Dynamic Recrystallization Behavior and Critical Strain of 51CrV4 High-Strength Spring Steel During Hot Deformation

Single-pass compression experiments have been performed on 51CrV4 spring steel using a Gleeble 3800 thermomechanical simulator at temperatures in the range of 800–1000°C and strain rate of 0.01 s −1 or 0.1 s −1 ; the maximum deformation degree was 50%. By considering the inflection of the ln θ – ε curve and minimum value of the − ∂(ln θ )/∂ ε – ε curve, the relationship between the critical strain ( ε c ) of dynamic recrystallization (DRX) and the deformation temperature was determined. The results showed that steady flow behavior could be observed during low-temperature (800°C, 850°C) deformation, and dynamic recovery (DRV) regulated the trend of the stress–strain curve. Dislocation cell structures and polygonization were formed during the DRV stage. DRX of the alloy occurred when the deformation temperature reached a higher value (900°C, 1000°C). The amount of ε c required for DRX decreased with increase in the deformation temperature, and the relationship between ε c and the peak strain ( ε p ) was determined as ε c = 0.49 ε p . Discontinuous DRX was clearly favored when the strain was lower than the critical value.