2A97-T3铝锂合金激光焊接接头微观组织与织构的EBSD研究

Investigation on Microstructure and Microtexture of Laser-Welded 2A97-T3 Al-Li Alloys by EBSD

从2A97-T3铝锂合金激光焊接头的上水平面、横截面、纵截面和下水平面进行取样,对接头的微观组织和织构进行了分析。利用电子背散射衍射(EBSD)技术的多种表征方法,如OIM、PF、IPF、取向角分布、ODF、晶粒形貌图,并结合激光焊过程的数值模拟,研究了激光焊作用下接头微观组织的演变机理。结果表明,由于薄板冷轧工艺和激光焊加工的非平衡特性,导致接头不同截面的晶粒形态、取向和微观织构存在明显差异。这种组织的不均匀性是接头性能各向异性的根本来源。因此,有必要对接头的不同截面进行分析,进而对微观组织和织构获得全面性和空间性的认识。激光诱导下,热影响区发生了动态再结晶和亚结构晶粒的形成和长大,焊缝区则产生了微观组织的重熔现象,该过程会导致母材原有织构特征在热影响区减弱、在焊缝区消失。

The laser-welded 2A97-T3 aluminum-lithium(Al-Li) alloy joints were sampled from upper horizontal surface, transverse section, longitudinal section, and lower horizontal surface to develop the comprehensive and spatial understandings for microstructure and microtexture evolution. Various characterization methods in terms of electron backscattered diffraction such as orientation imaging microscopy, pole figure, inverse pole figure, misorientation angles distribution, orientation distribution function, and numerical simulation were used. The results show obvious differences in the grain morphology, orientation, and microtexture in different areas of the joint, due to the nonequilibrium characteristic of cold rolling and laser beam welding. The laser beam can induce the formation and growth of dynamic recrystallization and sub-structure grains in the heat affected zone. Moreover, the original microtexture characteristics of the base metal is weakened and thus eliminated in both the heat affected zone and the weld zone.