Unveiling and harnessing the texture evolution in ultrasonic welding of copper via orientation-designed coatings

The texture evolution mechanism during metal processing serves as an important guideline for microstructure design and property optimization. For ultrasonic welding, this mechanism remains unclear due to the severe plastic deformation and synergistic effects of thermal, ultrasonic, and mechanical stress fields. In the present study, the texture evolution during ultrasonic welding was unveiled and harnessed by employing Cu coatings with different preferred orientations. At the early stage of welding, grain rotation occurred near the welding interface under shear deformation, leading to the formation of the {111} < 11¯0 > shear texture. At the later stage of welding, the {110} < 11¯0 > texture, indicative of good weld quality, was identified for the first time. Schmid factor analysis indicated that under the combined compressive-shear stress state of ultrasonic welding and the interfacial heat, multiple slip systems were activated, leading to the rotation of {111} < 11¯0 > texture around the RD axis to form the {110} < 11¯0 > texture. Based on the unveiled mechanism, (111)-oriented Cu coatings were designed and prepared to eliminate the energy consumption associated with grain rotation during shear deformation. The (111)-oriented Cu coatings exhibited a 13.9% higher heating rate during ultrasonic welding and a 28.3% enhancement in joint strength at 600 J compared to randomly oriented Cu joints.