Process instability in laser welding of aluminum alloys at the boundary of complete penetration

Intrinsic instabilities in the depth of penetration achieved when laser welding aluminum alloys were investigated in this article. Four types of weld pool configuration, resulting in different welds, were identified, only two of which are associated with full penetration. A simple phenomenological explanation of the unstable welding process at the boundary of complete penetration was proposed. The nature and cause of the instabilities were discussed and suggestions were offered for process control.