Enhancing physical and mechanical properties of Mg using nanosized Al 2 O 3 particulates as reinforcement
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Demand for light structural materials from automobile, aerospace, space, electronics, and sport industries has brought magnesium-based composites to the center of attraction due to their high specific stiffness and strength, good dimensional stability, high damping capacity, and fairly improved elevated temperature creep properties.[1–7] The end properties of composite materials are critically governed by type of processing and selection of reinforcement compatible with metallic matrix.[5,8] The most widely investigated reinforcing ceramics, for example, SiC particulates,[2–6] have limited success due to the high brittleness in nonreacting ceramic-Mg formulations. However, the reacting metallic oxide ceramic, Al2O3, promises rather ductile formulation due to formation of metallic bond compounds at the interface.[9] Al2O3, besides being available at low cost, also exhibits high specific stiffness, superior high-temperature mechanical properties,[10,11] which are even higher in nanoscale structure,[12] and excellent oxidation resistance. The result of literature search indicates that an attempt is made to develop magnesium-based nanocomposites by the technique of powder metallurgy.[3] However, no attempt is made to do the same using the cost-
S.F. HASSAN, Ph.D. Student, and M. GUPTA, Associate Professor, are with the Department of Mechanical Engineering, National University of Singapore, Singapore 117576. Contact e-mail: [email protected] Manuscript submitted April 19, 2004. METALLURGICAL AND MATERIALS TRANSACTIONS A
efficient solidification processing technique. Among the solidification processing routes, disintegrated melt deposition (DMD)[13] remains an attractive choice due to its capability of bringing together the advantages of spray processing and conventional casting. Disintegrated melt deposition exploits the cost effectiveness of the conventional foundry process and the scientific innovativeness and technical potential associated with the spray process. Unlike the spray process, the DMD technique employs higher superheat temperatures and lower impinging gas jet velocity with the end product being only bulk composite materials. Accordingly, the primary aim of the present work was to synthesize the nanosized Al2O3 particulates-reinforced magnesium composite using the DMD technique followed by hot extrusion. The materials thus synthesized were examined for microstructural, thermal, and mechanical properties. Particular emphasis was placed on the effects of nanosized Al2O3 particulates as reinforcement on the microstructural, thermal, and mechanical properties of pure magnesium. The DMD technique was used to cast magnesium (99.9 pct pure, supplied by ACROS Organics, Morris Plains, New Jersey) reinforced with 1.1 volume percentage (2.5 weight percentage) of nanosized (50 nm) Al2O3 particulates (supplied by Baikowski, Narashino City, Japan). The DMD technique for composites involved melting and superheating the magnesium turnings with reinforcement particulates to 750 °C under inert Ar gas atmosphere in a graphi
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