Effect of aging treatment on microstructure and properties of Fe-30.0Mn-9.6Al-1.0C low-density steel

The effects of aging treatment on microstructure and properties of Fe-30.0Mn-9.6Al-1.0C low- density steel were studied by OM， SEM， XRD， EBSD， and TEM. The strain hardening behavior and strengthening plasticizing mechanism were also analyzed. The results show that after aging at different temperatures， the microstructure of Fe-30.0Mn-9.6Al-1.0C low-density steel remains mostly full austenite with κ-carbide precipitates. As the aging temperature increases， the increase in κ-carbide precipitation has an enhancing effect on the strength of the low-density steel， but it will deteriorate its plasticity. After solid solution at 1050 ℃ and aging at 450 ℃， the tensile strength of the low-density steel is 811 MPa，the elongation is 106.9%，and the product of strength and plasticity is 86.7 GPa·%. When aging at 500 ℃， the tensile strength of the low-density steel is 861 MPa，the elongation is 33.2%，and the product of strength and plasticity is 28.6 GPa·%. After solid solution at 1050 ℃ and aging tensile deformation at different temperatures， the strain hardening index of the low-density steel exhibits a double n-value phenomenon， and the strain hardening behavior shows a multi-stage variation pattern. After tensile deformation of the low-density steel， a large number of dislocation walls， Taylor lattice and microband structures， and fine κ-carbides together enhance the strength and plasticity of the low-density steel.