Effect of pin-profiles on thermal cycle, mechanical and metallurgical properties of friction stir–welded aviation-grade aluminum alloy

Abstract

Current research is an attempt to choose suitable pin-profile for friction stir welding of aviation-grade aluminum alloy (AA6082). Six tool pin-geometries (T1–T6), that is, threaded cylindrical, taper cylindrical, four slotted, square, triangular and inverted tapered with two flat faces are used to fabricate joints. Mechanical and metallurgical properties of the joints are assessed and allied with nugget zone grain size and thermal properties. The swept volume ratio and pulsating-stirring action of pin-profiles are also quantified. It is observed that square pin-profile provides joint with superior mechanical and metallurgical properties owing to higher pulsating-stirring action and sufficient swept volume ratio. The maximum tensile strength of 300 MPa is obtained by employing square pin-profile tool. Beside this, electron backscatter diffraction analysis has been conducted to critically examine the effect of pin-profiles on grains distribution of nugget zone of friction stir–welded joints. The minimum grain size of 5.48 μm is obtained using square pin-profile.