Formation of Deformation-Induced Divorced Eutectoid Pearlite above the Ae1

A 0.21% C plain carbon steel was deformed in torsion to strains of ε = 0.15-3.0 at a strain rate of ε ̇= 4.5 s-1 over the temperature range 722-822°C in a 5%H2-Ar gas atmosphere. The experimental parameters were varied in order to study the formation of ferrite and pearlite by dynamic transformation (DT) in the intercritical region. This transformation was observed right up to the highest experimental temperature (822°C). The pearlite formed by DT contained cementite spheroids whose size distribution evolved during isothermal holding after deformation. In the first stage, corresponding to the first 800 s of holding, spheroid coarsening took place. When the holding time exceeded 800 s, the spheroids dissolved and the pearlite reverted into the original parent austenite. The results indicate that pearlite can form by DT at temperatures well above the Ae1 and that the reverse static transformation is much slower than the forward dynamic transformation.