摘要
利用显微硬度计和扫描电镜分别对电工纯铁DT4A、镍铍高弹合金97NiBe、化学镀镍层3种金属材料样品进行显微维氏硬度测试实验。绘制试验载荷与压痕对角线尺寸关系曲线,分析各曲线的拟合公式,建立模型。应用材料力学理论对模型进行深入分析,确定各参量的物理含义。根据各物理参量的含义,对微纳米尺度下出现硬度压痕尺寸效应现象的原因进行解释。结果表明,金属材料的显微维氏硬度表现出了显著的硬度压痕尺寸效应,用修正后的模型P0=a1d^2和HVmicro=0.1891×(a1/d+a2)可以描述和解释硬度压痕尺寸效应现象。未修正模型中,a0参数的物理含义是为了能准确反映设备试验力误差的物理量;a1参数的物理含义是与样品的弹性模量、接触刚度、显微硬度和宏观硬度有关的物理量;a2参数的物理含义是试验加载过程中压头压入试样表面产生塑性变形需要的压应力,其值近似等于5.288倍的宏观维氏硬度。金属材料显微维氏硬度压痕表面的接触刚度变化是其在微纳米尺度下存在压痕尺寸效应的主要原因。推导出的显微维氏硬度压痕表面的接触刚度计算模型为S=7Ed-7a1。
The micro Vickers hardness of DT4A,97NiBe and electroless Ni-P coating was tested by microhardness test and SEM.A model was established from the fitting curve by drawing the relationship between load and indentation diagonal line length.Based on the theory of material mechanics,the physical meaning of each parameter was determined in the model.According to the physical meaning of the parameters,the reason for the indentation size effect at micro-nano scale was explained.The results show that the microhardness indentation size effect of metal materials is remarkable.The corrected models are P0=a1d^2 and HVmicro=0.1891×(a1/d+a2).These models can well describe and explain the indentation size effect.The physical meaning of parameter a0 is a physical quantity to accurately reflect the load error of the equipment in the uncorrected model.The physical meaning of parameter a1 is a physical quantity related to elastic modulus,contact stiffness,microhardness and macrohardness.The physical meaning of parameter a2 is a compression stress required for the indenter to be pressed into specimen surface to form plastic deformation during test loading.It is approximately 5.288 times the macro hardness value.The change of contact stiffness of indentation surface is a main reason for the indentation size effect.The contact stiffness calculation model of hardness indentation surface was worked out:S=7Ed-7a1.
作者
刘松
LIU Song(AVIC Jincheng Nanjing Electrical and Hydraulic Engineering Research Center,Nanjing 211106,China)
出处
《失效分析与预防》
2019年第4期225-231,共7页
Failure Analysis and Prevention
关键词
压痕尺寸效应
微纳米尺度
显微硬度
宏观硬度
接触刚度
indentation size effect
micro-nano scale
microhardness
macrohardness
contact stiffness
