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－　　－2Masakatsu MAEDAProfessor, Department of Mechanical EngineeringMasakatsu Maeda is a professor at the Department of Mechanical Engineering, College of Industrial Technology, Nihon University. He received his bachelor and master degrees in materials science and engineering from Osaka University in 1992 and 1994, respectively, and his doctor degree in engineering from Osaka University in 2004. His research interests are on controlling the behaviors and properties of materials interfaces by solid state processing. He is conducting fundamental studies on solid state welding of refractory materials, semiconductors, and dissimilar materials, friction stir welding of aluminum alloys, synthesis of non-equilibrium materials and microstructures, ultrasonic bonding of heat-labile materials, Ohmic contact formation for wide-bandgap compound semiconductors, and precise boring of semiconductor materials. He worked at the Joining and Welding Research Institute, Osaka University from 1994 to 2014 and moved to Nihon University in 2014 to spread the solid-state materials processing technology and to provide solutions to various processes by demonstrating the technology. He is a member of the Japan Welding Society, the Japan Society of Mechanical Engineers, the Japan Institute of Metals and Materials, the Japan Light Metal Welding Association, the Japan Institute of Light Metals, the Japan Society for Technology of Plasticity, and two other academic and/or industrial societies.Research Achievements1)Solid-State Diffusion Bonding of Silicon Nitride Using Titanium Foils, Metallurgical and Materials Transactions A, 34A(8), 1647-1656, 2003. 2)Temperature Field in the Vicinity of FSW-Tool during Friction Stir Welding of Aluminium Alloys, Welding in the World, 49(3/4), 69-75, 2005.3)Interfacial Microstructure and Thermal Stability of Zr55Cu30Ni5Al10 Metallic Glass Joints Formed by Ultrasonic Bonding, Materials Transactions, 50(6), 1263-1268, 2009.4)Anomalous microstructure formed at the interface between copper ribbon and tin-deposited copper plate by ultrasonic bonding, Microelectronics Reliability, 51(6), 130-136, 2010.5)Interfacial microstructure between thick aluminium wires and aluminium alloy pads formed by ultrasonic bonding, Science and Technology of Welding and Joining, 18(2), 103-107, 2013.The figure on the right shows the temperature distribution during friction stir welding (FSW) of A7075-T6 aluminum alloy plates under the tool rotation speed and the welding speed of 1800 rpm and 2.5 mm/s, respectively. It is clearly observed that the isothermal contours of both top and bottom surfaces are expanded to the advancing side, i.e., the temperature at a point on the advancing side reaches higher than that at the corresponding point on the retreating side. Such an asymmetry in the temperature distribution during FSW appears even if the materials to be welded are the same. It is one of the unique properties of FSW compared to other ordinary welding techniques. As a result of the asymmetric process of FSW, the structure and mechanical properties of the joints on the advancing and retreating sides appear different. The difference become more obvious in FSW of dissimilar materials. Research themes to establish dissimilar materials welding technology are now being conducted.