Fabrication of Ti-Sn-Cr Shape Memory Alloy by PM Process and Its Properties

Ti-Sn-Cr shape memory alloys were fabricated by the powder metallurgy (PM) 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 between 1023 K and 1223 K using a pulse current sintering equipment. The sintered alloy was solution-treated and then aged. The phase structure and the tensile properties of the alloy obtained were investigated. The relative density of the as-sintered alloy increased with elevating sintering temperature, and the maximum relative density was 99.5 % at a sintering temperature of 1223 K. Although the as-sintered alloy was high density, the microstructure of the alloy was inhomogeneous. Thus it was found that the solution treatment was needed to obtain the homogeneous microstructure of the alloy. The alloy which is mainly consisted of the 3 phase was obtained by performing solution treatment. The plateau region due to the slip deformation was observed in the stress-strain curve of the solution treated alloy, but that due to the stress induced martensite transformation could not be done. The plateau region due to the stress induced martensite transformation, however, was appeared in the stress-strain curve of the aged alloy. This means that the aged alloy has shape memory properties. It was also found from the result of bending test that the alloy fabricated by the PM process has obviously shape recovery properties.