Experimental Investigation of Thermo-Mechanical Behaviors in Ni—Ti Shape Memory Alloy

The effect of annealing heat treated temperature, loading rate, environmental temperature, repeated loading cycle on the phase transformation and thermo-mechanical behaviors of shape memory alloy is investigated through a DSC test and a thermo-mechanical test. Shape memory alloy wire with the diameter of 1.1 mm is used and its composition is Ti-56.0wt%Ni. Annealing heat treated temperatures are 300, 400, 500, 600, and 700°C. Loading rates are 0.5, 1.0, 2.0, and 5.0 mm min ^-1 . Environmental temperatures are 17, 25, 32, 33, and 36°C. According to the results, phase transformation temperatures and the peak shapes of DSC curves are influenced by annealing heat treated temperatures. The thermo-mechanical behaviors of shape memory alloy are affected on annealing heat treated temperature, loading rate and environmental temperature. In addition, shape memory alloy might lose its unique characteristics even after unloading under repeated loading cycles or above higher than certain annealing heat treated temperature.