Nd:YAG激光焊接对铝锂合金组织和织构的影响

Effects of Nd:YAG Laser Welding on Microstructure and Texture of Aluminum-lithium Alloys

采用Nd:YAG激光进行了5A90铝锂合金薄板的对焊实验,借助光学显微镜、扫描电镜及EDS能谱、背散射衍射技术测试了焊缝的显微组织、合金元素分布及焊缝中的微观织构,并与母材进行了比较。结果表明:Nd:YAG激光焊接使5A90铝锂合金的微观组织和微观织构发生了很大的变化。焊缝区呈现出大量的等轴枝晶组织,这是由于焊缝中存在较多的异质形核点和较高的成分过冷度。焊缝中织构呈随机分布的状态,激光焊接完全改变了母材面心立方金属的冷轧织构组织。

5A90 aluminum-lithium(A1-Li)alloy thin sheets,machined with a square butt weld prepa-ration,were welded by Nd:YAG laser.Microstructure and texture characterization in the laser welds were studied by means of optical microscope(OM),scanning electron microscope(SEM)coupled with energy dispersive X-ray spectroscopy(EDS),electron back scattered diffraction(EBSD),and compared with the unaffected base metal.The results show that the weld metal(WM)microstructure is displayed significant changes in solidification structure,and microtexture.The predominantly fine equiaxed dendritic microstructure in the WM zone is observed and rationalized on the basis of solidifi-cation mechanism and heterogeneous nucleation mechanism.The pole figures of 5A90 A1-Li sample exhibit a typical cold rolling textures structure of FCC metals,while the laser welds in 5A90 A1-Li alloys are shown to exhibit a randomly textured microstructure.