ZK60与MB8镁合金光纤激光焊接研究

发布时间：2019-05-17 19:09

【摘要】：ZK60镁合金具有较好的力学性能,但其价格较高,而MB8镁合金具有优异的耐腐蚀性能,采用MB8镁合金代替ZK60镁合金可提高接头抗腐蚀能力和降低成本。为此,本文对ZK60和MB8镁合金薄板分别进行同材质及异材质的光纤激光焊接工艺研究,分析工艺参数对焊接接头的宏观形貌、显微组织、力学性能、断裂位置、断口形貌的影响,并采用渗透检测方法检验接头表面缺陷。试验结果表明,同材质ZK60镁合金焊缝组织为细小等轴晶,主要由α-Mg基体和MgZn2相构成;同材质MB8镁合金焊缝组织为等轴晶和柱状树枝晶,主要由α-Mg基体和Mn相构成;ZK60与MB8异材质镁合金焊缝组织为等轴晶和柱状树枝晶,主要由α-Mg基体和MgZn2相构成。经渗透检测均未发现表面缺陷,焊接接头成型良好,当工艺参数不合适时,有少量气孔存在。对于同材质ZK60镁合金焊接接头,抗拉强度最高可达到母材的92.1%,熔合线附近显微硬度较低,断裂多发生在焊缝中心至熔合线附近区域内,断口呈现韧性断裂为主导的混合断裂形貌;对于同材质MB8镁合金焊接接头,抗拉强度最高可达到母材的83.1%,熔合线附近显微硬度较低,断裂多发生在焊缝中心附近,断口呈现准解理断裂形貌。对于ZK60与MB8异材质镁合金焊接接头,其抗拉强度均显著大于同材质MB8镁合金焊接接头,且在较宽的工艺参数范围内,接头抗拉强度大于MB8母材抗拉强度。MB8侧熔合线附近显微硬度较低,断裂均发生在焊缝中心至MB8母材区域内,断口呈现准解理断裂形貌。
[Abstract]:ZK60 magnesium alloy has good mechanical properties, but its price is high, while MB8 magnesium alloy has excellent corrosion resistance. Using MB8 magnesium alloy instead of ZK60 magnesium alloy can improve the corrosion resistance and reduce the cost of the joint. In this paper, the optical fiber laser welding process of ZK60 and MB8 magnesium alloy sheets with the same material and different material is studied, and the effects of process parameters on the macroscopic morphology, microstructure, mechanical properties, fracture position and fracture morphology of the welded joints are analyzed. The surface defects of the joint were examined by osmotic detection method. The experimental results show that the weld microstructure of the same material ZK60 magnesium alloy is fine equiaxed crystal, which is mainly composed of 伪-Mg matrix and MgZn2 phase, and the weld microstructure of the same material MB8 magnesium alloy is isometric crystal and columnar dendritic crystal, which is mainly composed of 伪-Mg matrix and Mn phase. The weld microstructure of ZK60 and MB8 magnesium alloy is equiaxed crystal and columnar dendrite, which is mainly composed of 伪-Mg matrix and MgZn2 phase. No surface defects were found by osmotic test, the welded joints were well formed, and a small number of pores existed when the process parameters were not timely. For the welded joints of ZK60 magnesium alloy of the same material, the highest tensile strength can reach 92.1% of that of the base metal, the microhardness near the fusion line is low, and most of the fractures occur in the area from the center of the weld to the near the fusion line. The fracture surface shows a mixed fracture morphology dominated by ductile fracture. For the welded joints of MB8 magnesium alloy of the same material, the highest tensile strength can reach 83.1% of that of the base metal, the microhardness near the fusion line is low, the fracture mostly occurs near the center of the weld, and the fracture surface shows quasi-cleavage fracture morphology. For the welded joint of ZK60 and MB8 magnesium alloy, the tensile strength of the welded joint is significantly higher than that of the same material MB8 magnesium alloy welded joint, and in a wide range of process parameters, The tensile strength of the joint is higher than that of the MB8 base metal. The microhardness near the fusion line of MB8 side is lower, the fracture occurs in the area from the center of the weld to the MB8 base metal, and the fracture surface shows quasi-cleavage fracture morphology.
【学位授予单位】：陕西理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG456.7

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