Relationship between the microstructure and properties of thermomechanically processed Fe-17Mn and Fe-17Mn-3Al steels

Two austenitic Mn steels (Fe-17Mn and Fe-17Mn-3Al (wt%, so as the follows)) were subjected to thermomechanical processing (TMP) consisting of forging followed by solutionization and hot rolling. The rolled samples were annealed at 650 and 800℃ to relieve the internal stress and to induce recrystallization. The application of TMP and heat treatment to the Fe-17Mn/Fe-17Mn-3Al steels refined the austenite grain size from 169 μm in the as-solutionized state to 9-13 μm, resulting in a substantial increase in hardness from HV 213 to HV 410 for the Fe-17Mn steel and from HV 210 to HV 387 for the Fe-17Mn-3Al steel. The elastic modulus values, as evaluated by the nanoindentation technique, increased from (175±11) to (220±12) GPa and from (163±15) to (205±13) GPa for the Fe-17Mn and Fe-17Mn-3Al steels, respectively. The impact energy of the thermomechanically processed austenitic Mn steels was lower than that of the steels in their as-solutionized state. The addition of Al to the Fe-17Mn steel decreased the hardness and elastic modulus but increased the impact energy.