Composition design principles for Fe-Mn-Si-Cr-Ni based alloys with better shape memory effect and higher recovery stress

To investigate the factors affecting the recovery stress in Fe-Mn-Si-Cr-Ni shape memory alloy, the transformation behavior under constraints was studied through in situ electrical resistivity analysis. The recovery stress equations during constrained heating and cooling have been established. Composition design principles for Fe-Mn-Si-Cr-Ni shape memory alloys with better shape memory effect and higher recovery stress at room temperature have been proposed and they are different from ones which produce only the best shape memory effect. To test the principles, Fe-14.8Mn-4.78Si-7.95Cr-4.16Ni-0.18C alloy was designed according to the principles. The result shows that the recovery stress of the designed alloy is 360 MPa, 135 MPa higher than that of the alloy designed according to the principles for only obtaining the best shape memory effect under no constraints. Decreasing the amount of the plastic deformation and the ɛ martensite transformation can remarkably increase the recovery stress.