Laser welding of magnesium alloys

Abstract

There is increasing current interest in the use of magnesium alloys in the automobile industry since the low density (and hence high specific strength) of these alloys may play a part in meeting directives aimed at reducing overall vehicle mass with subsequent reduction in the emission of greenhouse gases such as carbon dioxide. However, if the usefulness of these alloys is to be realised in applications of this type, successful joining methods are required. In the achievement of weight reduction based on the use of steel and aluminium alloys, it has been found that a tailored blank strategy based on laser welding has been very successful. This points to the necessity of increasing effort in the adaptation of laser beam welding techniques for the case of magnesium alloys. This paper reviews the joining of magnesium alloys by laser welding. It considers the influence of laser beam process parameters (laser power, welding speed, assist gas and flow rate) on the weldability of these alloys, concentrating on factors such as the elimination of porosity and the achievement of weld ductility and strength. Where appropriate, these factors are related to the metallurgy of the alloys concerned. The joining by laser welding of magnesium alloys to dissimilar alloys (particularly aluminium alloys) is also considered.