Study On Application Of Nanoindentation To Characterize Microzone Mechanical Property On Metals

Based on the broad application prospect of nanoidentation in the material science area,the effect of sample preparation methods on the nanoidentation results of metals, relationship between micromechanical properties and crystalline orientation of grain in cubic metals,and application of the new analysis methods of nanoindentation data were studied in this paper.Commercial pure iron was treated by sample preparation methods of mechanical polishing,mechanical polishing+chemical etching,mechanical polishing+chemical etching+electrolytic polishing,and mechanical polishing+chemical etching+ electrolytic polishing+chemical etching,and then Young's modulus and hardness of the grain were tested by nanoindentation for each method respectively,the effect of sample preparation methods on nanoindentation results was gained.It was showed that the work harden layer existed on the sample surface prepared by mechanical polishing method,which induced Young's modulus and hardness higher than that of the sample treated by the other three methods.Work harden layer was just partly removed by mechanical polishing+chemical etching,which leaded the Young's modulus of the sample was equal to that of the sample treated by mechanical polishing+chemical etching+electrolytic polishing and mechanical polishing+chemical etching+electrolytic polishing+chemical etching,but it also had higher hardness because of the residual stress.The real Young's modulus and hardness were gained by the methods of mechanical polishing+chemical etching+ electrolytic polishing and mechanical polishing+chemical etching+electrolytic polishing+chemical etching.Mechanical properties and crystalline orientation of commercially pure iron, commercially pure copper grains and super-duplex stainless steel phases were tested with the combination of nanoindentation and EBSD to study the relationship between them.It was found that there existed nearly a linear relationship between,Young's modulus and hardness of commercially pure iron or commercially pure copper grains. For a grain with a high Young's modulus,there would be a high hardness belonging to it correspondingly.A similar relationship was gained for ferrite of super-duplex stainless steel,but there was no linear relationship between Young's modulus and hardness of austenite.There was similar regularities for the Young's modulus and hardness of both commercially pure iron and commercially pure copper grains as a function of minimum angle between the normal crystal direction of gains and <111> or <001> direction.The nearer the to <111> direction,the higher the Young's modulus was,and the nearer the to <001> direction,the lower the Young's modulus was.There were no obvious regularities for the Young's modulus as a function of minimum angle between the and <110> direction,and the hardness of grains as a function of minimum angle between the and <111>,<110> or <001> direction.There were also no obvious regularities for the Young's modulus and hardness of ferrite and austenite of super-duplex stainless steel as a function of those minimum angles.The nanoindentation data of fused silica and commercially pure copper were calculated by the analysis methods of Oliver&Pharr,Cheng&Cheng and Dejun Ma.It was found that the standard deviation of Young's modulus and hardness calculated by Oliver&Pharr and Cheng&Cheng were larger than that calculated by Dejun Ma, which showed that there was a better repeatability belonging to Dejun Ma.