Microstructural Characteristics and Mechanical Properties of Ultrasonic-Assisted Electron Beam Welding Joints of Rare-Earth Magnesium Alloy

The Mg-10Gd-0.4Zr rare-earth magnesium alloy was joined by ultrasonic vibration-assisted electron beam welding for the first time. The microstructures, pore defects, element segregation and mechanical properties of the ultrasonic vibration-assisted electron beam welding Mg-10Gd-0.4Zr joints were studied. The microstructure of the weld zone of the electron beam welded joint was uniform and fine equiaxed grains, and the precipitated Mg₂Gd phase was distributed at the grain boundary. The pore defects were eliminated by ultrasonic cavitation and acoustic flow effects. The grain diameter of the fusion zone was further refined by 19.05% by the ultrasonic vibration. The precipitates of Mg₃Gd phases continuously distributed at grain boundaries were effectively inhibited, and the solid solution of Gd atoms was promoted by the action of ultrasonic vibration. The tensile strength of the ultrasonic-assisted electron beam welding joints was 255 MPa, 8.1% higher than that of the electron beam welding joints.