To address metallurgical defects, including porosity and residual tensile stress in laser-welded AZ31B magnesium alloy joints, this study employed ultrasonic impact treatment (UIT) using an orthogonal experimental design. Research has demonstrated that UIT generates continuous grooves at the base metal/weld metal interface while producing a smooth transition geometry at the weld toe. Concurrently, this treatment disrupts the original microstructure and crystalline arrangement of the welded surface. Plastic deformation via mechanical impacts induces grain fragmentation at the weld toe, resulting in a more homogeneous and refined grain structure. Consequently, hardness increased by 4.8% in the weld seam and 21.7% at the weld toe. This treatment induced localized compaction of the weld seam surface, significantly enhancing wear resistance and strengthening the fracture-prone weld toe region. Following parameter optimization, sample no. 6 exhibited 2.9% higher ultimate tensile strength and 12.9% greater fracture elongation. Critically, the process transformed residual tensile stresses within the joint into compressive residual stresses, establishing a measurable residual compressive stress layer at the surface.
Xu et al. (Mon,) studied this question.
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