工艺参数对7003铝合金/AZ31镁合金板搅拌摩擦焊搭接组织及性能影响

Effect of Process Parameters on Joint Organization and Properties of 7003 Aluminum Alloy/AZ31 Magnesium Alloy Friction Stir Lap Welding

针对7003铝合金和AZ31镁合金两种金属进行搅拌摩擦焊工艺试验,研究不同焊接速度、搅拌速度、轴肩下压量等焊接工艺参数对其搭接接头微观组织、力学性能性能、断口形貌的影响。结果表明,后退侧Hook尺寸明显大于前进侧Hook尺寸且更为曲折,搅拌区内主要由网格状的Al_(12)Mg_(17)组成,网格内部由镁基体和Al_(12)Mg_(17)共同组成,前进侧上空存在一个沿水平方向延伸的金属间化合物(intermetallic compounds,IMCs)薄层;焊缝表面随着转速的提升变得光滑,后退侧Hook尺寸明显增加;行进速度过大会导致冶金反应不充分,焊缝表面出现犁沟,搅拌区底部出现隧道;下压量增大会使接头机械互锁程度增加,当下压量、焊接速度或旋转速度增加时,有效承载面积增大,拉剪力随着搭接接头有效承载面积的增加有不同程度提升;拉剪力最大值(4.02 kN)出现在950-30-0.7参数下,断裂方式为解理脆性断裂;焊缝中心由于Al-Mg金属间化合物的生成,硬度最高为144.8HV0.05。

Friction stir welding process tests were conducted on 7003 aluminum alloy and AZ31 magnesium alloy to investigate the effects of welding process parameters such as different welding speeds,stirring speeds,and shoulder pressure on the microstructure,mechanical properties,and fracture morphology of the joints.The results show that the Hook size on the retreating side is significantly larger and more curved than that on the advancing side.The stirring zone is mainly composed of network Al_(12)Mg_(17),and the interior of the network is composed of both Mg matrix and Al_(12)Mg_(17).There is a thin layer of intermetallic compounds(IMCs)extending horizontally over the advancing side.The weld surface becomes smooth as the speed increases,and the Hook size on the backing side increases significantly.Excessive travel speed leads to inadequate metallurgical reaction,plow grooves on the weld surface and tunneling at the bottom of the stir zone.An increase in the amount of downward pressure increases the degree of mechanical interlocking of the joint.When the plunge depth increases,the welding speed or the rotation speed increases,loading area(LA)increases,the tensile shear force increases to different degrees with the increase of the LA,and the maximum tensile shear force appears in the parameter set of 950-30-0.7,which is 4.02 kN,and the fracture mode is a brittle fracture.The weld center has a hardness of up to 144.8HV0.05 due to the generation of Al-Mg intermetallic compounds.