Generalization of intrinsic ductile-to-brittle criteria by Pugh and Pettifor for materials with a cubic crystal structure

Two classical criteria, by Pugh and Pettifor, have been widely used by metallurgists to predict whether a material will be brittle or ductile. A phenomenological correlation by Pugh between metal brittleness and its shear modulus to bulk modulus ratio was established more than 60 years ago. Nearly four decades later Pettifor conducted a quantum mechanical analysis of bond hybridization in a series of intermetallics and derived a separate ductility criterion based on the difference between two single-crystal elastic constants, C-12-C-44. In this paper, we discover the link between these two criteria and show that they are identical for materials with cubic crystal structures.

Automated summary

The study discovered that the Pugh and Pettifor criteria are identical for materials with cubic crystal structures, both predicting the brittleness and ductility of materials. The Pugh criterion is based on the shear modulus to bulk modulus ratio of a metal, while the Pettifor criterion is based on the difference between single-crystal elastic constants.