Characterization and tribological behavior of cast In-Situ Al (Mg,Mo)-Al 2 O 3 (MoO 3 ) composite
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DISCONTINUOUS particle-reinforced metal-matrix composites (DPMMCs) are commonly used today in many military, aerospace, and industrial applications. A variety of nonmetallic particles have been dispersed in different metallic systems to develop ex-situ DPMMCs. From technical and economic point of view, there are many challenges and difficulties facing the development and applications of this kind of composite.[1] As noted recently, in-situ generation of reinforcements in a metal matrix offers a route to achieve a wide range of attractive material properties that cannot be obtained either in ex-situ composites or conventional alloys. The superior material properties in in-situ composites are the direct result of relatively more uniform distribution of in-situ-generated reinforcing particles inside the matrix alloy, good wettability between the virgin surface of in-situ-generated particles and the molten matrix alloy, thermal equilibrium between the particles and the matrix alloy, and better bonding between the particles and the matrix where there is no interference from contamination.[2–6] ABDULHAQQ A. HAMID, Postdoctoral Research Scholar, Mechanical Engineering Department, College of Engineering, University of Mosul, Mosul, Iraq. Contact e-mail: [email protected] S.C. JAIN, Professor, Mechanical and Industrial Engineering Department, and P.K. GHOSH, and SUBRATA RAY, Professors, Metallurgical and Materials Engineering Department, are with the Indian Institute of Technology Roorkee, Roorkee (Uttranchal) – 247 667, India. Manuscript submitted August 1, 2005. METALLURGICAL AND MATERIALS TRANSACTIONS B
A variety of reinforcements of Al2O3, AlN, SiC, TiC, TiN, TaC, TiAl3, TiB2, etc. have been generated by in-situ reactions taking place in different metal matrices using a number of methods including LANXIDES,*[7] XD,**[8,9,10] *LANXIDES is a trademark of Lanxide Corporation, Newark, NJ. **XD is a trademark of Martin Marietta Laboratories, Baltimore, MD.
self-propagating high-temperature synthesis (SHS),[11,12] reactive gas injection,[13,14,15] and solidification processing.[16–19] However, the production of in-situ DMMPCs by solidification processing is also attractive due to their low cost, contributed also by the value added through release of alloying elements from relatively cheaper oxides, flexibility in operation, and potential to integrate with standard foundry practice. In the area of cast in-situ Al-Al2O3 composites, two different routes are used for generating oxide particles: (1) direct oxidation of molten aluminum alloy[13,14,20] and (2) substitution reaction between molten aluminum and metal oxide, such as TiO2,[21] MnO2,[16] SiO2,[17] CuO,[18,19] B2O3,[22] MoO3,[23] ZnO,[24] and Fe2O3.[25] In the latter method, cast in-situ aluminum alloy-Al2O3 composites are obtained as the resulting product when the externally added metal oxide gets reduced by molten aluminum to generate alumina particles and release useful alloying elements in the remaining molten aluminum. The incorporation of hard ceramic particles
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