The deformation and fracture of austenitic heat-resisting steel with grain-boundary reaction nodules

Abstract

The tensile properties in 21-4N austenitic engine valve steel containing pearlitic nodules due to the grain-boundary reaction have been investigated at room temperature. Some theoretical considerations on the deformation and fracture behaviour of this steel are also presented. In the steel with grain-boundary reaction nodules more than about 10% in area fraction, the ductility decreases considerably with their increase owing to the brittle fracture of rod-like precipitates in the nodules. Although the grain-boundary reaction also decreases the tensile stress and 0.2% proof stress, its effect is more noticeable on ductility than on strength. A theory is developed to explain the workhardening behaviour as well as the fracture mechanism using a model for composite materials and a good agreement between theoretical and experimental results is obtained.