A Study on Amorphous Formation of Alloys Solidified Under High Pressure

在几种体积膨胀和体积收缩元素的凝固组合中，估计了它们的高压相图，并对Bi-Sb合金（均固溶型）、Bi-In合金（中间化合物形成型）和Al-Ge合金（共晶型）三种合金体系进行了高压实验。在Bi-10-30Sb合金的x射线衍射图中，在2rheta=30-40°处检测到一个宽峰。峰值消失后，观察到的是常压相。显微组织中观察到细晶组织，认为这是高压相向常压相转变的结果。在高压下凝固的Bi-20at%In合金，x射线衍射图没有明显变化。但发现Bi/BiIn共晶数量增加，表明共晶成分向富Bi侧转移，并估计了Bi- in体系的高压相图。在20kbar左右凝固的Al-40at%Ge合金的x射线衍射图中，检测到亚稳相gamma_1 （Al_2Ge）和gamma_2 （AlGe）的峰，并且这些亚稳相在2个月后仍然存在。在BSE对比图像中，gamma_1和gamma_2相呈层状共晶，gamma_1/gamma_2共晶的平均Ge浓度比正常共晶α al /dia.cub.Ge高8at%。估算了Al-Ge体系的高压相图，估算了γ - _1/ γ - _2共晶产生的临界压力为10 ~ 20kbar。

On Several combinations of volume-expanding and -shrinking elements on solidification, their high-pressure phase diagrams were estimated and three alloy systems where amorphous formation could be expected, i.e., Bi-Sb alloys (homogeneous solid solution-type), Bi-In alloys (intermediate compound formation-type) and Al-Ge alloys (eutectic-type), were subjected to the high-pressure experiment. In the X-ray diffraction pattern of Bi-10-30Sb alloys, a broad peak was detected at 2rheta=30-40deg.and the peak was thereafter disappeared and, instead, the normal pressure phase was observed. In the microstructure, a fine-grained structure was observed and considered to appear as a result of phase transformation from a high-pressure phase to the normal-pressure one. In Bi-20at%In alloy solidified under high-pressure, no distinct change was observed in the X-ray diffraction pattern. However, an increase in the amount of Bi/BiIn eutectic was found, suggesting that the eutectic composition was shifted to Bi-rich side, and the high-pressure phase diagram of Bi-In system was estimated. In the X-ray diffraction pattern of Al-40at%Ge alloy, solidified at about 20kbar, the peaks of metastable phases, gamma_1 (Al_2Ge) and gamma_2 (AlGe), were detected and these metastable phases still existed after 2 months. The gamma_1 and gamma_2 phases were appeared as a laminar eutectic in the BSE comp. image and the average Ge concentration of the gamma_1/gamma_2 eutectic was found to be higher by 8at%Ge than that of normal eutectic, alphaAl/dia.cub.Ge. The high-pressure phase diagram of Al-Ge system was estimated and the critical pressure for the generation of the gamma_1/gamma_2 eutectic was estimated to be 10-20kbar.