Hot tensile deformation behavior and Bonora damage model of 25CrMo4 steel.

• Discussed the effects of temperature and strain rate on microstructure. • Observation shows that the fracture surface is mainly characterized by ductile dimples and ductile fracture. • Established a Bonora model for 25CrMo4 steel considering temperature and strain rate. In this research, hot tensile test was performed on 25CrMo4 steel in the temperature range of 1273 K to 1423 K and different strain rates in the range of 0.01 to 10 s−1.The relationship between deformation and factors such as temperature, strain rate and stress triaxiality was investigated.The results showed that decreasing the temperature and increasing the strain rate causes a significant increase in the flow stress curve of steel. Variation of the fracture behavior with temperature and strain rate was studied. The observed fracture types are all ductile fractures characterized by dimples. The maximum fracture strain was found to be 0.513 at temperature of 1273 K and strain rate of 10 s−1. At the same time, DRXed grain coarsing is observed with the decrease of strain rate and increase of tensile temperature. A fracture damage model for predicting fracture failure is proposed based on Bonora damage model. The predicted damage values obtained by the damage model have a good correlation with experimental, with only a maximum relative difference of 8.46%. [ABSTRACT FROM AUTHOR]