根部未焊合对AZ31B镁合金搅拌摩擦焊接头性能的影响

针对厚4.3 mm的AZ31B镁合金短针设计搅拌摩擦焊接,研究工艺参数对根部未焊合率的影响,并通过接头组织与拉伸断口形貌分析,分析了根部未焊合对接头抗拉强度的影响。结果表明:焊接速度一定时,当搅拌头旋转速度超过临界值950 r/min时,随着转速的增加,接头根部未焊合率降低。当旋转速度一定时,焊接速度对接头未焊合率几乎无影响。所有拉伸试样均在根部未焊合界面处起裂并发生断裂,而焊合区断口呈现典型的韧脆混合断裂特征。此外,接头抗拉强度随着根部未焊合率的降低而升高,当旋转速度为1 180 r/min、焊接速度120 mm/min时,接头的抗拉强度达到最大值188 MPa,为母材强度的76.4%。

Effect of root flaw on the mechanical properties of friction stir welded AZ31B alloy joint

The AZ31B magnesium alloy sheet with the thickness of 4.3 mm was welded with friction stir welding(FSW).The effects of different welding parameters on the root flaw were researched.According to the analysis of the microstructure and fracture surface morphology,the effects of root flaw on the tensile properties with different welding parameters were investigated.With the welding speed held constant,when the rotational speed beyond the critical condition of 950 r/min,the tensile strength decreased with increasing rotational speed.When the rotational speed held constant,the tensile strength remained at almost the same level with increasing welding speed.The tensile test results showed that all the fractures were in the position of root flaw and the fracture surface exhibited both ductile and brittle fracture characteristics.Furthermore,a lower ratio of root flaw led to higher yield strength.When the rotation speed is designated as 1 180 r/min,the welding speed of 120 mm/min is optimal for the tensile strength.The tensile strength of the joint reaches 188 MPa,i.e.80% of that of the base material.