Aging hardening response and β-Mn transformation behavior of high carbon high manganese austenitic low-density Fe-30Mn-10Al-2C steel

Aging treatments under three temperatures were performed to investigate the aging hardening response of high carbon high manganese austenitic Fe-30Mn-10Al-2C steel. The dramatic differences in hardness and microstructure were observed after aging under different temperatures. The aging treated at 500 ℃ had a typical aging hardness curve and the hardening response originated from the precipitation of κ-carbide, which plays an important role in performance improvement. When aging was conducted at 700 ℃, there was no significant change in hardness because a balance between aging hardening and high-temperature softening was built. On the contrary, the aging under 600 ℃ exhibited novel continuous increase in hardness and dramatic secondary hardening due to the formation of β-Mn which had an intrinsic high hardness. In addition, the β-Mn was also found after aging for long time under other temperatures. Unfortunately, the formation of β-Mn distributed along γ grain boundaries led to serious brittle fracture. For further investigation and application, the β-Mn transformation behavior was discussed based on the diffusion and redistribution of elements. Considering the dramatic difference in the formation kinetics of β-Mn depending on aging temperature, the diagram of β-Mn transformation was achieved to obtain optimized aging conditions.