Effect of microstructure on shape-memory effect in Fe-32Mn-6.5Si alloy

Abstract

The effect of heat treatment condition after cold rolling has been investigated on SME and transformation temperatures in an Fe-32Mn-6.5Si alloy. The specimens heat treated at 873K and 973K experience no and partial recrystallization, respectively. Above 1073K, grain size increases with increasing temperature and time. With a decrease in grain size, stress for inducing ε martensite increases. The unrecrystallized specimen shows the best SME due to training-like effect. In recrystallized specimens, SME becomes better with an increase in grain size, which may be attributed to easy transformation by deformation. Comparison of two specimens, which show best and worst SME, in the amount of induced ε leads to a suggestion that it is a major factor controlling SME. With lowering heat treatment temperature, As point decreases while Af point increases, expanding the transformation range. Therefore alloys with a large grain size exhibit a large shape change on a certain temperature change.