AA6061 (Al–Mg–Si) alloy is an age hardenable alloy having improved strength due to the precipitation of Mg2Si phase after artificial aging. Alloys of this category are thoroughly used in marine frames, pipelines, storage tanks and aircraft applications.

In comparison to many of the fusion welding processes that are regularly useful for joining structural alloys, friction stir welding (FSW) is a promising solid state joining process where the material which is being welded is not melted and recast throughout the welding process.

Frictional heat involved with the thermal cycle differs in the transverse direction of the weld. The maximum temperature is noticed in the FSW zone that leads to an alteration in the precipitate distribution existing in the base material. All these modifications in the heat and temperature distribution in the welding process change the strength and ductility of the joints.

Although FSW joints yield better joint efficiency as compared to fusion welding processes, the gap between strength values of the base metal and the weld metal is substantially large. If the fatigue strength of the weld metal could be improved by any method it will be of advantages.

The objective of this study is to examine the effect of post weld aging treatment on the fatigue strength of friction Stir welded AA6061 aluminium alloy joints. For additional understanding of fatigue results microstructure, microhardness and tensile properties also had been examined.

An artificial aging treatment (1600c for 18 hrs.) was applied on the welded joints. It had been identified that artificial aging treatment exhibit improved fatigue performance with much higher strength and hardness than those of respective as welded plates of the friction stir-welded AA6061 aluminium alloy joints.

Hemendra Kumar Srivastava, V. Balasubramanian, S. Malarvizhi and A. Gourav Rao of Centre for Materials Joining and Research (CEMAJOR), Department of Manufacturing Engineering, Annamalai University and Navel Materials Research Laboratory (NMRL).