Damage in an aluminum alloy induced by the combined action of shear stress and environmental exposure

Abstract

In this work, the damage mechanism and characteristics of the 2219-C10S aluminum alloy under the combined action of an exfoliation corrosion solution and shear stress were investigated. Simple shear specimens of the material (based on ASTM B831-14) were subjected to environmental exposure experiments under simple shear stress conditions. During testing, a small band-shaped zone of simple shear stress formed in the middle of the exposed region on the specimen surface. After the specified exposure duration in the corrosive medium, the corrosion micromorphology, crack nucleation location, and crack propagation direction were analyzed. The results demonstrated that under the combined action of the corrosion solution and shear stress, tiny pits appeared on the surface of the specimen after a certain exposure duration; the shear stress promoted slip dissolution of the material at the edge of the pit via the shear slip mechanism, resulting in the formation of microcracks from the edge of the pit along the shear stress direction. The microcracks still propagated along the grain boundary in the direction roughly parallel to the shear stress. The shear stress level had no clear effect on the average corrosion depth, but it had a substantial impact on the maximum corrosion depth. With increasing shear stress, the maximum corrosion depth markedly increased along with the risk for corrosion-induced specimen failure. On doubling the exposure duration, both the average corrosion depth and the maximum corrosion depth increased, but the growth rate for the average corrosion depth decreased and it increased for the maximum corrosion depth.