研究了粗大晶粒(直径10mm以上)纯Al多晶材料在循环形变中的滑移行为,与一般的多晶材料(晶粒大小为微米量级)的滑移行为比较有如下特点:(1)在一个晶粒内存在由于不同滑移系统的开动所造成的不同滑移区,可称之谓形变畴或滑移畴;在同一畴区内也可有几个滑移系统同时或先后强烈地操作,在试样表面形成美丽而整齐的滑移图像。(2)对于较大∑值或随机晶界结构,晶界对滑移形变的影响区约在距离晶界50—120μm的范围内。这类晶界往往在疲劳寿命早期就可萌生裂纹。晶界迁移、晶界滑动现象也能经常观察到;对那些低∑值的重位晶界,一般情况下滑移线都能连续地穿越晶界,在晶界区的形变不协调性小,这样的晶界往往不易成为裂纹的萌生地点。(3)三叉晶界的节点抑制了晶界滑动,是形变不协调较大的区域,造成较大的应力集中,尤其三条晶界中的高∑值的或随机的晶界,往往是沿晶开裂的优先部位。
Comparing with ordinary ploycrystalline materials sized to μm grade, the slip morphology of the coarse grained polycrystalline pure Al is characterized by: (1) several slip domains occur in a grain, and in same domain, several slip systems operate at same time or one after another intensely, a beautiful and neat slip pattern is forming on the specimen surface; (2)for high-∑value coincident and random grain boundaries , the grain boundary affecting zone (GBAZ), about 50--120 μm wide, is favourable site to form intergranular crack at early fatigue life easily, and migration or slide of the boundaries were often observed. While low ∑--value near-coincident grain boundaries show a higher degree of slip continuity and strain compatibili-ty than high ∑--value ones. Intergranular crack is not easily nucleated at low ∑--value near--coincident boundaries; and (3) due to suppression of grain boundary slip at triple grain boundary node, the high ∑--value and random grain boundary among the three boundaries of tricrystal crack easily during cyclic deformation.
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