Porosity mechanism of fiber laser welding with filler wire for aluminum alloy

Abstract

The mechanism of porosity formation and its suppression methods in laser welding with wire filler have been studied by using a 4 kW fiber laser to weld 5A06 aluminum alloy with SAl-Mg5 filler. It is found that the porosity formation is closely related to the stability of the keyhole and fluctuation of the molten pool in laser welding aluminum alloy. The filling wire increases the instability of the keyhole and weld pool, therefore, further increases the amount of porosities in the joint. Prefabrication a suitable gap for the butt joint can provide a natural passage for the flow of the liquid metal, which can weaken and even completely eliminate the disturbance of the filling wire to the formation of keyhole. And the gap can also provide a passage for the escape of the bubble. So, this method can greatly decrease the susceptibility of the porosity. Moreover, for a thin sheet, if the power of laser is sufficient to form a keyhole with stable penetration through the weld sheet, a weld bead without gas cavity can also be obtained because the closeness of the keyhole is almost impossible.The mechanism of porosity formation and its suppression methods in laser welding with wire filler have been studied by using a 4 kW fiber laser to weld 5A06 aluminum alloy with SAl-Mg5 filler. It is found that the porosity formation is closely related to the stability of the keyhole and fluctuation of the molten pool in laser welding aluminum alloy. The filling wire increases the instability of the keyhole and weld pool, therefore, further increases the amount of porosities in the joint. Prefabrication a suitable gap for the butt joint can provide a natural passage for the flow of the liquid metal, which can weaken and even completely eliminate the disturbance of the filling wire to the formation of keyhole. And the gap can also provide a passage for the escape of the bubble. So, this method can greatly decrease the susceptibility of the porosity. Moreover, for a thin sheet, if the power of laser is sufficient to form a keyhole with stable penetration through the weld sheet, a weld bead without gas cavity...