Evolution of Structure and Properties of Nickel-Enriched Ti-Ni Shape Memory Alloy subjected to Compressive Deformation

Abstract

The effect of compressive deformation of the nickel-enriched Ti-Ni shape memory alloy in a temperature range of 100 to 900 °С on phase composition, microstructure, mechanical and functional properties was studied. The temperature ranges of dynamic recovery, polygonization and recrystallization were determined as a result of comparative optical microscopy, XRD, DSC studies, HV measurements and shape recovery testing. Lowering of the compressive deformation temperature is accompanied by an increase in a hardness value from 280 to 350 HV and leads to decrease in average grain size from 33 to 16 μm. The dispersion hardening leads to an increase in shape recovery properties. The optimum deformation temperature range for thermomechanical treatment of Ti-Ni SMA from the viewpoint of ultrafine-grained structure and high functional properties formation was determined as 400 to 600 °C.