On the improvement of shape memory effect in Fe16Mn5Si9Cr4Ni alloys by thermomechanical treatment

Abstract

The shape memory effect in Fe-Mn-Si alloys was discovered in the early 80's. Since then many efforts have been made in improving the shape memory effect in this alloy. Obtaining a shape memory strain up to 5% in order to get practical use is still an endeavor. Complete shape memory effect has been found both in single crystalline and in polycrystalline Fe-Mn-Si alloys, but as the prestrains in those investigations were quite small, the recoverable strain is limited to about 2%. Recently, Yang et al. obtained in Fe-29Mn-5.5Si-4.5Cr-2Ni-3.5Co (wt%) and Fe-13.7Mn-6Si-8.3Cr-4.9Ni (wt%) alloys over 5% reversible strain by applying 8% prestrain in a bending test. But till now a full recoverable strain is only obtained for a prestrain less than 2%. In the present study, the shape memory effect of an Fe-16Mn-5Si-9Cr-4Ni (wt%) alloy was tested. By applying the training treatment of 3--5% prestrain and 600 C annealing, a 3.5% recoverable strain can be reached in this alloy. Reasons for the improvement of the shape memory effect are proposed.