LZ91镁锂合金薄板焊接工艺及接头组织性能研究

Study on Welding Process and Microstructure and Properties of LZ91 Magnesium-lithium Alloy

为了研究焊接电流对LZ91镁锂合金焊接接头组织和性能的影响,采用三种不同焊接电流(60 A、70 A、80 A)的脉冲钨极氩弧焊对1 mm厚的LZ91镁锂合金薄板进行了焊接,并利用金相光学显微镜、扫描电子显微镜、XRD、显微硬度仪和拉伸试验对焊接接头的微观结构和力学性能进行了表征,利用电化学工作站测试焊缝的耐腐蚀能力。结果表明:三种焊接电流条件下,焊接接头熔合良好,均无明显裂纹、气孔等焊接缺陷;其中70 A、80 A焊接电流的焊缝区较热影响区具有更小的晶粒;硬度以焊缝区最高,热影响区次之,均高于母材;焊接接头的抗拉强度均高于母材,其中焊接电流70 A时拉伸性能最佳,抗拉强度达到最大值125.20 MPa,伸长率保持在母材的35%以上;经电化学测试,在70 A焊接电流条件下得到的焊缝耐腐蚀能力最强。

In order to study the effect of welding current on the microstructure and properties of LZ91 magnesium⁃lithium alloy welded joints,three different welding current(60 A,70 A,80 A)pulsed tungsten argon arc welding was used to weld 1 mm thick LZ91 magnesium⁃lithium alloy sheet.The microstructure and mechanical properties of the welded joints were characterized by metallographic optical microscope,scanning electron microscopy,XRD,microhardness tester and tensile test.The corrosion resistance of each weld is tested by electrochemistry station.The results show that under the three welding current conditions,the fusion is good,dendrites are generated,and there are no obvious cracks,pores and other welding defects.The 70 A and 80A weld zones have smaller grains than the heat affected zone.The hardness of weld zone is the highest,followed by heat affected zone,which is higher than that of base metal.The tensile strength of the welded joint is higher than that of the base metal,among which the welding current 70 A is the best tensile strength,the maximum tensile strength is 125.20 MPa,and the elongation is more than 35%of the base metal.The electrochemical test shows that the corrosion resistance of the weld under 70 A is optimal.