Properties and serviceability of laser welded joints depend on the defect, weld geometry, and microstructures, which in turns are affected by molten pool behaviors. In this work, beam oscillation was used to improve microstructures and mechanical properties of welded joints by changing molten pool behaviors. The 2 mm-thick β-21S titanium alloy plates were welded using three beam oscillating modes (non-oscillation, transverse oscillation, and vertical oscillation). The molten pool behaviors for three oscillation modes were observed using high-speed cameras, and the weld morphology, microstructures and mechanical properties of the corresponding joints were examined. The results showed that defect-free joint with sound weld appearances could be achieved using beam oscillation that affected molten pool behaviors. The higher probability of equiaxed grain formation and significant grain refinement were found in the joints made using beam oscillation. The average grain sizes of welded joints for non-oscillating, transverse and vertical oscillating modes are 236, 184 and 168 μm, respectively. The welded joint made using beam oscillation also showed a higher tensile strength of 900 MPa at ambient temperature and 534 MPa at 450 °C. Furthermore, the Portevin-Le Chatelier (PLC) effect was observed in the stress-strain curves of welded joint at 450 °C, which was attributed to the precipitation of brittle ω phase.

激光焊接接头的性能和适用性取决于缺陷、焊缝几何形状和微观结构，而这些又受熔池行为的影响。在这项工作中，梁振荡用于通过改变熔池行为来改善焊接接头的微观结构和机械性能。使用三种光束振荡模式（非振荡、横向振荡和垂直振荡）焊接 2 mm 厚的 β-21S 钛合金板。使用高速相机观察三种振荡模式下的熔池行为，并检查相应接头的焊缝形貌、显微组织和力学性能。结果表明，使用影响熔池行为的梁振荡可以实现具有良好焊缝外观的无缺陷接头。在使用梁振荡制成的接头中发现等轴晶粒形成和显着晶粒细化的可能性更高。非振荡、横向和垂直振荡模式的焊接接头的平均晶粒尺寸分别为 236、184 和 168 μm。使用横梁振荡制成的焊接接头在环境温度下也表现出 900 MPa 的更高拉伸强度，在 450 °C 下为 534 MPa。此外，在 450 °C 时焊接接头的应力-应变曲线中观察到 Portevin-Le Chatelier (PLC) 效应，这归因于脆性 ω 相的析出。使用横梁振荡制成的焊接接头还表现出更高的抗拉强度，在环境温度下为 900 MPa，在 450°C 下为 534 MPa。此外，在 450 °C 时焊接接头的应力-应变曲线中观察到 Portevin-Le Chatelier (PLC) 效应，这归因于脆性 ω 相的析出。使用横梁振荡制成的焊接接头还表现出更高的抗拉强度，在环境温度下为 900 MPa，在 450°C 下为 534 MPa。此外，在 450 °C 时焊接接头的应力-应变曲线中观察到 Portevin-Le Chatelier (PLC) 效应，这归因于脆性 ω 相的析出。