Transformation and Deformation Mechanisms In High Temperature Shape Memory Alloys With Nanoprecipitates

An emerging class of Ni-based high temperature shape memory alloys (HTSMAs) display high reliability, light weight and increased capability while lowering space and power consumption for many energy and transportation applications. This research focuses on developing a fundamental understanding of the inherent microstructure-property relationship of Ni-rich HTSMAs, of which very little is currently known. Ni-Ti-X alloys where X=Pt,Hf,Au can exhibit high transformation temperatures, large transformation strains and small permanent strains. These variants are investigated in order to determine beneficial properties, which are strongly influenced by the formation of nanoscale precipitates. Advanced electron characterization techniques are used to
explore the martensitic interactions of these precipitates at low temperature, and dislocation activity at higher temperature. These insights are incorporated into microstructural modeling frameworks to understand how phase transformations, crystal plasticity, and time-dependent creep interact to affect the response of single crystal micropillar experiments under isothermal and load biased thermal cycling conditions.