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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。
The slip behavior of pure Al polycrystalline material with coarse grains (diameter above 10mm) during cyclic deformation was studied. Compared with the slip behavior of general polycrystalline material (grain size of micrometer order), the slip behavior of (1 ) There exist different slip zones in one grain due to the different slip systems’ start-up, so called deformable domains or slip domains. There may be several slip systems in the same domain either simultaneously or successively In operation, the sample surface to form a beautiful and neat slip image. (2) For larger Σ or random grain boundary structures, the effect of grain boundaries on the slip deformation is about 50-120 μm from the grain boundaries. Such grain boundaries tend to initiate cracks early in the fatigue life. Grain boundary migration and grain boundary slip phenomenon can often be observed; for those low Σ value reposition grain boundaries, under normal circumstances, the slip line can continue through the grain boundary deformation in the grain boundary area is not coordinated, Such grain boundaries are often not easy to crack initiation sites. (3) The nodes of the trigeminal grain boundary inhibit the grain boundary sliding, which is a region with large deformation uncoordination, resulting in greater stress concentration, especially the high Σ value or random grain boundaries in the three grain boundaries, often along the grain The preferred site of cracking.