INVESTIGATION ON MICROSTRUCTURE AND MICRO HARDNESS OF FRICTION STIR WELDED DISSIMILAR ALUMINUM ALLOY PLATES

Abstract

Assembly of two different grades of aluminum plates is need in many light weight vehicles structures like military, aerospace, ship building and automobile applications. This paper deals with joining of AA7075-T651 with AA6063-T6 aluminum alloys by friction stir welding (FSW) process using cylindrical straight and taper at Tool revolving speed, tool axial force and welding transverse speed of 1000,1100,1200rpm, 4, 5, 6 KN and 30,45,60 mm/min. The effect welding process parameters on weld appearance and hardness were examined experimentally. The microstructures were observed at various regions and analyzed by means of optical microscope. From this investigation were established that the use of taper cylindrical pin profile of tool provides to better flow of materials between both alloys and the formation of flaw free weld zone. The growth in Micro-Hardness is attributed to the development of fine grains and intermetallic in the weld zone, and in addition, the reduced size of weaker regions, such as TMAZ and HAZ regions, results in good metallurgical properties.