Al双晶体的晶界疲劳效应SCIEI

通过Al双晶体疲劳试验,研究了晶界对循环变形和疲劳裂纹扩展的影响。实验结果表明,晶界疲劳效应集中体现于晶界影响区,表现为不相容塑性应变在该区内产生内应力,并由此可激发次级滑移,甚至产生晶界裂纹;在常幅循环应力下,随超Ⅰ阶段裂纹逐渐接近晶界,裂纹分叉、前沿碎裂,扩展速率降低,直至在晶界影响区中央达到一最小值。本文提出了晶界诱发裂纹顶端屏蔽机制,并以此解释了上述超Ⅰ阶段裂纹对微观组织敏感的扩展行为。

EFFECT OF GRAIN BOUNDARY ON FATIGUE BEHAVIOUR OF Al BICRYSTALS

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.