S.Billard
,
E.Meslin
,
G.F.Dirras
,
J.P.Fondère
,
B.Bacroix
材料科学技术（英文）
Commercial purity Al has been processed by hot isostatic pressing consolidation of nanopowders. The resulting bulk material contained a small fraction of microcrystalline grains (>300 nm) embedded in a matrix of ultrafine grains (150 nm). The mechanical properties under compressive tests at various temperatures and at a strain rate of 2×10－4 s－1 have been investigated. At room temperature a brief hardening was observed followed by a stagnation of the flow stress up to failure. From 150 to 200℃ softening occurred after a short hardening stage. A change in the behavior showed up at 300℃: a quasi perfect plasticity was observed subsequently to a yield point. The major deformation mechanisms include dynamic recovery, grain fragmentation and sliding. Besides, when tested up to rupture at elevated temperature filament formation where observed at the fracture surface. The formation mechanism of the filaments is possibly linked to the presence of a viscous-like phase at grain boundaries.
关键词:
Aluminum
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null
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null
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null
Ting DU Longmei WANG Yeming WU Yuqing ZHANG Aisheng LIU Central Iron and Steel Research Institute
,
Beijing
,
100081
,
China
材料科学技术（英文）
The temperature dependences of the equilibrium constants for the reactions RES_((S))=[RE]+[S]. (RE=Ce,La,Nd,Sm,Y),of the standard Gibbs energies for the RES formed and of the interaction coefficients between RE elements and S for the Fe-base,Ni-base and Cu-base solutions are sum- marized.
关键词:
thermodynamics
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null
,
null
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null
,
null
Applied Physics Letters
Transport in S(2) molecules sandwiched between Au electrodes is investigated with a combination of density functional theory and the non-equilibrium Green's function method. We consider four different configurations and find that their conductances are related to the details of the bonding geometry. When S(2) connects to pyramidal-shaped electrodes at the top site, the transmission is governed by a resonance and is strongly affected by the bias. In contrast, the transport of the remaining three configurations is through several closely spaced broad molecular orbitals, and the transmission coefficient is almost flat around the Fermi level. (C) 2012 American Institute of Physics. [doi:10.1063/1.3665614]
关键词:
conductance;molecule
YUE Kexiang DONG Yuanchi East China Institute of Metallurgy
,
Ma'anshan
,
China
金属学报(英文版)
The equilibrium constants between Sr-O,Ba-O and Sr-S,Ba-S in liquid iron at 1570℃ and the interaction coefficients concerning these elements have been determined as follows: K_(Sro)=1.897×10~(-7),e_O~(Sr)=-43.8 K_(BaO)=8.204×10~(-8),e_O~(Ba)=-98.0 K_(SrS)=8.356×10~(-7),e_S~(Sr)=-3.9 K_(BaS)=4.083×10~(-7),e_S~(Ba)=-3.5
关键词:
equilibrium
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null
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null
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null
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null
Zeitschrift Fur Metallkunde
Young's equation is discussed on a thermodynamic basis. The result shows that the equation is a thermodynamic equilibrium of the wetting system rather than a force balance. The equilibrium satisfies the general equilibrium condition, that is, Gibbs free energy should be minimum when the wetting equilibrium is reached. The validity of Young's equation is only limited to some special cases, namely if the droplet shape is an exact sphere sector. It implies that Young's equation can only be used in the case without the action of gravity. If the curve of the liquid surface changes, the term of cos theta in Young's equation should be replaced by another functional form of the contact angle theta. In the discussion, the author suggests that, in the case of a solid, the surface energy should be considered rather than the surface tension, and the concept of a solid surface tension should be reconsidered based on the difference between a liquid surface and a solid surface.
关键词:
J.X. Zhou
,
R.X. Liu
,
L.L. Chen
,
D.M. Liao
,
H.S. Wei
金属学报(英文版)
Numerical simulation of casting's mold filling process is the main and the most important aspect of the foundry CAE technology. But it is time-consuming; it may take dozens of hours or several days. While with the development of computer hardware, numerical simulation of casting's mold filling process has made rapid progress. The simulation results, therefore, have become more and more practical. This study tries to find some clues of the computational time of mold filling process. Firstly, this paper introduces mathematic model and the basic route of numerical simulation of casting's mold filling process. Then the computational time of mold filling process has been carefully studied, and some new and useful results have been gained from the study of the computational time. Finally, this paper has given some real applications of numerical simulation of casting's mold filling process.
关键词:
numerical simulation
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null
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null
