CO2-LASER BEAM-WELDING OF MAGNESIUM-BASED ALLOYS

Magnesium has gained increased attention in recent years as a structur al metal - especially in the automotive industry - necessitating the d evelopment of welding techniques qualified for this new application. L asers are known to be an excellent tool for joining metals. This paper presents results of recent investigations on the weldability of sever al cast and wrought magnesium-based alloys. Plates with a thickness of 2.5-8 mm were butt joint welded with and without filler metal using a 2.5-kW CO2 laser. The investigations showed that magnesium alloys can be easily laser welded in similar and dissimilar joints. The beam cha racteristics of the laser leads to small welds and a deep penetration depth. Crackfree welds exhibiting low porosity and good surface finish can be achieved with appropriate process parameters. Generally, the l aser welding leads to either no change or a small increase in hardness in the fusion zone (FZ) and in the heat-affected zone (HAZ) relative to the base metal. Less promising results were obtained for the cast a lloy QE 22, in which cracking in the age-hardened condition and a sign ificant decrease in hardness occurred. Laser welded die cast alloys sh owed an extremely high level of porosity in the weld.