Utilizing Incomplete Phase Transformation to Characterize Elastocaloric Effect of Shape Memory Alloys

This study reports a correction to assist the elastocaloric effect characterization of shape memory alloys and obtain the latent heat of stress-induced martensitic transformation. The incomplete phase transformation analysis (IPTA) correction is developed based on the assumptions of linear transformation plateau of stress–strain and identical heat capacities for austenite and martensite phases.

Taking Ni50.8Ti49.2 alloy as a demonstration, an integrated test rig is built to validate IPTA correction and study the heat leak effect. Using water as heat transfer fluid and heat leak compensation it is possible to further improve the accuracy of imposing IPTA correction. The predictions of latent heat from direct and indirect approaches with IPTA correction are validated from the experimental data.

The required minimum martensitic phase fraction is only 10–20% when applying the IPTA correction, compared with 84–93% in traditional approaches. The IPTA correction extends the precondition of complete transformation to incomplete transformation in elastocaloric characterization.