抄録
In order to develop Ni-free biomedical superelastic alloys which can replace Ti-Ni, AuTi high temperature shape memory alloy is focused and its high martensitic transformation temperature is sufficiently decreased by 18mol%Co addition. In this paper, deformation behavior of Ti-32Au-18Co alloy with various aging treatments from 373K to 573K is investigated. Dynamic mechanical analysis (DMA) revealed that forward and reverse martensitic transformation temperatures are decreased below room temperature by aging treatment being higher than 373K. Cyclic loading-unloading tensile tests with constant strain increment of 1% revealed that, at room temperature (RT), (1) constant deformation stress appeared when martensitic transformation temperatures are above RT, and that (2) deformation stress is increased with increasing aging temperature when all the martensitic transformation temperatures are below RT. Therefore, the nonlinear shape recovery by unloading is caused by superelastic deformation. However, no superelastic deformation was recognized for Ti-31Au-19Co of which martensitic transformation temperatures are similar to those of Ti-32Au-18Co aged at 573K. These results suggest other condition(s) than martensitic transformation temperature must be required for the appearance of superelasticity.
