Investigation of a Hybrid Frictional Diffusional Bonding Approach to Increase Bond Strength in Solid-State Additive Manufacturing Repair of High-Strength Aluminum Alloys

Abstract Additive friction stir deposition (AFSD) is a solid-state additive manufacturing technique capable of repairing aluminum alloys with identical filler material, but there are few studies about the lubricant-free round feedstock variant or post-processing avenues for improving performance. The current study investigates the impact of hybrid frictional diffusional bonding (HFDB) as a post-processing route to improve the performance of aluminum alloy AA7075 repaired via AFSD. Implementation of a novel actuator force-control scheme enabled AFSD repairs to be conducted without the aid of lubrication as a potential contaminant. Repairs receiving a combination of HFDB and a post-deposition heat treatment (PDHT) exhibited > 90% of the yield strength and ultimate tensile strength of the wrought control, representing a marked increase relative to repairs that underwent PDHT without HFDB. Fatigue testing of repairs that underwent HFDB and PDHT revealed comparable cyclic performance to the wrought control in the high-cycle regime, indicating the potential of HFDB as a post-processing route to improve repair performance under static and cyclic loading.