Application of keyhole and heat-conduction modes to laser dissimilar metals welding of magnesium alloy and steel Available to Purchase

The characteristics of welding Mg-alloy to Zn-coated steel in lap joint configuration by disc laser were investigated. With Mg specimens on the top and a keyhole welding mode, two welding runs with moderate energy input were conducted to achieve uniform penetration into the steel specimens without affecting the process stability. However, the ensuing Zn enrichment and the increased thermal stresses resulted in cracking at the interface across the Mg fusion zone that reduced the joint strength significantly. High joint strength could be produced when the steel specimens were placed on the top of Mg specimens and the process parameters were optimized in a heat-conduction welding mode. The Zn-layer was completely melted at the welded interface and dissolved the oxide layer on Mg surface. This resulted in strong joining between the non-oxidized surfaces of Mg and steel. Compared with Zn-coated steel, higher joint strength could be produced between Mg and uncoated steel in the case of keyhole welding mode. However, welding of uncoated steel sheet to Mg plate could not be achieved with a heat-conduction mode.