Elastic Properties of TiNi Shape Memory Alloys Subjected to Various Heat Treatments

Abstract

Comparative experimental studies for elastic characteristics of commercial nitiline TiNi shape memory alloys subjected to various heat treatments have been performed nitinol in the temperature range 80–300 K, including the premartensitic and martensitic transitions. The distortion of the crystal structure during the premartensitic transition in the as-prepared sample is found to be accompanied by pronounced anomalies of the Young’s modulus and the internal friction near the phase transition temperature T_S ≈ 270 K both on h-eating and cooling. An additional heat treatment causes slight shifts of the premartensitic transition temperatures on heating T_Su and cooling T_Sd and an increase in the hysteresis, but the character of the elastic anomalies is changed only slightly. Conversely, anomalies of the elastic properties during the martensitic transition at T ~ 220 K are observed only on cooling, and the temperature and the character of the anomalies is significantly changed after a heat treatment.