Shape Memory Properties of PM Processed Ti-Sn-Cu Alloy

Ti-Sn-Cr shape memory alloys were fabricated by the powder metallurgy (PM) process and plastic working process. The mixed powders in composition of Ti-3at%Sn-7at%Cr were prepared using a V-blender. The mixed powders were filled into a graphite die, and then sintered at a temperature of 1223 K for 1.8 ks using a pulse current sintering equipment. The sintered alloy was solution-treated and then hot-rolled into a plate at 1150 K. The sintered alloy which mainly consisted of the β phase was obtained by performing solution treatment. The hot-rolled alloy showed a texture. The plateau region due to the stress induced martensite transformation was appeared in the stress-strain curve of the solution treated alloy, but it is not clearer than that of the alloy tempered at 1073 K because of a residual stress introduced by hot-rolling. Therefore, the hot-rolled alloy was annealed at a temperature between 573 K and 1273 K for 1.8 ks. The phase structure of the alloy annealed at 1073K consisted of the β phase and the α phase due to recrystallization, but that of the alloy annealed at 1273 K consisted of only the β phase. The plateau region due to the stress induced martensite transformation was appeared in the stress-strain curves of the alloy annealed at 1073 K and 1273 K. This means that the annealed alloy has superelasticity. It was thus found that the alloy fabricated by the PM process has obviously superelasticity by performing plastic working and annealing.