Homogenization of the interfacial bonding of compound-cast AA7075/6060 bilayer billets by co-extrusion

Abstract

A process chain of compound casting and co-extrusion of AA7075/6060 bilayer billets is introduced to manufacture hybrid components with strength in the core and good corrosion-resistance in the shell. Using optimized compound casting parameter, metallurgical bonding between the shell AA6060 and the core AA7075 can be achieved through remelting and recrystallization of the substrate AA7075. The locally unequal thermal conditions at the interface induces partially weak bonding. The bonding strength in greater distance from the casting gate is generally lower. Hot extrusion is applied to improve the interfacial bonding. Comparisons of the microstructure and the shear strength between as-cast billet and extrudate present the homogenization of the interfacial bonding through the process chain.

Co-Extrusion of Dissimilar Aluminum Alloys via Shear-Assisted Processing and Extrusion

“…Furthermore, the total elongation of the multilayered structures was lower than that of the single co-extruded plates and was attributed to the increased fraction of intermetallic compounds. The bimetallic billet assembly for conventional extrusion is typically achieved through compound casting, where the core is cast first then the shell [7,8] or is fusion-welded along the core-shell interface [9] to promote good metallurgical bonding in the cladded tubes. For instance, Chen et al [7] fabricated bimetallic billets through the compound-casting process using 7075 Al as the core and 6060 as the cladding, then completed hot co-extrusion of the cast billets.…”

“…The bimetallic billet assembly for conventional extrusion is typically achieved through compound casting, where the core is cast first then the shell [7,8] or is fusion-welded along the core-shell interface [9] to promote good metallurgical bonding in the cladded tubes. For instance, Chen et al [7] fabricated bimetallic billets through the compound-casting process using 7075 Al as the core and 6060 as the cladding, then completed hot co-extrusion of the cast billets. The extrudates exhibited a defect-free, metallurgically bonded interface between the core and cladding.…”