EFFECT OF GRAIN BOUNDARY ON FATIGUE BEHAVIOUR OF Al BICRYSTALS
Al双晶体的晶界疲劳效应

The effect of grain boundaries on cyclic deformation and fatiguecrack growth in Al bicrystals under stress controlling in laboratory atmospherehas been studied. The effect of a grain boundary is found to be restricted in anarrow area, termed as grain boundary affecting zone (GBAZ), where the incom-patible plastic strain by the two sides of the interface under cyclic loads creats in-ternal stress which conversely promotes inhomogeneous slip in the area and grainboundary cracking. As an extended stage I crack initiated from a notch approachesthe grain boundary under a constant cyclic load, the crack branches, the crackfront splits into several pieces, meanwhile, the growth rate reduces to a minimumvalue at the centre of GBAZ. Such microstructure-sensitive growth of extendedstage I cracks is mainly attributed to the grain boundary-induced crack tip shielding.