Thermal deformation model and recrystallization characteristics of low-density steel containing solely δ-ferrite
As a novel steel material,Fe-Al low-density steel has attracted extensive attention and research interest due to its low density,high plasticity,excellent corrosion resistance,cost-effectiveness and feasibility for mass produc-tion.In comparison to other competitive structural materials,the microstructure of high-aluminum Fe-Al low-density steel exhibits coarse δ-ferrite.In the absence of phase transformation,the challenge lies in how to refine the grain size of Fe-Al ferrite steel.A comprehensive investigation was conducted into the microstructural evolution and recrystallization behavior of high-aluminum Fe-7.5Al ferritic low-density steel under conditions of deformation tem-perature range of 850-1 100 ℃ and strain rates of 0.01-10 s-1.This investigation was performed using a combination of hot simulation testing equipment and microscopic organizational analysis.The aim was to provide the feasibility of achieving a favorable balance between strength and plasticity through dynamic recrystallization for refining grain size.Based on the true stress-strain curves of Fe-7.5Al steel,constitutive equations predicting peak stress was estab-lished,and the processing maps of Fe-7.5Al steel were generated using a dynamic materials model.The result indi-cated that the hot-working behavior of Fe-7.5Al steel conformed to that of alloy materials with moderate stacking fault energy.The deformation mechanism was governed by the dislocation slip and climb.The dynamic restoration mechanism of Fe-7.5Al steel was primarily dominated by dynamic recovery.Increasing deformation temperature and strain rate facilitated the occurrence of discontinuous dynamic recrystallization behavior.This discontinuous recrystallization nucleation was generated by strain-induced grain boundary migration,and the deformation activation energy of Fe-7.5Al steel was calculated as approximately 368.5 kJ/mol.At lower deformation(＜950 ℃)and higher strain rate(＞1 s-1)unstable domain,microband arrays were formed along the 8/8-ferrite grain boundaries,and wedge-shaped cracking occurs at the triple junctions.
low density δ-ferrite steelhot deformationmicrostructure evolutiondynamic recoverydiscontinues dynamic recrystallization
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