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This paper focuses on the T-joints of 3mm thick 5083 aluminium alloy, and the study was conducted by the self-designed welding tool. The results indicated that the trials achieved well-formed, defect-free welds with fillet transitions, and the weld areas experienced varying degrees of thinning. Microstructural analysis indicates that the grains are in equiaxed crystalline state around the nugget zone (NZ), while grown larger within the heat-affected zone (HAZ). The minimum tensile strength have reaches 306 MPa, exceeding 95% of the base material (BM), with fractures occurring in the base material area. The hardness distribution in descending order is NZ, BM and HAZ. Theoretical foundation and technical support are provided for the high-quality welding of thin aluminium alloy plates and has guiding significance for welding applications in production processes.

The influence of argon shielding configurations for the weld pool on microstructure formation and the retention of principal alloying elements during partial penetration of Al-Mg and Al-Zn-Mg-Cu alloys using fiber laser irradiation at a power of 900 W with a specific energy input of 100–130 J/mm was analyzed. The studies were conducted under the following conditions: (1) in an open chamber with local argon shielding; (2) in a sealed chamber filled with argon (pressure 1.05 MPa); (3) in the same chamber with additional argon flow onto the weld pool (flow rate 5–10 L/min); (4) in a sealed chamber with reduced argon pressure (170–190 Pa); and (5) in the same chamber with additional argon flow onto the weld pool (flow rate 5–10 L/min). For shielding schemes No. 1–No. 3, penetration depths of 0.20–0.23 mm were achieved. Application of schemes No. 4 and No. 5, as opposed to scheme No. 1, led to a reduction in oxide inclusions in the penetration cross-section from 3.0% to 1.5% or lower, which complied with ISO 13919-2:2001. However, this was accompanied by a decrease in the proportion of alloying elements, particularly Mg, Zn, and Cu, to 50%–70% or more, and a 10%–30% reduction in microhardness of the fusion zone relative to the base metal. The use of scheme No. 5 promoted a transition in penetration mode from heat conduction to deep penetration, accompanied by an increase in penetration depth up to five-fold and a reduction in alloying element burn-off. Laser penetration of the studied alloys was carried out in heat conduction mode. The regime promoted vertical crystallite growth, whereas in the deep penetration mode, transcrystallite counter-growth of crystallites at an angle to the central penetration zone was observed.