Effect of the Microstructure on the Deformation and Fracture Behavior of an Austenitic Heat Resisting Steel

The tensile properties in a 21-4N austenitic engine valve steel containing pearlitic nodules due to grain boundary reaction have been investigated. The theoretical consideration has been also made on the deformation and fracture behavior in this steel. In the steel with grain boundary reaction nodules, the ductility decreased considerably at room temperature, while it increased at elevated temperature. Although the grain boundary reaction also decreased the tensile strength and 0.2% proof stress, its effect was more noticeable on ductility than on strength. A theory is developed to explain the work hardening behavior as well as the fracture mechanism using a model for composite materials and a good agreement between theoretical and experimental results is obtained.