Current-manipulated martensite transformation to enhance strength-ductility synergy in a medium Mn steel

Abstract

In order to quantify the thermal and athermal effects during pulse current assisted deformation, the deformation behavior of medium manganese steel was studied using forced air cooling. At room temperature, the ultimate tensile strength of medium manganese steel is 1350 MPa and the total elongation is 47.3 %. However, in the pulsed current assisted deformation under forced air cooling, its strength and ductility are synergistically improved, with the ultimate tensile strength increased to 1380 MPa and the total elongation increased to 57 %. Athermal effects can delay deformation-induced martensite transformation by reducing austenite dislocation density and reducing stress concentration at austenite-ferrite phase boundaries, resulting in better strength and ductility in the pulsed tensile sample with forced air cooling. While the thermal effect increases the strain energy required for deformation-induced martensite transformation, resulting in a decrease in martensitic content and a decrease in accumulated dislocation density. Therefore, compared with the sample with forced air cooling, the ultimate tensile strength of the pulse tensile sample without forced air cooling is reduced.