A study on martensitic transformation behavior in shape memory alloys via a modulated differential scanning calorimetry technique

Abstract

Highly precise and efficient characterization of thermophysical parameters associated with martensitic transformation (MT) in shape memory alloys (SMA) is challenging based on conventional calorimetry methods. Moreover, existing methods for evaluating the elastocaloric effect of SMA typically require a series of tests and calculations. In addition, the present method cannot evaluate the nonreversible part during MT. This work proposed a technique rarely mentioned in previous studies on martensitic transformation of metals and alloys, i.e., utilizing the modulated differential scanning calorimetry (MDSC) to superimpose a sinusoidal signal over an underlying DSC ramp. By adjusting appropriate measurement parameters, the reversible and nonreversible parts of thermal events during MT of SMAs were revealed. Furthermore, a series of thermal parameters useful for the study of MT can be obtained by this method and thus may provide a perspective for studying the MT process. Based on MDSC technique, we took Ni-Mn-Sn-(Cu) alloys, a kind of ferromagnetic shape memory alloy, as an example to demonstrate the study of the MT process as well as the elastocaloric effect. From the perspective of energy dissipation, we analyzed the intrinsic relationship between nonreversible component and thermal hysteresis in the MT process. Conventional DSC test and experimental results on the adiabatic temperature change (ΔTad) were also provided to verify the MDSC prediction results.