Influence of Large Strain Hot Deformation on Microstructural Evolution in Alloy D9

In this work, a Ti-modified austenitic stainless steel used in the core of fast reactors is subjected to large strain deformation. The steel is deformed to 200% effective strain through high-temperature torsional loading in temperature domain 1173-1473 K. Three strain rates, namely 0.01 s(-1), 0.1 s(-1) and 1 s(-1), are used for this deformation, so that the combined effect of deformation temperature and strain rate on material response can be studied. The torsional loading conditions are correlated with microstructural mechanisms of work hardening, dynamic recrystallisation (DRX) and post-DRX grain growth, each of which are found to bear a different relation with processing parameters. The microstructural response to this thermo-mechanical treatment is contrasted with the response to a heat treatment that involves equivalent exposure to high temperature. It is found that the steel is amenable to large strain hot deformation, and a variety of microstructures can be generated through control of the hot deformation parameters.