Mechanisms of fatigue crack initiation in metals: role of aqueous environments

Abstract

Fatigue crack initiation in engineering materials has been the subject of considerable research. Most of these investigations focused on gaseous environment effects, and extensive review articles have appeared in recent times discussing the role of gaseous environments on crack initiation. Because of experimental difficulties, the effect of aqueous environments on mechanisms of fatigue crack initiation has received little attention, despite their unquestionable importance from an engineering standpoint. In this review, several of the fatigue crack initiation models are examined in detail and their anomalies discussed. The physics and micromechanisms of crack initiation during cyclic deformation in aqueous environments which are highly corrosive in nature are examined. The characteristics of the crack initiation process in aqueous environments are critically reviewed in the light of the specific role of several concurrent factors involving the nature of the aqueous medium, corrosion interactions, alloy chemistry, processing treatments, intrinsic microstructural effects and test variables.[/p]