The structures and mechanical properties of austenitic Fe-(20 or 30)Mn-(0 to 7)Al alloys at 77 to 295K were investigated with regard to phase transformations and deformation twinning. Additions of aluminum to the 20wt%Mn alloys decreased the γ → ε transformation temperature. The yield stress increased with increasing aluminum content, whereas strain hardening decreased. This tendency was prominent at low temperatures. In 30wt%Mn alloys, the yield stress and strain hardening were almost identical, regardless of the aluminum content. Additions of aluminum suppressed the γ → ε transformation and caused deformation twinning. The calculated stacking-fault energy, based upon a regular solution approach, showed that austenitic Fe-Mn-Al alloys which had stacking-fault energies higher than about 20mJ/m2 favored deformation-twinning, leading to an increase in low-temperature ductility.

Effects of Deformation Induced Phase Transformation and Twinning on the Mechanical Properties of Austenitic Fe-Mn-Al Alloys. K.Sato, M.Ichinose, Y.Hirotsu, Y.Inoue: ISIJ International, 1989, 29[10], 868-77