Indian Journal of Science and Technology

Abstract

Friction Stir Welding is a versatile metal joining process, which has been adopted to join composite materials. Many research activities have been conducted on this metal joining processes which lead to the process being used in diverse field of applications. AA6061 plates of 6mm thick each were joined through butt welding configuration by Friction Stir Welding process using a CNC milling machine and a non consumable tool with square pin profile. Six joints were made using the combination of three tool rotation speed 350 rpm, 550 rpm and 900 rpm and three weld traverse speed 55 mm/ min, 100 mm/min, 110 mm/min. The prepared joints were tested in order to analyze its microhardness, tensile strength, temperature distribution, force and microstructure along the joint. It was identified that for a given tool rotation speed, the microhardness increased proportionally with respect to the weld speed and depth along the joint. However it was noticed that for different tool rotation the maximum of the microhardness was obtained for 350 rpm. Measurement of tensile strength revealed that the strength was maximum when the weld speed and tool rotation speed was maximum. The tensile strength measurement indicated that the strength was directly proportional to the weld speed and tool rotation speed. Temperature measured during welding revealed that the temperature was maximum along the weld center, while same decreased away from the weld center. This was because of the dissipative effect of AA6061. Microstructure of the prepared joint revealed that the due to the influence of the tool, the grain structure reformed. There were finer grains at place traversed by the tool and coarse grains at place away from the tool. The joints thus fabricated can be used for applications which require reliable and defect free joints such as automobile frames and aeronautical structures. 
Keywords: AA6061, Friction Stir Welding, Microhardness, Microstructure, Temperature distribution