Recrystallization Mechanism and Processing Map of 18CrNiMo7-6 Alloy Steel during Hot Deformation

In this study, isothermal single-pass forming doformation of forged 18CrNiMo7-6 alloy steel was carried out by Gleeble-3500 thermal simulation testing machine. The constitutive equations and processing maps with parameters of deformation temperature and strain rate were established. The results show that the optimum hot deformation parameters are temperature 1050 degrees C, strain rate 0.1 s(-1) with the peak power efficiency being 0.432. The mechanism of grain refinement during hot compression was also characterized by electron backscatter diffraction (EBSD). The results show that continuous dynamic recrystallization (CDRX), discontinuous dynamic recrystallization (DDRX) and grain growth are the main microstructure evolution mechanisms during hot working. The rotation of sub-grains under CDRX mechanism is the main factor for the formation of new grains. In addition, the DDRX mechanism is formed by the bulging of HAGBs at the grain boundary triple junction of the original grains, and the CDRX mechanism forms finer grains. The study also found that temperature affected the organization evolution mechanism, the DDRX mechanism plays a leading role when the temperature is low. With the increase of deformation temperature, CDRX begins to play a leading role and forms finer grains. When the deformation temperature rises to 1150 degrees C, the grains continue to grow at a higher temperature.

Automated summary

This study investigated the isothermal single-pass forming deformation of forged 18CrNiMo7-6 alloy steel using a Gleeble-3500 thermal simulation testing machine. Constitutive equations and processing maps were established based on the deformation temperature and strain rate. The results showed that the optimal hot deformation parameters were a temperature of 1050 degrees C and a strain rate of 0.1 s(-1), with a peak power efficiency of 0.432. The grain refinement mechanism during hot compression was characterized by electron backscatter diffraction (EBSD), which revealed that continuous dynamic recrystallization (CDRX), discontinuous dynamic recrystallization (DDRX), and grain growth were the main microstructure evolution mechanisms during hot working.