铝镁合金焊接接头组织与力学性能的不均一性研究

采用Al-Mg合金焊丝多层多道MIG焊焊接10 mm厚铝镁锰合金热轧板材,运用金相组织分析、扫描电镜分析(含能谱和电子背散射衍射)等分析手段对焊接接头的组织不均匀性和力学性能进行了研究。结果表明,由于焊接循环热、冷却速率以及Al_3Zr等热稳定相粒子的不同作用,焊接接头不同区域内组织与力学性能均呈现出一定的不均匀性。焊缝区为典型的铸态组织,热影响区为保留部分形变特征的再结晶组织,熔池边界由于Al_3Zr粒子非匀质形核核心的作用,形成强化效果不明显的细晶薄层,其显微硬度值分别小于焊缝区和热影响区,而两焊道交界面的晶粒沿散热方向外延生长,粗化明显,显微硬度值最低。

Research on Inhomogeneity of Microstructure and Mechanical Properties in Al-Mg Alloy Welded Joints

The multi-layer and multi-pass MIG welding with Al-Mg alloy welding wire has been used to weld 10 mm thick hot rolled aluminum magnesium manganese alloy plate, followed by a detailed study on the microstructure and mechanical properties of welded joints by means of metallography, scanning electron microscopy (including energy spectrum and electron backscatter diffraction). The results show that the microstructure and mechanical properties of the welded joints in different regions show certain inhomogeneity due to the different effects of welding thermal cycle, cooling rate and such heat stabilized phase particles as Al3Zr. The weld zone is a typical casting microstructure, and the heat-affected zone is a recrystallized structure which with some deformation characteristics. Due to the effect of the inhomogeneous nucleation of Al3Zr particles on the boundary of the molten pool, the fine grain thin layer with little strengthening effect is formed, with the microhardness value smaller than that of the weld zone as well as the heat affected zone. However, the grain at the interface of the two passes grows along the direction of heat dissipation, with an obvious coarsening and the lowest degree of microhardness.