PHASE STABILITY AND MECHANICAL PROPERTIES OF Ti-Ni SHAPE MEMORY ALLOYS CONTAINING PLATINUM GROUP METALS

摘要

In order to develop Ti-Ni base shape memory alloys (SMAs), the effects of ternary additions on phase constitution and mechanical properties were investigated for TiNi alloys containing some platinum group metals: Ir, Rh and Pt. All the alloys fabricated were made by Ar arc melting method using high purity elemental materials followed by hot-forging at 1173-1673K in Ar and furnace cooling. Then X-ray diffraction analysis and tensile tests were carried out at room temperature (RT). It was found that, when the amount of ternary is lower than 10mol%, all the additions reduce martensitic transformation temperature (M_s) of TiNi and B2 phase becomes stable. ' Besides monoclinic, L1_0 and B19 phases appear for TiNi containing 40-50mol%Ir, 30-50mol%Rh and 20-50mol%Pt, respectively. The tensile ductility at RT decreases with increasing the amount of ternary additions, and the ductility becomes very limited when monoclinic (TiIr), L1_0 (TiRh) and B19 (TiPt) phases appear in