The AA7075 aluminum alloy with Ti6Al4V titanium alloy in lap configuration was successfully joined with laser fusion brazing method without filler wire. The effects of laser fusion brazing parameters, including defocus distance and laser power, on the joint appearance, interfacial microstructure and mechanical properties of the joints were explored. The results indicated that a good joint appearance could be obtained with variation of defocus distances. The adjustable range of laser power was expanded with the increase of defocus distance, from the range of 1600-1800 W with the laser spot diameter of 1.0 mm (defocus distance of +10 mm) to 2600 W–3400 W with the laser spot diameter of 2.7 mm (defocus distance of +20 mm). It was observed that the wettability of molten aluminum alloy on titanium alloy was improved with the increase of laser power, the wetting length was increased from 1.76 mm to 3.62 mm and the contact angle was decreased from 32.8° to 21.6° upon increasing the total laser power from 2400 W to 3000 W with the defocus distance of +15 mm. There was a continuous 0.7 ± 0.2 μm thick TiAl₃ IMC (intermetallic compound) layer at the brazing interface with the defocus distance of +15 mm and laser power of 3000 W. The tensile strength and fracture location of the joints were mainly dependent on the spreadability and IMC thickness along the interface. Poor spreadability and too thick IMC thickness at the inner part of interface will result in fracture along the Al/Ti interface and lower strength. The best mechanical properties of the joints with the fracture load of 3621 N on average could be obtained with the defocus distance of +20 mm and laser power of 3400 W.

AA7075 铝合金与 Ti6Al4V 钛合金搭接配置，通过无填充焊丝的激光熔融钎焊方法成功连接。探讨了激光融合钎焊参数，包括离焦距离和激光功率，对接头外观、界面微观结构和机械性能的影响。结果表明，随着散焦距离的变化，可以获得良好的接头外观。激光功率的可调范围随着离焦距离的增加而扩大，从1600-1800 W的激光光斑直径1.0 mm（离焦距离+10 mm）范围扩大到2600 W-3400 W的激光光斑直径2.7 毫米（散焦距离 +20 毫米）。观察到随着激光功率的增加，熔融铝合金对钛合金的润湿性提高，随着总激光功率从 2400 W 增加到 3000 W，离焦距离为 +15 mm，润湿长度从 1.76 mm 增加到 3.62 mm，接触角从 32.8° 减少到 21.6°。有一个连续的 0.7 ± 0.2 μm 厚的 TiAl₃ IMC（金属间化合物）层在钎焊界面，离焦距离为+15 mm，激光功率为3000 W。接头的拉伸强度和断裂位置主要取决于沿界面的铺展性和IMC厚度。界面内部铺展性差，IMC厚度过厚，会导致沿Al/Ti界面断裂，强度降低。当离焦距离为+20 mm、激光功率为3400 W时，平均断裂载荷为3621 N的接头力学性能最佳。