Effect of ultrasonic amplitude on interfacial characteristics and mechanical properties of Ti/Al laminated metal composites fabricated by ultrasonic additive manufacturing

Performance of ultrasonic additive manufacturing (UAM) part is critically determined by the quality of bonding between adjacent metal layers, which is significantly affected by ultrasonic amplitude. However, such correla-tions among them are still unclear. In this work, the interfacial bonding of Ti/Al laminated metal composites (LMCs) fabricated by UAM was examined at an atomic scale. Theoretical and experimental investigations were carried out on the influence of ultrasonic amplitude on microstructural characteristics, bonding quality, and mechanical properties. Our findings suggest that the shear deformation, interfacial temperature rise and acoustic softening effect (ASE) jointly induce the interfacial bonding via atomic diffusion. Multiple typologies of crystal oxides with several nanometers in thickness are identified in the interfacial oxide zone, and the metal-oxide -metal bonding mode was formed by phase transition of Al-O and Ti-O multiple oxides. As the amplitude in-creases from 28 & mu;m to 32 & mu;m, the maximum instantaneous temperature rise at the interface and the flow stress reduction generated by ASE in the Ti layer are increased by-50 celcius and-38.6 MPa respectively, which facil-itates the formation of Al or Ti nanocrystalline and Al3Ti compound around the interface for enhancing layer bonding strength. Overally reduced hardness and near-interface zone hardening of Ti layer caused by high amplitude are detrimental to the tensile and bending properties of composites, respectively, despite the stronger interfacial bonding obtained under this condition.