Microstructure evolution and fracture mechanism of H13 steel during high temperature tensile deformation

It is known that mechanical properties of hot working die steel deteriorate during service due to dynamic recovery, recrystallization and plastic deformation of tempered martensite. In order to clarify the associated microstructure evolution and fracture mechanism, a systematic investigation was carried out on a widely used hot working die steel. Samples were tensile deformed at different temperatures ranging from 25 degrees C to 640 degrees C and examined using SEM and TEM. Results obtained have shown that mechanical properties as well as fracture mode change with increasing testing temperature. These phenomena have been elaborated together with microstructure evolution during high temperature deformation. Deformation mechanisms and roles of different carbides in crack formation and propagation have been discussed.