抄録
In this research, the influences of repeated heat-treatment for extend on flexibility and scalability (critical stress for inducing martensite and recovery strain) of Ti-Ni shape memory alloy (SMA) for stent was investigated by loading-unloading tests with constant strain condition. The chemical composition of the alloy is Ti-50.4at%Ni. The specimen shape is a wire with 1 mm diameter and 20 mm gage length. The condition of repeated heat-treatment for extend was in the following; heat-treatment condition is 773K for 18ks, applied strain in each heat-treatment is varied from 4 to 8%, and total applied strain is 40%. Critical stress for inducing martensite increases and recovery strain decreases with increasing applied strain. Therefore, the flexibility and scalability decreases with increasing of applied strain. Meanwhile, decrements of flexibility and scalability during repeated loading-unloading tests decrease with increasing applied strain. From these results, the initial performance decreases with increasing applied strain. However, the degradation of performance is improved with increasing applied strain.
