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

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 σ0.2, so the traditional opinion that SME could be guaranteed by strengthening the parent matrix was not confirmed.