Understanding the relationship between kinematic compatibility and hysteresis in reversible martensitic phase transformations

The aim of this experiment is to investigate the microstructural origins of hysteresis and functional fatigue in materials that undergo reversible martensitic phase transformation (MPTs). MPT is a diffusionless transformation between high-symmetry and low-symmetry crystallographic phases. It is the enabling mechanism behind the behaviors of such advanced materials as shape memory alloys (SMAs). However, fundamental knowledge gaps regarding hysteresis and functional fatigue continue to be persistent barriers. Recently, empirical research showed that hysteresis dramatically decreases when kinematic compatibility is increased. Here, we will use in-situ X-ray topotomography (XRTT) during stress-induced MPT to characterize the effect of kinematic compatibility on microstructure. We will compare two NiTiPd SMAs: one with high compatibility/low hysteresis, and one alloy with low compatibility/large hysteresis.