Enhanced interfacial reaction and mechanical properties of laser welded-brazed Mg/Ti joints with Al element from filler

• Mg and Ti were joined successfully by laser welding-brazing with AZ91 filler.
• Effect of Al content from filler on interfacial reaction was comparatively studied.
• More Al atoms diffused into the interface with AZ91 filler.
• Newly formed reaction layer was identified at the AZ91/Ti interface.
• Reaction layer prevented crack propagation and improved joint strength.

Dissimilar metal joining between magnesium and titanium alloys was performed using laser welding-brazing process. Metallurgical bonding of immiscible AZ31 magnesium and TC4 titanium was successfully achieved by adding Al element into Mg based filler, compared to mechanical bonding when direct joining. An ultra-thin serrated-shape reaction layer was evidently observed at the interface of AZ91 (9%Al) fusion zone/Ti and identified as Ti3Al phase by transmission electron microscopy (TEM), which could prevent crack propagation effectively and thus improved the joint strength. The average fracture load of joint with AZ91 filler could reach 1947±61 N representing 47.3±1.5% joint efficiency relative to the magnesium base metal, which was 85% higher than that with AZ31filler.