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This research explored the influences of shielding gases on the appearance of weld beads and the microstructures and mechanical properties of thin-wall samples using conventional gas metal arc welding as the heat source by using 5356 aluminium alloy welding wire as the raw materials and nitrogen (N₂) and argon (Ar) as the shielding gases. The results showed that under the same parameters and after mono-layer single-bead welding was performed using N₂ as the shielding gas, the bead height was higher, the bead width was narrower, and the penetration depth was shallower. The grain size of the thin-wall sample protected by N₂ was 43.5–47.8 % smaller than that obtained under Ar protection. However, the sample protected by N₂ contained many flaky nitrides, whose presence improved the microhardness but reduced the ultimate tensile strength (UTS) and plasticity. The average UTS of the thin-wall …