针对航空工业应用广泛的BT20钛合金, 主要研究其激光焊接头的损伤行为和机理。在对钛合金激光焊接头组织和性能不均匀性分析的基础上, 采用SEM原位观察的方法对激光焊接头的塑性损伤行为进行研究, 从细观上揭示焊接接头的损伤演化与断裂机理。试验发现：焊缝的损伤形式为微裂纹在切应力与正应力共同作用下沿滑移带萌生, 在裂纹前端滑移带相交处, 应力集中会引发新的微裂纹, 并随后与主裂纹相连, 从而导致裂纹的“Z”字型扩展。

The damage behavior and mechanism of BT20 titanium laser welding, which is commonly used in aviation industry, was studied by SEM in situ observation to reveal the welding's damage evolution and mechanism from the details, based on the analysis of uneven distribution of titanium welding's structure and properties. Results show that: the form of weld damage is microcrackes and generate at slip band under shear stress and normal stress. Stress concentrate at the intersection of crack front and slip bands, cause new microcracks and then connected to the main crack. This lead to the crack's "Z" shaped extension.