Effect of Cold Working on Transformation Behavior and Shape Memory Characteristics of a Ti-50.2at% Ni Alloy

Abstract

Transformation behavior and shape-memory characteristics of Ti-50.2 at%-Ni alloy were investigated after solution-treatment followed by cold working. The B2 -> R -> B19' transformation occurred when the cold-worked samples were cooled, while the B2 -> B19' transformation occurred in the solution-treated sample. M* (the DSC peak temperature corresponding to the R -> B19' transformation) decreased with increase in the amount of cold working, while R* (the DSC peak temperature corresponding to the B2 -> R transformation) kept almost constant. Negligible transformation-elongation occurred under the stress of 10 MPa applied to the solution-treated sample, while that was dramatically increased up to 3 % when the equal level stress was applied to the cold-worked(9% area reduction) sample. The residual elongation increased with increase in the amount of cold-working under applied stress less than about 70 MPa, while it decreased under applied stress higher than about 70 MPa.