Microstructure and Crystallographic Texture Variations in the Friction-Stir-Welded Al-Al 2 O 3 -B 4 C Metal Matrix Compo
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THE increasing demand for better fuel economy, reduction of exhaust gas emission, and higher operating efficiency of cars and other vehicles are prompting intensive research on light weight structural materials. Based on the high strength-to-weight ratio, aluminum alloys offer potential for weight reduction of various vehicles and have thus become increasingly attractive for use in the different sectors such as automobile and aerospace industries. They are also used in bicycle frames, bridge railings, and various welded structures.[1–4] Metal matrix composites (MMCs) based on aluminum alloys are characterized by properties superior to that of the corresponding aluminum alloys. They have higher specific strength and stiffness, improved mechanical properties at high temperature, lower thermal expansion, and better wear resistance.[5–7] Accumulative roll bonding is a major severe plastic deformation MAHYAR MOHAMMADNEZHAD, Research Assistant, MORTEZA SHAMANIAN, Professor, MAHSHID TAHERI, VAHID JAVAHERI, and AMIR HOSSEIN NAVIDPOUR, Graduates, are with the Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran. Contact e-mail: [email protected] AZAM ZABOLIAN, Staff Member, is with the Department of Natural Resources, Isfahan University of Technology. MAJID NEZAKAT, Ph.D. Student, and JERZY A. SZPUNAR, Professor, are with the Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, SK, S7N5A9, Canada. Manuscript submitted August 27, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS A
process for manufacturing sheets of ultrafine-grained metal matrix composite.[7–10] However, owing to the size and shape limitation of sheets manufactured, the application of the accumulative roll bonding materials for the production of large or complex parts like car bodies is limited. Hence, to develop the application of these materials, their joining is a technologically important issue.[10–12] Earlier reports showed that friction-stir welding is one of the best methods to join ultrafine-grained and nanostructure materials, since it provides excellent mechanical properties and retains the fine-grained microstructure.[13–18] In recent years, there have been a number of studies characterizing the mechanical properties and microstructure developed during friction-stir welding. Ceschini et al.[7] studied effect of friction-stir welding on microstructure and mechanical properties of the aluminum composite. Their result indicated that in the weld zone a substantial grain refinement occurs due to dynamic recrystallization induced by the plastic deformation and frictional heating during welding and a significant reduction of the particles size occurs due to the abrasive action of the tool. Mechanical tests showed a high efficiency of the FSW joints and fracture mechanisms for the specimens were those typical of metal matrix composites: interfacial decohesion, void nucleation, and growth, as well as fracture of reinforcing particles. Sato et al.[11] investigated friction-stir welding of ult
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