In order to study the indentation size effect(ISE)of germanium single crystals,nano-indentation experiments were carried out on the(100),(110)and(111)plane-orientated germanium single crystals.The true hardness of eac...In order to study the indentation size effect(ISE)of germanium single crystals,nano-indentation experiments were carried out on the(100),(110)and(111)plane-orientated germanium single crystals.The true hardness of each crystal plane of germanium single crystals was calculated based on the Meyer equation,proportional sample resistance(PSR)model and Nix-Gao model,and the indentation size effect(ISE)factor of each crystal plane was calculated.Results show that,the germanium single crystals experience elastic deformation,plastic deformation and brittle fracture during the loading process,and the three crystal planes all show obvious ISE phenomenon.All three models can effectively describe the ISE of germanium single crystals,and the calculated value of Nix-Gao model is the most accurate.Compared with the other two crystal planes,Ge(110)has the highest size effect factor m and the highest hardness,which indicates that Ge(110)has the worst plasticity.展开更多
Nanoindentation tests performed in a commercial atomic force microscope have been utilized to directly measure the elastic modulus and the hardness of single crystal copper thin films fabricated by the vacuum vapor de...Nanoindentation tests performed in a commercial atomic force microscope have been utilized to directly measure the elastic modulus and the hardness of single crystal copper thin films fabricated by the vacuum vapor deposition technique. Nanoindentation tests were conducted at various indentation depths to study the effect of indentation depths on the mechanical properties of thin films. The results were interpreted by using the Oliver-Pharr method with which direct observation and measurement of the contact area are not required. The elastic modulus of the single crystal copper film at various indentation depths was determined as (67.0±(6.9) GPa) on average which is in reasonable agreement with the results reported in literature. The indentation hardness constantly increases with decreasing indentation depth, indicating a strong size effect.展开更多
Nanoindentation experiments were conducted under loading rates of 500–6000μN/s and applied peak loads of 4000-12000μN to measure the creep behavior of DD407 Ni-base single crystal superalloy at room temperature.Exp...Nanoindentation experiments were conducted under loading rates of 500–6000μN/s and applied peak loads of 4000-12000μN to measure the creep behavior of DD407 Ni-base single crystal superalloy at room temperature.Experimental results demonstrated that DD407 Ni-base single crystal superalloy had a good creep resistance,but its creep properties were sensitive to the loading rate and peak load.The fitting creep parameters significantly increased with increasing loading rate and peak load based on the Findley’s model,and the corresponding creep mechanism was governed by dislocation based on the calculation of creep stress exponent.During nanoindentation creep tests,it was found that the hardness and reduced modulus decreased with increasing the loading rate and peak load,and through a dimensionless analysis,it was also noted that the effect of the dimensionless loading rate was stronger than that of dimensionless peak load on the creep properties.展开更多
基金Project(51765027)supported by the National Natural Science Foundation of China.
文摘In order to study the indentation size effect(ISE)of germanium single crystals,nano-indentation experiments were carried out on the(100),(110)and(111)plane-orientated germanium single crystals.The true hardness of each crystal plane of germanium single crystals was calculated based on the Meyer equation,proportional sample resistance(PSR)model and Nix-Gao model,and the indentation size effect(ISE)factor of each crystal plane was calculated.Results show that,the germanium single crystals experience elastic deformation,plastic deformation and brittle fracture during the loading process,and the three crystal planes all show obvious ISE phenomenon.All three models can effectively describe the ISE of germanium single crystals,and the calculated value of Nix-Gao model is the most accurate.Compared with the other two crystal planes,Ge(110)has the highest size effect factor m and the highest hardness,which indicates that Ge(110)has the worst plasticity.
文摘Nanoindentation tests performed in a commercial atomic force microscope have been utilized to directly measure the elastic modulus and the hardness of single crystal copper thin films fabricated by the vacuum vapor deposition technique. Nanoindentation tests were conducted at various indentation depths to study the effect of indentation depths on the mechanical properties of thin films. The results were interpreted by using the Oliver-Pharr method with which direct observation and measurement of the contact area are not required. The elastic modulus of the single crystal copper film at various indentation depths was determined as (67.0±(6.9) GPa) on average which is in reasonable agreement with the results reported in literature. The indentation hardness constantly increases with decreasing indentation depth, indicating a strong size effect.
基金financial supports from the National Natural Science Foundation of China(Nos.11772236,11472195)。
文摘Nanoindentation experiments were conducted under loading rates of 500–6000μN/s and applied peak loads of 4000-12000μN to measure the creep behavior of DD407 Ni-base single crystal superalloy at room temperature.Experimental results demonstrated that DD407 Ni-base single crystal superalloy had a good creep resistance,but its creep properties were sensitive to the loading rate and peak load.The fitting creep parameters significantly increased with increasing loading rate and peak load based on the Findley’s model,and the corresponding creep mechanism was governed by dislocation based on the calculation of creep stress exponent.During nanoindentation creep tests,it was found that the hardness and reduced modulus decreased with increasing the loading rate and peak load,and through a dimensionless analysis,it was also noted that the effect of the dimensionless loading rate was stronger than that of dimensionless peak load on the creep properties.
