5083-H321铝合金板材搅拌摩擦焊缝焊核区组织特征

The microstructural characteristics of nugget zone in 5083-H321 aluminum alloy plates by friction stir welding

采用搅拌摩擦焊接法对5083-H321铝合金板材进行焊接,借助光学显微镜、扫描电镜、背散射电子衍射分析仪、显微硬度仪及取向显微成像分析技术,对焊核区及母材的组织与性能进行了对比性研究.结果表明:该合金板材的焊缝无宏观缺陷;搅拌摩擦焊使该合金板材中大量的小角度晶界转化为大角度晶界,母材和焊核区的晶粒尺寸分布范围分别为6～55μm和15～30μm,晶粒纵横比分布范围分别为2～8和1.5～3,焊核区组织呈现均匀化及等轴化的动态再结晶特征;焊缝表面硬度沿焊缝宽度方向分布不均匀,焊核区硬度略高,平均硬度接近母材硬度.

The 5083-H321 aluminum alloy plate was jointed by friction stir welding. The comparative studies on the microstructure and hardness of both nugget zone and base metal were investigated using optical microscopy, scanning electron microscopy, electron back scattered diffraction and orientation imaging microscopy, and mi- cro-hardness tester. The results showed that there were no macroscopic defects in the weld. A large number of low-angle grain boundaries were transformed into high-angle grain boundaries in the nugget zone by the technique of friction stir welding. The grain size of base metal and nugget zone was 6-55pm and 15-30gm, respective- ly, and the shape aspect ratio was 2-8 and 1.5-3, respectively. The grains in nugget zone showed homogeneous and equiaxed morphology with characteristic of dynamic recrystallization. The transverse hardness distribution of welded joint surface is not homogeneous. The hardness of nugget zone is slightly higher than others and the aver- age hardness is close to that of base metal.