Laser welding of aluminium alloys was performed with high power YAG, fiber or disk laser. Interaction between laser and plume, laser absorption, welding phenomena and weldability were investigated by using such lasers. The absorption of a focused fiber laser in aluminum alloy was found to be higher at high powers and low welding speeds than that in stainless steel.

Hybrid welding of A5052 alloy with YAG, fiber or disk and MIG arc was performed to understand welding phenomena, the mechanisms of weld penetration, porosity formation and prevention, etc. The conditions for the production of sound deep welds were clarified. Furthermore, the addition of the other filler wire during hybrid butt-joint welding was also investigated, and the effect of the increase in gap tolerance was confirmed.

Aluminum-to-steel joining was performed. It was confirmed that the joints with three weld beads were fractured in the base metal and possessed high strength. Moreover, the laser joining of PET plastic to aluminium alloy was also carried out using a diode laser under various conditions. High tensile strengths of lap weld joints were obtained when the laser was irradiated on an aluminum alloy sheet. It was observed that the PET sheet on the aluminum alloy plate was melted and chemically bonded through the oxide film on the base aluminium alloy. This novel bonding technique was applied to bond an aluminium alloy sheet to a steel one. It was consequently confirmed that the joint of aluminium alloy and steel with PET intermediate sheet was high.