基于铝合金激光深熔焊接小孔内等离子体直接光谱观测的小孔效应研究

项目名称： 基于铝合金激光深熔焊接小孔内等离子体直接光谱观测的小孔效应研究

项目编号： No.50875079

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 冶金工业

项目作者： 金湘中

作者单位： 湖南大学

项目金额： 34万元

中文摘要： 铝合金具有十分优良的物理和机械力学性能，且重量轻，广泛地应用于各行各业，特别是交通运输行业。但是，采用常规焊接方法焊接铝合金时，容易产生气孔、焊接裂纹以及因铝合金中低温合金元素在焊接过程中的烧蚀而导致焊接接头强度降低、焊接变形大等问题，制约了其在工业中的应用的推广。本项目针对铝合金焊接中存在的问题，采用特殊设计的实验装置和双层复合工件（一半为铝合金，另一半为透明的GG17玻璃），通过高速摄影的方法，实现了透过透明GG17玻璃从侧面直接观测激光深熔焊接铝合金时的小孔；基于实验观测的三维弯曲小孔形状，建立了小孔孔壁多次反射吸收、孔内等离子体反韧致吸收数学模型，计算得到了小孔孔壁通过Fresnel吸收和反韧致辐射吸收的激光功率密度分布；采用光谱仪，直接观测了小孔内等离子体的辐射光谱；采用光谱分析方法，计算了孔内等离子体的电子密度和电子温度分布；分析了激光深熔焊接铝合金时合金元素烧损与孔内等离子体辐射光谱的关系，研究了低温合金元素烧损对焊缝机械性能的影响；建立了基于实测小孔形状的激光深熔焊接铝合金和玻璃的传热传质数学模型，计算了激光深熔焊接铝合金的温度场与流场。

中文关键词： 铝合金；激光焊接；小孔效应；光谱分析；等离子体

英文摘要： Because of their excellent physical, mechanical properties and light weight, aluminum alloys have been widely used in many industrial fields, especially in transportation industry. However, such defects as porosity, cracks, distortion and reduction of strength are commonly encountered during welding aluminum alloys with traditional welding processes,which will prevent aluminum alloys from more applications. In order to solve the above problems, a novel experimental setup is designed and a compex double-layer sample is adopted. Then, with this setup,a clear keyhole is directly observed by a high-speed camera from the transparent GG17 glass during deep penetration laser welding of aluminum alloys. Based on the experimentally-obtained keyhole, a keyhole model combined Fresnel absorption caused by multiple reflections on the keyhole walls with inverse bremsstrahlung absorption of keyhole plasma are established, and the laser intensities absorbed on the keyhole walls through the above two absorption mechanisms are calculated. Using a spectrograph, spectra emitted from the keyhole plasma during laser welding of aluminum alloys are successfully detected directly. On the basis of so-obtained emission spectra, the electron density and the electron temperature of keyhole plasma are calculated by means of relative spectral density method. The effect of the buring loss of alloying elements with low melting point on the mechanical properties of the welds are studied. Finally, a heat and mass transfer model based on an actual keyhole is constructed, and the temperature field and flow field during deep penetration laser welding of aluminum alloy and GG17 glass are determined.

英文关键词： Aluminum Alloy; Laser Welding; Keyhole Effects; Spectral Analyzing; Keyhole Plasma