The as-quenched microstructure of the Fe-30%Mn-9%Al-5%Cr-0.7%C (in mass%) alloy was single-phase austenite. When the as-quenched alloy was aged at 550 C-750 C, fine (Fe,Mn) 3 AlC carbides were formed within the austenite matrix. In addition, as the aging temperature increased, a M 7 C 3 carbide + D0 3 ! M 7 C 3 carbide + B2 ! M 7 C 3 carbide + (ferrite) phase transition had occurred on the grain boundaries. This grain boundary precipitation behavior has never before been observed in FeMnAlC and FeMnAlCrC alloy systems.