Mechanical Properties of TiNi Shape Memory Alloy for Material and Spring

Abstract

Shape memory alloys receive wide attention as a functional material having an energy exchange function (thermal energy to mechanical energy). Applications of the alloy are actively developed and have already included some spring products.
Systematic studies of the alloy have been made in recent years, but very few reports on features of shape memory alloy springs are found.
This paper describes the investigation of the best fit heat treatment requirements for TiNi shape memory alloys and of their useful service range as a shape memory or a super elasticity material based on material and spring characteristics.
The result shows that the best fit heat treament temperature is 500°C because of the thermal hysteresis and the recovery force at the transformation point, the useful service range as a material is that the stress is not greater than 95kgf/mm² and the temperature is the Ms point plus 115°C or less, and the useful service range as a spring is that the shear strain is 3.7-6.0% or less and the temperature is not higher than the Ms point plus 127°C.