Evaluation of Additive Friction Stir Deposition for the Repair of Cast Al-1.4Si-1.1Cu-1.5Mg-2.1Zn

The deposition of new alloy to replace a worn or damaged surface layer is a common strategy for repairing or remanufacturing structural components. Solid state methods, such as additive friction stir deposition (AFSD), mitigate the challenges associated with traditional fusion methods by depositing material at temperatures below the melting point. In this work, AFSD of aluminum alloy 6061-T6 was investigated as a means to fill machined grooves in a substrate of cast aluminum alloy Al-1.4Si-1.1Cu-1.5Mg-2.1Zn. The combination of machining and deposition simulate a repair in which damaged material is mechanically removed, then replaced using AFSD. Three groove geometries were evaluated by means of metallographic inspection, and tensile and fatigue testing. For the process conditions and groove geometries used in this study, the effective repair depth was limited to 2.3 – 2.6 mm; below that depth, the interface between the filler and substrate materials exhibited poor bonding associated with insufficient shear deformation. The deposited filler alloy closely matched the cast alloy substrate in both strength and hardness. In addition, the fatigue life during fully reversed axial fatigue testing was 66% of that predicted from historical data for comparable stress amplitudes. The results suggest that there is potential to utilize AFSD of 6061 as a viable repair process for cast Al-1.4Si-1.1Cu-1.5Mg-2.1Zn and other comparable alloys.