H. Yu
,
Z.X. Lin and Y.H. Zhou 1) Department of Materials Engineering
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Nanchang Institute of Aeronautical Technology
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Nanchang 330034
,
China 2) The State Key Laboratory of Solidification Processing
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Northwestern Polytechnical University
,
Xi'an 710072
,
China
金属学报(英文版)
Based on the principle of infiltration mechanics in porous medium, high Reynolds number infiltration of liquid aluminum in porous medium has been investigated. Combined with the test results of hydraulic simulation, the mathematical model of the high Reynolds number infiltration of liquid aluminum in porous medium has been established, and it is found that infiltration is characterized by its second order nonlinear. The calculated results based on the model are in good agreement with those of the hydraulic simulation and the aluminum alloy infiltration. The way of high speed infiltration under medium pressure has been put forward to fabricate porous aluminum alloy with thin holes of 0.4mm diameter.
关键词:
infiltration
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null
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null
Andrej Atrens
材料科学技术（英文）
Corrosion research by Atrens and co-workers has made significant contributions to the understanding of the service performance of engineering materials. This includes: (1) elucidated corrosion mechanisms of Mg alloys, stainless steels and Cu alloys, (2) developed an improved understanding of passivity in stainless steels and binary alloys such as Fe-Cr, Ni-Cr, Co-Cr, Fe-Ti, and Fe-Si, (3) developed an improved understanding of the melt spinning of Cu alloys, and (4) elucidated mechanisms of environment assisted fracture (EAF) of steels and Zr alloys. This paper summarises contributions in the following: (1) intergranular stress corrosion cracking of pipeline steels, (2) atmospheric corrosion and patination of Cu, (3) corrosion of Mg alloys, and (4) transgranular stress corrosion cracking of rock bolts.
关键词:
Stress corrosion cracking
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null
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null
Applied Physics a-Materials Science & Processing
The Pr(1+x)Ba(2-x)Cu(3)O(7+/-delta) solid solution was investigated by means of X-ray powder diffraction combined with Rietveld analysis. A Pr123 single phase could be synthesized under Pr-rich conditions by sintering at 950 degreesC in air. The solubility range of Pr(1+x)Ba(2-x)Cu(3)O(7+/-delta) solid solution is 0.08 less than or equal to x less than or equal to 0.80. The structure of Pr(1+x)Ba(2-x)Cu(3)O(7+/-delta) for 0.08 less than or equal to x less than or equal to 0.30 is orthorhombic. The structure transforms into tetragonal for 0.30 less than or equal to x less than or equal to 0.80. To form the Pr123 single phase, the Ba sites in the Pr123 structure must have partial Pr ions, and the least amount is x = 0.08. Ba ions cannot occupy the sites of Pr ions. In the Pr123 structure, Ca ions can replace Pr ions; the highest value is x = 0.4 in the PrBa(2-x)Ca(x)Cu(3)O(7+/-delta) system under our experimental conditions. However, Ca ions cannot replace B a ions. The ionic radius plays a more important role than the chemical properties in the substitution between Pr, Ba and Ca ions in the Pr123 structure.
关键词:
cu-o system;approximately 950-degrees-c;superconductivity;diagram;pr;growth;nd;prba2cu3o7-delta;praseodymium;property
Materials Science & Engineering C-Biomimetic Materials Sensors and Systems
Bamboo, one of the strongest natural structural composite materials, has many distinguishing features. It has been found that its reinforcement unit, hollow, multilayered and spirally-wound bast fiber, plays an extremely important role in its mechanical behavior. In the present work, on the basis of the study on bamboo bast fiber and wood tracheid, a biomimetic model of the reinforcing element, composed of two layers of helically wound fiber, was suggested. To detect the structural characteristics of such a microstructure, four types of macro fiber specimens made of engineering composites were employed: axially aligned solid and hollow cylinders, and single- and double-helical hollow cylinders. These specimens were subjected to several possible loadings, and the experimental results reveal that only the double-helical structural unit possesses the optimum comprehensive mechanical properties. An interlaminar transition zone model imitating bamboo bast fiber was proposed and was verified by engineering composite materials. In our work, the transition zone can increase the interlaminar shear strength of the composite materials by about 15%. These biomimetic structural models can be applied in the design and manufacture of engineering composite materials.
关键词:
bamboo;bast fiber;biomimetics;engineering composites
Science
Strengthening materials traditionally involves the controlled creation of internal defects and boundaries so as to obstruct dislocation motion. Such strategies invariably compromise ductility, the ability of the material to deform, stretch, or change shape permanently without breaking. Here, we outline an approach to optimize strength and ductility by identifying three essential structural characteristics for boundaries: coherency with surrounding matrix, thermal and mechanical stability, and smallest feature size finer than 100 nanometers. We assess current understanding of strengthening and propose a methodology for engineering coherent, nanoscale internal boundaries, specifically those involving nanoscale twin boundaries. Additionally, we discuss perspectives on strengthening and preserving ductility, along with potential applications for improving failure tolerance, electrical conductivity, and resistance to electromigration.
关键词:
strain-rate sensitivity;stacking-fault energy;nano-scale twins;cu-al;alloys;nanocrystalline metals;mechanical-properties;activation;volume;copper;deformation;behavior
Applied Physics Letters
The effect of nonmagnetic Y partial substitution at the Dy site in Dy(1-x)Y(x)MnO(3) up to x=0.2 on magnetism, specific heat, and ferroelectricity is investigated, which resulted in a preliminary multiferroic phase diagram. It is revealed that the Y partial substitution suppresses the Dy-spin ordering point (T(Dy)) and ferroelectric ordering point (T(FE)) but enhances the Mn-spin ordering point (T(N)). The interaction between the spins of Dy and Mn is remarkably affected by Y substitution. The measured electrical polarization depends on the Y substitution in a complex way because the ferroelectricity is sensitive to the interaction between the spins of Dy and Mn. (c) 2011 American Institute of Physics. [doi: 10.1063/1.3536506]
关键词:
ferroelectricity;polarization
Physica B-Condensed Matter
The magnetic properties and magnetocaloric effect of Tb(1-x)Y(x)CoC(2) (x = 0, 0.1, 0.2, 0.3, 0.4) compounds have been investigated systematically. All the compounds undergo second-order transitions from paramagnetic to ferromagnetic states without thermal and magnetic hysteresis. With increasing Y content from 0 to 0.4, the Curie temperatures decrease nearly linearly from 28 to 18 K. The nature of the second-order phase transitions can be confirmed by Arrott plots. For Tb(0.6)Y(0.4)CoC(2) compound, the maximum value of the magnetic entropy change -Delta S(M) at 20 K is 9.35 J kg(-1) K(-1) for an external field change of 5T (5.14 J kg(-1) K(-1) for 2T). The large reversible magnetic entropy change makes Tb(0.6)Y(04)CoC(2) compound an attractive candidate for the application at hydrogen liquefaction temperature. (C) 2010 Elsevier B.V. All rights reserved.
关键词:
Curie temperature;Magnetocaloric effect;Magnetic properties;ac susceptibility
