The fracture mechanism during fracture toughness testing was investigated on a coarse-grained magnesium alloy, with an average grain size of ∼50 µm, and a low fracture toughness. The results show that {1012}-type deformation twins were formed at the crack tip and many dislocations pile up on these boundaries. The accumulated strains at these boundaries become the origin of fracture; i.e. cracks propagate along these boundaries between the deformation twins and the matrix.

Fracture Mechanism of a Coarse-Grained Magnesium Alloy during Fracture Toughness Testing. H.Somekawa, A.Singh, T.Mukai: Philosophical Magazine Letters, 2009, 89[1], 2-10