Abstracts Category : Other

Porosity Reduction and Elimination in Laser Welding ofAA6014 Aluminium Alloys for Automotive Components Manufacture andIndustrial Applications

by Shaer Ahmad Al

Automotive and aerospace industries consume asignificant amount of Al alloys in structures and framing. Thereis, however, a significant challenge to join the alloy componentsby laser welding. A key problem is the presence of large amount ofporosity in the welds. This research work aimed to understandfactors affecting porosity formation in laser welding of AA6014 Alalloy and identification and verification of a suitable method forthe porosity reduction and elimination. AC-170PX (AA6014) Al alloywas welded, for the first time, using a 5 kW disk laser in twodifferent configurations: fillet edge and flange couch joints usinga number of different filler wires. The experimental results showedthat laser power (2-5 kW) and welding speed (20-50 mm/s) had asignificant influence on porosity generation. Also, theintroduction of a 0.2 mm gap between the sheets significantlyreduced porosity for the fillet edge joint while it had a marginaleffect for the flange couch joint. The effect of the chemicalcomposition of the filler wire on the AA6014 weld quality was alsoevaluated for the first time by using different filler wires(AA3004, AA4043, AA4047 and AA5083) over a range of laser powersand welding speeds. The increase in Mg and Mn content in the fillerwires composition was found to reduce porosity in comparison withhigh silicon content filler wires.Nanosecond pulsed Nd:YAG lasercleaning was investigated as a surface preparation method for laserwelding for AA6061, and its effect on porosity at various weldingparameters was examined. The effect of laser cleaning on porosityreduction during laser welding using a filler wire has not beenreported before. The surface characteristics before and after lasercleaning were analysed. The results showed that laser cleaningplayed an essential role in significantly reducing porosity in boththe fillet edge and flange couch joints at different levels ofpower and laser welding speed. The developed surface preparationtechnology as a method for porosity reduction in laser welding hasbeen successfully implemented in one of the largestUK/international car manufacturers.To study the laser cleaningprocess, a novel Smoothed particle hydrodynamics (SPH) meshlessmodel has been implemented using a new 3-D multi-phase transientmodel. For the first time, a study was conducted to validate thetemperature field distribution predicted in SPH method undernanosecond pulsed laser heating. The need for special surfacetreatment of the kernel truncation was also investigated. Theproposed model accurately predicted the laser ablation depth andthe crater shape and was validated using a significant number ofexperimental and numerical data reported in the literature.Moreover, a primitive laser welding model has been created topredict the material flow inside the welding pool.The research workhas resulted in four publications in peer-reviewed journals. Theresearch highlighted that future work should include thedevelopment of a more advanced SPH model for the prediction ofAdvisors/Committee Members: ROGERS, BENEDICT BD, Li, Lin, Rogers, Benedict.