Dynamic recrystallization behavior and hot deformation characteristics in 4340 steel

4340 steel is extensively utilized in the automotive industries and for a large number of general purposes. Due to the importance of thermo-mechanical processing in the production of steels, the dynamic recrystallization (DRX) characteristics of 4340 steel were investigated in the present study. Namely, hot compression tests on 4340 steel have been performed at a temperature range of 900–1200°C, a strain rate range of 0.01–1 sec –1 , and a strain of 0.9. The resulting flow stress curves show the occurrence of dynamic recrystallization . The flow stress decreases with increase in deformation temperature and decrease in strain rate. The microstructure of 4340 steel has been studied. It is suggested that the evolution of DRX grain structures can be accompanied by a considerable migration of grain boundaries. The constitutive equations were developed to model the hot deformation behavior of this alloy. Finally the activation energy obtained in this research is 427.169 kJ/mol.