EBSD Study on Proeutectoid Ferrite and Eutectoid Ferrite Refinement Mechanism of D2 Wheel Steel Under a Rolling Condition

This study used scanning electron microscopy with an backscatter diffraction system to the refinement mechanism of proeutectoid ferrite (Pro-F) and eutectoid (Eut-F) in a D2 wheel steel under rolling contact conditions. The results indicate that as shear strain increased (γ < 0.21), dislocation density continuously, formed cells were distributed uniformly grains. Subsequently, cell boundaries changed into low-angle (LABs); these LABs gradually became high-angle (HABs), average grain size was refined from 8 μm 710 nm. Under 0.21 ≤ γ 0.84, pile-up occurred at side ferrite–cementite interface, spatial misorientation between two adjacent ferrites gradually. lamellar divided bamboo-like grains by LABs, equiaxed When 0.84 3.314, number HABs inside increased, they kinds are repeatly equiaxial “elongation-bamboo like refinement-elongation” process, which reduced difference. As further completely mixed same morphology, dramatically, ultra-fine approximately 110 nm formed.