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

The influence of ausforming (deformation of austenite above Md, the uppermo st 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 ausformi ng at 700 degreesC for 9% tensile strain, in the process of which the orien ted stacking faults and dislocations were evolved and regularly distributed in austenite. By taking the above-mentioned well-restored substructures as nuclei for gamma --> epsilon transformation, the regularly oriented and un iformly distributed epsilon martensites were stress-induced and were observ ed with atomic force microscope to be highly reversible. The best SME did n ot correspond to the lowest proof stress sigma (0.2), so the traditional op inion that SME could be guaranteed by strengthening the parent matrix was n ot confirmed. (C) 2001 Published by Elsevier Science B.V.