Effect of ultrasonic spinning with welding on the microstructure and mechanical properties of 7075 aluminum alloy welded joints

The ultrasonic spinning with welding method is a novel approach combining mechanical force field and ultrasonic energy field to control welding deformation of thin-walled components during welding. Its core lies in applying ultrasonic spinning within the specific plastic recovery temperature range behind the molten pool during the welding process, which generates high-frequency ultrasonic vibration in the workpiece while inducing plastic deformation of high-temperature metal through high-speed rotation of the concentrator. Through the combined action of ultrasonic vibration and rotational compression, this method extends the shrinkage deformation of solidified metal, refines grain size, achieving control of welding deformation, improvement of welded joint microstructure, and enhancement of mechanical properties. An ultrasonic spinning with welding platform was designed and constructed, and relevant welding experiments were conducted on 7075 aluminum alloy. The relationship between deformation control effectiveness and torch-concentrator distance was obtained, while microstructural and mechanical property analyses were performed on the welded joints. Electron back scatter diffraction (EBSD) results demonstrate that the weld zone of 7075 aluminum alloy processed by this method exhibits significant grain refinement, with average grain size decreasing from 60 μm to 46.8 μm, accompanied by reduced columnar crystal quantity and increased equiaxed crystal quantity. The welded joints obtained through this method show improved hardness and tensile strength, with average weld zone hardness increasing from 109.7 HV to 128 HV, and tensile strength rising from 294.71 MPa to 324.64 MPa.