Synergic Evolution of Microstructure-Texture-Stored Energy in Rare-Earth-Added Interstitial-Free Steels Undergoing Static Recrystallization

Synergic evolution of microstructure-texture-stored energy in interstitial-free (IF) steels has been investigated to elaborate the effect of dissolved rare-earth (RE) elements on static recrystallization. Grain size, texture fraction and geometrically necessary dislocation distribution of IF steel samples annealed for different times were compared, suggesting that RE elements could postpone recrystallization nucleation but accelerate grain coarsening. The visco-plastic self-consistent model was primarily adopted and verified, then used to calculate the relative activities of different slip systems. It was proved that the compatible deformation of IF steels was very sensitive to dissolved RE elements, in particular the {110} 6 <111> 2 slip systems became extremely inactive, leading to an α -fibre textures rich configuration of RE-IF steels. Although both IF steels have the same stored energy sequence of which γ -fibre takes precedence in nucleation followed by α -fibre, the nucleation rates of α / γ -fibres driven by the reduced stored energy slowed down in RE-IF steels. Further nucleation-path analyses revealed that shear bands within γ -fibre mainly sacrificed for grain nucleation of {111}<110> orientation, while α -fibre especially prior grain boundaries therein preferred supplying nucleation sites for {554}<225> grains, which accounting for the competitive growth of γ -fibre textures in RE-IF steels rather than being dominated by a single orientation. After grain growth, the major texture of Normal-IF steels had been transferred to {554}<225> from {111}<110>, while {554}<225> in RE-IF steels still inherited the orientation advantage and grew up rapidly, thus inducing the grain coarsening. As this work offers a significant understanding of RE microalloying effect on static recrystallization, it will provide references for alloy design and industrial application of IF steels.