DISLOCATION SOURCES IN CRYSTALS
DISLOCATION SOURCES IN CRYSTALS
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DOI：
10.1063/1.1735005
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发表时间：
1959-01-01
影响因子：
3.2
通讯作者：
GILMAN, JJ
中科院分区：
文献类型：
--
作者：
GILMAN, JJ
< jats: p>为了研究氟化锂晶体中位错的形核，对氟化锂晶体施加了短应力脉冲（长度为1-10 μsec）。发现几种不均匀性可导致位错成核：（a）解理步骤，（B）位错环，（c）滑移带，（d）夹杂物或"污垢“颗粒，（e）沉淀物（生长时），和（f）辐射诱导沉淀物。< jats: p>此外，还发现，在中等温度（200-600 ℃）下退火处理，然后“快速”冷却（> 5 ℃/小时），使先前钉扎的位错段变得移动的。这些移动的片段在晶体中移动时成倍增加。< jats: p>尝试了几种处理方法，但对产生位错成核无效。这些包括：温度变化，表面润湿，同时照射和应力，从自由表面的反射，和对角弯曲。< jats: p>将仔细清洁的玻璃球压入LiF晶体的无位错区域。以这种方式，达到了比晶体的正常屈服应力（100 G/85）大100倍的剪切应力，而不引起均匀位错成核。< jats: p>结果表明，在真实的晶体中，小的异质性是位错形核的主要原因。均匀成核仅在高应力（100 G/30）下发生。相对较少的位错倍增结果从经典的弗兰克-里德来源（几乎没有在LiF）。大多数位错增殖发生在先前的位错移动通过晶体时。
< jats: p> Lithium fluoride crystals were subjected to short stress pulses (1–10 μsec in length) in order to study dislocation nucleation in them. It was found that several heterogeneities can lead to dislocation nucleation:(a) cleavage steps,(b) dislocation loops,(c) glide bands,(d) inclusions or``dirt''particles,(e) precipitates (as grown), and (f) radiation-induced precipitates.< jats: p> Also, it was found that annealing treatments at moderate temperatures (200–600 C) followed by``rapid''cooling (> 5 C/hr) made segments of previously pinned dislocations become mobile. These mobile segments multiplied as they moved through the crystals.< jats: p> Several treatments were tried that were ineffective in producing dislocation nucleation. These included: temperature changes, surface wetting, simultaneous irradiation and stressing, reflections from free surfaces, and diagonal bending.< jats: p> Carefully cleaned glass spheres were pressed into contact with dislocation-free regions of a LiF crystal. In this way, shear stresses that were 100 times greater than the normal yield stress of the crystal (∼ G/85) were reached without causing homogeneous dislocation nucleation.< jats: p> It is concluded that small foreign heterogeneities cause most of the dislocation nucleation in real crystals. Homogeneous nucleation occurs only at high stresses (∼ G/30). Relatively little dislocation multiplication results from classical Frank-Read sources (almost none in LiF). Most dislocation multiplication occurs as a prior dislocation moves through a crystal.