YANG Yuanzheng MA Xueming DONG Yuanda Institute of Solid State Physics
,
Academia sinica
,
Hefei
,
China Professor.Institute of Solid State Physics Academic Sinica
,
Hefei 230031
,
China
金属学报(英文版)
Mechanical alloying was employed to produce super—saturated solution of Fe_1-xCu_x ,which is virtually immiscible under an equilibrium condition at ambient temperature.XRD results show that the solutions formed in the concentration ranges of x≤O.15 and x≥0.40 are of bee structure of x-Fe and fee structure of Cu,respectively.For the region in between (0.15solid solutions.
关键词:
mechanical alloying
,
null
,
null
,
null
,
null
B.W. Wang
,
H. Shen
金属学报(英文版)
Ni-Cr System solar selective thin solid films were prepared by d.c. magnetron reactivesputtering under the atmosphere of O2 and N2. Ni-Cr alloy was chosen as targetmaterial and copper sheets as substrate. Using SEM, Spectrophotometer and Talystepto analyze the relations between the selective characteristic and the structure, theformation and the thickness of the thin films. The aim is to obtain good solar selectivethin films with high absorptance and low emittance, which is applied to flat plate solarheat collectors.
关键词:
solar selective thin film
,
null
,
null
,
null
MA Zongyi YAO Zhongkai Harbin Institute of Technology
,
Harbin
,
China
金属学报(英文版)
The SiC_w/Al composite prepared by squeeze casting has a combination of superior room temperature specific strength and modulus together with excellent thermal properties.The extrusion can make an improvement on the strength and ductility of the composite from 582 MPa as squeeze casted up to 639 MPa,and on the transformation from isotropic to the anisotropic structure.This seems to be explained by the orientation of whiskers and the densification of dislocations in matrix.TEM observation indicates that the stacking fault is the usual planar defect on the SiC_w surface. composite;;SiC whisker;;Al alloy;;microstructure
关键词:
composite
,
null
,
null
,
null
Physical Review B
Metastable Fe100-xAlx alloys have been formed by ball milling of elemental Fe and Al powders: supersaturated body-centered-cubic solid solutions for x less than or equal to 70, and an amorphous phase for x > 70. Quantitative x-ray-diffraction measurements show that the total root-mean-square displacement (rms) and the static rms in the Fe100-xAlx solid solutions increase significantly with increasing Al content, The total rms at the instability point, however, reaches only 6.8% of the nearest-neighbor distance and is far below the critical value predicted by the Lindemann melting criterion, suggesting that the Lindemann melting criterion is not applicable for the solid-state amorphization. Instead. the Debye temperature of the supersaturated Fe100-xAlx alloys was observed to drop by similar to 22% at the point of amorphization, implying a corresponding softening in the average shear modulus of similar to 40%, which agrees with the microhardness measurements. These results strongly support the empirical elastic instability criterion For the solid-state amorphization process.
关键词:
to-glass transition;crystal;transformation
Journal of Alloys and Compounds
Growth kinetics and interfacial morphologies of the intermetallic compounds (IMCs) between single crystal Ag and Sn-4Ag, Sn-3Cu and Sn-37Pb solders were investigated by solid-state aging at 160 degrees C and liquid-state aging at 260 degrees C. Isothermal equation of chemical reaction and phase diagrams were used to explain the effects of Ag, Cu and Pb on the growth kinetics of IMCs under solid-state and liquid-state aging conditions. The diffusion coefficients for the three solder joints of Sn-4Ag/Ag, Sn-3Cu/Ag and Sn-37Pb/Ag were calculated after solid-state and liquid-state aging. It is found that Pb can effectively retard the growth of IMCs during liquid-state aging but has little influence on the growth rate of IMCs during the solid-state aging. Some local small cracks were frequently observed in the Cu(6)Sn(5) particles near interfaces of the Sn-3Cu/Ag solder joints after solid-state aging for several days. However, there were no such local small cracks when solders or interfaces did not contain the Cu(6)Sn(5) particles after the same aging time. (C) 2008 Elsevier B.V. All rights reserved.
关键词:
Ag single crystal substrate;Lead-free solder;Intermetallic compounds;(IMCs);Growth kinetics;Local cracks;lead-free solders;electroless ni(p) metallization;intermetallic;compound;cu-sn;joints;ni;bi;nanoindentation;microstructure;wt.percent
Journal of Applied Physics
Interdiffusion-induced solid-state amorphization reaction (SSAR) in polycrystalline Ni/amorphous Si multilayers has been studied using an in situ x-ray diffraction technique together with transmission electron microscope observations, The amorphization reaction was found to occur both on the Ni/Si interfaces in terms of a planar-layer growth model and along the grain boundaries in the Ni sublayers. Thermodynamic and kinetic interpretations for the SSAR at grain boundaries are presented and an amorphous growth model is also suggested for elucidating the SSAR in polycrystalline Ni/amorphous Si multilayers.
关键词:
x-ray-diffraction;thin-films;silicon
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing
We report on studies of solid state redox reactions induced by mechanical alloying (MA). The displacement reaction in the Fe-CuO system during MA may be completed by two steps: a rapid self-sustaining combustion reaction process, followed by a gradual reaction process. High densities of point and lattice defects, as well as a fine dispersion of reactants, are introduced in the powder mixture during MA. In addition, the displacement reaction in the Fe-CuO system produces a large negative heat. This combination of factors makes the redox reaction occur in the reaction regions, accompanied by self-heating. The self-heating may raise the temperature up to ignition temperature for a combustion reaction; this ignition temperature is greatly decreased by ball-milling. Combustion then takes place. The displacement reaction may be carried out rapidly during combustion. Complete reduction of copper oxides, including the intermediate oxidation state phase, Cu2O, appearing immediately after combustion, is observed after prolonged milling, during which the reduction is gradual; a similar self-sustaining reaction mechanism works in local reaction regions.
关键词:
amorphous-alloys;powders
