Stressing of Annealed NITINOL: The Electrical Resistance and Calorimetric Effects

摘要

The effects of stress on the electrical resistance and scanning calorimetry curves of NITINOL during its phase transformation are substantial. The generation of a peak occurs in the resistance curve, and an additional peak is generated in the calorimetry curve for the transformation during cooling, as compared to annealed metal. Explanation of the relation between stress and the formation of these peaks is presented for both cooling and heating cycles. Straining the wire in the martensitic versus the austenitic condition also can result in differences in the subsequent phase transformation. These differences can be exploited for one-time higher temperature applications of this shape memory alloy.