Grain-Boundary Migration and Cavitation during Fatigue

Abstract High-purity copper, magnesium, and Magnox AL80 have been fatigued at temperatures of 0.5T m and above. Grain-boundary migration and cavitation were observed after fatigue, and quantitative measurements of the angular distributions of total and cavitated boundaries were made. These showed that grain boundaries tended to migrate to planes of maximum shear stress during fatigue, the driving force most probably being provided by the imbalance of dislocations across boundaries due to inhomogeneity of slip. Similarly, the incidence of cavitated boundaries showed a maximum around the planes of maximum shear stress. The results support the theory of the growth of cavities by absorption of lattice vacancies continuously generated in the grains by alternating plastic strain.