 200 ppm) or after deliberate addition (0.25 wt.%) in secondary Al-7Si-3Cu-0.3Mg alloy was mainly bound to interdendritic, insoluble intermetallics, such as Al6Cu3Ni and Al9(FeCu)Ni phases. The presence of ~ 200 ppm Ni was sufficient to diminish to a certain extent the precipitation hardening effect of Cu. Interdendritic Zr/V/Ni-rich phases remained undissolved into the α-Al matrix during solution heat treatment. Therefore, the supersaturated transition metals in α-Al solid solution obtained during solidification was only involved in the solid-state precipitation occurring during heat treatment. Unlike Cu/Mg-rich strengthening precipitates that commonly form during aging, the Zr/V-rich precipitates tended to form during solution heat treatment. Other transition metals, such as Mn, Fe, Cr and Ti, which were present as impurities in secondary Al-7Si-3Cu-0.3Mg alloy significantly promoted the formation of nano-sized Zr/V-rich precipitates inside α-Al grains. These thermally more stable precipitates, including novel α-Al(MnVFe)Si, were credited for the enhanced high-temperature strength properties of Al-7Si-3Cu-0.3Mg alloy by ~ 20 %.
Zhang, Duyao. "Thermodynamic characterisation of semi-solid processability in alloys based on Al-Si, Al-Cu and Al-Mg binary systems". Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/32538.
Texto completoPauly, Simon [Verfasser], Jürgen [Akademischer Betreuer] Eckert y Gianaurelio [Akademischer Betreuer] Cuniberti. "Phase formation and mechanical properties of metastable Cu-Zr-based alloys / Simon Pauly. Gutachter: Jürgen Eckert ; Gianaurelio Cuniberti. Betreuer: Jürgen Eckert". Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://d-nb.info/1069938998/34.
Texto completoAsgharzadeh, Javid Fatemeh [Verfasser], Jürgen [Akademischer Betreuer] Eckert y Michael [Gutachter] Zehetbauer. "Phase formation, martensitic transformation and mechanical properties of Cu-Zr-based alloys / Fatemeh Asgharzadeh Javid ; Gutachter: Michael Zehetbauer ; Betreuer: Jürgen Eckert". Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://d-nb.info/1119362547/34.
Texto completoZhang, Xian. "Atmospheric corrosion of zinc-aluminum and copper-based alloys in chloride-rich environments : Microstructure, corrosion initiation, patina evolution and metal release". Doctoral thesis, KTH, Yt- och korrosionsvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-151180.
Texto completoBättre molekylär förståelse för metallers atmosfäriska korrosion kräver en fördjupad kunskap i det dynamiska samspelet mellan atmosfärens korrosiva beståndsdelar och metallytan. Denna doktorsavhandling omfattar laboratorie- och fältundersökningar av korrosions- och metallfrigöringsprocesser av två grupper av legeringar som exponerats i kloridrika atmosfärsmiljöer: två kommersiella Zn-Al beläggningar på stål, Galfan™ (Zn med 5% Al, förkortat Zn5Al) och Galvalume™ (Zn55Al), samt fyra kopparbaserade legeringar (Cu4Sn, Cu15Zn, Cu40Zn och Cu5Zn5Al). Undersökningar har genomförts i renodlade laboratorie-miljöer med för-deponerade NaCl-partiklar i en atmosfär av varierande relativ fuktighet. Syftet har varit att utvärdera betydelsen av kloriders deposition och legeringarnas mikrostruktur på korrosionsmekanismen samt bildandet av korrosionsprodukter. Jämförelser av korrosionsmekanismer har även gjorts efter flerårsexponeringar av samma legeringar i en marin fältmiljö i Brest, Frankrike. Undersökningarna har baserats på ett brett spektrum av analysmetoder för detaljerade studier dels under pågående atmosfärisk korrosion (in-situ), och dels efter avslutad korrosion (ex-situ). Legeringarnas mikrostruktur och tillhörande variation i ädelhet hos olika faser har undersökts med svepelektronmikroskopi och energidispersiv röntgenmikroanalys (SEM/EDS) samt med en variant av atomkraftsmikroskopi (engelska: scanning Kelvin probe force microscopy, SKPFM). Korrosionsprodukternas tillväxt har analyserats in-situ med infraröd reflektions-absorptionsspektroskopi (IRAS), samt morfologi och sammansättning av bildade korrosionsprodukter ex-situ med SEM/EDS, konfokal Raman mikro-spektroskopi (CRM) samt röntgendiffraktion vid strykande ifall (GIXRD). Det multi-analytiska tillvägagångssättet har medfört att det komplexa samspelet mellan de skilda legeringarnas mikrostruktur, korrosionsinitiering och bildandet av korrosionsprodukter kunnat studeras i detalj. En tydlig påverkan av mikrostruktur på det initiala korrosionsförloppet har kunnat påvisas. Korrosionsinitieringen sker företrädesvis i mer zinkrika faser för såväl Zn-Al- som Cu-Zn-legeringar och orsakas av mikro-galvaniska effekter mellan de mer zinkrika, mindre ädla, faserna och omgivande faser. Deponerade NaCl-partiklar påskyndar den lokala korrosionen oberoende av mikrostruktur. Snarlika sekvenser av korrosionsprodukter har kunnat påvisas såväl efter laboratorie- som fältexponeringar. För Zn-Al-legeringar bildas först ZnO, ZnAl2O4 och/eller Al2O3, därefter Zn6Al2(OH)16CO3·4H2O och Zn2Al(OH)6Cl·2H2O och/eller Zn5(OH)8Cl2·H2O. På ren koppar bildas ett inre skikt dominerat av Cu2O, ett mellanskikt av CuCl och ett yttre skikt med i huvudsak Cu2(OH)3Cl. Beroende på legeringstillsats har även SnO2 och Zn5(OH)6(CO3)2 kunnat identifieras. En mekanism för flagning av korrosionsprodukter på kopparbaserade legeringar i kloridrika atmosfärer har utvecklats. Tendensen för flagning har visat sig vara mycket mer uttalad på ren Cu och Cu4Sn än på Cu15Zn och Cu5Al5Zn. Skillnaden kan förklaras med hjälp av det tidiga bildandet av Zn5(OH)6(CO3)2 och Zn6Al2(OH)16CO3·4H2O på Cu15Zn och Cu5Al5Zn som fördröjer bildandet av CuCl, en föregångare till Cu2(OH)3Cl. Därigenom hämmas även den observerade volymexpansionen som sker när CuCl omvandlas till Cu2(OH)3Cl, en process som visar sig vara den egentliga orsaken till att korrosionsprodukterna flagar. Resultaten bekräftar barriäreffekten hos de mer svårlösliga faserna Zn5(OH)6(CO3)2 och Zn6Al2(OH)16CO3·4H2O, vilken dels resulterar i en minskad växelverkan mellan klorider och de legeringsytor där dessa faser kan bildas, och dels i en reducerad metallfrigöringshastighet.
QC 20140915
Autocorr, RFSR-CT-2009-00015 Corrosion of heterogeneous metal-metal assemblies in the automotive industry
Atmospheric corrosion and environmental metal dispersion from outdoor construction materials
Guo, Siao-wei y 郭筱薇. "Developement of High-temperature Lead-free solders: Zn-Sn-Al-Cu Based Alloy". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/d63szw.
Texto completo國立臺灣科技大學
材料科學與工程系
99
Despite numerous studies on the research and development for high-temperature lead free solders, high-lead solder are still in used because high-temperature lead free solders also has been facing several serious problems during these years. Establishing high-temperature lead-free solder is an urgent priority. This study investigates the development of high-temperature lead-free solders and their properties by improve its wettability and oxidation resitivity after addition of Ni and Ge in Zn-Sn-Al-Cu based alloy. The solders are examined for microstructure, thermal properties, mechanical properties and investigate the interfacial reaction between Zn-Sn-Al-Cu based alloy with Cu and Ni/Cu at 300 and 350oC for 1, 2 and 4 hours. The experimental results indicate that the liquilidus temperature of Zn-Sn-Al-Cu based alloys is between 275oC to 375oC with Zn content. As Zn contents increase the (Zn) and CuZn5 increase, therefore resulting in the increase of micro-hardness and ultimate tensile strength and the addition of Al improve mechanical properties. Three or four intermetallic compounds (IMCs) are formed at the interface in the Cu/alloy diffusion couple. The reaction phases are identified as CuZn5, Al4Cu3Zn, ??nphase and CuZn is formed facing to the Cu substrate. The ??nphase is formed or not that is related to Al/Zn ratio. The IMCs are indentified as CuZn5, Al4Cu3Zn, (Zn), (Al) and?n??Sn phase in the alloys near the Ni/Cu substrate after reflow.
Hsu, Jhe-Ming y 許哲銘. "GaN-based Light-Emitting Diodes with Highly Reflective Ag-Pd-Cu Alloy Reflectors". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/pwz7my.
Texto completo國立交通大學
照明與能源光電研究所
102
This paper mainly aims to study the differences in photoelectrical characteristics between reflective metal pads (APC/Cr/Au and Ag/Cr/Au) on a GaN-based light emitting diode device and the application of a chromium metal adhesion layer. Reflective metal pads with Cr/APC/Cr/Au are expected to have high reflectance than those with Cr/Ag/Cr/Au,these reflective metal pads with Cr/APC/Cr/Au also have high light output power when used on a GaN-based light emitting diode device. The reflective metal pads with Cr/APC/Cr/Au further have lower specific contact resistance when they are used on N-GaN and ITO/P-GaN, respectively. Therefore, their applications in a GaN-based light emitting diode device can more effectively reduce the series resistance of the entire device, thereby causing the overall device to have lower forward voltage. First, the measured reflectance reveals that the reflectance of Cr/APC/Cr(10Å/600Å/500Å), Cr/APC/Cr(20Å/600Å/500Å),Cr/Ag/Cr(10Å/600Å/500Å), and Cr/Ag/Cr(20Å/600Å/500Å) in the 450 nm wavelength are 89.9%, 75.0%, 92.2%, and 81.9%, respectively. They have higher reflectance by comparing with the reflectance of Cr/Au(500Å/800Å), i.e., 38.9%. Second, this paper studies the ohmic contact properties of reflective metal pads (Cr/APC/Cr/Au and Cr/Ag/Cr/Au) on N-GaN and ITO/P-GaN, respectively. Under the conditions of Cr/APC/Cr/Au(10Å/600Å/500Å/800Å), Cr/APC/Cr/Au (20Å/600Å/500Å/800Å),Cr/Ag/Cr/Au(10Å/600Å/500Å/800Å),and Cr/Ag/Cr/Au(20Å/600Å/500Å/800Å), their specific contact resistances on N-GaN and ITO/P-GaN are 5.49 × 10-4, 6.55 × 10-5, 9.61 × 10-4, 8.91 × 10-5 and 6.58 × 10-2, 5.96 × 10-2, 8.69 × 10-2, and 7.82 × 10-2 Ω-cm2, respectively. This finding shows that the reflective metal pads with Cr/APC/Cr/Au can more effectively reduce the higher specific contact resistances with Cr/Ag/Cr/Au on N-GaN and ITO/P-GaN. Third and last, this paper probes the photoelectric properties of reflective metal pads(Cr/APC/Cr/Au and Cr/Ag/Cr/Au) on a GaN-based light emitting diode device. Using a 20mA injection current, the corresponding series resistances are 23.2, 20.5, 33.6, and 26.2Ω, whereas the corresponding forward voltages are 3.25, 3.14, 3.58, and 3.41 V, respectively, under the conditions of Cr/APC/Cr/Au(10Å/600Å/500Å/800Å), Cr/APC/Cr/Au(20Å/600Å/500Å/800Å), Cr/Ag/Cr/Au(10Å/600Å/500Å/800Å), Cr/Ag/Cr/Au(20Å/600Å/500Å/800Å). Moreover, the corresponding light output powers are 23.2, 21.7, 23.6, and 22.0 mW, whereas the corresponding wall plug efficiencies are 42.3%, 39.5%, 43.1%, and 40.1%, respectively. Compared with conventional Cr/Au pad (500 Å/800 Å), their light output powers increase by 17.2%, 9.6%, 19.21%, and 11.0%, whereas their corresponding wall plug efficiencies increase by 11.6%, 8.1%, 3.1%, 0.9%, respectively. To sum up, reflective metal pads with Cr/APC/Cr/Au can more effectively reduce higher series resistances and forward voltages than those with Cr/Ag/Cr/Au on a GaN-based light emitting diode device. These reflective metal pads with Cr/APC/Cr/Au can also more effectively increase the low wall plug efficiency than those with Cr/Ag/Cr/Au on a GaN-based light emitting diode device and have high light output power.
Hong, Pei-Chun y 洪珮純. "Preparation and Microstructures of the Copper-Based (Cu–Al–Ni) Shape Memory Alloy". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/tkxm4f.
Texto completo國立高雄應用科技大學
機械與精密工程研究所
103
The work output density of shape memory alloys (SMA) are well recognized for their shape memory effect (SME) and pseudo-elastic(PE). Because of that, these alloys have attracted much attention to be used in micro/nano electromechanical systems(MEMS/ NEMS). The SMA thin films are confirmed that the shape memory properties with narrow hysteresis and a wide range of martensitic transformation temperature (Ms) of copper-based alloys thin films, towards applications for micro-actuators. Several aspects have been considered, such as fabrication procedures, characterization of the microstructure and shape memory properties. In the past, the arc-melted has to be in the majority. In this work the fabrication procedures are both of arc-melted and electron beam-melted for Cu-Al-Ni alloy bulks. Furthermore, The microstructures and the crystal structures of the Cu-Al-Ni SMA were studied by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). In this experimental procedure show that the precipitate and the second phase due to influence of fabrication procedures and Composition, in which the both of two kinds of martensites, i.e. 2H and 18R , coexisting adjacent to each other in the specimen were observed. The change between the 18R and 2H stacking sequences was investigated by diffraction technique. Further experiments revealed that the β1´ martensite structure is actually of the M18R type (modified 18R) monoclinic one with its β angle very close to 90°. There is results showed the emergence of precipitates, indicating precipitation phenomenon form from metastable phase by electron beam energy of TEM. In the SMA, these precipitates affect the transformation temperatures (Ms, Mf, As, Af) and deteriorate the shape memory recoveries of these specimens. Therefore, this study investigate the processing-property and microstructure evolution of the SMA alloys. The purpose of this work is evaluating to the effectiveness of e-beam evaporation deposition for SMA thin films and comparative study composition of different on copper-based SMA. Theoretical analysis of the optimal fabrication procedures of Cu-based SMA and the nature by the method in this work can be obtained. This results will have some contribution of our study on the development of micro-electromechanical systems.
Huang, C. K. y 黃佳貴. "Brazability of Ti-6Al-4V Alloy with Ag-Cu Based Active Filler Metal". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/61014112430872533123.
Texto completo中華大學
機械與航太工程研究所
87
Brazeability of Ti-6Al-4V alloy brazed with Ag-Cu based active filler metal in vacuum environment has been investigated. Brazing processes were carried out in a vacuum of 5×10-5torr at 850℃,875℃,900℃,925℃,and 950℃for 10 minutes.The microstructure of the brazed interface was observed by using optical microscopy(OM) and scanning electron microscopy (SEM). In order to evaluate the bond joints quality, the tensile test and corrosion test were conducted as well. The Ti-6Al-4V/Ag-Cu based filler/Ti-6Al-4V brazements brazed at 875℃ for 10 minutes, the bonding strength was 601±42Mpa, which is 60% of Ti-6Al-4V base alloy’s tensile strength. The microstructures at the joints are silver solid solution and lamellar Ti-Cu-Ag and Ti-Cu-Al intermetallic compounds.Corrosion tests found these brazements failed at the brazed joint for the intermetallic compounds,which formed at its joint clearance.When the brazing system brazed at 950℃ for 10 minutes,the main microstructure at joint clearance of brazements is Ti-Cu dendritic structure and its bonding strength was only 304±36MPa.
姚其均. "Amorphization behavior of Cu and Ni-based amorphous alloy powders by adding yttium element". Thesis, 2002. http://ndltd.ncl.edu.tw/handle/18203430184270428074.
Texto completoWu, Ting-Ying y 吳亭瑩. "The Study of Large Area Graphite Film Preparation Based on Cu-Ni Alloy System". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/f7gtvy.
Texto completo國立臺北科技大學
材料及資源工程系研究所
98
Graphene is a two-dimensional crystal of carbon atoms arranged in a honeycomb lattice, it has high mechanical strength, high thermal conductivity, high specific surface area, and high electron mobility. Graphene is the ideal material for many dream applications, such as single electron transistors, transparent electrodes, UV light emitting diodes, gas sensors, super capacitor and biochips. This study is based on the mechanism of transition metal catalyzed graphite to diamond transition under high pressure and temperature. Copper and nickel transition metal powders are adopted to react with graphite powders in high temperature vacuum sintering furnace. After melting, the graphite flakes can be catalytically mended together by the transition metal alloy. This process is self assembling and self healing, so graphite layers can be formed on the surface of the ingot. With optimal alloy/graphite ratios and holding time, large area graphite film can be successfully prepared. The experiment consists of three parts: (1) Ratio - The ratios of C : Cu-Ni(30-70)=1 wt% : 99 wt%, and C : Cu-Ni(50-50)=0.5 wt% : 99.5 wt% are optimal. Besides, in view of the graphite film forming mechanism, graphite powder is first precipitated and separated by melting alloy then assembled as flakes in the melting alloy. After that, graphite flakes are transformed into graphite film on the surface of alloy ingot as a result of catalytic conversion process and density difference. (2) Various holding time – We observed the best character of graphite films under the condition of five-hour holding time. (3) Heat treatment – The best heat treatment temperature is 500℃ and hold for 1hr .
Zhang, Yi-zong y 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.
Texto completo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.
Liao, Mei-Fang y 廖美芳. "Synthesis of ternary and quaternary Cu-Ti-Ni –based amorphous alloy by mechanical alloying technique". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/02277393979442996027.
Texto completo大同大學
材料工程研究所
93
This study examined the amorphization behavior of Cu-Ti-Ni based alloy powders synthesized 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 analysed by the differential scanning calorimeter. Several amorphous powders were found to exhibits a wide supercooled liquid region before crystallization. The temperature interval of the supercooled liquid region defined by the difference between Tg and Tx, ie ΔT(ΔT=Tx-Tg), is 75K for Cu40Ti40Ni20 , 83K for Cu40Ti40Ni17Sn3 ,99K for Cu40Ti40Ni16Sn4, 95K for (Cu40Ti40Ni20)96Sn4, and 82K for Cu40Ti40Ni15Si5 .As the results demonstrated, small addition of Sn and Si significantly improved the glass forming ability (GFA) of the Cu-Ti-Ni amorphous alloy.
Yang, Yu-Min y 楊瑜民. "The Study of Cu-based Bulk Amorphous Alloys". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/07334818149514038329.
Texto completo國立清華大學
材料科學工程學系
95
The purpose of this study was to explore binary and ternary Cu-based bulk metallic glasses (BMG), which were divided into three systems: Cu-Hf-Al, Cu-Y-(M), Cu-Ti-M alloys, where M is an additive element. First, high Cu-content binary Cu-Hf BMG modified with Al, (Cu65Hf35)100-xAlx (x= 1, 2, 3, 4, 6) were studied. With only x= 2, the glass-forming ability (GFA) is greatly improved to form bulk glassy rod up to at least 3 mm in diameter. The microstructure consists of inhomogeneous amorphous phases. The Cu-Y binary system was chosen to study the GFA on compositions around the eutectic points and their modification. The microstructure of as-cast Cu-Y rods contained amorphous and crystalline mixture phases. According to the XRD results the best glass forming alloy is Cu78Y22. The further addition of Ag improves the GFA. The composition (Cu78Y22)97Ag3 was very close to form fully 1 mm BMG rod. Finally, we tried to develop the ternary BMGs based on high Cu content Cu-Ti BMG. The best result is the Cu50Ti40Zr10 glassy rod with the diameter at least 1 mm. The Cu-Y-M ternary alloys are brittle and poor electrochemical resistance due to their structure that contained amorphous and crystalline phases. Fully amorphous Cu-Hf-Al system showed the best mechanical properties with a compressive fracture strength up to 2340 MPa and a plastic strain up to about 1 % due to the inhomogeneous amorphous phases. Cu50Ti40Zr10 alloy performed low corrosion current density, 10-5 A/cm2, in 1 N H2SO4 + 0.01 N NaCl solution showed excellent electrochemical property, and its compressive fracture strength is up to about 2000 MPa.
Tai, Shu-Chen y 戴淑媜. "Formation and Characterization of Cu-based Amorphous Alloys Powders". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/64051392036855920620.
Texto completo大同大學
材料工程研究所
91
This study examined the amorphization behavior of Cu-based alloy powders synthesized 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 the DSC measurement. According to the results, after 5 hours of milling, the mechanically alloyed powders were amorphous at Cu-based alloys with B and Si. The thermal stability of the Cu-based amorphous powders was also investigated by differential scanning calorimeter (DSC). As the results demonstrated, the amorphous powders were found to exhibit a wide supercooled liquid region before crystallization. The temperature interval of the supercooled liquid region defined by the difference between Tg and Tx, i.e. ΔT (ΔT=Tg-Tx), are: Cu50Zr27Ti20B3(72K)、Cu50Zr25Ti20B5(77K)、Cu50Zr24Ti20B5Si1(85K)、Cu50Zr20Ti20B5Si5(89K). Finally, small additions of B and Si significantly improved the glass forming ability(GFA) of the Cu-based amorphous alloys.
Chang, Y. S. y 張晏碩. "Vaccum Brazing Diamond of using Cu-Mn-Based Alloys". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/54105061895598775442.
Texto completo國立臺北科技大學
製造科技研究所
92
In this study, four kinds of Cu-Mn based brazing alloys were developed with the active element Si addition. The compositions of the brazing alloys were identified according to their microstructure phase diagrams. Besides, the melting points of these developed brazing alloys were evaluated through the DSC analysis. The brazing temperatures were identified in accordance with the compositions and melting points mentioned above. Two brazing experiments were then performed: First, braze diamond grits onto 304 stainless steel substrate using the developed brazing alloys as filler metals. Second, place the brazing alloys on top of CVD diamond films and heat them to the brazing temperatures. Then, by means of chemical etching technique, the researcher removed the diamond grits from the matrix. The surface of the diamond grits removed was then analyzed by scanning electron microscopy and X-ray diffractometry. In addition, the performances of the brazing alloys on top of diamond films were evaluated via wettability observation, scanning electron microscopy(SEM), X-ray diffractometry(XRD), Raman analysis, and microhardness tests. The results of the study show that the M3 brazing alloy has the lowest melting point(834°C), smallest wetting angle and best spreading ability. It is also observed that silicon and manganese both diffused to the vicinity of diamond. The intermetallic layer was formed between diamond grits and brazing alloys. The intermetallic layer was identified as Mn7C3 for M0, M1 alloys and Mn5SiC for M2, M3, M4 alloys. The findings will hopefully contribute to the manufacture of diamond tools.
Kang, Hung-Cheng y 康宏誠. "SYNTHESIS OF CU-BASED AMORPHOUS ALLOYS WITH 10% ZIRCONIUM". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/35913556405397586922.
Texto completo大同大學
材料工程學系(所)
101
This study is examined the amorphization behavior of the Cu-Ti-Zr-based alloy powders with 10 at% Zr (99.0 at% purity) synthesized by mechanical alloying technique. The compositions of the alloys were near the eutectic compositions in the Cu-Ti-Zr ternary phase diagram by CALPHAD technique. As the results demonstrated , the ternary Cu-Ti-Zr alloys of compositions ranging from Cu-50-80 at% , Ti-10-40 at% and 10 at% Zr were not found to exhibit a glass transition temperature(Tg). By addition of silicon to the Cu60Ti30Zr10 system , some amorphous powders were found to exhibit a wide supercooled liquid region before crystallization. The temperature interval of the supercooled liquid region (ΔTx) and the activation energy of crystallization (Ec) are 76K , 221.7 kJ/mole for (Cu60Ti30Zr10)99Si1 and 84.7K , 237.8 kJ/mole for (Cu60Ti30Zr10)97Si3 , respectively . Finally , small additions of Si significantly improved the glass forming ability of the Cu-Ti-Zr-based amorphous alloys.
Cronauer, Joseph T. "A comparison of high damping shape memory alloys with Cu-Mn-based and Fe-Cr-based alloys". Thesis, 1987. http://hdl.handle.net/10945/22673.
Texto completoTsai, Jian-Cheng y 蔡建丞. "Sutdy on Zr-based amorphous alloys roll bonding with Cu sheet". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/k4p8z9.
Texto completo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.
Lai, Yong-Siang y 賴永祥. "Formation of Cu-Ti-based Bulk Amorphous Alloys by Powder Metallurgy Route". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/86490466740363125971.
Texto completo大同大學
材料工程學系(所)
96
This study examined the amorphization behavior of Cu-Ti based alloy powders synthesized by mechanical alloying technique and investigation of consolidation by vacuum hot pressing and vacuum hot extrusion. The phase stabilities of as-milled powders were studied by DSC measurement at 5K/min heating rate. The amorphous powders were found to exhibit a wide supercooled liquid region before crystallization. The temperature interval of the supercooled liquid region (ΔTx) is 114K for Cu40Ti40Ni15Sn5, 59K for Cu40Ti40Ni15Si5, 78K for Cu50Ti40Sn5B5, 88K for Cu50Ti40Ni5B5 respectively. Surface oxidation of powders in milling and consolidation processes led to larger amount of porosity and extruding failure. In addition, the hardness of the bulk amorphous alloys is 658.6HV for Cu40Ti40Ni15Sn5, 624.5HV for Cu40Ti40Ni15Si5, 617.6HV for Cu50Ti40Sn5B5, and 604.5HV for Cu50Ti40Ni5B5. It leads to better wear resistance for less weight loss as hardness increasing. Furthermore, Cu40Ti40Ni15Sn5 and Cu40Ti40Ni15Si5 amorphous alloys were found to exhibit a better corrosion resistance evaluated by potentiodynamic polarization measurements in 3.5wt% NaCl solution.
Asgharzadeh, Javid Fatemeh. "Phase formation, martensitic transformation and mechanical properties of Cu-Zr-based alloys". Doctoral thesis, 2015. https://tud.qucosa.de/id/qucosa%3A29817.
Texto completoThe 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.
Zhang, Yong y Yi Li. "Glass Forming Ability in Pr-(Cu, Ni)-Al Alloys". 2002. http://hdl.handle.net/1721.1/3974.
Texto completoSingapore-MIT Alliance (SMA)
Yeh, Ming-Chi y 葉銘騏. "Hemocompatibility valuation of Cu-based bulk amorphous alloys prepared by copper mold casting". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/82088256127447843079.
Texto completo國立高雄應用科技大學
機械與精密工程研究所
94
This research chooses the Cu54Zr22Ti18Ni6-xSix alloys to study, and uses the vacuum melting furnace to melt alloys under the argon atmosphere. The additions of silicon replace with nickel to mix the Cu-based alloys. The Cu-based bulk amorphous alloys prepared by arc melting and copper mold casting. The sample uses DSC for analysis of thermal property, uses micro-sclerometer for analysis of the mechanical property, uses XRD for the analysis of phase, and uses TEM for the analysis of microstructure. The Cu-based bulk amorphous alloys carry on the clotting time assay and valuate the hemocompatibility. The research exhibited the glass transition temperature(Tg)of the Cu-based bulk amorphous alloys at about 725K. And the Cu54Zr22Ti18Ni4Si2 amorphous alloys have the highest ΔTx at 64K. The Cu-based bulk amorphous alloys have the highest hardness at Hv 708±12 than those have the hardness at Hv 543±8 of Cu-based crystalline alloys. The Cu-based bulk amorphous alloys also have good hemocompatibility.
Chen, Tse-yu y 陳則友. "Synthesis of ternary and quaternary Mg-Cu-based amorphous alloys by mechanical alloying technique". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/72952442863568352232.
Texto completo大同大學
材料工程學系(所)
94
This study examined the amorphization feasibility of Mg-Cu-based alloy powders synthesized by mechanical alloying technique with a high energy SPEX 8000-D ball mixer. The microstructural evolution and phase stabilities during mechanical alloying of the mixed powders were investigated by X-ray diffraction and scanning electron microscopy and differential scanning calorimeter. Several amorphous powders were found to exhibit a wide supercooled liquid region , ie ΔT(ΔT=Tx-Tg), is 55K for Mg40Cu40Ti20, 53K for Mg40Cu35Ti25, 51K for Mg40Cu35Ti23B2, 62K for Mg40Cu35Ti21Sn4, and 74K for Mg40Cu35Ti21Ni5. As the results demonstrated, small addition of Sn and Ni significantly improved the glass forming ability (GFA) of the Mg-Cu-Ti amorphous alloy.
Chen, Tse Yu y 陳則友. "Synthesis of ternary and quaternary Mg-Cu-based amorphous alloys by mechanical alloying technique". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/82075962416441698413.
Texto completo大同大學
材料工程研究所
94
This study examined the amorphization feasibility of Mg-Cu-based alloy powders synthesized by mechanical alloying technique with a high energy SPEX 8000-D ball mixer. The microstructural evolution and phase stabilities during mechanical alloying of the mixed powders were investigated by X-ray diffraction and scanning electron microscopy and differential scanning calorimeter. Several amorphous powders were found to exhibit a wide supercooled liquid region , ie ΔT(ΔT=Tx-Tg), is 55K for Mg40Cu40Ti20, 53K for Mg40Cu35Ti25, 51K for Mg40Cu35Ti23B2, 62K for Mg40Cu35Ti21Sn4, and 74K for Mg40Cu35Ti21Ni5. As the results demonstrated, small addition of Sn and Ni significantly improved the glass forming ability (GFA) of the Mg-Cu-Ti amorphous alloy.
Yang, Shang-Chi y 楊上旗. "Synthesis of ternary and quaternary Cu-Ti-based amorphous alloys by mechanical alloying technique". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/02361767860472027504.
Texto completo大同大學
材料工程學系(所)
94
This study examined the amorphization behavior of Cu-based alloy powders synthesized by mechanical alloying technique. The microstructural evolution during mechanical alloying of the mixed powders was investigated by both X-ray diffraction(XRD)and scanning electron microscopy(SEM). The phase stabilities of the as-milled powders were analysed by the differential scanning calorimeter. Several amorphous powders were found to exhibit a wide supercooled liquid region before crystallization. The temperature interval of the supercooled liquid region defined by the difference between the glass transition temperature(Tg)and the crystalline temperature(Tx), ie DT(DT=Tx-Tg), is 117.95 K for Cu50Ti40Fe10, 77.62 K for Cu50Ti35B15, 73.99 K for Cu60Ti40Mg10, 91.82 K for Cu55Ti40Sn5, 95.02 K for Cu50Ti40Sn10, 81.13 K for Cu60Ti35Sn5, 102.3 K for Cu50Ti45Sn5, 103.25 K for Cu50Ti40Sn9B1, 95.86 K for Cu50Ti40Sn7B3, and 110.88 K for Cu50Ti40Sn5B5. As the results demonstrated, small addition of B significantly improved the glass forming ability(GFA)of the Cu-Ti-Sn amorphous alloy.
Zhang, Yong, Irene Mei Ling Lee, Hao Tan, Qin Jing y Yi Li. "Effect of Microstructure Changes on Mechanical Properties of La₆₆Al₁₄(Cu, Ni)₂₀ Amorphous and Crystalline Alloys". 2003. http://hdl.handle.net/1721.1/3824.
Texto completoSingapore-MIT Alliance (SMA)
Huang, Rong Kai y 黃榮凱. "Motorcycle Exhaust Thermoelectric Properties of Cu-Added bismuth Telluride Based Alloys by Cold-Pressing Sintering". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/ptf22c.
Texto completo國立臺北科技大學
車輛工程系所
104
This study focuses on the thermoelectric generating properties of an alloy, fabricated by mixing P-type (Bi2Te3)x(Sb2Te2)x ternary alloy powder with copper and through a cold-pressed sintering manufacturing process. The characteristics of these alloys were studied using X-ray diffraction, energy dispersive spectroscopy, and scanning electron microscopy. Moreover, these thermoelectric chips were analyzed with respect to their thermoelectric properties such as thermal conductivity, electric conductivity, Seebeck coefficient, thermoelectric merits. The electric power was measured on motorcycle exhaust at temperature difference. Three types of thermoelectric ternary alloy were fabricated in this study, namely P-type (Bi2Te3)x(Sb2Te2)x, N-type Bi2Te3-xSex, and P-type blended with 3% copper. The maximum Dimensionless figure of Merit(ZT) of the P-type corresponds to a temperature of 381.2 K, with a maximum value of 0.259216, a coefficient of thermal conductivity of 1.15 W/mK, an conductivity of 138 S/m, and a Seebeck coefficient of 237.3 μV/K. For the N-type powder, these values were 381 K, 0.0762, 1.08 W/mK, 107 S/m, and -141.9 μV/K, respectively. For the P-type blended with copper, these were 400.8 K, 0.28056, 2.12 W/mK, 786 S/m, and 137.2 μV/K, respectively. The calculated ZT of the P-type with copper was 9% higher than that of the P-type without copper. Thermoelectric generator fabricated with copper foil using unprocessed P-type and N-type powders had their highest power values at 382.32 pW when the temperature difference was 109 K. Thermoelectric generator fabricated with pure copper via sputtering process using unprocessed P-type or N-type powders had their highest power (247.296 pW) at a temperature difference of 114.5 K. Thermoelectric generator made of P-type powder with copper and thermoelectric generator made of unprocessed N-type powder with copper foil had the highest power at a temperature difference of 109.5 K, corresponding to a maximum power value of 469.268 pW. These results show that the Dimensionless figure of Merit of the P-type thermoelectric alloy blended with copper is 0.28056, highest at 400.8 K temperature. The Dimensionless figure of Merit value is greater than that of the P-type thermoelectric alloy without copper, which is 0.2574. Due to the increase of electric conductivity of 470%, much higher than the increase of thermal conductivity of 84%, the overall Dimensionless figure of Merit increase is 9% when we input the data into the Dimensionless figure of Merit calculation formula. The result demonstrates that the excellent conductivity of copper can enhance the Dimensionless figure of Merit value. The Dimensionless figure of Merit value can increase by 9% when adding 3% copper to the alloy.
Zaki, Gergis Adel Shaker. "On the performance of low pressure die-cast Al-Cu based automotive alloys : role of additives". Thèse, 2014. http://constellation.uqac.ca/3240/1/Zaki_uqac_0862N_10119.pdf.
Texto completoLi, I.-Hung y 李怡鴻. "Infrared Vacuum Brazing Fe3Al Intermetallics Using Au-based Filler Metals and Studies on the Development of Novel Cu-based Braze Alloys". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/08229176766827581730.
Texto completo國立臺灣大學
機械工程學研究所
98
Microstructural evolution and bonding strength of infrared brazed Fe3Al and stainless steels(SS) using Au-based and CuMn-based fillers, respectively, are studied. Firstly the wetting experiments using these braze alloys are conducted to make sure the suitable brazing temperature. Al2FeNi, Fe3Al and AlAu2 intermetallics are found in the joint of AuPdNi (Au-8wt.%Pd-22wt.%Ni) braze alloy brazed at 980℃ and all specimens are fractured in brittle. For AuCu(Au-20wt.%Cu) braze alloy, the brazed joint is fractured along the central β-phase in which the fracture exhibits ductile/brittle mode(s) with different brazing conditions. The highest shear strength for AuCu filler is 327MPa for specimen brazed at 880℃×300s. Raising the brazing time or temperature will deteriorate the strength due to the fracture mode transfers to brittleness. For infrared brazed 304, 422 and 440C stainless steels using Cu-33.7%Mn filler, a continuous interfacial (γFe,γMn) phase is found in between the braze and SS which is not well bonded with (Cu,γMn) primary phase in the brazed joint. Thus some cracks are observed in between (γFe,γMn) and (Cu,γMn) due to the thermal expansion mismatch of these two phases. In addition, solidification shrinkage voids or impurities are also observed in the central region of the joint and the fracture mode along this central voids/impurities is ductile with the shear strength of 280MPa for brazing 304 and 422 SS brazed at 875oC×180s. Cu-33.7%Mn filler alloyed with Ni can improve the joint properties, but increase slightly the fillers’ melting points. The Ni alloyed CuMn fillers can effectively wet all SS at appropriate temperatures and the interfacial cracks in between (γFe,γMn) and (Cu,γMn) phase are greatly reduced with increasing the Ni addition.
PARISI, ERICA ISABELLA. "Sistemi film-forming a base di PVA per la rimozione di prodotti di corrosione da leghe base-Cu (Film forming PVA-based cleaning systems for the removal of corrosion products from Cu-based alloys)". Doctoral thesis, 2016. http://hdl.handle.net/2158/1073126.
Texto completoNabawy, Ahmed. "Influence of zirconium and scandium on the microstructure, tensile properties, and hot-tearing susceptibility of Al-2WT%Cu-based alloys". Thèse, 2010. http://constellation.uqac.ca/289/1/030139020.pdf.
Texto completoLi, Yao y 李垚. "Infrared Vacuum Brazing Fe3Al Intermetallics Using Ag/Cu Filler Metals and Studies on The Development of Novel Low-temperature Ag-based Braze Alloys". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/52793226811972258103.
Texto completo國立臺灣大學
材料科學與工程學研究所
97
Microstructural evolution and bonding strength of infrared brazed Fe3Al using Ag, Cu, and BAg-8 braze alloys have been studied. The joint of the Ag-brazed specimen only contains Ag-rich phase alloyed with Al. The shear strength isn’t affected by the brazing time and reaches 127MPa for specimens brazed at 980oC×300s with the ductile fracture of Ag-rich phase. The microstructure and shear strength of infrared brazed Fe3Al using pure Cu at 1100oC are strongly dependent upon the brazing time in which the brazed joint changes from Cu-rich phase into β1’ (N18R) martensite phase, and causes different fracture mechanism and bonding strength. The highest shear strength reachs 291MPa for the specimen brazed at 1100℃×300s with the mixture of brittle and ductile phases in the joint. The microstructure of the Fe3Al joint brazed by BAg-8 contains Ag-rich and Cu-rich phases eutectic for all brazing conditions. The shear strength increases slightly with increasing the brazing time because the Al is alloyed in the Cu-rich matrix. The highest shear strength of 181MPa is acquired from the 800℃×600s brazed specimen. The analyses of dynamic wetting angles and microstructures of Ag-based braze alloys on 304, 422 and 440C substrates are performed. Experimental results shows that Sn added into Ag-Cu braze alloy can reduce its melting point effectively but can not improve its wettability for stainless steel. The Ag-Cu-Sn braze alloy with adding Mn can reduce the wetting angle on stainless steel. The more the Mn content , the better the wettability it has. The best wettability is the Ag-Cu-Sn-10wt.%Mn alloy and its microstructure after wetting tests consistsd of Ag-rich and copper-rich phases. Meanwhile, increasing the Mn content results in the copper-rich phases in the braze changing from complex phases (Cu3Sn, Cu4MnSn, Cu-rich phases) into single Cu-rich phase with many Ag-rich precipitates.