Abstract
Effect of prior strain on the static softening taking place in hot deformed austenite was studied by means of interrupted tensile tests and metallographic observation. For this purpose a 0.15%C-1.5%Mn steel was deformed at a temperature of 1 133 K and a strain rate of 2×10-3s-1. The softening curve after dynamic recovery consists of two stages which can be controlled by classical recovery and recrystallization. By contrast, the softening curve after dynamic recrystallization (DRX) consists of three distinct stages accompanied, by three plateaus, and can not go to the full softening. These can be controlled by metadynamic recovery and recrystallization in addition to classical recovery and recrystallization. The softening ratio caused by each of the mechanisms can be roughly proportional to the volume fraction of DRX nuclei, growing DRX grains and strain hardened DRX grains. Metadynamically recovered grains which contain moderate dislocation density can exist stably at high temperature, leading to incomplete softening as well as relatively lower grain growth rate and relatively smaller grains.
