Characteristic of Burst Transformations in Pseudoelasticity and Shape Memory Effect- a Review

This paper reviews effect of the burst transformations in pseudoelasticity and shape memory effect in shape memory alloys (SMA). However, we will give some of our un-published results on tensile testing of Ti-49.83 at% Ni SMA wire sample which shows that burst transformations accompanying in-homogenous deformation of the stress-strain curve in pseudoelasticity region (above austenite finish temperature-Af) proceeds to the upper yielding followed load drop similar to the upper and lower yield observed in the mild steel specimens. Though our stress-strain curve look similar to the one reported by P. Feng and Q. P. Sun, the stress before getting yield was 720 MPa as compared to approx. 380 MPa reported by them. An attempt was made to explain upper and lower yield point phenomenon with help of micro-mechanical modeling. Further research has to be directed to identify the relationship between microstructural changes with respect to the burst transformations and test temperature of the sample.