Repair of aluminum 6061 plate by additive friction stir deposition

Abstract

The deposition of new alloy to replace a worn or damaged surface layer is a common strategy for repairing or remanufacturing structural components. For high-performance aluminum alloys common in the automotive, aerospace, and defense industries, however, traditional fusion-based deposition methods can lead to solidification cracking, void formation, and loss of strength in the heat-affected zone. Solid-state methods, such as additive friction stir deposition (AFSD), mitigate these challenges by depositing material at temperatures below the melting point. In this work, a solid-state volumetric repair was performed using AFSD of aluminum alloy 6061-T6 to fill grooves machined into the surface of a plate of 6061-T651. The groove-filling process is relevant to replacement of cracked or corroded material after removal by localized grinding. Three groove geometries were evaluated by means of metallographic inspection, tensile testing, and fatigue testing. For the process conditions and groove geometries used in this study, effective mixing of the substrate and deposited alloy were achieved to a depth of 3.1–3.5 mm. Below that depth, the interface between the substrate and AFSD alloy exhibited poor bonding associated with insufficient shear deformation. This suggests a practical limitation of approximately 3 mm for the depth of repair by groove filling using the current combination of process parameters, materials, and tool design. The mechanical properties of the filler alloy, the depth of the heat-affected zone, and areas for further optimization are discussed within the context of precipitation hardened aluminum alloys.