Optimization of hot workability and microstructure control in a 12Cr-10Ni precipitation hardenable stainless steel: An approach using processing maps

Optimization of hot working parameters and corresponding microstructure control were explored in a 12Cr-10Ni precipitation hardenable martensitic stainless steel. From hot compression tests, 1073-1373 K (800°-1100 °C) and five (0.001-10 s−1) different strain rates, processing maps were developed, and various domains of microstructure evolution (in the austenite phase) were identified. The stable domain of the processing maps appeared to indicate dynamic recrystallization (DRx) in the austenite phase: as evident by the appearance of inflection point in the strain hardening rate versus flow stress plots. The suspected DRx domain was further confirmed by detailed microstructural investigations of the respective water-quenched specimens. The DRx domain showed a refinement of the martensite packet size and of the prior transformation austenite grain size. The later was shown with optical microstructure and reconstructed (modelled) microtexture data of the prior austenite grains. Additionally, the DRx domain showed a significant difference in activation energy as estimated from appropriate constitutive modelling.