EFFECT OF TOOL ROTATIONAL SPEED ON MECHANICAL AND MICROSTRUCTURAL PROPERTIES OF FRICTION STIR WELDED ALUMINUM MMCS
Keywords:
Friction Stir Welding, MMCs, Tensile Properties, MicrostructureAbstract
Metal matrix composites (MMCs) are very attractive materials, due to their high stiffness, high temperature stability, and superior wear resistance compared to the unreinforced alloys. In particular, the discontinuously SiCp reinforced aluminium based composites, due to their lower cost and the possibility to be processed by conventional metal working processing such as extrusion, forging, rolling are excellent candidates for structural components in the aerospace and automotive industries. Despite the intense effort put into the development of high performance composites, relatively little work has been directed towards joining these materials. The main hurdle in joining especially Al-(SiC) MMC is related to the mismatch in melting points, thermal coefficient, thermal conductivity between the reinforcement and the matrix alloy, and also interfacial chemical reactions between the reinforcements and the molten matrix alloy, and the inhomogeneous reinforcement distribution after welding. In recent years a new solid-state joining technique, the Friction Stir Welding (FSW) process, has been successfully applied to several Al alloys, leading to joint properties in some cases higher than that of the base material. The main objective of the present work is to study the effect of tool rotational speed on the formation of microstructure in friction stir processed zone(FSP), thermo mechanically affected zone and heat affected zone of friction stir welded Aluminum - 10% SiCp reinforced metal matrix composites. The tensile properties of the joint were evaluated and they are related with microstructure and tool rotational speed of the process. The microstructure characterization of the FSP zone shows evidence of a substantial grain refinement of the aluminium alloy matrix due to dynamic recrystallization induced by the plastic deformation and frictional heating during welding. A maximum weld joint efficiency of around 68.34% was yielded by the joint fabricated at a tool rotational speed of 1100 rpm.
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