AZ31B镁合金DE-GMAW焊接头组织与力学性能研究

Microstructures and mechanical properties of DE-GMAW welded joints of AZ31B magnesium alloy

为研究DE-GMAW(双电极气体保护焊)焊接2 mm厚AZ31B镁合金板材时旁路电流对焊缝成型、焊缝显微组织和力学性能的影响,利用光学显微镜和X射线衍射分析技术(XRD)对接头的显微组织、相及相的成分进行分析,同时用维氏硬度试验计和万能试验机对焊接接头的显微硬度和抗拉强度分别进行测量。结果表明:焊缝区主要由α-Mg和β-Mg17Al12两种相组成;旁路电流为160 A时焊缝外观成型良好,没有焊接缺陷,焊缝质量高;随着旁路电流增加,熔宽基本保持不变,熔深逐渐减小,同时焊缝区晶粒尺寸逐渐减小;焊接接头显微硬度逐渐增大,接头抗拉强度呈先增大后减小的变化规律,在旁路电流为160 A时达到最大值。

The effects of bypass current on the weld forming, joint microstructures and mechanical properties of 2 mm thick AZ31B magnesium alloy plates welded by double-electrode gas metal arc welding （DE- GMAW） were investigated. The microstructures, phase and phase composition of the welded joints were investigated by optical microscope, X-ray Diffraction. The microhardness and ultimate tensile strength （UTS） were measured through microhardness tester and universal testing machine. The results show that the welded zone consists of α-Mg and β-Mg17Al12. When the bypass current is 160 A, a weld with good appearance, no defects and high quality can be obtained. With the increase of the bypass current, the weld penetrations decrease gradually, and the weld width basically remains unchanged. The grain size of the weld decreases gradually with the increase of the bypass current, and the microhardness of the weld seam increases gradually. The tensile strength of welded joints increases gradually at first, and then decreases with an increase of the bypass current, the tensile strength reaches the maximum when the bypass current is 160 A.