Stress-induced martensitic transformation in (Ni47Ti44)100-xNbx
(1.北京市清华大学核能与新能源技术研究院2.江西省南昌市华东交通大学学院机械与电子工程学院3.Jiangxi Key Laboratory of Surface Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013, China4.江西科技师范学院 江西省材料表面工程重点实验室, 南昌 3300135.Department of Materials for Special Environments, Institute of Metal Research,Chinese Academy of Sciences, Shenyang 110016, China)
Abstract: The effect of deformation via stress-induced martensitic transformation on the reverse transformation behavior of the (Ni47Ti44)100-xNbx (x=3, 9, 15, 20, 30, mole fraction, %) shape memory alloys was investigated in detail by differential scanning calorimetry (DSC) after performing cryogenic tensile tests at a temperature of Ms+30 ℃. The results show that Nb-content has obvious effect on the process of stress-induced martensitic transformation. It is also observed that the stress-induced martensite is stabilized relative to the thermally-induced martensite (TIM) formed on cooling, and Nb-content in Ni-Ti-Nb alloy has great influence on the reverse transformation start temperature and transformation temperature hysteresis of stress-induced martensite(SIM). The mechanism of wide transformation temperature hysteresis was fully explained based on the microscopic structure and the distribution of the elastic strain energy of (Ni47Ti44)100-xNbx alloys.
Key words: Ni-Ti-Nb alloy; shape memory alloy; martensitic phase transformation; wide hysteresis; differential scanning calorimetry