The influence and its mechanism of NbC precipitates on the shape memory effect of Fe-Mn-Si-Cr-Ni shape memory alloy

Abstract

In order to evaluate the effect that the existence of small coherent NbC precipitates in austenitic matrix greatly influences the shape memory recovery, seven FeMnSiCrNi shape memory alloys containing (0.1∼0.5%) NbC and (3∼5%) Si have been prepared and investigated in this paper. The result shows that solution-aging treatment correlated with the NbC precipitates and the Si content is the most important to the shape memory effect. Among these alloys, the shape memory recovery rate with 0.5% NbC and 3%Si addition is the lowest. The best result has been achieved in the Fe14Mn5Si9Cr5Ni0.5NbC alloy by solution treated at 1200°C for lOh and then aging at 800°C for 6h. Under 5% deformation, its shape memory recovery rate is up to about 3.7%, which is comparable of the result of thermomechanical cycle. The NbC precipitates were observed by TEM in the paper. Its influence and mechanism on shape memory effect and the relationship between the second phase precipitates and the resultant good shape memory are discussed in details. The pre-requirement for the FeMnSiCrNi alloy to get training free has been proposed.