Aging treatment of a cold rolled Fe-Mn-Al-Si-C steel

Due to constant challenge of designing ever lighter, stronger and more efficient vehicles to reduce fuel consumption and carbon dioxide emissions, the automotive industry keeps searching for new materials that have superior properties. The Fe-Mn-Al steels have very interesting characteristics, since it presents low density (about 10% to 13% lower than conventional steels), besides showing excellent properties of cold forming. Suitable heat treatments, such as hardening by the precipitation of κ (Fe,Mn)Al₃C carbides, are used to improve their performance. In the present work, the high manganese steel with the composition Fe-31.2 Mn-7.5 Al-1.3 Si-0.9 C was cold rolled and subsequently subject to aging treatment. The rolling was performed with different percentages of thickness reduction (20%, 40% and 80%). The aging was carried out at 600 ° C for 1h, 2h, 4h, 8h, 16h, 32h, 64h and 128h. Rockwell B or C hardness tests were performed for each treatment condition in order to obtain the hardness curves with the aging time, comparing the effects caused by the variation of cold work. MEV, optical microscopy and DR-X tests were used to characterize the material. The samples showed a peak of aging hardness around 64h treatment time.