1060铝/AZ31镁合金异种金属搅拌摩擦搭接焊组织与力学性能研究

Microstructure and Mechanical Properties of 1060 Al/AZ31 Mg Alloy Dissimilar Metal Friction Stir Lap Welding

采用搅拌摩擦搭接焊对1060铝和AZ31镁合金异种金属进行焊接试验,利用三维表面形貌仪、光学显微镜研究了接头组织形貌,采用显微硬度仪、电子万能试验机和扫描电子显微镜研究了接头力学性能和断口形貌。结果表明:焊接参数对焊缝表面形貌影响显著,在1500 r/min,50 mm/min时,焊缝表面形成均匀弧纹。在1000 r/min,70mm/min时焊核区及焊缝界面处晶粒经动态再结晶后细化,随转速/焊速比增加,焊核区金属间化合物含量增加。显微硬度结果表明镁合金侧、铝侧和界面处接头显微硬度有相同的变化趋势,焊核区硬度明显高于铝镁母材区域。断口形貌观察结果表明,1060铝/AZ31镁合金异种金属搅拌摩擦搭接焊断裂模式为脆性断裂,接头拉剪性能在2000 r/min,30mm/min时最差,仅为1750N,这可能与焊缝内金属间化合物的增加有关。

The dissimilar metals of 1060 Al and AZ31 magnesium alloy were welded by friction stir lap welding.The microstructure of the joints was studied by three-dimensional surface topography instrument and optical microscope.The mechanical properties and fracture morphology of the joints were studied by microhardness tester,electronic universal testing machine and scanning electron microscope.The results show that the welding parameters have a significant effect on the weld surface morphology,and uniform arc lines are formed on the weld surface under 1500 r/min and 50 mm/min.Under 1000 r/min and 70 mm/min,the grains in the nugget zone and the weld interface are refined after dynamic recrystallization.With the increase of rotational speed/welding speed ratio,the content of intermetallic compounds in the nugget zone increases.The microhardness results show that the microhardness in nugget zone of the joints at the magnesium alloy side,aluminum side and interface has the same trend,and the hardness of the weld nugget zone is obviously higher than that of the aluminum,magnesium base metal area.The fracture morphology results show that the fracture mode of 1060 Al/AZ31 Mg alloy dissimilar metal friction stir lap welding is brittle fracture,and the tensile shear strength of the joint is the smallest of 1750 N at2000 r/min and 30 mm/min,it may be related to the increase of intermetallic compounds in the weld.