The plasticity deformation mechanism of Fe–12Mn–6Al-0.2C steel at elevated temperature

Abstract

The sample deformed at 700 °C abnormally exhibited low plasticity, which was attributed to the precipitation behavior of Al11Mn4.6 particles at the phase boundaries. In the early stage of deformation at 700 °C, the plastic deformation started firstly at the phase boundaries and strain-induced dynamic transformation (SIDT) was the main deformation mechanism, which caused the migration of the phase boundaries from ferrite to austenite. Element partitioning and dynamic interfacial migration facilitated the precipitation of Al11Mn4.6 at 700 °C, which further induced the accumulation and proliferation of strain and dislocations at the boundaries. The increase of Al11Mn4.6 particles hindered the dynamic migration of the phase interface and suppressed the SIDT. Meanwhile, ferrite underwent main plastic deformation after necking due to working hardening in austenite, which further weakened the contribution of austenite and its SIDT effect to plasticity. During necking, the softening of ferrite at phase boundaries by continuous dynamic recrystallization (CDRX) and the hardening of austenite by deformation amplified the difference in deformation capacity and further enhanced the stress concentration at the phase boundaries, which promoted the nucleation of cracks near precipitates and their rapid propagation along phase boundaries.