AZ31B镁合金水环境搅拌摩擦焊接研究

Research of Submerged Friction Stir Welded AZ31B Magnesium Alloy

摘要:

对比研究了AZ31B镁合金空气环境搅拌摩擦焊接 (Friction Stir Welding, FSW) 和水环境搅拌摩擦焊接(Submerged Friction Stir Welding, SFSW) 接头的微观组织与力学性能。结果表明：SFSW接头焊核区为细小等轴状再结晶晶粒。随着焊接速度的增大，焊核区晶粒尺寸增大，显微硬度值降低。FSW接头表层处的显微组织比中心处粗大，且分布不均匀；而SFSW接头表层处的显微组织比中心处明显细小。FSW接头的表层硬度值低于中心处的硬度；而SFSW接头的表层硬度值高于中心处的硬度。当旋转速度为950 r·min-1、焊接速度为75 mm·min-1时，SFSW接头的抗拉强度值达到最大，为母材强度的72 %，拉伸断口表现为解理断裂特征

Abstract:

AZ31B magnesium alloy was joined by friction stir welding (FSW) and submerged friction stir welding (SFSW), respectively, and the microstructure and mechanical properties of the joints were investigated. The experimental results show that the nugget zone in SFSW joint is characterized by fine and equiaxed recrystallized grains. Increasing of the travel speed will induce an increase in grain size and a decrease in microhardness in the nugget zone. The microstructure of the FSW joint on the surface is coarser and more inhomogeneous than that in the center, while the microstructure of the SFSW joint on the surface is obviously finer than that in the center. The microhardness of the FSW joint on the surface is lower than that in the center, while the SFSW joint has the opposite trend. When the rotation speed is 950 r·min-1 and the travel speed is 75 mm·min-1, the maximum ultimate tensile strength of the SFSW joint reaches 72% that of the base material. The fracture surface of the SFSW joints exhibits cleavage-like feature