Hot deformation behavior of a nickel-modified AISI 4330 steel

Abstract

Hot compression of a nickel-modified AISI 4330 steel was studied over a wide range of temperatures and strain rates using Gleeble 3800 thermomechanical simulator. Samples were quenched at different stages of deformation to study microstructure evolution using optical and electron microscopies. Stress-strain curves showed that both dynamic recovery (DRV) and dynamic recrystallization (DRX) take place for certain deformation conditions. However, in comparison to low alloyed steels with lower nickel content, the nickel-modified AISI 4330 steel showed significantly lower workability particularly, resulting from the temperature and strain rate ranges over which DRX takes place. The kinetics of recrystallization were studied and the stress constants and apparent activation energies were determined for the investigated alloy and compared with similar alloy with lower nickel content so as to quantify the influence of nickel. The obtained results are interpreted in terms of the influence of nickel on dislocation dynamics and therefore the softening process at high temperature under various ranges of strain rate. The findings will help a better design of the forging process of these alloys which are prone to hot cracking during open die forging.