Stress-Corrosion Cracking and the Interaction Between Crack-Tip Stress Field and Solute Atoms

Abstract

Based on the elastic interaction between a solute atom and a tensile crack-tip stress field, a mechanism of stress-corrosion cracking was proposed and analyzed. This elastic interaction provides a potential for solute atoms to migrate toward the tip of a crack. The elastic interaction and the equilibrium concentration of solute atoms near a crack tip were calculated. The solute atom concentration increases rapidly toward the crack tip if the solute atom is interstitial or if it relaxes the crack-tip stress field. The high concentration of solute atoms at the tip of a crack will enhance the reaction between solute and solvent atoms. The weak fracture strength of the reaction product may cause crack growth. Two crack growth models were analyzed: One is based on the assumption of the “homogeneity” of the fracture and deformation properties of a material, and the other takes a structural size of a material into consideration. The proposed models are compared with available data on magnesium-aluminum alloy, 4340 steel, and soda-lime glass.