Effect of Homogenization and Extrusion on Microstructure and Mechanical Properties of Cladding Billet by Cladding Casting

An AA4032/AA6069 cladding billet, fabricated by cladding casting process, was homogenized at 520°C for 12 h and then indirectly extruded into cladding pipe. The evolution in interfacial region was investigated in detail by the methods of optical microscope (OM), field emission electron scanning microscope (FESM), Vickers hardness, tensile and shear test. The interface region maintained original layered structure during the homogenization and extrusion process. During the process of homogenization, the eutectic silicon phases in AA4032 and Mg2Si in AA6069 became rounded markedly but still distributed dendritically. The homogenization improved the Vickers hardness and tensile strength of the interface region due to the precipitation strengthening and solution strengthening benefiting by element diffusion, and rarely affected the interfacial shear strength. The eutectic silicon and Mg2Si were spherized further and transformed into dispersive particles after extrusion process. Compared with that before deformation, the hardness of interface region got an obvious increase. The process of cladding casting and indirect extrusion is an idea method to fabricate cladding pipe.