Intergranular Stress Corrosion Cracking of Pure Copper 〈111〉 Tilt Bicrystals

Abstract

Behaviour of stress corrosion cracking (SCC) in a series of pure copper bicrystals with a symmetrical 〈111〉-tilt boundary has been investigated. Tests were performed by the slow strain rate technique (SSRT) in 1M NaNO₂ solutions. The small-angle tilt bicrystals fractured in both intergranular and transgranular manners accompanied by a large amount of plastic strain to fracture while the large-angle bicrystals fractured in almost intergranular manner with a smaller plastic strain. Susceptibility of SCC increases with increasing misorientation and becomes relatively constant in large-angle grain boundaries. The local minima appeared at the Σ7(321) and Σ3(211) boundaries, suggesting that the susceptibility was partially affected by grain boundary energy. Stress concentration generated by the pile-up of trapped dislocations at the grain boundary could account for the high susceptibility of the intergranular SCC in large-angle grain boundaries.