Effect of phase transformation on localized deformation in Ti-Ni shape memory alloy
Jiang Xiaoping; Hida Moritaka; Takemoto Yoshito; Sakakibara Akira; Fujii Shuzo
Abstract:Localized deformation of Ti-50.6at. pct Ni shape memory alloy subjected to tensile loading at different temperatures ( approximately greater than Af) was studied by means of the observation of internal structure. The rolled sheet specimens were subjected to three types of heat treatments, i.e. annealing at 673K (AC), solution-treatment at 1 173K (AQ), and aging at 873K after solution-treatment (AS). It was found AQ and AS specimens that the deformation after the yielding in tensile test was caused by the stress-induced martensite (SIM) transformation, and also by the movement of dislocations which was restricted in martensite bands. The deformation in AQ and AS specimens, therefore, were more localized than in AC specimen where the dislocations were introduced both in the matrix and martensite. Key Words:localized deformation, phase transformation, Af transformation, temperature, stress-induced martensite (SIM), martensite band, dislocations, ductile fracture