INTERFACIAL STRUCTURE AND MECHANICAL PROPERTIES OF ALUMINIUM FOAM JOINTS FLUXLESS-SOLDERED WITH Zn-Al-Cu BASE ALLOY
Zn-Al-Cu基合金无钎剂钎焊泡沫铝的界面结构及力学性能

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.