过共析钢温变形过程中的组织演变-铁素体的等轴化

he microstructure evolution of hypereutectoid steels during warm deformation were investigated by uniaxial hot compression simulation experiment and by means of SEM, TEM and EBSD, especially for the formation of equiaxial ferrite grains and the effect of aluminum on the formation of equiaxial ferrite grains. The results indicated that the microstructure evolution of hypereutectoid steel during warm deformation involed the spheroidization of lamellar cementite, the equiaxial of ferrite and the re-precipitation of cementite particles. At the beginning of warm deformation, lots of dislocations were introduced into ferrite and subgrain boundaries were formed by dynamic recovery of ferrite. With the strain increasing, subgrains rotated due to the pinning effect of cementite particles, leading to the formation of high angle grain boundaries, i.e. the formation of equiaxial ferrite grains was actualized by the dynamic continuous recrystallization of ferrite. By the addition of Al, the coarsening of cementite was hindered, the sizes of cementite particles and ferrite grains were refined and the fraction of high angle grain boundary was increased.