The effect of the friction stir welding tool shape on tensile properties of welded Al 6061-T6 joints

This study employs various Friction Stir Welding (FSW) tools to investigate mechanical properties of Al 6061-T6 joints. Welding tools were cut to form one-sided conical shape pin with a groove to enable material flow in the stirred zone over welding passes. Weld joints were made through six different FSW tool shapes. One-sided conical shape pins consisted of different cone angles 0 degrees (simple cylinder pin), 5 degrees, 10 degrees, 15 degrees, 20 degrees, and 25 degrees. Tensile tests were then carried out to evaluate elastic modulus, ultimate tensile strength, and elongation of joint samples. Measured hardness values and grain sizes within weld regions were affected by the welding tool shape. Tensile properties of aluminum joint samples were improved as cone angle increased from 0 degrees to 20 degrees through different welding tools. This was attributed to excess of plastic flow evolution over the weld zones during welding operation. Beyond cone angle of 20 degrees, tensile strength and elongation of the joint sample dropped noticeably. Drop in tensile properties of joint sample welded with cone angle of 25 degrees was attributed to small contact surface of conical tool with welded slabs resulting in weak connection on the opposite side of the weld joint, while lower cone angles of pins showed no such technical challenges.