Comparison of nano-indentation hardness to microhardness

Abstract With a nano-indenter and a microhardness testing machine, nano-indentation hardness and microhardness are measured in a wide load range (0.1–19600 mN) for five materials. Even fused silica and silicon almost have constant hardness during the load range, the nano-indentation hardness of copper, stainless steel and nickel titanium alloy shows obvious indentation size effect, namely that the hardness decreases with the increase of depth. For the measured materials, the nano-indentation hardness is about 10–30% in magnitude larger than the microhardness. The main reasons can be explained as the analysis of the nano-indentation hardness using the projected contact area at peak load A c instead of the residual projected area A r , as well as the purely elastic contact assumption describing the elastic/plastic indentation process. The analysis based on a simple model indicates that A c is always smaller than A r , and the more heavily the indent piles up (or sinks in), the larger the difference between the nano-indentation hardness and microhardness.

[1]  Shizhu Wen,et al.  The Failure of Fluid Film at Nano-Scale , 1999 .

[2]  I. N. Sneddon.  The relation between load and penetration in the axisymmetric boussinesq problem for a punch of arbitrary profile , 1965 .

[3]  J. Vlassak,et al.  Determination of indenter tip geometry and indentation contact area for depth-sensing indentation experiments , 1998 .

[4]  Alexei Bolshakov,et al.  Influences of pileup on the measurement of mechanical properties by load and depth sensing indentation techniques , 1998 .

[5]  Huajian Gao,et al.  Indentation size effects in crystalline materials: A law for strain gradient plasticity , 1998 .

[6]  M. M. Chaudhri.  Subsurface strain distribution around Vickers hardness indentations in annealed polycrystalline copper , 1998 .

[7]  Bharat Bhushan,et al.  Micro/Nanomechanical Characterization of Ceramic Films for Microdevices , 1999 .

[8]  A. Evans,et al.  Elastic/Plastic Indentation Damage in Ceramics: The Lateral Crack System , 1982 .

[9]  Alexei Bolshakov,et al.  Understanding nanoindentation unloading curves , 2002 .

[10]  L. Qian,et al.  New two-dimensional friction force apparatus design for measuring shear forces at the nanometer scale , 2001 .

[11]  Yang-Tse Cheng,et al.  On two indentation hardness definitions , 2002 .

[12]  D. Tabor.  Hardness of Metals , 1937, Nature.

[13]  G. Pharr,et al.  An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments , 1992 .

[14]  L. Qian,et al.  Tribological Properties of Self-Assembled Monolayers and Their Substrates Under Various Humid Environments , 2003 .

[15]  Michael V. Swain,et al.  Observation, analysis, and simulation of the hysteresis of silicon using ultra-micro-indentation with spherical indenters , 1993 .

[16]  Xudong Xiao,et al.  Investigation of Humidity-Dependent Capillary Force , 2000 .

[17]  Yang-Tse Cheng,et al.  What is indentation hardness , 2000 .

[18]  Tongxi Yu,et al.  Anomalous relationship between hardness and wear properties of a superelastic nickel–titanium alloy , 2004 .

[19]  Tod A. Laursen,et al.  A study of the mechanics of microindentation using finite elements , 1992 .

[20]  M. M. Chaudhri,et al.  Nanohardness mapping of the curved surface of spherical macroindentations in fully annealed polycrystalline oxygen-free copper , 2002 .

[21]  Yang-Tse Cheng,et al.  Effects of 'sinking in' and 'piling up' on estimating the contact area under load in indentation , 1998 .

[22]  I. Gutiérrez,et al.  Correlation between nanoindentation and tensile properties influence of the indentation size effect , 2003 .

[23]  Wolfgang Grellmann,et al.  Performance and analysis of recording microhardness tests , 1977 .