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首页> 外文期刊>Journal of Manufacturing Processes >Laser beam oscillation welding of aluminum alloy using the spatially modulated beam by diffractive optical element (DOE)
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Laser beam oscillation welding of aluminum alloy using the spatially modulated beam by diffractive optical element (DOE)

机译：衍射光学元件（DOE）使用空间调制光束的铝合金激光束振荡焊接

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摘要

In laser welding, the spatial beam intensity profile of the laser beam is an important parameter as it has a considerable effect on the temperature distribution and cooling rate of the melt pool, which determine the weld properties. In this study, a laser beam with a spatially modulated intensity profile by a diffractive optical element (DOE) was applied to the laser beam oscillation welding of an aluminum alloy (AA5052), and the weld characteristics of modulated beam welding (MBW) were analyzed in relation to those of Gaussian beam welding (GBW). According to the result of experiment verifying full penetration condition, the MBW generally required a slower maximum beam speed for full penetration than the GBW due to laser energy spreading by the core and ring beam constitution. On the other hand, this dispersed laser energy of the modulated beam was more effective in formation of a stable melt pool, which in turn reduced weld defects (bumpy bead surface, pores, and cracks) compared with the GBW. It also played a role in improving the asymmetric morphology of the weld by generating a relatively even temperature distribution of the melt pool. From an electron back scatter diffraction (EBSD) analysis, it was found that columnar grains were mostly distributed at the edge area of the weld, and equiaxed grains were largely distributed at the center area of the weld. The asymmetric feature in the microstructure was also found because of the asymmetric beam oscillation pattern and the resultant cooling rate difference. It was found that the area solidified at the lower cooling rate exhibited relatively large columnar grains. For the MBW, the asymmetric feature in the proportion of the low and high angle grain boundaries within the weld zone was diminished, which resulted from the relatively uniform temperature distribution by the dispersed laser energy. Due to the slow cooling rate, the MBW sample could have larger grains than GBW; this, however, slightly reduced the tensile strength of the joint welded by the modulated beam. The highest tensile strength obtained from the GBW and the MBW sample was equivalent to 88 % and 83.4 % of the base material's tensile strength, respectively. It was found that the hardness value and its distribution across the weld zone was similar for the GBW and MBW samples. It was also found that the weld zone has a lower hardness value than base material owing to the increase of grain size through recrystallization.
机译：在激光焊接中，激光束的空间束强度曲线是重要参数，因为它对熔池的温度分布和冷却速率具有相当大的影响，该熔池池确定焊接性能。在该研究中，通过衍射光学元件（DOE）具有空间调制强度分布的激光束对铝合金（AA5052）的激光束振荡焊接，分析了调制光束焊接（MBW）的焊接特性关于高斯光束焊接（GBW）的关系。根据实验验证完全穿透条件的结果，MBW通常需要比核心和环形结构的激光能量扩展，最大的最大光束速度比GBW完全渗透。另一方面，该调制光束的分散激光能量在形成稳定的熔融池中更有效，而与GBW相比，该熔融池形成又减少焊接缺陷（凹凸珠表面，孔隙表面，孔隙和裂缝）。通过产生熔体池的相对甚至温度分布，它还在提高焊缝的不对称形态方面发挥作用。从电子背面散射衍射（EBSD）分析中，发现柱状晶粒主要分布在焊缝的边缘区域，并且等轴晶粒在很大程度上分布在焊缝的中心区域。由于不对称的光束振荡模式和所得的冷却速率差，也发现了微结构中的非对称特征。发现在较低冷却速率固化的面积表现出相对大的柱状晶粒。对于MBW，焊接区内的低角度晶界比例的非对称特征减少，这是由分散激光能量的相对均匀的温度分布导致。由于冷却速度缓慢，MBW样品可以具有比GBW更大的谷物;然而，这略微降低了由调制光束焊接的接头的拉伸强度。从GBW和MBW样品获得的最高拉伸强度分别相当于基材的拉伸强度的88％和83.4％。发现硬度值及其对焊接区的分布类似于GBW和MBW样品。还发现，由于通过再结晶的晶粒尺寸的增加，焊接区具有比基材更低的硬度值。

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