SOLUBILITY CHARACTERISTICS OF GaAs IN Bi AND THEIR PHASE DIAGRAM

A modified liquid phase epitaxy apparatus for semiconductor materials was used to measurethe solubility of GaAs in Bi.Two phase diagrams rich in Bi under H_2 and N_2 atmosphereswere obtained according to the results of measurement.A new phenomenon,in which theparameter Q value(quantity of GaAs dissolved in Bi in fixed time/saturation quantitu,ofGaAs in Bi)was different from each other at various temperatures and there existed a maxi-mum Q value at definite temperature,was observed.This phenomenon may be regarded as acommon feature of a simple binary metallic system which has the phase diagram similar tothat of Bi-GaAs.The difference observed from the dependence of Q values on temperature inboth H_2 and N_2 atmospheres was discussed.     

Mechanical and magnetostrictive properties of Tb0.36Dy0.64（Fe1-xMnx）1.9 alloys

The magnetization, magnetostriction and compressive strengths of arc-cast polycrystalline and directionally solidified Tb0.36Dy0.64（Fe1-xMnx）1.9 （x=0, 0.05, 0.10, 0.15, 0.20） rods were investigated by VSM, standard strain gauge method and compressive tests, respectively. The results show that the magnetostriction λs, saturation magnetization Ms and magnetocrystalline anisotropy constant K1 decrease with increasing the Mn concentration. The optical micrographs and XRD patterns show that the Tb0.36Dy0.64（Fe1-xMnx）1.9 alloys are composed of MgCu2-type Laves phase as matrix and a small amount of rare-earth rich phase. It is found that the distribution of the rare-earth rich phase has an important effect on mechanical property of Tb0.36Dy0.64（Fe1-xMnx）1.9 samples. For the arc-cast samples, smaller equal-axial grains are arranged irregularly, which results in higher compressive strengths. However, the rare-earth rich phase is arranged as parallel arrays in the directionally solidified samples, which leads to smaller compressive strengths.     

外场在材料制备和加工过程中的应用

总结了近几年来电流、磁场、振动、微重力场和超重力场等外场在金属凝固过程的应用,及其对固态相变过程的影响;从理论上分析和论述了外场影响凝固过程和固态相变的作用机理,并展望了外场技术的发展前景.     

真空离子液-气相渗硼的研究

介绍了用自制的无毒无腐蚀的有机渗硼剂——硼酸三甲酯对排气阀热嵌模进行真空离子液-气相渗硼，经检测，整个化合物层和扩散层中含有B和Fe2B，并呈高度弥散分布状态，起到了抗重载热冲击、抗热磨损、抗反复低周循环热疲劳的良好作用，能大大提高热镦模的使用寿命。     

往复挤压Mg2Si增强镁铝基复合材料的组织与性能

采用石墨型铸造制备了Mg2Si增强镁铝基复合材料,并对该材料进行了不同道次的往复挤压,探讨往复挤压工艺对复合材料组织与力学性能的影响,以寻求改善Mg2Si相形貌并细化其尺寸的新途径。研究表明,往复挤压对该复合材料中Mg2Si相具有较好的破碎作用,而且挤压道次越多,对Mg2Si相的破碎效果越好,Mg2Si相在复合材料中的分布越均匀。往复挤压可显著提高复合材料的室温抗拉强度,但对150℃时材料的抗拉强度提高效果不大。铸态Mg2Si增强镁铝基复合材料在150℃下具有较高的耐热性,抗拉强度为180.5MPa,这主要得益于Mg2Si相的高熔点及其良好的热稳定性。     

Nacl—Bacl2—Srcl2三元熔盐相图的计算

本文运用作者提出的从三个对应的二元系的热力学性质预示三元溶液的热力学性质的新对称几何模型,推导得到三元溶液中三个组元的偏摩尔热力学性质的数学表达式。进而将这一结果应用于NaCl-BaCl_2-SrCl_2三元熔盐相图的计算中,得到此三元系的液相析出面及若干等温截面。计算所得结果与实测结果偏差小于5℃,说明此模型在一些熔盐体系中有较好的适用性。     

Properties and Performance of High-Purity Thermal Barrier Coatings

It has been found that reducing the level of impurity oxides (particularly SiO₂ and Al₂O₃) in 7YSZ, from about 0.2 wt% to below 0.1 wt% raises the sintering resistance and the phase stability of plasma-sprayed coatings. The implications for the usage of these coatings at elevated temperatures are examined. It is concluded that using relatively high-purity powder of this type is likely to confer substantial benefits in terms of the thermomechanical stability of the coatings under service conditions. This article is an invited paper selected from presentations at the 2007 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Global Coating Solutions, Proceedings of the 2007 International Thermal Spray Conference, Beijing, China, May 14-16, 2007, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2007.     

Low-melting-point titanium-base brazing alloys—part 1: Characteristics of two-, three-, and four-component filler metals

The melting point, microstructure, phase, and electrochemical behavior of Ti-21Ni-15Cu alloy, together with two-, three-, and four-component low-melting-point titanium-base brazing alloys, are presented in this paper. Five filler metals were selected for the study, in which melting points were measured by differential thermal analysis, phases identified by x-ray diffractometry, and corrosion behaviors tested by potentiodynamic polarization. The experimental results show that the three-component Ti-15Cu-15Ni and the newly developed Ti-21Ni-14Cu alloys exhibit the combination of lower melting point and superior corrosion resistance compared to the two-and four-component titanium alloys, 316L stainless steel, and a Co-Cr-Mo alloy in Hank’s solution at 37 °C. On a short time basis, the presence of Ti₂Ni and Ti₂Cu intermetallics in the Ti-15Cu-15Ni and Ti-21Ni-14Cu alloys should not be preferentially dissolved in galvanic corrosion with respect to the dissimilar Ti-6Al-4V alloy.     

基于动态相变的细晶双相低碳钢组织控制

利用Gleeble1500热模拟单向压缩实验机，通过观察不同原奥氏体晶粒的过冷奥氏体在动态相变过程中的组织演变，分析了动态相变过程中马氏体岛形貌以及分布的演变特征，并考察了原奥氏体晶粒大小、形变温度和形变速率等参数对组织转变动力学的影响，探讨了基于动态相变的细晶双相低碳钢的组织控制规律、结果表明，通过调整原始奥氏体晶粒尺寸并控制过冷奥氏体动态相变进程，可以获得在均匀细小的铁素体（2～3μm）基体上弥散分布着不同体积分数、颗粒状细小马氏体岛的双相钢。     

7090/SiC_p复合材料的固溶工艺制度研究

研究了移动坩埚式喷射沉积制备的7090/SiCp复合材料的两种固溶热处理工艺对其组织和性能的影响。观察了材料挤压态、固溶态及时效后样品的微观组织及X射线衍射图谱。通过两种固溶制度的比较,表明经过挤压变形处理的移动坩埚式喷射沉积制备的7090/SiCp复合材料,经475℃×1h+120℃×24h处理后材料的最高抗拉强度仅有715MPa,而经450℃×3h+500℃×3h+120℃×18h热处理后复合材料达到峰时效,材料的最高抗拉强度可以达765MPa。