Abstract
Laser welding-brazing technique, using a continuous wave (CW) fibre laser with 8000W of maximum power, was applied in conduction mode to join 2mm thick steel (XF350) to 6mm thick aluminium (AA5083-H22), in a lap joint configuration with steel on the top. The steel surface was irradiated by the laser and the heat was conducted through the steel plate to the steel-aluminium interface, where the aluminium melts and wets the steel surface. The welded samples were defect free and the weld micrographs revealed presence of a brittle intermetallic compounds (IMC) layer resulting from reaction of Fe and Al atoms. Energy Dispersive Spectroscopy (EDS) analysis indicated the stoichiometry of the IMC as Fe2Al5 and FeAl3, the former with maximum microhardness measured of 1145 HV 0.025/10. The IMC layer thickness varied between 4 to 21 μm depending upon the laser processing parameters. The IMC layer showed an exponential growth pattern with the applied specific point energy (Esp) at a constant power density (PD). Higher PD values accelerate the IMC layer growth. The mechanical shear strength showed a narrow band of variation in all the samples (with the maximum value registered at 31.3kN), with a marginal increase in the applied Esp. This could be explained by the fact that increasing the Esp results into an increase in the wetting and thereby the bonded area in the steel-aluminium interface.
Highlights
Laser welding-brazing technique, using a continuous wave (CW) fibre laser with 8000 W of maximum power, was applied in conduction mode to join 2 mm thick steel (XF350) to 6 mm thick aluminium (AA5083-H22), in a lap joint configuration with steel on the top
Laser welding-brazing has the capability of limiting the microstructural damage due to intermetallic compounds (IMC) formation as it allows aluminium to melt and wet the steel surface
It is worth noting that Al has some limited solid solubility in Fe, while Fe does not have any solubility in Al
Summary
Laser welding-brazing technique, using a continuous wave (CW) fibre laser with 8000 W of maximum power, was applied in conduction mode to join 2 mm thick steel (XF350) to 6 mm thick aluminium (AA5083-H22), in a lap joint configuration with steel on the top. Some researchers were focused on the study of Fe-Al reaction between molten Al and solid steel, controlling the time-temperature and evaluating the IMC layer composition and growth [1,2,3], whilst others assessed the influence of other alloying elements on the IMC layer thickness growth [4,5]. Meco et al / Optics and Lasers in Engineering 67 (2015) 22–30 the substrate) Explosion welding has another advantage, as the process happens so quickly there is almost no time for the reaction between Fe and Al and so the IMC layer is very thin as demonstrated in [8,9,10]
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