Development and Validation of Processing Maps for Hot Deformation of Modified AISI 321 Austenitic Stainless Steel

Hot deformation studies and optimization of hot working parameters and corresponding microstructure evolution were explored in a modified AISI 321 austenitic stainless steel. Hot compression tests were carried out in the temperature range of 800 degrees C-1,100 degrees C and five different strain rates (0.001-10 s(-1)). Processing maps were developed based on the results of hot compression tests, employing the principles of dynamic materials model and various domains of microstructure evolution were identified. The stable and unstable domains, as well as various domains indicating other microstructural reconstitutive mechanisms, including dynamic recrystallization (DRx), were identified with the aid of a processing map. The domain for DRx was confirmed by microstructural analysis of deformed specimens and also from the inflections in hardening curves. The processing regime for microstructural control was identified, and the results were validated by actual forging trials on a 1,000-T hydraulic forging press. The grain size of laboratory-tested hot-compressed samples and industrially forged billets exhibited excellent correlation. Constitutive equation for hot deformation was also developed for the steel based on hot compression test results.