Understanding the formation mechanism of subsurface damage in potassium dihydrogen phosphate crystals during ultra-precision fly cutting
Understanding the formation mechanism of subsurface damage in potassium dihydrogen phosphate crystals during ultra-precision fly cutting
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DOI：
10.1007/s40436-019-00265-2
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发表时间：
2019-09-01
影响因子：
5.2
通讯作者：
Zhang, Liang-Chi
中科院分区：
文献类型：
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作者：
Zhang, Yong;Hou, Ning;Zhang, Liang-Chi
磷酸二氢钾（KDP）晶体在高能激光系统中起着重要的作用，但其激光损伤阈值（LDT）低于预期。在KDP晶体中产生的亚表面损伤显著影响LDT。然而，检测由加工引起的表面下损伤是非常具有挑战性的，因为KDP是软的、易碎的并且对外部环境（例如，湿度、温度和施加的应力）。传统的表征方法，如透射电子显微镜是无效的，用于此目的。提出了一种掠入射X射线衍射（GIXD）无损检测方法，用于研究KDP晶体超精密飞切过程中亚表面损伤的形成。利用GIXD在处理过的亚表面中检测到一些晶面，即（200）、（112）、（312）、（211）、（220）、（202）、（301）、（213）、（310）和（303），这对KDP晶体块体提供了非常不同的结果。这些结果意味着单个KDP晶体由于亚表面中的机械应力而变为晶格错位结构（LMS）。这些晶面与KDP晶体的滑移系相匹配，这意味着位错成核并沿沿着系传播，从而导致在剪切和压缩应力下形成LMS。亚表面LMS的发现为KDP晶体激光损伤的本质提供了新的认识。
Potassium dihydrogen phosphate (KDP) crystals play an important role in high-energy laser systems, but the laser damage threshold (LDT) of KDP components is lower than expected. The LDT is significantly influenced by subsurface damage produced in KDP crystals. However, it is very challenging to detect the subsurface damage caused by processing because a KDP is soft, brittle, and sensitive to the external environment (e.g., humidity, temperature and applied stress). Conventional characterization methods such as transmission electron microscopy are ineffective for this purpose. This paper proposes a nondestructive detection method called grazing incidence X-ray diffraction (GIXD) to investigate the formation of subsurface damage during ultra-precision fly cutting of KDP crystals. Some crystal planes, namely (200), (112), (312), (211), (220), (202), (301), (213), (310) and (303), were detected in the processed subsurface with the aid of GIXD, which provided very different results for KDP crystal bulk. These results mean that single KDP crystals change into a lattice misalignment structure (LMS) due to mechanical stress in the subsurface. These crystal planes match the slip systems of the KDP crystals, implying that dislocations nucleate and propagate along slip systems to result in the formation of the LMS under shear and compression stresses. The discovery of the LMS in the subsurface provides a new insight into the nature of the laser-induced damage of KDP crystals.