30 kW-level laser welding characteristics of 5A06 aluminum alloy thick plate under subatmospheric pressure

•The processing widow of ultra-high laser welding under atmosphere was very narrow.•A qualified 130 mm-thick 5A06 aluminum alloy butt joint was obtained under 10 Pa.•The lowest tensile strength of the joint was up to 95% of the base metal.•The element Mg was the key factor of improving tensile strength rather than grain size.