Papers by Keyword: Al Matrix Composites

Abstract: Carbon nanotube (CNT) has been one of promising candidates as a reinforcement in metal matrix composites (MMCs) for its variety of excellent properties such as lightweight, high strength etc. It is necessary to disperse CNT to the level of each one in order to lead to efficiently reflect the excellent essential physical properties of CNT in the composites. This research investigates fabrication processes linked with dry ball milling and cold pressing followed by sintering to uniformly disperse CNT in aluminum (Al) matrix. It was found that dispersibility of CNT were improved with increasing ball milling time based on observation of morphology of mixed powders and the composites using SEM. Vickers hardness and tensile strength of CNT/ Al composites increased with increasing ball milling time up to 24 hours, while they were constant or decreased because of increase of voids in case of longer than 24 hours of ball milling time.

Abstract: Si particles reinforced Al matrix composites (Sip/Al) have been widely used in the electronic packaging filed, and the higher mechanical and themo-physical properties are required for their application. In the present work, the effect of Si content (from 0.28 to 6.95 wt. %) in the matrix alloy on the microstructure, mechanical and thermo-physical properties of Sip/Al-Si-Mg composites have been investigated. Sip/Al-Si-Mg composites with 55 vol. % Si particles were prepared by pressure infiltration method. It has been found that the increment of Si content led to the improvement of relative density of composites. Moreover, the bending strength and thermal conductivity of Sip/Al-Si-Mg composites reached its maximum at Si content of 1.98 wt.%, which were 238.8MPa and 159.5W/(m∙K), respectively. Furthermore, the coefficient of thermal expansion (CTE) of Sip/Al-Si-Mg composites decreased with the increase of Si content. The mechanism of Si content on the microstructure of performance of Sip/Al-Si-Mg composites has been discussed.

Abstract: The study investigates the influence of different fraction of Mg₂B₂O5 whiskers (5, 10, 15 and 20vol.% ) on the microstructure of the hot extruded composite as well as on the mechanical properties in the same condition. The results indicate that the process is available for producing the composite, image analysis shows the whisker tends to cluster together with increasing content of reinforcement. When the content of the reinforcement is 10%, the composites exhibit the best mechanical properties, meanwhile, it demonstrate cluster is unfavorable to the improvement of properties of materials. The ductile failure of 6061Al matrix, the reinforcement fracture and the whisker-matrix interface debonding acted as the main mechanism of fracture nucleation.

Abstract: A new Al₂O₃ particle reinforced Al matrix composite was fabricated through in-situ chemical reaction between Al and glass powder. The microstructures and element distributions of the composite were observed and analyzed through OM, SEM and EDS, respectively. The results show the reinforced Al₂O₃ particle synthesized by in-situ chemical reaction are aggregated on the grain boundary. The grains can be refined with the increasing of powder. Eutectic silicone with granulous shape was found in the microstructure, which attributes to the modification of Na and Ca to eutectic silicone.

Abstract: (SiC_p+Al₂O_3f)/7075Al composites as potential friction materials were prepared in this paper by pressure infiltration and some related properties were compared with traditional friction materials. The addition of Al₂O₃ fiber to SiC preform could contribute to enhance compressive strength of the preform as well as tensile strength of the composites. The tensile strength of as-fabricated composites with 35vol%SiC_p + 15vol% Al₂O_3f could reach 402MPa and the friction coefficient is about 0.4 and the thermal conductivity is higher than 120W/mK. Compared with traditional materials such as nodular cast iron, the composites exhibit better comprehensive properties and are suitable as brake materials for automobile.

Abstract: In this paper, Al matrix composites reinforced with Al-Ti intermetallics/Ti metal compound spherical agents were successfully fabricated through powder metallurgy way. Al-Ti intermetallic including Al₃Ti and TiAl phases are main reinforcements and inner Ti metal could not only play reinforce role but also reduce the crack sensitivity of Al-Ti intermetallics. This kind of reinforcements bonded strongly with Al matrix. As expected, the resultant composites exhibit promising mechanical properties at ambient temperature. And the mechanical property could be improved through regulating the relative thickness of the Al-Ti intermetallics and Ti metal layers.

Abstract: Self-propagating synthesis of Ti-Al-C powder mixture was used for fabrication of master alloys suited to industrial scale manufacturing of Al-TiC composites. The cold compacted powder pellets were heated in a protective atmosphere until the melting point of aluminium. Then the temperature of pellets increased rapidly due to intense exothermic reaction between molten Al and Ti, resulting in simultaneous formation of Al₃Ti and Al₄C₃. When the temperature exceeded ~1090°C, TiC particles started to form as a result of the mutual reaction between Al₃Ti and Al₄C3. Resulting reaction products consisted of fine (~_{Subscript textu}b>2µm) TiC particles uniformly distributed in the Al matrix. The composition of powder mixture was optimized to attain master alloy pellets containing ~50 vol.% TiC. Such pellets were then diluted in molten aluminium to produce Al+TiC composites. In-situ formation of TiC in Al matrix provided favourable interfacial quality, which avoided dewetting and rejection of particles from molten aluminium. The parameters for composite casting were optimized in order to reduce the effect of reversible reaction leading to undesired formation of Al₃Ti or Al₄C₃. The final composites showed significantly increased Young’s modulus and strengths. The potential of using the approach for the fabrication of fine, nearly spherical TiC particulate reinforced Ti composites is briefly discussed. The simple process is very promising for economical manufacturing of highly efficient lightweight structural materials.

Abstract: The influences of solution treatment, deformation strain, and nanometric Al2O3 particulate on hardness for nanometric Al2O3 particulate reinforced Al alloy matrix Composites manufactured by casting were investigated. The result showed that both the hardness of AL matrix and the hardness of the composites increased dramatically with increasing solution temperatures. The hardness increased slightly with increasing deformation strain for the composites. The hardness of the composites is higher than the AL matrix after the same deformation and heat treatment. Microstructure observation revealed that the grain sizes of the composites increased with increasing solution temperature and decreased with more severe deformation.

Abstract: The Poly-crystal alumina short fiber reinforcing 2024 matrix composites was produced by the gas pressure infiltration, and a new apparatus has been developed for the infiltration of MMCs by the gas pressure infiltration technique. The reasonable sintering parameter for the preform were determined.The preform was heated at 450°C to remove the organic binder and pore-forming material, and then heated at 1050°C for 2.5h to obtain the comprehensive properties.Scanning electron microscope was used to observe the tensile fracture of Aluminum matrix composites, and the fracture feature of composites produced in different temperature was analyzed. The melting temperature of 2024Al was 800°C and holding time was 20mins; the infiltration gas pressure was 0.5Mpa and holding time was 20s.And then interface reaction is appropriate between the fiber and matrix ,a good performance of composites was produced.

Abstract: Nanometric Al2O3 particulate reinforced Al alloy Composites bar manufactured by casting were hot compressed to 20% of its height, and solution treated at temperatures of 480°C, 490°C 510°C for 3 hours, then aged at a temperature of 120°C for 24 hours. Wear properties and hardness were investigated by wear tester and durometer, and microstructures were observed by optical microscopy. The result shows that the hardness of Al2O3 particulate reinforced Al composites increases with increasing solution temperatures, while wear loss and friction coefficient decreases with increasing solution temperatures. Microstructure observation revealed that the Al2O3 particulate reinforced Al alloy Matrix composites is of lamellar grain structure and the grain size increases with increasing solution treatment temperatures.