Stability of Microstructure in Al3003 Builds Made by Very High Power Ultrasonic Additive Manufacturing

Very High Power Ultrasonic Additive Manufacturing (VHP-UAM) system was used to produce aluminum parts from 150 µm thick Al3003-H18 foils. The build was processed at 36 μm vibration amplitude, 8 kN normal load, and 35.6 mm/s weld speed at 20 kHz frequency. Almost 100% linear weld density was achieved. A deformation-interaction volume of ~20 μm was observed below the bonded interface. The microstructural stability including grain boundary structures, and crystallographic orientations was evaluated after annealing these samples at 343oC for 2 hours and 450oC for 2 hours. After heat treatment, small grains persisted at the interfaces with sluggish grain growth kinetics. In contrast, normal grain growth kinetics was observed in the middle of the foils. Possible mechanisms for such phenomena are discussed.