文档介绍：基于铝合金的激光深熔焊接研究 II 摘要铝合金具有重量轻、耐腐蚀性、导电性及导热性好和在低温下能保持良好的力学性能等优点, 因此铝合金在汽车工业与航空航天工业等领域应用越来越广泛。由于铝合金的导热系数很大和其它一些物理性质,使得铝合金的焊接性能很差, 用传统的焊接方法( 比如 TIG 焊与 MIG 焊) 焊铝一般都比较困难并且存在很多焊接缺陷,如在焊后容易出现裂纹和气孔,同时焊接过程还会造成低熔点合金元素( 如镁、锌)的烧损,这些焊接缺陷严重阻碍了铝合金进一步的应用。激光焊接铝合金正是解决上述问题的有效方法之一。小孔效应是激光深熔焊接的基础,而在研究小孔效应在焊接中的作用之前, 必须先得到小孔的形状和尺寸。可是在激光焊接金属材料时小孔位于工件的内部, 这使得小孔的形状很难直接观测到。在本文中设计一个在激光焊接铝和 GG17 玻璃时, 透过 GG17 玻璃用高速相机拍摄到小孔相片的特殊实验装置,并从这些拍摄到的相片中得到了小孔的形状和尺寸,这为后续的研究奠定了基础。本文还通过试验研究表明激光功率和焊接速度对小孔的形状和尺寸都有很大的影响。根据前面试验得到的小孔尺寸,本文建立了一个激光焊接异种材料热传导方程的数学模型,并通过有限差分法和编制 Matlab 程序对数学模型进行求解。通过数值模拟,得出激光功率和焊接速度对温度场的影响很大,并且由于铝合金与玻璃的物性参数相差太大,温度场在两块材料中的分布极不对称。相同的问题出现在激光焊接金属时“匙孔”内的等离子体和熔池内各种元素烧损的光谱很难被观测到。为了研究低熔点合金元素( 如镁、锌) 烧损对焊接机械性能的影响,本文通过相同的试验装置,首次透过玻璃来直接观测到了小孔的辐射光谱。光谱分析的结果表明,高的激光功率和低的焊接速度将会加剧低温合金元素镁、锌的烧损。这些试验结论将对激光焊接铝合金时选择合适的工艺参数来减少低温合金元素镁、锌的烧损有一定的实际指导作用。关键词:小孔; 铝合金; 激光焊接; 光谱分析基于铝合金的激光深熔焊接研究 III Abstract Aluminum alloys have such advantages as light weight, s uper inoxidizability, excellent electrical and thermal conductivity, and good mechanical properties under the low-temperature conditions . Hence, aluminum alloys ha ve been widely used in automobile industry and aerosp ace industry. However, The weldabilities of aluminum alloys are quite poor because of their high thermal conductivity and some other physical properties, such welddefects as por osities and burning loss of some volatile elements (. Mg and Zn) are apt to be pr oduced in the welds in traditional welding processes (. TIG and MIG), wh ich prevent aluminum alloys from wide application. Laser welding is one of the effective methods to solve the above problems. Keyhole effect is the base of deep pene tration laser beam welding. In order to study the keyhole effect during laser welding, the shape of the keyhole must be known first. However, because the keyhole is located inside the workpiece, it is difficult to observe directly in laser welding of metals. In this paper, the keyhole is experimentally observed by using a specially