Zn-Al-Cu基合金无钎剂钎焊泡沫铝的界面结构及力学性能

以Zn--Al--Cu基合金为钎料, 对74.7%---91.6%不同孔隙率的泡沫铝采用无钎剂钎焊方法进行连接实验. 采用OM和SEM观察钎缝组织及界面结构, EDS测定界面元素分布, XRD分析界面物相, 通过热力学分析验证钎料中Cu和Zn与母材中Al元素的相互作用和除膜机理, 对钎焊接头试样进行拉伸和剪切性能实验, 分析孔隙率与接头试样强度之间的关系.结果表明, 该无钎剂钎焊方法在泡沫铝端 面之间形成密实结构的连续钎料层,未改变母材结构特征; 钎缝组织由Al(Zn) 固溶体、Zn(Al) 固溶体、Cu₄Zn及MgMnO₃组成; 连接界面主要由Al(Zn)固溶体组成, Zn,Al和Cu在界面上相互扩散而形成一定扩散梯度, 熔合良好, 钎焊接头抗拉强度与母材相当, 剪切强度略高于相同孔隙率母材的剪切强度,抗拉强度和剪切强度均随孔隙率增加而明显降低.

INTERFACIAL STRUCTURE AND MECHANICAL PROPERTIES OF ALUMINIUM FOAM JOINTS FLUXLESS-SOLDERED WITH Zn-Al-Cu BASE ALLOY

Al foam is a structural metal in which gas bubbles are separated by thin Al cell--walls, and exhibits a unique combination of functional properties mainly derived from their cellular structure. Joining is one of important considerable secondary processes that are required for use of work pieces made from Al foam or manufacture of large size Al foam plate. Almost all of the current joining methods have some problems in corrosion resistance, fatigue tolerance, formation of weld and mechanical properties. The joint is further complicated by various cellular structure characteristics that can have a significant impact on the joining process and mechanical properties of the joints. With Zn--based alloy as filler metal, a fluxless soldering method for joining Al foams with porosities of 74.7%---91.6% is proposed. The microstructure of the soldered interfacial region, elemental distributions and phase identification were determined by OM, SEM, EDS and XRD. The tensile and shear strengths of soldered joints, and the relationship between joint bonding strength and porosity were also investigated. The results show that the joining method does not change the cellular structure near the soldered joint, but a dense soldering seam layer is formed. The soldered region consists of Al(Zn) and Zn(Al) solid solutions, Cu₄Zn and MgMnO₃. Major elements of the filler alloy and bases easily diffuse  into each other. The tensile strength of the joints is close to that of the Al foam base, and the shear strength of joint is higher than that of Al foam. The strengths of joints decrease with the increase of Al foam porosity.