Sensitivity to Fatigue Cracks Initiation of Symmetrical < 110 > Tilt Grain Boundaries in Pure Copper Bicrystals in 1M NaNO2 Solution

Sensitivity to corrosion fatigue (CF) crack initiation has been investigated in a series of pure copper bicrystals with a symmetrical < 110 > -tilt grain boundary. Tests were performed by axial tension-compression tests 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 to CF cracks increases with increasing misorientation. It seems that effect of grain boundaries structures, i.e., Sigma-values is small in this experiment. Stress concentration generated by the pile-up of trapped dislocations at the grain boundary could account for the high susceptibility of the intergranular cracks in large-angle grain boundaries.