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Theoretical Modelling of Brittle-to-Ductile Transition Load of KDP Crystals on (001) Plane during Nanoindentation and Nanoscratch Tests
Journal of Materials Research and Technology ( IF 6.4 ) Pub Date : 2020-10-14 , DOI: 10.1016/j.jmrt.2020.09.131
Chen Li , Yong Zhang , Guangzhe Zhou , Zongjie Wei , Liangchi Zhang

KDP single crystals are widely used in inertial confinement fusion and high power lasers due to the wide transmission band, high laser damage threshold, large nonlinear optical coefficient, etc. However, surface and subsurface damages are easily induced into the KDP crystal components during the machining process due to its high brittleness and distinct anisotropy. These damages will reduce the service accuracy and life of KDP crystal components. It is of great significance to study the brittle-to-ductile transition of KDP crystals to achieve high efficiency and precision machining of crystal components. In this work, a theoretical model of brittle-to-ductile transition load during the nanoindentation and nanoscratch processes of KDP crystals was established based on the energy conservation law and dislocation theory. This model took the anisotropy of KDP crystals into account. Nanoindentation and nanoscratch experiments by using different indenters were performed to verify the theoretical model of brittle-to-ductile transition load. The experimental results of the brittle-to-ductile transition load agreed well with the theoretical results, which indicated that the model was reliable. Both experimental and theoretical results showed that the critical load of brittle-to-ductile transition during the nanoindentation and nanoscratch processes increased as the half cone angle increased. In addition, the critical load of brittle-to-ductile transition load of the scratch was lower than that of the indentation under the same condition. The results also demonstrated that KDP crystals had distinct anisotropy during the nanoindentation and nanoscratch process. Brittle fracture was most likely to occur along [100] orientation during the scratch process. Under the same scratching condition, [110] orientation was prone to achieving ductile machining with high surface quality compared with other orientations.



中文翻译:

纳米压痕和纳米划痕测试期间(001)平面上KDP晶体脆性至延性转变载荷的理论模型

KDP单晶具有宽的传输频带,高的激光损伤阈值,较大的非线性光学系数等特性,因此广泛用于惯性约束聚变和高功率激光器中。但是,在加工过程中,KDP晶体组件容易引起表面和亚表面损伤由于其高脆性和独特的各向异性,因此加工。这些损坏会降低KDP晶体组件的使用寿命和使用寿命。研究KDP晶体的脆性-延性转变对实现晶体组件的高效精密加工具有重要意义。在这项工作中,基于能量守恒定律和位错理论,建立了KDP晶体纳米压痕和纳米划痕过程中脆性-延性转变载荷的理论模型。该模型考虑了KDP晶体的各向异性。通过使用不同的压头进行了纳米压痕和纳米划痕实验,以验证脆性-延性转变载荷的理论模型。脆性-延性转变载荷的实验结果与理论结果吻合良好,表明该模型是可靠的。实验和理论结果均表明,随着半锥角的增加,纳米压痕和纳米划痕过程中脆性-延性转变的临界载荷增加。另外,在相同条件下,划痕的脆性-延性转变载荷的临界载荷低于压痕的临界载荷。结果还表明,KDP晶体在纳米压痕和纳米划痕过程中具有明显的各向异性。在刮擦过程中,最可能沿[100]方向发生脆性断裂。在相同的刮擦条件下,与其他方向相比,[110]方向易于实现具有高表面质量的延性加工。

更新日期:2020-10-15
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