Optimization of Laser Welding Process Parameters of AA7020 Aluminium Alloys
Optimization of Laser Welding Process Parameters of AA7020 Aluminium Alloy.
This research work aims at getting the optimum process parameters of laser welding of aluminium alloys. The objectives of this research are to cast aluminium alloy by varying different process parameters so as to obtain the best regime at which welding is most efficient, and analysis the welded sample to reveal the microstructure, defects and mechanical properties of the welded region. The sample AA7020 was casted and hot rolled at a temperature of 4700С to a thickness of 1mm. After hot rolling, the sample undergone two step age hardening heat treatment at a temperature of 1000С and 1700С respectively. Some of the aged hardening samples were electropolished and dried in the furnace at a temperature of 1500С for 15minutes why some were not. The samples were then welded with Al-3%Ti-1%B and pure aluminium as a filler material at a different laser welding process parameters. The welding was carried out at an optimized welding speed of 1mm/s, overlap of 0.25mm, duration of 14ms and flow rate of 15l/mm. Parameters such as peak power and focus beam were varied to get a good fusion. The peak power used was 0.49KW, 0.5KW and 0.55KW with a focus beam of -2, -2 and -3 respectively. After welding, the samples were age hardened again to obtain some precipitation in the fusion zone using the same regime as the previous. Post welding analysis reveals that there were precipitation of Cr, Mn, Mg and Zn in the fusion zone. The grain size of the joints with Al-3%Ti-1%B as filler materials were also obsereved to be finer and has better mechanical properties when compared with the joint with pure aluminium. It was also observed that the joints that were electropolished before welding contains less porosity compared with those that were not electropolished. AA7020 has a wide application which includes transportable bridging, weapons industry, armour plating, engineering corps equipment.