Effect of Deformation Mode on Microstructural Evolution of Microalloyed Steel during Hot Deformation

In this study, we investigate the effects of shear and compressive deformation on microstructural evolution during hot working of low carbon micro-alloyed steel containing 0.03 mass% Nb. By systematically introducing shear and compressive strains under controlled conditions, we clarified the role of shear strain in phase transformation and grain refinement. Results show that when the equivalent strain exceeds 2 with shear strain (γ ≈ 2.2) at 800 °C, effective nucleation sites are generated, promoting the formation of ultrafine ferrite grains (<1 µm). These findings highlight the importance of the deformation mode and strain path in controlling final microstructures, offering insights for optimizing the thermomechanical processing of steels and alloys.