MICROSTRUCTURAL STABILITY OF THE TI-50.8 AT.% NI ALLOY ACHIEVED BY THERMAL CYCLING

Abstract

The influence of thermal cycling with a large number of cycles on the microstructure of a Ti-50.8 at.%Ni shape-memory alloy in coarse-grained (CG) and ultrafine-grained (UFG) states was investigated.The effect of microstructural stability was found in both coarse-grained and ultrafine-grained statesstarting from the 100th cycle of martensitic transformations. In addition, starting from 100 cyclesof martensitic transformation, sections of the structure are observed in which packets of martensiticplates are visible (plate thickness in the range of 50–300 nm). Present in individual plates at highmagnifications were composite (001) B19′ nanotwins of type I with a width of up to 5 nm. Theformation of nanotwins is probably associated with saturation of the structure after a certain numberof cycles.