Microstructure of Graphitized Steel during Warm Compression

A Gleeble 3500 physical modeling complex is used to deform graphitized steel (0.46% C) with a microstructure mainly consisting of ferrite and graphite by warm uniaxial compression at 600°C and a strain rate of 0.01 s–1. The rheological strain curve shows that the rheological strain of the steel increases to 190 MPa when the strain rate increases to 0.302; then, it decreases with increasing strain, which means that the steel undergoes softening. EBSD analysis shows that ferrite grains gradually transform from isometric to fibrous ones with increasing strain. The further increase in the strain results in many isometric fine grains in a deformed grain. The number of high-angle grain boundaries increases; that is, the ferrite matrix softens, i.e., undergoes dynamic recrystallization. The main types of texture during deformation are 〈100〉 and 〈111〉. The intensity of the 〈100〉 grain orientation increases gradually with the strain, and the intensity of the 〈111〉 grain orientation first increases and then decreases. Taylor factor analysis shows that the degree of ferrite recrystallization around graphite inclusions is lower than that of the ferrite matrix, which can be explained by the fact that deformed graphite inclusions prevent recrystallization.