Quasibrittle fracture and cleavage initiation in Fe–2·6Si single crystals in different environments

Abstract

Crack propagation and cleavage initiation measurements were carried out on Fe–2·6Si single crystals. It was shown that the brittleness of fracture can be characterized quantitatively by the ratio a _n = ∆a/δ, where ∆a is the crack growth per cycle and δ is the plastic crack-tip opening. The transition from ductile to quasibrittle fracture, characterized by rising a _n values, was examined as a function of the plastic crack-tip opening velocity in vacuum and in low-pressure hydrogen gas.