Effects of Nb Microaddition and Thermomechanical Treatment Conditions on Hot-Deformation Behavior and Microstructure of Mn-Al TRIP Steels

摘要

The paper presents the results of the compression tests carried out at various temperatures using the Gleeble thermomechanical simulator. A softening kinetics was determined in a double-hit compression test. It was found that the dynamic recovery is a main thermally activated process controlling work hardening both for continuous and multi-stage deformation. The Nb microalloyed steel has higher flow stresses and peak strains than the Nb-free steel. A solute drag effect of Nb results in a slower softening kinetics of Nb containing steel and the high difference in flow stresses for final deformation stages of four-cycle compression between Nb-microalloyed steel and the base steel without niobium is probably due to the initiation of Nb(C, N) precipitation. The effect of the slow cooling in the γ → α transformation range and the temperature of isothermal holding of steel in a range from 350°C to 450°C on a final multiphase bainitic-martensitic-austenitic microstructure was presented.