中间层Ni对TC4/2A14异种金属搅拌摩擦焊接头组织和性能的影响

Effect of Ni Interlayer on Microstructure and Properties of TC4/2A14 Dissimilar Metal Joints Welded by Friction Stir Welding

目的添加0.05mm厚的Ni箔作为中间层,对3mm厚的TC4钛合金和2A14铝合金进行搅拌摩擦焊,分析Ni对接头力学性能的影响。方法采用扫描电镜、EDS能谱及XRD衍射等微观表征分析方法,对焊接接头的断口形貌、成分进行分析,探究Ni箔对焊接接头力学性能的影响。结果由于钛合金和铝合金存在较大的物理化学性能差异,Ti/Al异种金属焊接性较差,界面容易产生TiAl_(3)、TiAl、Ti_(3)Al等金属间化合物,其中脆性相TiAl_(3)对接头性能的影响最大,会导致综合力学性能下降。当加入中间层材料Ni后,由于Ni与Al晶体结构均属于面心立方,因此Ni与Al的扩散系数大于Ti与Al的扩散系数,Ni和Al之间优先形成金属间化合物且弥散分布于焊缝中,从而缩短了Ti与Al之间的相互扩散时间,减少了TiAl_(3)相的生成。结论在未添加中间层材料时,接头平均抗拉强度为237.3 MPa,约为2A14铝合金母材抗拉强度的56.7%;当添加中间层Ni后,对焊缝中金属间化合物的种类和数量进行了调控,减少了对性能影响最大的TiAl_(3)相的生成,接头平均抗拉强度达到285.3MPa,为2A14铝合金母材抗拉强度的68%。

The work aims to analyze the effect of Ni on the mechanical properties of the joint by adding 0.05 mm thick Ni foil as interlayer and weld 3 mm thick TC4 titanium alloy and 2A14 aluminum alloy by friction stir welding.Scanning electron microscopy,EDS spectroscopy,and XRD diffraction micro characterization analysis methods were adopted to analyze the fracture morphology and composition of welded joint and explore the effect of Ni foil on the mechanical properties of the welded joint.The weldability of Ti/Al dissimilar metals was poor due to the significant differences in physical and chemical properties between titanium alloy and aluminum alloy,and the intermetallic compounds such as TiAl_(3),TiAl,and Ti_(3)Al were easily gener-ated at the interface,in which the brittle phase TiAl3 had the greatest impact on the joint performance,leading to a decrease in overall mechanical properties.After the interlayer Ni was added,due to the fact that both Ni and Al crystal structures were the face centered cubic structure,their diffusion coefficient with Al was higher than that of Ti and Al,leading to the preferential formation of intermetallic compounds between Ni and Al and their dispersion in the weld seam,thereby reducing the mutual diffusion time between Ti and Al and the generation of TiAl_(3) phase.The average tensile strength of the joint is 237.3 MPa,which is about 56.7%of that of the 2A14 aluminum alloy base material without interlayer material.On the other hand,the type and quantity of intermetallic compounds in the weld seam are regulated,reducing the generation of TiAl_(3) phase that has the greatest impact on performance,and making the average tensile strength of the joint reach 285.3 MPa,which is 68%of the ten-sile strength of the 2A14 aluminum alloy base material after the interlayer Ni is added.