KDP晶体二倍频晶面纳米压痕实验研究

The nanohardness is from 1.44 to 2.61 GPa,the Vickers hardness is from 127 to 252 Vickers,and elastic modulus is from 52 to 123 GPa by the nanoindentation experiments on the doubler plane of KDP crystal. An indentation size effect is observed on the doubler plane in the test as the nanohardness and elastic modulus decreases with the increase of the maximum load.Slippage is identified as the major mode of plastic deformation, and pop-in events are attributed to the initiation of slippage.And the variation of unloading curve end is the result of stick effects between the indenter and the contact surface.The depth of the elastic deformation,which is between 40 and 75 nm,is responsible for the elastic deformation.The doubler plane of KDP crystal has anisotropy,and the relative anisotropy of nanohardness is 8.2%and the relative anisotropy of elastic modulus is 8.0%.     

磷酸二氢钾单晶体纳米压痕的力学行为

磷酸二氢钾(KH2PO4, KDP)单晶体的纳米力学特性是研究其超精密加工重要依据之一.试验针对(001)晶面和三倍频晶面采用带有针尖半径为50 nm的Berkovich压头的纳米压痕仪对KDP晶体进行力学特性分析,结果表明,两个晶面的纳米硬度H和弹性模量E都表现出强烈的载荷依赖效应.应用Meyer定律和修正比例样件阻尼(Modified proportional specimen resistance, MPSR)模型揭示和说明KDP晶体纳米压痕尺寸效应现象是一种载荷和压痕深度非线性比例阻尼的结果;对加工样件的Raman光谱分析结果表明,加工表面残余应力是影响压痕尺寸效应的非线性程度的重要因素.对材料加载位移曲线的进一步观测发现存在加载突进现象,该现象和材料的弹塑性转变密切相关.