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Crack-free autogeneous one-sided laser welding of a 6013 aluminum alloy T-joint for aircraft applications

This paper is available in a repository.
This paper is available in a repository.

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Preprint: policy unknown
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Postprint: policy unknown
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Abstract

T-joined laser beam welded stringer–skin panels are of common use on aluminum aircraft structures. Usually, the aircraft stringer-skin joints are manufactured by simultaneously welding on both sides of the T-joint and by using of a Si-rich aluminum alloy filler. Recently, we had shown a simpler welding geometry in which T-joints of the 1.6 mm thick AA6013 sheets were welded with a Yb:fiber laser by only one side without any filler material. In this welding configuration, the presence of micro-cracks limits the weld joint tensile strength up to 70-80 % of base material. For an AlMgSi alloy (6XXX) the cracking susceptibility is usually reduced by introducing in the weld pool a Si-rich filler material or by modifying the welding heating and cooling rates. These rates can be modified by introducing a secondary heating source or by changing the laser beam interaction time T L which depends on the welding speed V and the laser beam diameter D L (T L = D L /V). In this work, we investigated the influence of these process parameters on the welding solidification crack susceptibility using two different beam diameters, 100 µm and 190 µm. Crack-free weld T-joints were obtained for a 100 µm beam diameter only for 17 mm/s welding speed. The same condition was obtained for a beam diameter of 190µm, but with welding speed increased to 50 mm/s. The results indicate the crack-free welding conditions are obtained when T L is greater than 3-4 ms. In such crack-free condition, the ultimate tensile stresses for Hoop and T-pull tests were 300 MPa and 260 MPa respectively, which approach the mechanical strength of the base material.