Yufei Shao Shaoqing Wang
材料科学技术（英）
Nanoindentation simulations on single crystals Al and Cu via the quasicontinuum method have been performed. Two kinds of atomic-level local stress calculation methods, i.e. the coarse-grained local stress and the virial local stress, are employed to calculate the stress state of the contact area. Various comparisons between the coarse-grained local stress and the virial local stress have been made. Firstly, the averaged normal stress beneath the contact surface calculated by coarse-grained method agrees well with continuum mechanical pressure measurement, while the virial method gives unphysical results sometimes. Secondly, the coarsegrained results reflect the indenter size effect on the critical shear stress quite accurately, while the virial calculations fail. Thirdly, the distribution of maximum shear stress of the coarse-grained method predicts the
defects nucleation locations reliably, while the distribution of virial local stress gives an incorrect prediction sometimes. Thus it is concluded that the coarse-grained method can offer a more reliable description of the local stress states of atoms in spatially inhomogeneous solids.
关键词:
Nanoindentation
,
Atomistic stress
,
Quasicontinuum
Zengsheng Ma
材料科学技术（英）
In order to improve the accuracy and comparability of hardness and elastic modulus measurements in nanoin-
dentation, an evaluation of the creep behavior and its influence on the mechanical properties of the electrode-
posited nickel film has been conducted. The influence of loading time and hold period on the hardness and
elastic modulus results at maximum load 5000 μN has also been examined. It is found that with increasing
the loading time, the creep value is decreased. However, the creep value is increased when the hold period is
increased. The elastic modulus results are more reliable if the hold period is longer. If the hold period is long
enough, the loading time has no remarkable effect on the hardness and elastic modulus measured.
关键词:
Nanoindentation
Nairong TAO
,
Weiping TONG
,
Zhenbo WANG
,
Wei WANG
,
Manling SUI
,
Jian LV
,
Ke LU
材料科学技术（英）
A porosity-free and contamination-free surface layer with grain sizes ranging from nanometer to micrometer in Fe samples was obtained by surface mechanical attrition treatment (SMAT) technique. Mechanical and wear properties of the surface layer in the SMATed and annealed Fe samples were measured by means of nanoindentation and nanoscratch tests, respectively. Experimental results showed that the hardness of the surface layer in the SMATed Fe sample increased evidently due to the grain refinement. The elastic moduli of the surface layers in the SMATed and annealed Fe samples were unchanged, independent of grain size in the present grain size regime. Compared with the original Fe sample, the wear resistance enhanced and the coefficient of friction decreased in the surface layer of the SMATed Fe sample.
关键词:
Nanocrystallites
,
null
,
null
,
null
,
null
Yuxin ZHAO
金属学报(英文版)
Nb/Ti multilayers with different modulation periods were prepared by magnetron sputtering deposition. Microstructure and mechanical properties were investigated by XRD, SEM and Nanoindentation. It turns out that hardness of samples increases with decreasing modulation wavelength (Λ) and then dropped at small Λ Through scrutinizing other results in literature, we found that the coherent stress rather than modulus mismatch played more important role for hardness enhancement with decreasing Λ of the bcc-hcp multilayers. Annealing of samples in low (or high) vacuum at 400 ℃ for 30 min led to large (or medium) enhancement of hardness, while the modulated structure was still maintained. It was found that annealing in low vacuum resulted in oxygen penetration into the multilayers as revealed by auger electron spectroscopy, but hardly changed metallic sheet resistivity. XRD results suggested that some niobium oxides were formed in Nb layers and oxygen distributed interstitially in Ti layers. The large hardness enhancement after annealing is mainly due to the strengthening effect from dispersive distribution of nano-scale niobium oxides and interstitial oxygen in the multilayers. In addition, interfaces between adjacent layers were more distinct after annealing which indicated good thermal stability of laminated structure.
关键词:
Nb/Ti multilayer
Chunzhong LIU
材料科学技术（英）
Nanoindentation was used to probe softening of the eutectic microstructure in a SnBi/Cu interconnect following thermal aging. Tests were conducted at constant loading rates and under constant loads to characterize the flow stress and creep behavior of the eutectic microstructure. Aging was found to reduce the flow stress but to increase strain-rate sensitivity of the eutectic SnBi microstructure. While the reduction in the flow stress was related to the coarsening of the eutectic microstructure, the increased creep rate sensitivity was resulted from additional contribution of grain boundary movement to indentation creep.
关键词:
Solder
,
null
,
null
,
null
,
null
H.Huang
,
X.Z.Hu
,
Y.Liu
,
M.Bush
,
K.Winchester
,
C.Musca
,
J.Dell
,
L.Faraone
材料科学技术（英）
An experimental investigation of mechanical properties of thin films using nanoindentation was reported. Silicon nitride thin films with different thicknesses were deposited using plasma enhanced chemical vapor deposition (PECVD) on Si substrate. Nanoindentation was used to measure their elastic modulus and hardness. The results indicated that for a film/substrate bilayer system, the measured mechanical properties are significantly affected by the substrate properties. Empirical formulas were proposed for deconvoluting the film properties from the measured bilayer properties.
关键词:
Mechanical property
,
null
,
null
,
null
