Mao Jianhui, Liu Wenjun, Li Dongfang, Zhang Chenkai, Ma Yi
College of Mechanical and Electrical Engineering, Quzhou College of Technology, Quzhou 324000, China.
College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310014, China.
Micromachines (Basel). 2021 Mar 30;12(4):369. doi: 10.3390/mi12040369.
As an excellent multifunctional single crystal, potassium dihydrogen phosphate (KDP) is a well-known, difficult-to-process material for its soft-brittle and deliquescent nature. The surface mechanical properties are critical to the machining process; however, the characteristics of deformation behavior for KDP crystals have not been well studied. In this work, the strain rate effect on hardness was investigated on the mechanically polished tripler plane of a KDP crystal relying on nanoindentation technology. By increasing the strain rate from 0.001 to 0.1 s, hardness increased from 1.67 to 2.07 GPa. Hence, the strain rate sensitivity was determined as 0.053, and the activation volume of dislocation nucleation was 169 Å. Based on the constant load-holding method, creep deformation was studied at various holding depths at room temperature. Under the spherical tip, creep deformation could be greatly enhanced with increasing holding depth, which was mainly due to the enlarged holding strain. Under the self-similar Berkovich indenter, creep strain could be reduced at a deeper location. Such an indentation size effect on creep deformation was firstly reported for KDP crystals. The strain rate sensitivity of the steady-state creep flow was estimated, and the creep mechanism was qualitatively discussed.
作为一种优异的多功能单晶，磷酸二氢钾（KDP）因其软脆和潮解的特性而成为一种众所周知的难加工材料。表面力学性能对加工过程至关重要；然而，KDP晶体的变形行为特征尚未得到充分研究。在这项工作中，依靠纳米压痕技术在KDP晶体的机械抛光三倍频面上研究了应变速率对硬度的影响。通过将应变速率从0.001提高到0.1 s，硬度从1.67 GPa增加到2.07 GPa。因此，应变速率敏感性确定为0.053，位错形核的激活体积为169 Å。基于恒载保持法，在室温下对不同保持深度的蠕变变形进行了研究。在球形压头下，蠕变变形会随着保持深度的增加而大大增强，这主要是由于保持应变增大所致。在自相似的贝氏压头下，在较深位置蠕变应变会减小。这种压痕尺寸对蠕变变形的影响首次在KDP晶体中被报道。估算了稳态蠕变流动的应变速率敏感性，并对蠕变机制进行了定性讨论。
