Effect of teeth shape on ultrasonic spot welding joints of nickel foam sheet and aluminum solid sheet

Nickel foam sheet and pure aluminum solid sheet for electrodes and catalyst carrier were successfully welded via ultrasonic spot welding. Two kinds of sizes of anvil teeth which were in contact with the nickel foam were designed. Effects of anvil teeth shapes on plastic deformation and performances were compared. Influence of teeth shapes and welding parameters on tensile properties and fracture morphologies were analyzed. The results showed that the 30 J specimen welded by small teeth anvil had the optimal tensile strength and fracture energy, which reached 58% and 69.1% of nickel foam base metal, respectively. The anodic polarization curves of two kinds of welded joints in 3.5% NaCl solution were compared. The results of energy-dispersion spectrum analysis showed that the element diffusion across the interface diffusion was insufficient, and no obvious intermetallic compound layer in the welding interface was observed. The welding process was solid state process.