Ti-Ni-Mo Shape-Memory Alloys for Medical Applications

Abstract

Near equiatomic Ti-Ni shape memory alloys have been known to transform from the B2 (cubic) parent phase to the B19' (monoclinic) martensitic phase. Elongation transformation and hysteresis transformation associated with the B2-B19) transformations were reported to be large. The former is about 70/0 and the latter is about 50 K [I, 2]. In contrast to the B2-B19) transformation, elongation and hysteresis transformations associated with the B2-R (rhombohedral) transformation, were reported to be small. The former is about 0.80/0 and the latter is about 2 K [3]. The B2-R transformation is known to be induced as follows: 1. thermal cycling the near equiatomic Ti-Ni alloys [4]) 2. annealing the Ni-rich Ti-Ni alloys [5], 3. thermo-mechanically treating the near equiatomic Ti-Ni alloys [6], 4. adding AI,Fe,Mo to the near equiatomic Ti-Ni alloys [7-9].