Laser beam welding of aluminum alloys is expected to offer both the technical and economical advantages. In most cases welding wire addition is necessary from the viewpoints to suppress hot cracks, improve mechanical properties of the weld as well as to reduce demands on the edge preparation, fit-up tolerance, and beam alignment. In practice, the filler wire could be added to the weld pool either in the leading or trailing direction. In this experimental work reported, the influence of the wire addition direction on the weld efficiency and process stability was investigated by using a 5kW CO2 laser to weld aluminum alloy 6009 with a plate thickness of 3mm. Beam-on-plate welds were made either in the autogeneous mode or with filler wire AlSi12. Illuminated by a double frequency Nd: YAG laser, the weld pool dynamics and the wire melting process were observed applying a high speed camera. The experimental results demonstrate that welding with filler wire in the trailing direction is more efficient and stable than in the leading direction. The high speed camera photographs show that the filler wire is mainly melted through the weld pool heating and the plasma heating in the former case and through the direct laser irradiation and the plasma heating in the later case. The weld pool is of vibration when welding in the autogeneous mode or with filler wire in the leading direction. However, the weld pool is much calmer when the wire is added in the trailing direction to the weld pool.

介绍了一种利用电流的磁流体动力学效应强化铝合金CO2激光焊接的方法及初步试验结果。在激光焊接过程中，通过一个布置于熔池前方的附加电极向熔池提供电流，该电流在熔池中产生磁场和电磁力，致使熔池运动状态及相应的热交换条件发生改变，从而提高激光能量的有效利用率和加工效率、控制焊缝成型。利用该方法，焊缝深度最高增加约32%，面积增加约20%，而焊缝宽度减小约28%

A hybrid Nd:YAG laser beam welding technique has been investigated in welding of aluminum alloy. Connecting the filler wire with one pole of a DC power supply and the workpiece with the other, a closed electric circuit is built. By this means, the wire is resistively preheated, so that less energy from the laser beam is dissipated in melting the filler metal. On the other hand, the current flowing in the weld pool generates a magnetic field and electromagnetic forces which affect the fluid flow of the weld pool and then the welding process. It is found that the weld depth increases and the weld seam becomes slender when a certain current is supplied. To clarify which effect, the thermal effect or the electromagnetic effect, dominates, welding with pure hot wire was carried out. The experimental results demonstrate that the pure hot wire addition has no obvious affect on the welding efficiency and the weld cross section, but worsens the process instability. Thus we can conclude that the influences of the current do not result from the resistive heat from the wire, but the electromagnetic effects. This new approach provides a possibility to increase the processing efficiency and flexibility, improve the process stability and weld quality, and also shape the seam cross section.

激光器的光束质量、功率、光的波长以及偏振状态是影响激光加工的几个主要参数。本文论述了材料加工对激光光束质量的要求以及光束质量的评定标准，分析了光束质量、直径与波长对光的传输、聚焦与加工性能的影响，归纳了不同功率密度时激光能量的吸收机制以及波长的影响，讨论了激光的偏振及其应用。

报道通过积分镜将激光光束聚焦成宽光带、配合同轴保护矩形送粉喷头实现大功率激光宽带熔覆的装置及其工艺试验结果，激光功率为14kW时，单道熔覆层宽度达45mm，厚度达3mm，熔覆层表面平整，厚度均匀。

提出用试验设计与人工神经网络相结合的方法，建立了一个激光切割工艺参数的选择优化的智能系统。通过试验设计的方法，只需做少数几次切割试验，将试验结果输入人工神经网络中进行训练和学习，系统便可经过自学得到切割结果与切割参数之间的隐含的定量关系，获得切割知识。在实际切割时，系统根据学到的切割知识，可以对任何给定的切割条件进行推理，对切割参数进行结果预测和优化。这种方法既不需要做大量的工艺试验，也不是单纯的专家经验，而是结合了两者的优点，使结果预测建立在既有试验数据又有专家知识的基础上，因而更加可靠、准确。该系统在激光方位切割的具体应用表明，系统能够准确给出定量的加工参数。

采用20kWCO2激光加工系统焊接低碳钢，研究了辅助气体对等离子体屏蔽临界功率密度的影响。研究结果表明，辅助气体不同时等离子体屏蔽临界功率密度由小到大的排列顺序为：Ar→N2→CO2→He。Ar作为辅助气体时，等离子体屏蔽的临界功率密度可以低至1.85×106W/cm2。辅助气体对等离子体屏蔽临界功率密度的影响主要取决于气体的热性和解离能，相比而言，气体电离能的影响是次要的。采用Ar作为辅助气体时，等离子体屏蔽临界功率密度低的原因主要在于Ar的导热性能差，激光支持的燃烧波（Laser-supported Combustion Waves—LSC）波容易过热和扩展。

本文结合作者多年的研究工作，论述了高强铝合金激光焊接的特点和难点，介绍了采用填充焊丝和填充粉末的高强铝合金的激光焊接技术，对比了勉和YAG激光焊接高强铝合金的工艺，讨论了双光束激光焊接和“激光+电弧”的复合焊接工艺，最后介绍作者发明的采用辅助电流的高强铝合金激光焊接技术。

采用20kWCO2激光器，设计了一组试验方法，研究光致等离子体对焊接深度和聚焦光束的影响，探讨高功率CO2激光焊接时光致等离子体的屏蔽机制。研究表明，光致等离子体显著改变了聚焦光束的形态，使其焦点下移、光斑扩大，等离子体的这种透镜效应随着等离子体的上升而增强。相对于等离子体吸收，等离子体的透镜效应是等离子体屏蔽的主要机制。