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Metastable phase separation and rapid solidification of undercooled Co-Cu alloy under different conditions
Cao Chong-De,
曹崇德

中国物理 B , 2006,
Abstract: The metastable liquid phase separation and rapid solidification behaviours of Co61.8Cu38.2 alloy were investigated by using differential thermal analysis (DTA) in combination with glass fluxing, electromagnetic levitation (EML) and drop tube techniques. It is found that the liquid phase separation process and the solidification microstructures intensively depend on the experimental processing parameters, such as undercooling level, cooling rate, gravity level, liquid surface tension and the wetting state of crucible. Large undercooling and surface tension difference of the two liquids tend to facilitate further separation and cause severe macrosegregation. On the other hand, rapid cooling and low gravity effectively suppress the coalescence of the minority phase. Severe macrosegregation patterns are formed in the bulk samples processed by both DTA and EML. In contrast, disperse structures with fine spherical Cu-rich spheres homogeneously distributed in the matrix of Co-rich phase have been obtained in drop tube.
Phase separation of Cu-Pb monotectic alloy during rapid solidification
急冷条件下Cu-Pb偏晶合金的相分离研究

Xu Jin-Feng,Dai Fu-Ping,Wei Bing-Bo,
徐锦锋
,代富平,魏炳波

物理学报 , 2007,
Abstract: The rapid solidification and microstructure formation of Cu-Pb monotectic alloy were investigated by melt spinning method. The relationship between liquid separation and physical parameters such as cooling rate and solidification time etc. was analyzed theoretically by coupling the heat transfer equation and Navier-Stokes equation. It is revealed that the rapid cooling of the melt has more remarkable effect on microstructure forming of the monotectic alloys than liquid flow under rapid solidification. The rapid solidification can suppress the liquid separation, which results in the formation of uniform microstructure for various Cu-Pb monotectic alloys. With the rise of cooling rate, the grain size clearly decreases, the microstructure was markedly refined and the microstructural morphology changes from coarse dendrite to uniform and fine equiaxial crystallites. Increasing the cooling rate and shortening solidification time are the essential conditions to suppress liquid phase separation and obtain the uniform monotectic microstructure in gravity field.
DYNAMIC SCALING OF PHASE SEPARATION IN-AMORPHOUS Cu12.5Ni10Zr41Ti14Be22.5 ALLOY
非晶态Cu12.5Ni10Zr41Ti14Be22.5合金相分离的动力学标度

LIU JUN-MING,WU ZHUANG-CHUN,LIU ZHI-GUO,
刘俊明
,吴状春,刘治国

物理学报 , 1997,
Abstract: The dynamic scaling of phase separation in amorphous Cu12.5Ni10Zr41Ti14Be22.5 alloy has been investigated by means of smallangle neutron scattering. A detailed scaling analysis of the scattering function indicates that the dynamic scaling state of the scattering is reached in the early stage of the phase separation. We demonstrate that the dynamic scaling hypothesis can be applied to the phase separation sequence in deeply supercooled liquid.
Core-shell microstructure formed in the ternary Fe-Co-Cu peritectic alloy droplet
FuPing Dai,BingBo Wei
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-009-0103-9
Abstract: The metastable liquid phase separation occurs in the ternary Cu50Fe37.5Co12.5 peritectic alloy droplets during free fall. The separated alloy melt rapidly solidifies and evolves core-shell microstructure composed of L1(Cu) and L2(Fe,Co) phases. Based on the determination of the phase transition temperature, the core-shell microstructure evolution, the interfacial energy, the temperature gradient and the Marangoni migration are analyzed. The interfacial energy of the separated liquid phase increases with the decrease of the temperature. The temperature gradient changes from large to small along the radius direction from inside to outside in the alloy droplet. The Marangoni force (F M) acting on the micro-droplet of L2(Fe,Co) phase increases with the increase of the size of the L2(Fe,Co) phase, and decreases with the increase of undercooling. Driven by F M, the micro-droplet of L2(Fe,Co) phase migrates from outside to inside in the alloy droplet, collides and coagulates each other during migration, and then forms different types of core-shell microstructures.
Core-shell microstructure formed in the ternary Fe-Co-Cu peritectic alloy droplet

FuPing Dai,BingBo Wei,

科学通报(英文版) , 2009,
Abstract: The metastable liquid phase separation occurs in the ternary Cu50Fe37.5Co12.5 peritectic alloy droplets during free fall. The separated alloy melt rapidly solidifies and evolves core-shell microstructure composed of L1(Cu) and L2(Fe,Co) phases. Based on the determination of the phase transition temperature, the core-shell microstructure evolution, the interfacial energy, the temperature gradient and the Marangoni migration are analyzed. The interfacial energy of the separated liquid phase increases with the decrease of the temperature. The temperature gradient changes from large to small along the radius direction from inside to outside in the alloy droplet. The Marangoni force (F M) acting on the micro-droplet of L2(Fe,Co) phase increases with the increase of the size of the L2(Fe,Co) phase, and decreases with the increase of undercooling. Driven by F M, the micro-droplet of L2(Fe,Co) phase migrates from outside to inside in the alloy droplet, collides and coagulates each other during migration, and then forms different types of core-shell microstructures. Supported by the National Natural Science Foundation of China (Grant Nos. 50121101, 50395105) and NPU Youth Scientific and Technological Innovation Foundation (Grant No. W016223)
OPTIMIZED COMPOSITIONS OF Ti-(Cu,Ni)-Sn ALLOY FOR METALLIC GLASS FORMATION AND THEIR CORRELATION WITH EUTECTIC REACTION
Ti-(Cu,Ni)-Sn合金形成金属玻璃的成分优化及其相关联的共晶反应

LIU Yuanshuai XU Jian Shenyang National Laboratory for Materials Science,Institute of Metal Research,Chinese Academy of Sciences,Shenyang,
刘元帅
,徐坚

金属学报 , 2008,
Abstract: Adopting the “3D pinpointing approach”, compositional dependence of glass--forming ability (GFA) for Ti-(Cu1-xNix)-Sn (0.20≤x≤0.30, atomic fraction) quaternary alloys was systematically investigated. The alloy with the optimized GFA is located at Ti38Cu37.8Ni16.2Sn8. Its critical diameter for metallic glass formation is near 1.0 mm for the rods fabricated using Cu mold casting. This metallic glass exhibits the supercooled liquid region ΔTx of 56 K and the reduced glass transition temperature Trg of 0.57. By characterizing the microstructure of the arc-melted Ti38Cu37.8Ni16.2Sn8 alloy, it is indicated that solidification of the alloy melt undergoes a pseudo-binary eutectic reaction of L→Ti5Sn3Cu+TiCuNi.
Molecular dynamics study of the ternary Cu50Ti25Zr25 bulk glass forming alloy  [cached]
Senturk Dalgic S,Celtek M.
EPJ Web of Conferences , 2011, DOI: 10.1051/epjconf/20111503008
Abstract: The structure and thermodynamic properties of a ternary Cu50Ti25Zr25 metallic glass forming alloy in solid-liquid to glass phases were studied using molecular dynamics (MD) method based on tight-binding (TB) potentials. An atomic description of the melting, glass formation and crystallization process has been analyzed using different heating and cooling rates. The computed Glass Forming Ability (GFA) parameters are in good agreement with experimental data. The structure analysis of the Cu50Ti25Zr25 based on molecular dynamics simulation will be also presented and compared with available MD results. We have also discussed the crystallization transition with two different interatomic potentials used in this work
Quantitative analysis of atomic disorders in full-Heusler Co2FeSi alloy thin films using x-ray diffraction with Co-Ka and Cu-Ka sources  [PDF]
Yota Takamura,Ryosho Nakane,Satoshi Sugahara
Physics , 2010, DOI: 10.1063/1.3350914
Abstract: The authors developed a new analysis technique for atomic disorder structures in full-Heusler alloys using x-ray diffraction (XRD) with Co-Ka and Cu-Ka sources. The developed technique can quantitatively evaluate all the atomic disorders for the exchanges between X, Y, and Z atoms in full-Heusler X2YZ alloys. In particular, the technique can treat the DO3 disorder that cannot be analyzed by ordinary Cu-Ka XRD. By applying this technique to full-Heusler Co2FeSi alloy thin films formed by rapid thermal annealing (RTA), RTA-temperature (TA) dependence of the atomic disorders was revealed. The site occupancies of Co, Fe, and Si atoms on their original sites were 98 %, 90 %, and 93 %, respectively, for the film formed at TA = 800 degree C, indicating that the RTA-formed Co2FeSi film had the L21 structure with the extremely high degree of ordering.
INVESTIGATION OF PHASE SEPARATION OF THE Fe-Ni-Co-Al-Cu-Ti PERMANENT MAGNET ALLOY
WG Chu,WD Fei,DZ Yang,
W.G. Chu
,W.D. Fei and D.Z. Yang

金属学报(英文版) , 2000,
Abstract: Microstructure formed in the Fe-Ni-Co-Al-Cu-Ti permanent magnetic alloy with different treatments was studied by means of TEM observation, XRD method and SAXS technology. The results indicated that spinodal decomposition and orderiing transformation coexisted in the alloy and spinodal decomposition was completed in a short time. The ratio of component of spinodal and ordered microstructure was dependent on the cooling rate. The variation of gyration radius RG of the rod-like precipitates could be accounted for by the different growth modes of the precipitates related to strain energy and interface energy.
More on``Atomic motions in the crystalline Al$_{50}$Cu$_{35}$Ni$_{15}$ alloy''  [PDF]
Gerrit Coddens
Physics , 2002,
Abstract: We refute recent claims that ultrafast atomic jumps as observed in quasicrystals (QC) could be called phasons in many crystalline alloys by pointing out that there is a genuine conceptual difference between the hopping dynamics in an imperfect crystal containing a substantial number of vacancies, and the hopping dynamics due to phason motion in QC.
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