An Experimental Investigation of Effects of Fluxes (Na 3 AlF 6 and K 2 TiF 6 ), Element Alloys (Mg), and Composite Powde
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ALUMINUM alloys reinforced with ceramic particles, such as SiC,[1,2] B4C,[2–5] TiC,[6–9] and Al2O3,[9,10] are currently being developed for various high-performance applications. These composites can be produced in a wide variety of procedures, ranging from powder metallurgy methods to different kinds of casting processes.[9–14] The wetting of ceramic surfaces by molten metals and incorporation and homogenous distribution of ceramic particles in the melt matrix are the most important phenomena to consider when designing a metal matrix composite material. The wetting of ceramics by molten metals usually involves interfacial reactions.[15] The inconsistencies in the wetting behavior, in part, can be ascribed to the purity of the atmosphere employed during the experiments and its direct effect on the aluminum oxide film on the droplet. The oxide films prevent the molten Al from achieving intimate contact with the ceramic, and its breakdown at high YOUNES MAZAHERI, RAHMATOLLAH EMADI, and MAHMOOD MERATIAN are with the Department of Materials Engineering, Isfahan University of Technology, P. O. Box 8415683111 Isfahan, Iran. Contact e-mail: y.mazaheri136528@yahoo. com MEHDI KARIMI ZARCHI is with the Department of Materials Science and Engineering, Engineering School, Shiraz University, P. O. Box 71348-15939, Shiraz, Iran. Manuscript submitted August 22, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
temperatures is vital to achieve wetting. To overcome the barrier effects of oxide films, fluoride salts, also known as fluxing agents, can be used, which have the capability to dissolve aluminum oxide.[7,16,17] Another way to improve the wettability of ceramic particles is by adding the alloying elements to the molten aluminum. Alloying elements can improve the wettability of reinforcement particles by reducing the surface tension of the melt, reducing the solid-liquid interfacial energy of the melt, or inducing wettability by chemical reaction. It is expected that the addition of alloying elements to the melt can influence the disruption of the alumina film, allowing a faster direct metal/ceramic contact.[18] In one of the studies, SiC particle coated with Al powders, and injection of the particulate (Al-SiCp)CP composite powder instead of untreated SiC particles into the melt, enhances the wettability between the molten matrix alloy and the reinforcements and improves the distribution of the reinforcement particles in the solidified matrix.[19] Wetting of pure aluminum on TiC ceramics is reported to occur in the range of 750 K to 1373 K (477 °C to 1100 °C), along with the formation of either Al4C3 or TiAl3 phase.[18,20,21] Also, production of Al-B4C composites by mixing particles into the molten metal below 1373 K (1100 °C) is difficult.[4,11] In the Al-B4C composites, the terms of process phases, such as Al3BC, AlB2, and TiB2, can be identified.[3,4,22] In order to enhance the wettability and incorporation of ceramic particles and to improve their incorporation behavior
into Al melts, different methods are used.[23] In this s
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