DEVELOPMENT OF SHAPE MEMORYALLOYS WITH SPECFIC PROPERTIES

本研究的目的包括以下四个方面。1)低温超弹性合金的发展，2)中高温形状记忆和超弹性合金，3)医用β-Ti和Zr形状记忆和超弹性合金，4)可与Ti-Ni媲美的新型形状记忆合金。在第一个目的中，虽然我们试图利用多阶段马氏体相变（MMT）现象来开发低温超弹性合金，但我们无法获得良好的性能。然而，我们系统地阐明了母晶尺寸、合金成分和热处理条件对MMT的影响。在第二个目的中，Ti-Pd和Ti-Pt合金是高温形状记忆和超弹性材料的有希望的候选者，通过透射电子显微镜（TEND）研究了它们的显微组织。测定了Ti-Pd合金中反相畴的原子排列和Ti-Pt合金中B19马氏体的内部缺陷。第三种用途是开发出具有不同屈服应力的高性能β-TiMoSn合金。然而，在β-Zr合金中没有发现形状记忆和超弹性的来源α”马氏体相变。用研制的β-钛合金制成了医用导丝的试制品。第四，在Co-Zr-Ni和Co-Zr-Pd三元体系中开发了具有形状记忆效应和高延展性的新型B2型金属间化合物。然而，它们的性能无法与TiNi合金相比。

The purpose of the present study consists of four folds as listed below.1) Development of low temperature superelastic Alloy, 2) Medium and high temperature shape memory and superelastic alloy,3)β-Ti and Zr shape memory and superelastic alloys for medical use, 4) New shape memory alloy comparable to Ti-Ni.In the first purpose, although we have tried to utilize the multistage martensitic transformation (MMT)phenomena to develop the low temperature super elastic alloy, we cannot obtain the sound property. However, we have systematically clarified the effect of parent grain size, alloy composition and heat treatment conditions on the MMT.In the second purpose, microstructures in Ti-Pd and Ti-Pt alloys which are promising candidates of high temperature shape memory and superelastic materials have been investigated by transmission electron microscopy (TEND).The atomic arrangement of antiphase domain in Ti-Pd alloy and the internal defects of B19 martensite in Ti-Pt alloy have been determined.High performance β-TiMoSn alloys with various yield stresses have been developed in the third purpose. However, α"martensitic transformation which is origin of shape memory and superelastic properties cannot detected in β-Zr alloys. The trial product of medical guide wire has been made of the developed β-Ti alloy.In the fourth purpose, new B2 type intermetallic compounds with shape memory effect and high ductility have been developed in Co-Zr-Ni and Co-Zr-Pd ternary systems. However their performance is not comparable to that of TiNi alloys.