镁/钢异种材料电阻点焊接头中Zn的作用机理
Mechanism of Zn in the Joint of Magnesium and Steel by Resistance Spot Welding
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摘要: 针对2.0 mm厚的AZ31B镁合金以及1.0 mm厚的SPHC镀锌钢板,采用KDWJ-17型三相次级整流电阻焊机进行焊接试验,利用光学金相、扫描电镜等方法分析接头挤出的锌镁化合物的组织结构和成分分布。从原子扩散以及热力学的角度分析了Zn在接头形成过程中的作用,并通过试验和Mg-Zn二元相图推测接头处形成的Mg-Zn化合物。结果表明:Zn元素的存在可以使Al元素在接头处形成浓度梯度,促进Al元素扩散;挤出的Zn-Mg化合物为MgZn2能起到机械密封保护的作用。Abstract: 2.0 mm thick AZ31B magnesium alloy and 1.0 mm thick SPHC galvanized steel were welded by KDWJ-17 three-phase secondary rectification resistance welding machine for welding test. The organizational structure and distribution of composition of the joints were analyzed. The role of Zn in the joint's formation was analyzed by atomic diffusion and thermodynamics. The Mg-Zn compound of the joint was speculated by the test and Mg-Zn binary phase diagram. The results show that the presence of Zn elements can form a concentration gradient in the joints and promote the diffusion of Al element. The extruded Zn-Mg compound can play a role in protection as mechanical seal.