A review of laser welding techniques for magnesium alloys

CO2 and diode laser welding of AZ31 magnesium alloy

Study on the weld joint of Mg alloy and steel by laser-GTA hybrid welding

The microstructures, tensile properties, strain hardening, and fatigue strength of fiber-laser-welded (FLW) and diode-laser-welded (DLW) AZ31B-H24 magnesium alloys were studied. Columnar dendrites near the fusion zone (FZ) boundary and equiaxed dendrites at the center of FZ, with divorced eutectic β-Mg17Al12 particles, were observed. The FLW joints had smaller dendrite cell sizes with a narrower FZ than the DLW joints. The heat-affected zone consisted of recrystallized grains. Although the DLW joints fractured at the center of FZ and exhibited lower yield strength (YS), ultimate tensile strength (UTS), and fatigue strength, the FLW joints failed at the fusion boundary and displayed only moderate reduction in the YS, UTS, and fatigue strength with a joint efficiency of ~91 pct. After welding, the strain rate sensitivity basically vanished, and the DLW joints exhibited higher strain-hardening capacity. Stage III hardening occurred after yielding in both base metal (BM) and welded samples. Dimple-like ductile fracture characteristics appeared in the BM, whereas some cleavage-like flat facets together with dimples and river marking were observed in the welded samples. Fatigue crack initiated from the specimen surface or near-surface defects, and crack propagation was characterized by the formation of fatigue striations along with secondary cracks.

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Microstructure and Mechanical Properties of Fiber-Laser-Welded and Diode-Laser-Welded AZ31 Magnesium Alloy

This article reports the influences of welding processes such as gas tungsten arc welding (GTAW), friction stir welding (FSW), and laser beam welding (LBW) on tensile properties of AZ31B magnesium alloy. The lowest hardness distribution profile (LHDP) is constructed across the weld section to identify the fracture path. From this investigation, it is found that LBW joints exhibited superior tensile properties compared to GTAW and FSW joints and this is mainly due to the formation of very fine grains in the fusion zone and absence of heat-affected zone (HAZ).

Influences of Welding Processes on Microstructure, Hardness, and Tensile Properties of AZ31B Magnesium Alloy

Welding of AZ31 Mg alloy was conducted using various welding techniques, namely, tungsten inert gas (TIG) welding with Ar shielding gas, TIG welding with He shielding gas, CO2 laser welding, and YAG laser welding. The results were comparatively evaluated in terms of weld bead formation and microstructural characterisation. It was found that TIG welding with both Ar and He gas shielding produced good welds without major defects. The penetration capacity can be improved using He gas shielding. Owing to their high energy density, CO2 and YAG lasers can produce weld beads having high aspect ratio. Among the four techniques used, the YAG laser produced the finest weld microstructure, whereas TIG with Ar gas shielding produced the coarsest microstructure. Shielding is a key factor controlling the O contents in the welds. The more effective the shielding provided the lower the O content in the weld. Hardness reduction in the weld metals and heat affected zones was observed for all the techniques owing to...

Z. Sun

Papers

Comparative evaluation of tungsten inert gas and laser welding of AZ31 magnesium alloy