Micro-cracks and their relation to flow and fracture in single crystals of magnesium oxide

Abstract

Evidence on mechanisms of fracture in magnesium oxide single crystals subjected to tensile loading is given. As-cleaved crystals contain micro-cracks typically 10⁻⁴ in. long and slip originating from near these cracks occurs during deformation. At a later stage the cracks grow gradually until they increase to a critical size when catastrophic propagation occurs. If the cracks are removed by polishing ductility is enhanced five to ten times Some crystals were reactor irradiated to doses in the range 10¹⁴-10¹⁹ n.v t. (epithermal) and the effects of this testament on flow and fracture are described and discussed.