Influences of aging and thermomechanical treatments on the martensitic transformation and superelasticity of highly Ni-rich Ti-51.5 at.% Ni shape memory alloy

This paper evaluates influences of aging and thermomechanical treatments on the martensitic transformation and superelasticity of a highly Ni-rich Ti-51.5 at.% Ni. For this purpose, the alloy was subjected to aging and thermomechanical treatments. One group of sample was aged for 1 h at 300-700 degrees C with 100 degrees C intervals. The other group firstly was cold rolled to a reduction of 20% and then aged for I h at the previous temperature range. Results showed that solution annealed and aged samples at 700 degrees C showed no superelasticity because of high nickel content in the matrix of the alloy. For the aged samples, complete superelasticity was observed by aging at 400 and 500 degrees C. Applying 20% cold rolling before aging led to increase aging temperature for observing good superelastic behavior. Compared to the aged samples at 300 and 600 degrees C, for cold worked and aged samples at 300 and 600 degrees C, recovered strain after unloading at 5% strain, was increased 0.8 and 0.7%, respectively. (C) 2015 Elsevier B.V. All rights reserved.