Mechanical and Metallurgical Properties of Multipass Friction Stir Welded Joints of Aluminium 6061 Alloy

Abstract

Solid state joining process named Friction Stir Welding was developed in 1991 which has attracted
considerable interest from the aerospace and automotive industries, since it is able to produce defect free joints
particularly for light metals i.e. magnesium and aluminium. Aluminium alloy AL 6061 is medium strength architectural
alloy, normally used in intricate extrusions. Due to difficulties in welding Aluminium using conventional welding
processes, Friction Stir Welding has been used to weld aluminium alloy AL 6061. The effect of single pass and double
pass was studied using combination of different parameters i.e. Square tool pin profile, tool rotational speed (1200 rpm),
welding speed (45mm/min) and tool shoulder diameter 20 mm. The square pin (7×7 mm) profile was used to make a butt
weld joint by using single pass, double pass (same side) and double pass (reversed side).Results was compared by
studying the effect of number of passes on the tensile strength and micro hardness Test. After testing, the effect of single
pass and double pass on friction stir welded aluminium alloy 6063 using square tool pin profile are concluded, it was
observed that the maximum value of UTS i.e. 172.5 N/mm² was obtained at 1200 rpm tool rotational speed, 45 mm/min
welding speed with square tool pin profile with double pass (same side) friction stir welding. The Vickers hardness value
was maximum at stir zone i.e. 91 Hv with 1400 rpm tool rotational speed, 45 mm/min welding speed with square pin
profile with double pass (same side)and(reversed side) as compared with the heat affected zone (HAZ) and thermo
mechanically affected zone (TMAZ).