Dynamic Recrystallization and Recovery in Very High‐Power Ultrasonic Additive Manufacturing

Abstract

Ultrasonic additive manufacturing (UAM) is a novel solid‐state freeform fabrication process that utilizes ultrasonic energy to merge similar/dissimilar metal tapes. Metallurgical bonding between the metal tapes can be achieved instantaneously once the sonotrode rotates through. Herein, five‐layered Al‐1100 ultrasonically consolidated samples are fabricated under various parameter combinations of ultrasonic amplitude and normal force settings. The microstructure and texture evolution of the built component among layers are characterized using electron backscattered diffraction (EBSD). The results reveal that among the upper layers, recrystallization only occurs at very local interface regions due to the local shear deformation, while the bulk region of each layer still remains the starting microstructure unaffected. However, after this cyclic accumulating process, dynamic recovery (DRV) and dynamic recrystallization (DRX) are observed to take place in the bottom of the built samples. The evolution of microstructures and textures of the bottom layer is a function of input energy, which well explains the effect of ultrasonic energy on the microstructure evolution at the metallurgical bonding regions.