Effect of kappa Carbides on Deformation Behavior of Fe-27Mn-10Al-1C Low Density Steel

Fe-Mn-Al-C steel, which is a potential lightweight material for automobiles, has a variety of microstructures and good mechanical properties. The effect of kappa carbides on the mechanical properties and strain hardening rate of Fe-27Mn-10Al-1C (wt.%) low density steel was studied by short-time heat treatment to control the precipitation behavior of kappa carbides. Quenched specimens have an excellent combination of strength and plasticity and continuous high strain hardening rate, which is due to the uniform distribution of kappa carbides with an average size of 1.6 nm in an austenite matrix. The fracture mode of the sample changed from ductile fracture to cleavage fracture, which was because the aging treatment promoted the precipitation of B2 phases and kappa carbides at grain boundaries. The size and volume fraction of nanoscale kappa carbides in austenite grains increase with the increase of aging temperature, and the yield strength increases but the density of slip bands decreases, resulting in the gradual decrease of strain hardening rate.