DSC study of the reverse martensitic transformation behavior in a shape memory alloy pipe-joint

The reverse martensitic transformation behavior of a Ni–Ti–Nb shape memory alloy pipe-joint was investigated systematically by means of differential scanning calorimetry. It was found that the reverse transformation start temperature (A′s) of the pre-deformed pipe-joint increased while the transformation temperature interval decreased when the wall thickness declined. The reverse transformation temperature interval was widened by inserting a connecting pipe into the hole of the pipe-joint, demonstrating that the connecting pipes impeded the reverse transformation of the pre-deformed pipe-joints. On the basis of the kinetics of thermoelastic martensitic transformation, the specific characteristics of the reverse martensitic transformation behavior of shape memory alloy pipe-joints were explained.