Athermal effects of electric current aging treatment on microstructures and properties of Fe-Mn-Al-C lightweight steel at different temperatures

Electric current aging treatment (EAT) has been considered as a simple and efficient heat treatment method. Especially, the athermal effect of electric current provide additional and critical roles, but there are few reports on the relevant mechanism. This work investigated the athermal effects of EAT on a Fe-18Mn-9Al-1C (wt.%) lightweight steel at 450 ∼ 650 °C, through comparison with conventional aging treatment (CAT) at the same temperature holding for a long time. At 450 °C, the EAT for 6.0 min could produce a higher density of intragranular κ-carbides in austenite (2.58 × 10 24 ·m -3 ) than the CAT for 180 min (1.69 × 10 24 ·m -3 ), attributed to the accelerated nucleation and diffusion. At 550 °C, comparable κ-carbide precipitation occurred in both EAT (6.0 min) and CAT (180 min) steels, indicating weakened athermal effects at this temperature. However, at 650 °C, the EAT dissolved intragranular κ-carbides due to increased Gibbs free energy by electric current, while the CAT steel exhibited significant κ-carbide coarsening. Consequently, the EAT-450 steels achieved 40 ∼ 59 MPa higher yield strength and ∼18% greater elongation than the CAT-450 steel. Furthermore, the EAT-650 steels maintained at least 10% elongation, whereas the elongation of CAT-650 steel plummeted to 2% due to the coarse κ-carbides. These findings demonstrate that the EAT can athermally modulate κ-carbide evolution and enable rapid optimization of strength-ductility balance across different temperatures. This provides reference ideas for in-depth understanding of the mechanism of the athermal effect of electric current and the development of efficient aging treatments for lightweight steel.