Influence of heat treatment parameters on the functional behavior and corrosion performance of a shape memory wire actuator

Abstract

In the present study, the effect of heat treatment parameters on the functional response, corrosion behavior and microstructural evolution of NiTi shape memory alloys were investigated. Various heat treatment regimes were utilized to study the impact of temperature and duration on the actuation behavior of wire samples under bending. Results clarified that austenite transformation temperatures As and Af increased at higher treatment temperatures. Cyclic response in the range of 0 to 15 degrees indicated that the actuation force exhibits an inverse relation with the treatment temperature. Higher treatment durations below 500°C elevated both the hardness and the sustained load. Bending force levels above 1500gf were achieved after a 90 min treatment at 400°C, whereas that over 500°C brought about a noticeable drop in strength. Investigations on the corrosion behavior of NiTi alloy was utilized in the simulated body fluid revealing that the sample heat treated at 400°C for 90 min showed the highest corrosion resistance.