Publication: Mechanical and formability analysis of low power laser welded dissimilar aa5052-h32 and aa6061-t6 aluminium alloys
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Date
2024-08-01
Authors
Mohd.Fadzil, Jamaludin
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Abstract
Laser welding of aluminium alloys using high-power lasers presents significant challenges, such as the high energy requirements needed to overcome the material’s high reflectivity and thermal conductivity, the formation of porosity due to keyhole instability, and embrittlement in the weld or heat affected zone resulting from rapid cooling rates. Low power laser welding offers a potential solution to these issues by operating below the keyhole formation threshold, resulting in reduced energy consumption, decreased porosity, improved weld quality, and enhanced process stability. However, its limited penetration depth necessitates strategic approaches for welding sheet metal applications, particularly for automotive tailor welded blank (TWB) fabrications. This study investigates the feasibility of low power welding for joining similar AA5052-H32 as well as dissimilar AA5052-H32 and AA6061-T6 aluminium alloys in a butt-weld configuration. The influence of laser power (270 W to 310 W) and welding speed (10 mm/s to 20 mm/s) on weld characteristics, including penetration depth, weld zone geometry, mechanical strength, springback behaviour, and formability, is examined using specimens with thicknesses of 1.0 mm, 1.5 mm, and 2.0 mm. A full factorial design of experiments (DoE) was employed to evaluate the effects of these parameters on similar alloys with different thicknesses, different alloys with similar thicknesses, and different alloys with different thicknesses. Achieving an average weld penetration depth of only 0.77 mm, a double-sided welding strategy was employed for full penetration. This resulted in successful full penetration for 1 mm thick weld interfaces, while partial penetration occurred for 1.5 mm and 2.0 mm interfaces. Weld strength increased with higher laser power and lower welding speeds for thicker specimens and interfaces, while minimal variation was observed for thinner specimens. Results showed that weld strength increases with higher laser power and lower welding speeds for thicker specimens, while thinner specimens exhibited minimal variations. Response surface methodology (RSM) was utilized to optimize the laser power and welding speed for maximum tensile strength in the most varied joint configuration of 1.0 mm (AA6061-T6) to 1.5 mm (AA5052-H32). The optimized parameters of 302 W laser power and 22 mm/s welding speed resulted in a very low heat input of 13.7 J/mm. Post-weld assessments revealed springback angles of 3° to 4° for similar AA5052-H32 alloy welds, while dissimilar alloy combinations displayed values between the respective base metals. TWB dome heights were 52-62% of the base metal values, indicating significantly lower formability for welded blanks. This research demonstrates the potential of low-power laser technology for joining dissimilar aluminium alloys in TWBs using a double-sided welding strategy for full penetration, particularly for applications requiring thin metal sheet forming.