The influence of solidification rate on microstructures of aluminum-matrix particulate composites (original) (raw)
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Solidification During Casting of Metal-Matrix Composites
Automobile pistons, cylinder liners, piston rings, connecting rods Reduced wear, antiseizing, cold start, lighter, conserves fuel, i mproved efficiency Copper/graphite Sliding electrical contacts Excellent conductivity and antiseizing properties Aluminum/SiC Turbocharger impellers High-temperature use Aluminum/glass or carbon microballoons. .. Ultralight materials Magnesium/carbon fiber Tubular composites for space structures Zero thermal expansion, high-temperature strength, good specific strength and specific stiffness Aluminum/zircon, aluminum/SiC, aluminum/silica Cutting tools, machine shrouds, impellers Hard, abrasion-resistant materials Aluminum/char, aluminum/clay Low-cost, low-energy materials. . .
Engineering metal-matrix composites exhibit considerable flexibility in designing and achieving unique property combinations, and have begun to emerge as trustworthy substitutes for conventional materials in automotive, aerospace, and other industries. This unique advantage is bestowed by the use of a remarkable variety of reinforcement and matrix combinations that encompass continuous and short fibers, whiskers, foils and laminates, particulates, platelets, micro-balloons, and nanotubes of ceramic and refractory materials, and matrix alloys= that range from low-melting point metals to superalloys and intermetallic compounds. Of the three generic composite fabrication routes, namely, solid-state, liquid-state, and vapor-state methods, the liquid-state methods, based on solidification and casting techniques, enjoy unsurpassed popularity owing primarily to low viscosity of liquid metals, ease of fabrication, flexibility in designing the microstructure, and adaptability of the fabrication technology to existing casting production practices. This paper presents an overview of the recent progress in developing foundry-friendly cast metal-matrix composites with an emphasis on their fabrication, casting characteristics, microstructure design, interfacial phenomena, selected properties, and examples of their applications in pistons, engine blocks, connecting rods, brake rotors and other industrial and consumer products. Fundamental technological challenges in the synthesis of cast composites, in particular, wettability and interfacial compatibility, are highlighted, and recent progress to understand and address these issues is discussed.
JOM, 2020
This paper reviews the progress of solidification processing of cast metal matrix composites over 50 years since their original discovery, which was first published in 1969. Current use of metal matrix composite components in automotives, railways, space, computer hardware, and recreational equipment are presented. Some cast metal matrix composites which are discussed include aluminum reinforced with graphite, silicon carbide, alumina, and fly ash. Several critical issues in solidification processing of metal matrix composites, including nucleation, growth, the effects of reinforcements of fluidity, and the thermo-physical properties of the melts on micro-segregation, and particle pushing or engulfment during solidification of the are discussed. Current and future directions and challenges in solidification processing of cast metal matrix composites are presented, including the synthesis of selflubricating, self-healing, and self-cleaning composites using solidification processing.
Preparation and properties of cast aluminium-ceramic particle composites
Journal of Materials Science, 1981
A casting technique for preparing aluminium-alumina, aluminium-illite and aluminiun~silicon carbide particle composites has been developed. The method essentially consists of stirring uncoated but suitably heat-treated ceramic particles of sizes varying from 10 to 200#m in molten aluminium alloys (above their liquidus temperature) using the vortex method of dispersion of particles, followed by casting of the composite melts. Recoveries and microscopic distribution of variously pretreated ceramic particles in the castings have been reported. Mechanical properties and wear of these composites have been investigated. Ultimate tensile strength (UTS) and hardness of aluminium increased from 75.50MN m-2 and 27 Brinell hardness number (BHN)to93.15 MN m-~ and 37 BHN respectively due to additions of 3 wt % alumina particles of 100 #m size. As a contrast, the tensile strength of aluminium-11.8wt% Si alloy decreased from 156.89 MN m-2 to 122.57 MN m-2 due to the addition of 3 wt% alumina particles of the same size. Adhesive wear rates of aluminium, aluminium-11.8 wt % Si and aluminium-16 wt % Si alloys decreased from 3.
Influence of the Shape of the Particles in the Solidification of Composite Materials
Procedia Materials Science, 2012
The shape of a solidifying interface is generally affected when it encounters foreign inert particles. The degree of deformation depends on the morphology and physical properties of the particles, the melt, the solid and the external fields, affecting the pushing and capture process of the particles. The particle can be trapped by the interface at slower solidification velocity than that predicted by simple models which do not include any deformation of the interface. In all cases this interaction strongly determines the segregation of particles in the microstructure and therefore affecting the physical and physicochemical properties of the final material. In the present report the interaction between particle and interface is analyzed by means of a mathematical model employing the finite element method. The effect on interface shape of different particle shapes and relative thermal conductivities between particle and melt was studied. Thermal field results show that when the particle is more conductive than the melt, the interface is concave. Comparing the concave interfaces for different particle shapes it is observed that, when the particle is not spherical the separation particle-interface at the edge of the particle is the smallest. As a consequence of this phenomenon, which occurs in non-spherical particles, there is a remaining amount of melt between particle and solid which is the last in solidify.
Preparation and casting of metal-particulate non-metal composites
Metallurgical Transactions, 1974
A new process for the preparation and casting of metal-particulate non-metal composites is described. Particulate composites of ceramic oxides and carbides and an A1-5 pct Si-2 pct Fe matrix were successfully prepared. From 10 to 30 wt pct of A12Oa, SiC, and up to 21 wt pct glass particles, ranging in size from 14 to 340 ~z were uniformly distributed in the liquid matrix of a 0.4 to 0.45 fraction solid slurry of the alloy. Initially, the non-wetted ceramic particles are mechanically entrapped, dispersed and prevented from settling, floating, or agglomerating by the fact that the alloy is already partially solid. With increasing mixing times, after addition, interaction between the ceramic particles and the liquid matrix promotes bonding. Efforts to mix the non-wetted particles into the liquid alloy above its liquidus temperature were unsuccessful. The composite can then be cast either when the metal alloy is partially solid or after reheating to above the liquidus temperature of the alloy. End-chilled plates and cylindrical slugs of the composites were sand cast from above the liquidus temperature of the alloy. The cylindrical slugs were again reheated and used as starting material for die casting. Some of the reheated composites possessed "thixotropy." Distribution of the ceramic particles in the alloy matrix was uniform in all the castings except for some settling of the coarse, 340/~ in size, particles in the end-chilled cast plates.
Solidification analysis of AMMCs with ceramic particles
In the research work the result of the reinforcement displacement and solidification analysis for aluminium cast composites with ceramic particles have been presented. The results of research on the solidification process are compared for the applied aluminium matrix alloy (AlSi12CuNiMg2), for composites containing glass carbon particles (Cg) and heterophase reinforcement (mixture of silicon carbide (SiC) + glass carbon particles (Cg)).
Production of rapidly solidified Al/SiC composites
Journal of Materials Science, 1988
Rapidly solidified metal matrix composites have been produced on a laboratory scale either by (1) melt spinning a composite after introduction of the ceramic phase and extrusion of the flakes obtained, or (2) blending melt-spun powder (basic alloy) with the ceramic phase and subsequent extrusion. AIMg(Si) alloys were used as matrix material while SiC particles with diameters of 3 or 20#m were used as the ceramic phase. For the composites prepared by route 1 it was found that the basic alloy was reinforced by the addition of 3#m particles whereas for the 20#m particles reinforcement was observed only for very ductile matrices. The bond between SiC particles and matrix was good. A diffusion and wetting bond was formed. For the composites prepared by route 2 it was found that reinforcement did not occur and that the bond between particles and matrix was weak. Debonding of the particles took place in the case of tensile fracture. The advantage of a rapidly solidified matrix for these composites is that relatively high ductilities are combined with good reinforcement effects. Prior contact of the ceramic phase and the aluminium melt is needed for a good bond between SiC and the matrix material. It is concluded that route 1 should be preferred for the production of rapidly solidified aluminium matrix composites.