EFFECT OF INTERFACIAL STRUCTURE AND ENERGY ON CORROSION AND STRESS-CORROSION-CRACKING IN Cu-Al ALLOY BICRYSTALS

Stabilities of the symmetrical <110>and -tilt and -twist boundaries of an a Cu-AI alloy against both dissolution and Stress-Corrosion-Cracking (SCC) are discussed. The susceptibilities of the boundaries to SCC are strong1 y dependent upon the misorientation. Cusps exist at some angles which are corresponding to relatively small C-values. These boundaries indicating great resistances to SCC also possess high stabilities against dissolution. It is considered that these high stabilities against both dissolution and SCC reflect the stable structures and the low interfacial energies of the boundaries. The susceptibility of a grain boundary to SCC is much enhanced by a stress field arising from piled-up dislocations in the immediate vicinity of the boundary. It becomes evident that the susceptibility to intergranular SCC is suddenly decreased with decreasing the misorientation from approximately 15'. This may result from the increase of passing dislocations through the boundary, by which a stress concentration is avoidable, with decreasing the misorientation from the angle.