Journal of Materials Research
The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.
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room-temperature
中国腐蚀与防护学报
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材料科学技术（英文）
The effect of interstitial hydrogen on the cohesion of the Al Sigma=11(113) grain boundary (GB) is investigated based on the thermodynamic model of Rice-Wang using the first-principles density function calculation. The results indicate that interstitial H behaves as an embrittler from "strengthening energy" analysis. The reduced GB cohesion due to the presence of H at the GB is attributed to the low affinity between H and Al, and the weakened bonding of Al atomic pairs perpendicular to GB plane.
关键词:
hydrogen;grain boundary;Al-Mg alloys;pseudopotentials;1st-principles
Xiaoguang LIU
,
Xiaowei WANG
材料科学技术（英文）
The effect of interstitial hydrogen on the cohesion of the Al ∑=11(113) grain boundary (GB) is investigated based on the thermodynamic model of Rice-Wang using the first-principles density function calculation. The results indicate that interstitial H behaves as an embrittler from "strengthening energy" analysis. The reduced GB cohesion due to the presence of H at the GB is attributed to the low affinity between H and Al, and the weakened bonding of Al atomic pairs perpendicular to GB plane.
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Hydrogen
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null
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Physical Review B
We reconsider and interpret the mechanical properties of the recently proposed allotrope of carbon, T-carbon [Sheng et al., Phys. Rev. Lett. 106, 155703 (2011)], using density functional theory in combination with different empirical hardness models. In contrast with the early estimation based on Gao et al.'s model, which attributes to T-carbon a high Vickers hardness of 61 GPa comparable to that of superhard cubic boron nitride (c-BN), we find that T-carbon is not a superhard material, since its Vickers hardness does not exceed 10 GPa. Besides providing clear evidence for the absence of superhardness in T-carbon, we discuss the physical reasons behind the failure of Gao et al.'s and Simunek and Vackar's (SV) models in predicting the hardness of T-carbon, residing in their improper treatment of the highly anisotropic distribution of quasi-sp(3)-like C-C hybrids. A possible remedy for the Gao et al. and SV models based on the concept of the superatom is suggested, which indeed yields a Vickers hardness of about 8 GPa.
关键词:
superhard rhenium diboride;elastic-constants;ambient-pressure;metal;borides;crystals;diamond;search;boron
Physical Review B
By use of the linear-combination-of-atomic-orbital (LCAO) method for a cluster model, we studied the electronic structure of gamma-from Sigma 11 [1 (1) over bar0](11 (3) over bar) grain boundary doping with N and Mn atoms. The effect of the segregation on the cohesion of the grain boundary is investigated based on the Rice-Wang thermodynamic model. It is found that N could not only largely enhance the cohesion of the grain boundary but also eliminate the detrimental effect of Mn. The cosegregation effect of Mn and N on the cohesion of the grain boundary depends on where they segregate. Nitrogen could be reliably used in alloyed steels as an efficient strengthening element.
关键词:
electronic-structure;phosphorus segregation;stainless-steel;embrittlement;austenite;nitrogen;boron;impurities;fracture;metals
