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形状记忆及超弹性合金；4)可与钛镍相媲美的新型形状记忆合金。第二个目的是利用透射电子显微镜(Tend)对高温形状记忆材料和超弹性材料的显微组织进行了研究，确定了Ti-Pd合金中反相区的原子排列和Ti-PT合金中B19马氏体的内部缺陷。第三个目的是开发了具有不同屈服应力的高性能β-TiMoSn系合金。本文的第四个目的是在Co-Zr-Ni和Co-Zr-Pd三元系中开发出具有形状记忆效应和高延展性的新型B2型金属间化合物，但其性能却无法与α合金相媲美。

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.