The present work was conducted to evaluate the effects of substructure development on the strain hardening behavior of Fe–17.5Mn–8.3Al-0.74C–0.14Si lightweight steel. This was performed applying tensile testing method at ambient temperature. The significant strain hardening capability of the experimental steel is attributed to the cell structure formation and its progressive evolution to subgrains over a wide range of applied strain. The continuous subgrain refinement with the applied strain could lead to the nano-size partitioning of the austenite (~ 530 nm) and ferrite (~ 500 nm) grains. The size of substructure (mesh length) appears to be stabilized at true strains above 0.35, thereby reducing the rate of work hardening and inducing subgrain rotation to higher misorientations. The contribution of substructure refinement is significant and possesses a high portion of the measured flow stress (~ 550 MPa for austenite and ~ 70 MPa for ferrite at the true strain of 0.5).
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