Improvement of shape memory effect by ausforming in Fe–28Mn–6Si–5Cr alloy

Abstract

The influence of ausforming (deformation of austenite above Md, the uppermost temperature for stress-induced martensitic transformation) on the shape memory effect (SME), microstructures and mechanical behavior in Fe–28Mn–6Si–5Cr (wt.%) alloy were systematically studied. It was found that the SME of the alloy Fe–28Mn–6Si–5Cr (wt.%) could be effectively improved by ausforming at 700°C for 9% tensile strain, in the process of which the oriented stacking faults and dislocations were evolved and regularly distributed in austenite. By taking the above-mentioned well-restored substructures as nuclei for γ→ε transformation, the regularly oriented and uniformly distributed ε martensites were stress-induced and were observed with atomic force microscope to be highly reversible. The best SME did not correspond to the lowest proof stress σ 0.2, so the traditional opinion that SME could be guaranteed by strengthening the parent matrix was not confirmed.