Studies on the spatter behaviour when welding AA5083 with a Yb-fibre laser

Abstract

The processing advantages of welding with high brightness and 1 μm wavelength laser sources have been well reported. However, it is also reported that such high brightness laser sources, whilst providing the necessary penetration depth and welding speed, may result in unacceptable levels of weld spatter. So far, the effects of process parameters on spatter formation have not been well studied on aluminium alloys. In this paper, systematic experimental trials were carried out on the AA5083 aluminium alloy plates to study the effects of different process parameters on the spatter generated. High speed imaging and numerical modelling (using the computational fluid dynamic, CFD) were used to understand the formation mechanisms of the spatter. Results show that the process parameters having the most influence on spatter formation are laser power, welding speed × focal length of the focusing unit, laser power squared × welding speed, laser power squared × focal length of the focusing unit. The welding process in aluminium alloy AA5083 aluminium alloy is quite unstable, the occurrence of spatter ejections is closely related to the turbulence in the melt pool, and full penetration welds tend to produce less spatter than partial penetration welds. To minimise spatter ejection, it is recommended that a high welding speed is used with the laser power just sufficient to achieve full penetration the joint geometry, and the focus position of the laser beam should be appropriately away from the top surface of the workpiece.