【作者】 杨武雄；

【导师】 陈铠；

【作者基本信息】 北京工业大学 ， 材料加工工程， 2004， 硕士

【摘要】 摘 要高强铝合金在航空航天、汽车、轻型轨道交通等工业部门得到了广泛应用。由于高强铝合金很难用一般的熔焊方式来焊接，用来做结构件时通常用螺栓、铆钉来连接，但这些连接方法会增加结构重量和增加经济消耗。激光束具有很高的能量密度，所以用激光进行焊接不仅速度快，而且变形小，但是激光焊接铝合金同样会遇到一般熔焊方法焊接铝合金时出现的气孔、裂纹等缺陷。为了消除这些缺陷，在激光焊接过程中加入焊丝是一种非常实用的方法，国际上有关此方面的研究已很深入并开始走向工业应用。与焊丝相似，金属粉末同样可以作为填充材料，而且更具柔性化，但有关此方面的研究极少，本文的主要研究内容就是从机理和实验两方面研究采用填充粉末的方式对铝合金进行激光焊接。为达到送粉焊接的目的，我们在对现有喷粉头进行了深入地研究分析后，设计出了一种自汇聚同轴三层结构送粉头，它不仅可以将粉末汇聚到焊接要求的束径，同时能对焊缝进行有效地的保护。经实验证实，此送粉头完全能满足送粉焊接的要求。对填粉焊接过程进行的高速摄像和金相分析表明，焊接过程比未加粉稳定，金属蒸汽和等离子体被有效压缩，使用成分为 AlSi12 的填充粉末可以有效地消除热裂纹和气孔。利用优化的焊接工艺参数，我们在 YAG 激光器上成功地对 7075 为主的几种高强铝合金成功地进行了激光填粉焊接，焊缝整齐美观，无咬边、下陷、不连续等宏观缺陷。拉伸实验证实，7075 焊后的平均拉伸强度为 370Mpa,为母材的 80%左右。更多还原

【Abstract】 High strength aluminum alloys are used in a wide range of engineeringapplications, which include aerospace, automobile, light railway etc. Since thesealloys are not easy to weld, they must be joined by bolts and rivets when assembled asstructures. Such mechanical joints are disadvantageous for reduce weight andconstruction cost. Laser beam has very high power intensity, there is an increasinginterest in applying laser beam welding to aluminum alloys since it offers advantagessuch as high welding speeds and low distortion. However, porosity and hot crack areoften encountered in laser welding as well as in conventional processes. To minimizethis problem, filler wire are used in laser welding. Just like filler wire ,powder metalhave the same effect, otherwise, it is more flexible than wire in the weld. In this paper,we do some theoretical and experimental studying on aluminum powder welding. To meet the specialty of laser powder welding, we designed a three-plyself-bundling coaxial powder injecting head which can both feed the powder metaland provide shielding gas. Its function has been approved in experiments is good. High speed camera shoot show the moving of the welding pool is steady anduniform. By metallographic analyzing of the welded seam, the conclusion can bemade that it can well eliminate the hot crack and porosity when the weld adopt AlSi12powder alloy metal. Adopting optimized processing parameters we have welded 7075 aluminumsuccessfully by injecting powder filler metal to the welding pool with high powerYAG laser. Both sides of the welded seam is full filled and without defect such asundercut, excessive penetration, discontinuous etc on the surface of seam .the porosityis low and the hot crack is eliminated also. The tension experiment shows that thetensile strength of the 7075(T73)Al alloy can reach 370MPa.更多还原