Stress Corrosion of Ionic and Mixed Ionic/Covalent Solids

Slow crack growth data, surface reaction studies, and solubility results for sapphire and magnesium fluoride crystals are used to identify stress corrosion mechanisms for each material. Results suggest that stress corrosion in sapphire proceeds by the dissociative chemisorption of environmental species on strained crack tip bonds. Crack growth rates measured in nonaqueous environments and isotopically labeled water suggest that ion solvation rather than dissociative chemisorption dominates the crack tip interaction in magnesium fluoride.