A numerical model of 1.5 mm 6061/5182 aluminum alloys thin sheets lap joints under laser sinusoidal oscillation (sine) welding and laser welding (SLW) weld was developed to simulate temperature distribution and melt flow. Unlike the common energy distribution of SLW, the sinusoidal oscillation of laser beam greatly homogenized the energy distribution and reduced the energy peak. The energy peaks were located at both sides of the sine weld, resulting in the tooth-shaped sectional formation. This paper illustrated the effect of the temperature gradient (G) and solidification rate (R) on the solidification microstructure by simulation. Results indicated that the center of the sine weld had a wider area with low G/R, promoting the formation of a wider equiaxed grain zone, and the columnar grains were slenderer because of greater GR. The porosity-free and non-penetration welds were obtained by the laser sinusoidal oscillation. The reasons were that the molten pool volume was enlarged, the volume proportion of keyhole was reduced and the turbulence in the molten pool was gentled, which was observed by the high-speed imaging and simulation results of melt flow. The tensile test of both welds showed a tensile fracture form along the fusion line, and the tensile strength of sine weld was significantly better than that of the SLW weld. This was because that the wider equiaxed grain area reduced the tendency of cracks and the finer grain size close to the fracture location. Defect-free and excellent welds are of great significance to the new energy vehicles industry.

1.5 mm 6061/5182 铝合金薄板搭接接头在激光正弦振荡（正弦）焊接和激光焊接（SLW）焊接下的数值模型被开发来模拟温度分布和熔体流动。与SLW常见的能量分布不同，激光束的正弦振荡极大地均匀了能量分布并降低了能量峰值。能量峰值位于正弦焊缝的两侧，形成齿形截面。本文通过模拟说明了温度梯度（G）和凝固速率（R）对凝固组织的影响。结果表明，正弦焊缝中心区域较宽，G/R较低，促进了较宽的等轴晶区的形成，柱状晶由于GR较大而更细长。通过激光正弦振荡获得无孔隙和非渗透焊缝。其原因是熔池体积增大，小孔体积比例减小，熔池中的湍流缓和，这是通过熔体流动的高速成像和模拟结果观察到的。两种焊缝的拉伸试验均呈沿熔合线的拉伸断裂形式，正弦焊缝的抗拉强度明显优于SLW焊缝。这是因为更宽的等轴晶粒区域降低了裂纹的趋势和靠近断裂位置的更细的晶粒尺寸。无缺陷、优良的焊缝对新能源汽车行业具有重要意义。其原因是熔池体积增大，小孔体积比例减小，熔池中的湍流缓和，这是通过熔体流动的高速成像和模拟结果观察到的。两种焊缝的拉伸试验均呈沿熔合线的拉伸断裂形式，正弦焊缝的抗拉强度明显优于SLW焊缝。这是因为更宽的等轴晶粒区域降低了裂纹的趋势和靠近断裂位置的更细的晶粒尺寸。无缺陷、优良的焊缝对新能源汽车行业具有重要意义。其原因是熔池体积增大，小孔体积比例减小，熔池中的湍流缓和，这是通过熔体流动的高速成像和模拟结果观察到的。两种焊缝的拉伸试验均呈沿熔合线的拉伸断裂形式，正弦焊缝的抗拉强度明显优于SLW焊缝。这是因为更宽的等轴晶粒区域降低了裂纹的趋势和靠近断裂位置的更细的晶粒尺寸。无缺陷、优良的焊缝对新能源汽车行业具有重要意义。两种焊缝的拉伸试验均呈沿熔合线的拉伸断裂形式，正弦焊缝的抗拉强度明显优于SLW焊缝。这是因为更宽的等轴晶粒区域降低了裂纹的趋势和靠近断裂位置的更细的晶粒尺寸。无缺陷、优良的焊缝对新能源汽车行业具有重要意义。两种焊缝的拉伸试验均呈沿熔合线的拉伸断裂形式，正弦焊缝的抗拉强度明显优于SLW焊缝。这是因为更宽的等轴晶粒区域降低了裂纹的趋势和靠近断裂位置的更细的晶粒尺寸。无缺陷、优良的焊缝对新能源汽车行业具有重要意义。