Thermodynamic Approach to Study Thermal Cycling Effect of NiTi Shape MemoryAlloys

摘要

A thermodynamic approach was used to study the thermal cycling effect of NiTibinary shape memory alloys. It was found that enthalpy and entropy changes of martensitic transformation increase as the thermal cycling numbers increase, and the magnitude of the increasing enthalpy is smaller than that of the entropy. The dislocation thermodynamic analysis was performed to study the variation between the two as a function of dislocation density. The experimental results and theoretical analysis suggests that the thermal cycling effect of NiTi binary alloys is originated from the influence of dislocations introduced by thermal cycling on enthalpy and entropy. The contribution of dislocations to the enthalpy is relatively less than to the entropy. (AN).