AZ31镁合金板材自动氩弧焊接工艺研究

利用六轴焊接机器人夹持氩弧焊枪进行AZ31镁合金自动氩弧焊接工艺研究，焊后利用金相显微镜、扫描电子显微镜、X射线衍射仪和万能试验机等对焊接接头进行微观组织表征及力学性能测试。结果表明，在焊接电流160 A、焊接速度0.45 m/min、填丝速度0.6 m/min、钨极针与板材距离0.5 mm（前半段）和2.0 mm（后半段）以及保护气体流量16 L/min（正面）和21 L/min（背面）的条件下，能得到外观形貌良好、质量可靠的AZ31镁合金焊接接头。焊接接头的金相组织显示，焊缝区微观组织可清晰地分为母材区，热影响区和熔化区。焊接过程在热影响区和熔化区出现了大量的沉淀相，X射线衍射结果表明，该沉淀相为β Mg17Al12沉淀相。拉伸结果显示，焊接接头的抗拉强度达到了母材的81.02%，在断口观察到了大量的解离面和韧窝的存在，呈现出脆性断裂与韧性断裂相结合的混合断裂特征。

Study on automatic arc welding procedure of AZ31 magnesium alloy plates

The six-axis robot was employed to weld AZ31 magnesium alloy plates. The automatic arc welding parameters of the AZ31 magnesium alloy plates were investigated in detail. After welding, microstructure, precipitates, and tensile properties of AZ31 joint were studied by using the optical microscope, scanning electron microscopy, X-ray diffraction and universal testing machine. A sound joint was obtained under the welding parameters: welding current 160 A, welding speed 0.45 m/min, wire speed 0.6 m/min, distance between tungsten and plate (first half 0.5 mm, later half 2.0 mm), front face shielding gas 16 L/min, and back face shielding gas 21 L/min. The microstructure of AZ31 auto-welded joints consisted of base metal (BM), heat affected zone (HAZ), and fusion zone (FZ). A large amount of the hard β-Mg17Al12 phases were formed in FZ and HAZ. The ultimate tensile strength of the AZ31 joint was up to 80.02% of the BM. The fracture surface of the tensile specimen exhibited obvious ductile brittle mixed facture, which were characterized by some dimples and cleavage surfaces.