Deformation Behavior of Functionally Graded Ti-Ni Shape Memory Alloys

Abstract

Deformation behavior of temperature gradient anneal(TGA) treated Ti-50.0Ni(at%) alloys were investigated by means of thermal cycling tests under constant load and tensile tests. TGA treated Ti-Ni alloy wires showed a sequential deformation behavior along the length of the specimen since the stress required for the B2-B19’ transformation increased with decreasing annealing temperature. Considerably large residual elongation(about 0.4 %) occurred in the TGA treated Ti-Ni alloy under the applied stress of 80 MPa, which is ascribed to the fact that yield stress of the sample annealed at 823 K is lower than the stress required for the B2-B19’ transformation of the sample annealed at 658 K.