Correlation between shape memory effect and density of annealing twin boundary in an FeMnSiCrNi alloy during special heat treatments with different parameters

It remains unclear whether a negative dependence of shape memory effect (SME) still exists on the density of annealing twin boundary (ATB) in FeMnSi-based alloys during special heat treatments without optimal parameters. To address this issue, the evolutions of grain size and martensite amount in an Fe-14.5Mn-5.5Si-8.2Cr-5.2Ni-0.016C alloy were investigated in addition to the evolution of ATB density during the special heat treatments, i.e. training and thermomechanical treatment with different annealing temperatures. The results showed that the SME still showed a strong negative dependence on the ATB density independent of the special heat treatments. An obvious positive dependence of SME existed on the density of low angle grain boundary concomitant with the reduced ATB density. No obvious correlation between the SME and the grain size existed when the pre-deformation was rather lower (<4%). Larger grain size and less pre-existing martensite were conducive to realizing larger recovery strains.