Effect of tool dwell time on the microstructure and mechanical properties ofprojection friction stir spot welded 2024 aluminum alloy

Automotive industry has developed a variant of the Friction Stir Welding named Friction Stir Spot Welding (FSSW), having a strong influence on welding of thin sheets of aluminum alloys. However, one of the disadvantages of FSSW technique is that a keyhole generally remains at the center of the stir zone. Keyhole defect can reduce the mechanical properties of FSSW joints. A novel friction stir spot welding technique was developed with the purpose to improve the mechanical property of the joints by removing the keyhole. This novel FSSW method was applied to 2024 Al alloy sheets, 1 mm in thickness, under different dwell times. The effect of this welding parameters on the microstructural and mechanical properties of the spot joints has been. The final joints have a smooth surface without keyhole and show improved mechanical properties. The welding parameters variations change the length of metallurgical bonding zone and mechanical properties of the welds in terms of peak load and energy absorption.

Keywords:

Friction stir spot welding , 2024Aluminium alloy , Microstructure , Mechanical properties