Bonding characteristics during very high power ultrasonic additive manufacturing of copper

Welding of copper foils (150 μm thick) achieved at room temperature by very high power ultrasonic additive manufacturing was seen to involve appreciable softening and enhanced plastic flow. The initial coarse-grained structure (25 μm) in the material changed into fine dynamically recrystallized grains (0.3–10 μm) at the foil interface within the order of a few milliseconds of processing. This phenomenon led to metallurgical bonding through grain boundary migration and allowed for successive welding of tapes to form a three-dimensional part.