Abstract Al/steel butt joints were successfully obtained using a dual–spot laser welding–brazing process with different R (R = EFe:EAl = 4:6, 5:5, and 6:4; EFe and EAl represented the energy ratios of the laser near steel and Al, respectively). The molten filler metals wet and spread well along the front and back surfaces of the steel when R was 5:5 and 6:4, whereas an undercut occurred when R was 4:6. The interfacial intermetallic compound (IMC) along the brazing interface consisted of only thin–layered τ5–Fe1.8Al7.2Si when R was 5:5 and 4:6. The IMC had a greater thickness when R was 5:5 owing to its higher peak temperatures than when R was 4:6. A mixed IMC (θ–Fe(Al,Si)3+τ5–Fe1.8Al7.2Si) was newly formed in the top region of the brazing interface when R was 6:4. TEM observations revealed that two types of grains existed in θ–Fe(Al,Si)3: normal and twinned. Numerical simulations for the thermal cycles along the brazing interface indicated that the IMC thickness was determined by the interfacial peak temperature, while the IMC homogeneity was determined by the temperature gradient. The results of an experiment involving the tensile properties indicated that the highest average joint strength (193 MPa) and largest average fracture displacement (0.64 mm) when R was 5:5, owing to its satisfactory weld formation and reasonable IMC distribution.

中文翻译：

---

能量比对双光点激光钎焊铝/钢对接接头的影响

摘要 采用不同 R（R = EFe:EAl = 4:6、5:5 和 6:4；EFe 和 EAl 代表能量比）的双点激光焊接 - 钎焊工艺成功获得了铝/钢对接接头。激光分别靠近钢和铝）。当 R 为 5:5 和 6:4 时，熔化的填充金属沿着钢的前表面和后表面很好地润湿和铺展，而当 R 为 4:6 时发生咬边。当 R 为 5:5 和 4:6 时，沿钎焊界面的界面金属间化合物 (IMC) 仅由薄层 τ5–Fe1.8Al7.2Si 组成。当 R 为 5:5 时，IMC 具有更大的厚度，因为其峰值温度高于 R 为 4:6 时的峰值温度。当 R 为 6:4 时，在钎焊界面的顶部区域新形成了混合 IMC (θ–Fe(Al,Si)3+τ5–Fe1.8Al7.2Si)。TEM 观察显示 θ–Fe(Al,Si)3 中存在两种类型的晶粒：正常和孪生。沿钎焊界面热循环的数值模拟表明，IMC 厚度由界面峰值温度决定，而 IMC 均匀性由温度梯度决定。拉伸性能实验结果表明，当 R 为 5:5 时，由于其焊缝成形良好，IMC 分布合理，平均接头强度最高（193 MPa）和最大平均断裂位移（0.64 mm）。