High Temperature Behavior of Isothermally Compressed M50 Steel

The isothermal compression of M50 steel is carried out on a Gleeble-3500 thermo-mechanical simulator in temperature range of 1223–1423 K and strain rates range of 10–70 s−1. The results show that the carbides play a significant role in the flow behavior and microstructure evolution during isothermal compression of M50 steel. The average apparent activation energy for deformation in isothermal compression of M50 steel is (281.1±42.6) kJ’mol−1 at the strains of 0.4–0.8. The dynamic recrystallization of austenite grains occurs in isothermal compression of M50 steel at 1363 K and 1393 K, enhancing with the increase of strain rate and/or strain. The volume fraction of the carbides decreases with the increase of deformation temperature during isothermal compression of M50 steel and the fine carbides inhibit the dynamic recrystallization of austenite grain. With the occurrence of dynamic recrystallization, the austenite grains are refined, leading to a minor increase in the flow stress and apparent activation energy for deformation in isothermal compression of M50 steel. The austenite grains begin to coarsen at 1423 K and dynamic recrystallization is limited. Hot working of M50 steel should not be performed above 1393 K in order to achieve good workability.