Commercial Al Li alloy plates have a tendency to form intergranular delamination cracks extending in the rolling direction during fracture.

Abstract

The poor grain boundary strength induces low toughness failures when the principal stress acts through the thickness. On the other hand, a delamination toughening mechanism occurs when the stress is applied in longitudinal and transverse directions. During fatigue crack growth at low R load ratios a strong closure effect occurs. AES analyses on freshly broken surfaces reveal that intergranular fracture occurs also with absence from the grain boundaries not only of Li, but also of K or Na impurities.