Microstructure Characteristics and Mechanical Properties of Al 413/Mg Joint in Compound Casting Process
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MAGNESIUM alloys are the lightest engineering metals offering attractive alternatives to aluminum alloys for the manufacture of many low-weight castings, notably components for transport vehicles. However, magnesium alloys have some undesirable properties including poor wear and creep resistances, which limit extensive application of magnesium alloys in many industrial fields.[1,2] Using combined structures composed of wearand creep-resistant aluminum alloys and lightweight magnesium alloys may be the most effective way to meet the demands for lightweight high-performance components. Among the different ways used for processing highperformance combined structures, joining of materials with complementary properties is of particular interest.[3] A variety of attempts have been dedicated to joining Al/Mg alloys using different fusion welding and solidstate joining methods such as tungsten inert gas welding,[4] laser welding,[5–7] spot welding,[8] friction-stir welding (FSW),[9–11] and vacuum diffusion bonding.[12,13] The major problems in these joining processes are the existence of oxide films on the surface of aluminum and magnesium and the formation of Al-Mg intermetallic compounds with high hardness and brit-
E. HAJJARI, Ph.D. Graduate Student, M. DIVANDARI, Associate Professor, and S.H. RAZAVI, Assistant Professor, are with the Department of Metallurgy and Materials Engineering, Iran University of Science and Technology, 16846-13114 Tehran, Iran. Contact e-mail: [email protected] T. HOMMA, Associate Professor, and S. KAMADO, Professor and Director, are with the Research Center for Advanced Magnesium Technology, Nagaoka University of Technology, Nagaoka 940-2188, Japan, and also with the Department of Mechanical Engineering, Nagaoka University of Technology. Manuscript submitted June 22, 2011. METALLURGICAL AND MATERIALS TRANSACTIONS A
tleness, between the aluminum and magnesium as an interlayer, which are deleterious to the mechanical properties. Solid-state joining processes such as FSW and vacuum diffusion bonding can achieve relatively higher joining strengths compared to fusion methods, due to the elimination of defects such as pores and oxide inclusions; however, for the direct contact between the base aluminum and magnesium, there are also Al-Mg intermetallic compounds in the joints.[10,14] In addition, long process time and high corresponding operating cost of the vacuum diffusion bonding and specific requirements for the shape of the substrate in FSW may render these solid-state joining processes difficult for practical and industrial applications. Compound casting is a process through which two metallic materials—one in solid state and the other liquid—are brought into contact with each other. In this way, a diffusion reaction zone between the two materials and thus a continuous metallic transition from one metal to the other is formed.[15] This method enables forming the shape of the product and bonding other parts with complex structures to castings at the same time. Applying this method in production proce
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