Deformation Behavior and Processing Maps of 42CrMo Alloy Casting Blank Subjected to Double-Pass Isothermal Compression

Abstract

The hot deformation behavior of 42CrMo alloy casting blank was studied using a double-pass isothermal compression. The effects of strain allocation in different passes on the stress softening degree and processing maps were analyzed. It is found that the stresses at the double-pass strains of 0.45 + 0.45 and 0.3 + 0.6 decrease with increasing temperature and decreasing strain rate. The softening fraction of recrystallization in deformation interval increases with increasing strain rate and temperature. The deformation behavior in the second-pass is significantly affected by the first-pass. The stress softening models considering partitioned strain at the double-pass compression are established, respectively. The deformation intervals exert an obvious effect on the efficiency of power dissipation (EPD) and optimum parameters. The main mechanism of microstructure evolution is dominated by dynamic recovery accompanied by a slight DRX. By combining the developed processing maps and microstructures, the optimum processing windows in the double-pass strain of 045 + 0.45 are found to be at a strain of 0.8, temperatures of 1000-1200 °C and strain rates of 0.45-1 s−1 with EPD of 38-49%, and for the double-pass strains of 0.3 + 0.6, the optimum windows at a strain of 0.8, temperatures of 1050-1200 °C and strain rates of 0.4-1 s−1 with EPD of 40-48% are recommended.