The effect of Al on mechanical properties and microstructures of Fe-32Mn-12Cr-xAl-0.4C cryogenic alloys

Abstract

The effect of Al addition (O-3 wt%) on tensile properties and microstructures of Fe-32Mn-12Cr-xAl-0.4C cryogenic alloys were investigated at temperatures ranging from - 196 to 250°C. The Al is an austenite stabilizer suppressing the formation of the strain induced 8-martensite, while it behaved as a J-ferrite stabilizer when added to 3 wt%. The Fe-32Mn-12Cr-OAl-0.4C alloy showed the strain induced &-martensite after tensile deformation at - 196°C. Deformation twins were observed in deformed cryogenic alloys except Fe-32Mn-12Cr-2A1-0.4C alloys at temperatures ranging from - 196 to 25°C. The formation of both the deformation twins and the strain induced &-martensite enhanced the tensile elongation by retarding local necking. The Fe-32Mn-12Cr-(0~1,3)A1-0.4C alloys exhibited elongation peaks within a temperature range forming the deformation twins. AS the stacking fault energy increases with increasing Al content, the elongation peak shifted to lower temperature with increasing Al content in Fe-32Mn-12Cr-xAl-0.4C alloy. The continuous formation of strain induced phases, deformation twins and &-martensite, up to a large strain was important to increase the tensile elongation of Fe-32Mn-12Cr-sAl-0,4C cryogenic alloys.