The effect of post welded heat treatment on mechanical properties and microstructure of friction stir welded Al 6063

Aluminium is the third most abundant element (after oxygen and silicon), and the most abundant metal in the Earth's crust. Aluminium is remarkable for the metal's low density and for its ability to resist corrosion due to the phenomenon of passivation. Structural components made from aluminium and its alloys are vital to the aerospace industry and are important in other areas of transportation and structural materialsWelding plays a crucial role or say as a back bone of manufacturing industry to join the components. Friction stir welding (FSW) is a relatively new joining process that has been demonstrated in a variety of metals such as steel, titanium, lead, copper and aluminium. The unique properties of friction stir welds make possible some completely new structural designs with significant impact to ship design and construction. Friction stir welding is especially advantageous for joining aluminium and has been exploited commercially around the world in several industries. In the present work the effects of welding speed have been investigated on the microstructural and mechanical properties of friction stir welded aluminium alloy 6063. FSW was carried out at rotational speed of 1300 rpm (constant) and transverse speeds of 35, 50 and 65 mm/min. Mechanical performance has been investigated in terms of hardness, wear resistance and tensile strength. To study the effect of post welding heat treatment on properties of friction stir welded joint, the artificial ageing was carried out at 1600 C for a soaking period of 20 hours in the muffle furnace. The study revealed that friction stir welded joint prepared at welding speed of 35 mm/min exhibited better tensile strength, hardness and wear resistance. Better mechanical properties of the joint prepared at welding speed of 35 mm/min may be attributed due to fine, homogeneous and equaxed grain structure of stir zone. Post welding heat treatment of friction stir welded joint improved the wear resistance and microhardness of the joint. However tensile properties deteriorated with the post welding heat treatment of joint.