We elucidate here the temperature and strain rate sensitivity of a duplex stainless steel through the development of deformation maps and by studying the flow behaviour during hot compression tests in the temperature range of 1223–1473 K and at strain rates between 0.01 and 30 s⁻¹. The flow curves exhibited softening after attaining a peak condition and the flow stress increased with the decrease of temperature and increase of strain rate. The observed change in the activation energy is attributed to strain partitioning between the two constituent phases and the deformation maps were characterised by two regions of flow instability. On the other hand, the microstructural evolution indicated that the strain rate and deformation temperature had a significant impact on the flow behaviour. In the flow stability region, the continuous dynamic recrystallisation (DRX) of ferrite was strongly activated, while in the flow instability region, both the continuous dynamic recrystallisation in ferrite and discontinuous DRX in austenite were weak.

High strength/high elongation continues to be the primary challenge and focus for medium-Mn steels. It is elucidated herein via critical experimental analysis that the cumulative contribution of transformation-induced plasticity (TRIP) and microstructural constituents governs high strength/high elongation in 0.2C–3Al–(6–8.5)Mn–Fe steels. This was enabled by an effective heat treatment involving a combination of intercritical hardening and tempering to obtain high strength/high ductility. An excellent combination of high ultimate tensile strength of 935–1112 MPa and total elongation of 35–40% was obtained when the steels were subjected to intercritical hardening in the temperature range of 700–750 °C and low tempering at 200 °C. The intercritical hardening impacted the coexistence of austenite, ferrite, and martensite, such that the deformation behavior varied with the Mn content. The excellent obtained properties of the steels are attributed to the cumulative contribution of the enhanced TRIP effect of austenite and the microstructural constituents, ferrite and martensite. The discontinuous TRIP effect during deformation involved stress relaxation, which was responsible for the high ductility. Lamellar austenite, unlike the equiaxed microstructure, is envisaged to induce stress relaxation during martensitic transformation, resulting in the discontinuous TRIP effect.