X.J.Xu
,
D. Zhang
,
Z.L. Shi
,
C.Z.Zhao and R.J. Wu (State Key Laboratory of Metal Matrir Composites
,
Shanghai Jiaotong University
,
Shanghai 200030
,
China)
金属学报(英文版)
In this paper,the superplastic characteristics of the beta-SiC whisker reinforced 2024aluminum composite, fabricated by squeeze casting and hot-rolling after extrusion were investigated. The compsite had a fine grain size of about 2μm, and exhibited a strain rate sensitivity of about 0.35 and a maximum elongation of 350% at an initial strain rate of 1.1×10-1s-1 at 803K. In addition, the superplastic deformation mechanisme of the composite were also examined.
关键词:
high strain rate superplasticity
,
null
,
null
Express Polymer Letters
The state-of-art and key problems of carbon nanotube (CNT) based polymer composites (CNT/polymer composites) including CNT/polymer structural composites and CNT/polymer functional composites are reviewed. Based on the results reported up to now, CNTs can be an effective reinforcement for polymer matrices, and the tensile strength and elastic modulus of CNT/polymer composites can reach as high as 3600 MPa and 80 GPa, respectively. CNT/polymer composites are also promising functional composite materials with improved electrical and thermal conductivity, etc. Due to their multi-functional properties, CNT/polymer composites are expected to be used as low weight structural materials, optical devices, thermal interface materials, electric components, electromagnetic absorption materials, etc. However, the full potential of CNT/polymer composites still remains to be realized. A few key problems, such as how to prepare structure-controllable CNTs with high purity and consistently dependable high performance, how to break up entangled or bundled CNTs and then uniformly disperse and align them within a polymer matrix, how to improve the load transfer from matrix to CNT reinforcement, etc, still exist and need to be solved in order to realize the wide applications of these advanced composites.
关键词:
polymer composites;carbon nanotubes;mechanical properties;electrical;properties;thermal properties
WANG Zhongguang SUN Zhengming YU Weicheng ** State Key Laboratory for Fatigue and Fracture of Materials
,
Institute of Metal Research
,
Academia Sinica
,
Shenyang.110015
,
China+ To whom correspondence should be addressed
材料科学技术（英）
Based mainly on the work done at the authors' laboratory in recent years,this paper examines what is currently known about the cyclic deformation and fatigue properties of metal matrix composites, with particular emphasis on discontinuous fiber (whisker or particulate)-reinforced Al composites. The following items are discussed:fatigue strength and life,cyclic deformation and microstructural evolution,microcrack initiation and growth,fatigue crack propagation behaviour.
关键词:
metal matrix composite
,
null
,
null
,
null
Composites Part a-Applied Science and Manufacturing
Coating on reinforcements affects the interface bonding of a composite, and is therefore usually used for improving the composite's properties. The behaviour of SiC coating on carbon fibre in reinforced aluminium metal castings, Fe on carbon fibre-reinforced copper and alumina coating on K2O . 6TiO(2) whisker-reinforced aluminium composites were investigated, respectively, by modern techniques such as TEM, SEM etc. with the goal of controlling the interfacial interaction and wettability of reinforcement with the matrices. SiC coating produced by a polycarbosilane solution process effectively improved the strength because it successfully controlled oxidation of the carbon fibres themselves and the harmful reaction between the carbon fibres and molten aluminium during the fabrication process and heating process of the composites. The metal coating, Fe, made by electrical plating, strengthened the bonding of carbon fibres with copper by changing the bonding state of the interface from a mechanical one to a partly chemical one. Therefore the strengths of the resulting composites were improved. The alumina coating on K2O . 6TiO(2) also controlled the diffusion of the K element from the whiskers into the aluminium matrix and altered the reaction with aluminium, and led to the optimization of interfacial bonding between the whiskers and a superior composite. Copyright (C) 1996 Elsevier Science Limited
关键词:
coatings;interface;material properties;metal matrix composites;carbon-fibers;aluminum
Journal of Materials Processing Technology
The surface state of the reinforcements for composites plays an important role in the fabrication process and in determining the properties of metal-matrix composites. This article explores the effect of a reinforcement coating on the fabrication process and the properties of metal-matrix composites. For a carbon-fiber-reinforced aluminum composite system, it is difficult to obtain a uniform distribution of the carbon fibers in the aluminum matrix and to control the fabrication process parameters because of poor wettability. For example, the fabrication pressure must be set properly, otherwise a higher pressure will cause fiber fracture, whilst a lower pressure will cause holes in the matrix. When coating the fibers with SiC by a polycarbosilane solution process, the wettability between the fibers and the aluminum is improved. Consequently, the fabrication process can be controlled easily and the properties of the composites improved substantially. (C) 1998 Elsevier Science S.A.
关键词:
fiber coating;fabrication;metal-matrix composites;aluminum
Journal of Materials Science
Solid state amorphizations in mechanically deformed Ni/Ti multilayer composites have been investigated by differential scanning calorimetry and X-ray diffraction. The growth of amorphous alloy in our Ni/Ti composites was facilitated by the large number of grain boundaries and relatively large degree of disorder induced in the metal layers by the cold rolling. The formation of different products of solid-state reaction in the Ni/Ti composites has bee,n elucidated in terms of magnetic and enthalpy analysis. It is thought that the solid state amorphization occurs first during heating, followed by the formation of intermetallic compounds through direct solid-state reaction of elemental nickel and titanium and by the crystallization of the amorphous alloy already formed by the solid state amorphization reaction. The values of the activation energy for interdiffusion and interdiffusion coefficient for the formation of amorphous alloy in the Ni/Ti composites have also been calculated.
关键词:
diffusion couples;interdiffusion reactions;elemental composites;thin-films;ni/zr;ni;planar;binary;growth;alloys
Solid State Communications
Magnetic anisotropy fields at room temperature of ternary tetragonal compounds of R2Fe14C(R = Lu, Gd, Nd) and R2Fe14B(R = Gd, Nd) were determined by Singular-Point-Detection (SPD) technique. The magnetocrystalline anisotropies of the carbides were found to be larger than those of their corresponding borides, indicating that the outstanding permanent-magnetic properties may be obtained in the R2Fe14C-based alloys.
关键词:
ChunXiang CUI
,
Yutian SHEN
,
Fanbin MENG
,
Seuk Bong Kang
材料科学技术（英）
This paper deals with a series of novel processing techniques based on the in situ production of metal matrix composites (MMCs). In situ techniques involve a chemical reaction resulting in the formation of a very fine and thermodynamically stable reinforcing ceramic phase within a metal matrix. As a result, this provides thermodynamic compatibility at the matrix-reinforcement interface. The reinforcement surfaces are also likely to be free of contamination and, therefore, a stronger matrix-dispersion bond can be achieved. Some of these technologies including DIMOX(TM), XD, PRIMEX(TM), reactive gas infiltration, high-temperature self-propagating synthesis (SHS), and liquid-solid, or solid-gas-liquid reactions as well as plasma in situ MMCs are expressed in this paper.
关键词:
Yinxiao DU
,
Ming LEI
,
Hui YANG
材料科学技术（英）
By a facile and efficient solid-state reaction route using an organic reagent cyanamide (CN2H2) as a precursor with another one being metal oxides, we successfully synthesized seven technologically important metal nitrides including cubic VN, CrN, NbN, hexagonal GaN, AlN, BN, and WN at moderate temperatures. The experimental results show that cyanamide (CN2H2) is a powerfully reducing and nitridizing reagent and the metal oxides are completely converted into the corresponding nitride nanoparticles at lower temperatures than that reported in the conventional methods. It is found that CN2H2 can exhibit some interesting condensation processes, and the final products, highly active carbon nitride species, play a crucial role in the reducing and nitridizing processes.
关键词:
Nitride
,
null
,
null
,
null
