Quasi-Static and Dynamic Deformation Behavior of Medium Manganese Automotive Steel under Interrupted Tension

Abstract

This work investigates the mechanical properties of medium manganese automotive steel across a strain rate range from 2 × 10⁻⁴ to 200 s⁻¹. The results indicate that the tensile strength is the lowest at a low strain rate (0.0002 s⁻¹), primarily due to the high mechanical stability of austenite, which results in low work-hardening ability during deformation. As the strain rate increases, the softening effect because of temperature rise, and the dislocation density increase. Consequently, the deformation mechanism is transitioned from the transformation induced plasticity (TRIP) effect (ε < 2 × 10⁻² s⁻¹) to the co-occurrence TRIP and twinning induced plasticity effect (ε ≥ 2 × 10⁻² s⁻¹). Furthermore, in the initial stages of dynamic deformation (ε < 0.1), the same work-hardening phenomenon occurs under the influence of geometrically necessary dislocations as in quasi-static deformation. However, in the later stages of dynamic deformation (ε > 0.25), the weakening of the copper texture density occurs due to an increase in stacking fault energy within the austenite.