Development of Ti-Pd-Ni High Temperature Shape Memory Alloys

(1)开发了一种评估高温形状记忆特性的新装置，利用差动变压器来避免系统各部分热膨胀的影响。虽然一开始遇到了一些麻烦，但通过使用热膨胀非常低的石英玻璃棒来检测试件的应变，这些麻烦就被消除了。 (2)发现在上述合金中添加B可有效抑制晶粒长大，从而提高合金的延伸率。 TiB_2 也实现了预期的沉淀，但尺寸太大而无法发挥作用。研究发现TiB_2析出物的大晶粒长大源于均匀化退火过程。因此，此后避免了均质化处理。 … 更多 (3) 由于 TiB_2 的沉淀硬化效果不佳，因此尝试了另一种沉淀硬化。即，Ti的组成从Ti_ 50 Pd_ 30 Ni_ 20 的化学计量变化。结果发现，引入另一种沉淀物后该方法是有效的。制备了化学计量的富钛以及两者的组合。然后，通过成分和热处理的优化实验，发现富钛侧合金的高温形状记忆特性最好，在773K下热处理1h。 (5) 在合金的回复·再结晶方面得到了非常有趣的结果。即，发现恢复·再结晶是由逆转变控制的，使得前者跟随后者。 (6) 发现了非常有趣的现象，即在马氏体状态下发生再结晶。然而，这意味着马氏体状态下的再结晶成为决定合金温度上限的因素之一。 (7)利用上述新装置进行循环实验。然而，由于实验非常耗时（即10小时/样本），次年仍将继续进行循环实验。较少的

To improve the shape memory characteristics of Ti_<50>Pd_<50-x>Ni_x (0<=x<=50) high temperature shape memory alloys, various experiments were carried out, and the following results were obtained. (1) A new apparatus to assess high temperature shape memory characteristics was developed, utilizing differential transformers to avoid the effect of thermal expansion of various parts of the system. Although some troubles were encountered at the beginning, the troubles were eliminated by using quartz glass rods with very low thermal expansion to detect the strains of specimens. (2) The addition of B to the above alloys were found to be effective to prohibit grain growth, and to the resultant increase of elongation of the alloys. The expected precipitates of TiB_2 were also realized, but the size was too large to be effective. The large grain growth of TiB_2 precipitates were found to originate in the homogenization annealing prosess. Thus, the homogenization treatment was avoided thereafter. … More (3) Since the precipitation hardening of TiB_2 was not effective, another type of precipitation hardening was tried. i.e.the composition of Ti was changed from the stoichiometry of Ti_<50>Pd_<30>Ni_<20>. As a result, the method was found to be effective with introduction of another precipitates. (4) Starting from Ti_<50>Pd_<30>Ni_<20> alloys, 4 types of alloys with B addition, Ti-rich from stoichiometry, and the combination of both, were prepared. Then, as a result of optimization experiment with respect to composition and heat-treatment, the high temperature shape memory characteristics were found to be best for the alloy on Ti-rich side, which were heat-treated at 773K for 1h. (5) Very interesting results were obtained on the recovery・recrystallization of the alloys. i.e. The recovery・recrystallization was found to be controlled by the reverse transformation such that the former follows the latter. (6) Very interesting phenomenon was found such that recrystallization occurs in the martensitic state. However, this means that the recrystallization in the martensitic state becomes one factor determining the upper temperature limit of the alloys. (7) Cyclic experiments are being done using the above new apparatus. However, the cyclic experiments are to be continued in the following year, since the experiments are very time-consuming (i.e.10h/specimen). Less