Effect of thermomechanical cycling in an FeMnSiCrNi shape memory alloy

Abstract

Previous studies on the effect of cycling in Fe-Mn-Si alloys have shown an increase in reversibility with increasing number of thermal cycles. In Fe-Mn-Si-Cr-Ni and Fe-Mn-Si-Co-Ni alloys, the shape recovery strain during thermomechanical cycling increased when the strain amplitude for each successive cycle is kept constant. Where the total strain (i.e., the sum of the transformation and permanent strain) is held constant, a small decrease in strain recovery with increasing number of cycles occurs. Nonetheless, an increase in reversibility with increasing number of thermomechanical cycles is a common feature for most studies. While previous studies have shown that training or thermomechanical transformation cycling may improve the shape recovery in these alloys, the mechanism is not still clear. Characterization of the transformation behavior during cycling is an important prerequisite for practical use of such alloys. In this paper the authors report microstructural changes during thermomechanical cycling of an Fe-Mn-Si-Cr-Ni shape memory alloy.