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采用光纤激光器作为焊接热源的激光熔焊工艺对双相钢DP600和变形镁合金AZ31进行添加Sn箔的搭接焊研究。通过调整焊接参数获得最佳焊接成形,采用卧式金相显微镜、带有能谱仪(EDS)和电子背散射衍射(EBSD)探头的扫描电镜(SEM)和X射线衍射仪(XRD)等观察焊接接头的微观组织、相分布、晶粒大小、元素分布和相结构组成。结果表明,添加Sn箔激光熔焊是一种适用于Fe和Mg异种材料连接的有效方法,通过过渡区域形成新相可实现Mg/Fe有效连接。实验还发现,钢上、镁下搭接激光熔焊上层双相钢的热影响区未出现明显的软化组织,焊接熔池和钢/镁接头过渡区域未见大规模氧化物和气孔缺陷,钢侧过渡区域生成Fe Sn、Fe1.3Sn、Fe3Sn等Fe-Sn相,镁侧过渡区域生成柱状枝晶的Mg2Sn相,这些新相的存在可实现钢/镁异种金属的“双向”冶金结合。
Laser welding process using fiber laser as welding heat source The double lamellar steel DP600 and the deformed magnesium alloy AZ31 were subjected to the lap welding of Sn foil. The best welding shape was obtained by adjusting the welding parameters. The samples were observed by means of horizontal metallographic microscope, scanning electron microscope (SEM) and X-ray diffraction (XRD) with EDS and EBSD probes Welding joint microstructure, phase distribution, grain size, elemental distribution and phase structure. The results show that the addition of Sn foil laser welding is an effective method for joining dissimilar Fe and Mg dissimilar materials. The formation of a new phase through the transitional region can achieve the effective connection of Mg / Fe. The experiment also found that there is no obvious softening microstructure in the heat-affected zone of the upper duplex steel under laser welding of magnesium, but there is no large-scale oxide and porosity defects in the transition zone between the welding pool and the steel / magnesium joint. The side transitional regions produce Fe-Sn phases such as Fe Sn, Fe1.3Sn, Fe3Sn and Mg2Sn phases with columnar dendrites in the transitional region of Mg. The presence of these new phases allows the “bidirectional” metallurgical bonding of dissimilar steels .