Factors affecting the shape of the ductile-to-brittle transition

Abstract

This paper uses a statistical model of cleavage fracture to examine the effect of various material parameters on the mean toughnesses of ferritic steels in the transition region. Individually, changes in the flow properties, in the effective surface energy, and in the distribution of particles from which cleavage is initiated, all affect the curvature of the mean fracture toughness ( K c) versus temperature ( T) curve. The range of applicability of the Master Curve description of K c versus T is due to real metallurgical processes causing counteracting changes in more than one parameter at a time. As a result, if the Master Curve is applicable before irradiation hardening, plastic deformation or tempering, then it may well remain applicable after these processes. It will not apply both before and after segregation (intergranular failure) or warm prestressing. The study also illuminates the differences between plates, welds and forgings in their response to irradiation or thermo-mechanical processing.