The effect of solution treatment temperature on SIEM and shape recovery of Fe–Mn–Si shape memory alloy

Abstract

Solution treatment process is stepwise process in manufacturing of iron based shape memory alloy. It is well known that the grain size of austenite in the solution treatment condition depends on the austenitizing/solutionizing temperature. Moreover, the solution treatment temperature influences the transformation temperatures of SMAs. It has been found by researchers that solution treatment temperature brings about modification in the grain size, the grain boundary angles, and the annealing twins. The major objective of the present work is therefore to assess the influence of modifications in the microstructural features by using different solution treatment temperatures. Optical microscopic studies reveal the microstructural changes brought about by changing the solution treatment temperature. DSC shows that somewhat change of transformation temperatures in regarding to the conjugated solution treatment temperature, but the martensite transformation temperatures are still in the range of ambient temperature. X-ray diffraction results refer to the enhancement of SIEM in the alloy that was solution treated at 1000 °C. TEM observations prove that uniform stacking faults have been generated at the austenite of the alloy that has been solution treated at 1000 °C. In addition, SADP shows that ε-martensite is the domain structure generated after 3.1% pre-strain of the sample that has been solution treated at 1000 °C. The results indicate that solution treatment at an optimal temperature of 1000 °C leads to increase of shape memory effect of iron base shape memory alloy.