Investigation of Shoulder diameter to Sheet Thickness (D/T) Ratio on Tensile Properties Friction Stir Welded AA2014-T6 Aluminum Alloy Joints

2xxx and 7xxx high strength alloy are well suited for components and structures that include a greater strength ratio and are typically used in the fabrication of fuselage, wing skins. AA2014 is hard to join using a fusion welding process because of its good thermal conductivity, oxidation behaviour and low fusion point, which can easily lead to burn through and porosity. To overcome the above difficulty, friction stir welding (FSW) is used. The formation of sound weld depends on process and tool parameters. The tool shoulder is the most predominant factor. About two-third of heat is generated at the interface of tool and sheet. Hence, in this investigation, the influence of the tool shoulder diameter (D) to sheet thickness (T) ratio on the tensile properties of FSW AA2014 joints was analysed. Five tools with varying D/T ratios (2.0, 2.5, 3.0, 3.5 and 4.0) were used. Microstructure and hardness measurement were performed to correlate strength properties of FSW joints. It is found that the joint welded with a D/T ratio of 3.0 disclosed superior joint tensile properties compared to other D/T ratios. It is mainly due to the development of fine-grained structure in stir zone of D/T 3.0 joints.