Abstract In this work, laser welding of dual phase steel (DP 600) to aluminium alloy (AA 6061) was studied both experimentally and by computational modeling. Three different laser energy densities (640 J/mm2, 850 J/mm2 and 1250 J/mm2) were chosen to study the effect of heat input on microstructural changes and strength of the joint. It was inferred from the results that the laser energy density had a direct influence on the formation of intermetallic phases such as Fe2Al5 and FeAl3. At relatively high laser energy density (1250 J/mm2), thick intermetallic layer and crack propagations were observed at the interface of the weld, which deteriorated the strength of joint. Whereas, maintaining the laser energy density at 850 J/mm2 enhanced the weld quality by lowering the intermetallic thickness in the range of 6–10 μm and defects such as cracks were also lowest at the weld interface. The formation of the cracks in the interfacial region was largely influenced by the hard and brittle intermetallics, which was evident from the microhardness results. The microhardness value along the interface exhibited a maximum of 836 HV at 1250 J/mm2, which was much higher than the base metal hardness (AA 6061 – 65 HV, DP 600 - 255 HV). A two-dimensional computational model was used to predict the temperature histories at different laser energy densities during welding. The results of the computational model (penetration depth and material ablation) correlated well with the experimental results.

中文翻译：

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Yb：双相钢与铝合金的YAG激光焊接

摘要 在这项工作中，通过实验和计算模型研究了双相钢 (DP 600) 与铝合金 (AA 6061) 的激光焊接。选择了三种不同的激光能量密度（640 J/mm2、850 J/mm2 和 1250 J/mm2）来研究热输入对接头微观结构变化和强度的影响。从结果推断，激光能量密度对Fe2Al5和FeAl3等金属间相的形成有直接影响。在相对较高的激光能量密度（1250 J/mm2）下，焊缝界面处出现较厚的金属间化合物层和裂纹扩展，降低了接头强度。然而，将激光能量密度保持在 850 J/mm2 可以通过将金属间化合物厚度降低 6-10 μm 来提高焊接质量，并且焊接界面处的裂纹等缺陷也最低。界面区域裂纹的形成很大程度上受硬脆金属间化合物的影响，这从显微硬度结果中可以看出。沿界面的显微硬度值在 1250 J/mm2 时最大为 836 HV，远高于母材硬度（AA 6061 – 65 HV，DP 600 – 255 HV）。二维计算模型用于预测焊接过程中不同激光能量密度下的温度历程。计算模型的结果（穿透深度和材料烧蚀）与实验结果具有很好的相关性。界面区域裂纹的形成很大程度上受硬脆金属间化合物的影响，这从显微硬度结果中可以看出。沿界面的显微硬度值在 1250 J/mm2 时最大为 836 HV，远高于母材硬度（AA 6061 – 65 HV，DP 600 – 255 HV）。二维计算模型用于预测焊接过程中不同激光能量密度下的温度历程。计算模型的结果（穿透深度和材料烧蚀）与实验结果具有很好的相关性。界面区域裂纹的形成很大程度上受硬脆金属间化合物的影响，这从显微硬度结果中可以看出。沿界面的显微硬度值在 1250 J/mm2 时最大为 836 HV，远高于母材硬度（AA 6061 – 65 HV，DP 600 – 255 HV）。二维计算模型用于预测焊接过程中不同激光能量密度下的温度历程。计算模型的结果（穿透深度和材料烧蚀）与实验结果具有很好的相关性。这远高于母材硬度 (AA 6061 – 65 HV, DP 600 – 255 HV)。二维计算模型用于预测焊接过程中不同激光能量密度下的温度历程。计算模型的结果（穿透深度和材料烧蚀）与实验结果具有很好的相关性。这远高于母材硬度 (AA 6061 – 65 HV, DP 600 – 255 HV)。二维计算模型用于预测焊接过程中不同激光能量密度下的温度历程。计算模型的结果（穿透深度和材料烧蚀）与实验结果具有很好的相关性。