The role of temperature in the microstructural evolution of HPT-processed NiTiHf high-temperature shape memory alloy

Abstract

Ni50.3Ti29.7Hf20 alloy was subjected to high-pressure torsion (HPT) process at room temperature (RT) and 300 °C. The mix of amorphous phase and nanocrystalline debris was found by TEM observation in sample processed at RT. Two types of structure were clearly distinguished after HPT at 300 °C: the first one is martensite-like plates oriented in single direction; the second is nanocrystalline structure with narrow amorphous bands. The fraction of amorphous phase is significantly larger after RT deformation.