E21 Fe3AlC carbide (κ) in the Fe-Al-C ternary system is known to have superior strength and limited ductility at room temperature. It forms a lamellar structure similar to the pearlite with a ferrite (α) phase through a eutectoid-likc reaction from an austenite (γ) phase and improved mechanical properties were found by replacing cementite to κ phase. In this study, investigated were the effects of γ grain size and plastic pre-deformation of γ on the eutectoid-like reaction to improve the process time for the decomposition, and the mechanical properties of those specimens at ambient and elevated temperatures. In both the fine y specimen and the cold-rolled specimen, the transformation of γ to α+κ is faster than that in the coarse y specimen. The mean inter-lamellar spacing of α+κ dual phase structure of cold-rollcd specimen aged at 973K is almost the same with that of fine γ specimen aged at 973K. At room temperature, it was found that compressive yield stress depends only on the mean inter-lamellar spacing. This implied that the yield stress of α+κ dual phase alloys is governed by the mean inter-lamellar spacing, like pearlite steels. Creep-like deformation behavior was also observed at elevated temperatures.