Comparative study on the effect of samarium additions on thermo-mechanical behaviour of shape memory alloys

Abstract

In the present work, a comparative study of the shape memory and thermo-mechanical behaviour of four alloys containing different amount of samarium have been carried out at a strain rate of 0.08 × 10-6s-1. After hot rolling, annealing and solution treatment, the alloy samples were tensile deformed at room temperature from 1% to 5% and were then recovered at 600 °C for 20 minutes repeatedly for six times to complete six training cycles. It is found that thermo-mechanical treatment (training) results in improvement of shape memory effect and has a significant influence on mechanical parameters like proof stress (σ: 0.002), critical stress (σ: 0.0008) and strain hardening exponent. The improvement in shape memory effect by thermo-mechanical treatment can be regarded as the effect of reduction in the values of proof stress and critical stress during training which facilitates the formation of ε (martensite). It has also been noticed that excessive training may result in the formation of ά (martensite) due to continuous softening of the alloy during training, thus degrading the shape memory effect. Finally, it has also been noticed that the addition of samarium increases the values of proof stress, critical stress and strain hardening exponent. Although the addition of samarium increases the values of proof stress, critical stress and strain hardening exponent yet it has not an adverse effect on shape memory effect. In this paper, the effect of thermo-mechanical treatment on mechanical parameters such as proof stress, critical stress, strain hardening exponent and their influence on shape memory effect is discussed.