Aligning Cr23C6 Particles to Improve Shape Memory Effect in an FeMnSiCrNi Alloy by Ageing after Pre-Deformation at Different Temperatures

Our previous work had shown that shape memory effect (SME) of FeMnSiCrNi alloys can be remarkably improved by aligning Cr23C6 particles through introducing directional interfaces of austenite and deformation -induced martensite at room temperature before ageing. In present paper, we investigated the effects of ageing after pre-deformation at 203 K and room temperature on the precipitation of aligned Cr23C6 particles in an Fe15.3Mn5.8Si8.5Cr4Ni0.2C alloy to further improve the SME. The results showed that regardless of the deformation temperature, the SME improvement by the ageing was obviously higher after pre-deformation by 12% than 5% due to more aligned Cr23C6 particles. The ageing did not improve the SME more obviously after 12% pre-deformation at 203 K than room temperature although the number of directional interfaces between the austenite and martensite was higher. This abnormality could be rationalized by the more dislocations after pre -deformation at room temperature and concurrent comparable number and size of aligned Cr23C6 particles.