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 anα-fibre textures rich configuration of RE-IF steels.Although both IF steels have the same stored energy sequence of whichγ-fibre takes precedence in nucleation followed byα-fibre,the nucleation rates ofα/γ-fibres driven by the reduced stored energy slowed down in RE-IF steels.Further nucleation-path analyses revealed that shear bands withinγ-fibre mainly sacrificed for grain nucleation of{111}<110>orientation,whileα-fibre especially prior grain boundaries therein preferred supplying nucleation sites for{554}<225>grains,which accounting for the competitive growth ofγ-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.

Effects of rare earth elements on inclusions and impact toughness of high-carbon chromium bearing steel

High-carbon chromium bearing steels with different rare earth (RE) contents were prepared to investigate the effects of RE on inclusions and impact toughness by different techniques. The results showed that RE addition could modify irregular Al2O3 and MnS into regular RE inclusions. With the increase of RE content, the reaction sequence of RE and potential inclusion forming elements should be O, S, As, P and C successively. RE inclusions containing C might precipitate in molten steel and solid state, but the precipitation tem perature was significantly higher than that of carbides in high-carbon chromium bearing steel. For experim ental bearing steels, the volume fraction of inclusions increased steadily with the increase of RE content, but smaller and more dispersed inclusions could be obtained by 0.018% RE content compared with bearing steel without RE, whereas the continuous increase of RE content led to an increasing trend for inclusion size and a gradual deterioration for inclusion distribution. RE addition could improve the transverse impact toughness and isotropy of bearing steel, and for modified highcarbon chrom ium bearing steel by RE alloying, the increase of RE content continuously increased both transverse and longitudinal im pact toughness until excessive RE addition.