The　variable-polarity　plasma　arc　(VPPA)　keyhole　welding　technology　offers　an　efficient　solution　for　producing　defect-free　aluminum　alloys,　but　a　keyhole　is　left　at　the　end　of　the　welding　process.　Traditional　manual　TIG　welding,　which　involves　filling　keyholes,　often　lacks　productivity　and　can　result　in　inconsistent　weld　quality,　hindering　the　production　of　high-strength　and　high-precision　parts.　In　this　study,　a　keyhole　self-closing　method　was　proposed,　and　the　microstructure　and　mechanical　properties　of　keyholes　closed　by　the　proposed　method　were　compared　to　those　closed　by　manual　TIG　welding.　The　results　showed　that　the　self-closed　keyhole　had　a　smaller　fusion　line　wide,　and　the　weld　zone　had　a　uniform　distribution　of　equiaxed　crystal,　with　fewer　pore　defects.　While　the　manual　TIG　welding-filled　keyhole　had　a　higher　density　of　dislocations,　which　leads　to　an　increase　in　the　microhardness.　The　presence　of　pores　in　the　manual　TIG　welding-filled　keyhole　reduces　its　tensile　strength　and　elongation,　which　were　lower　than　those　of　the　self-closed　keyhole　by　61.5　MPa　and　5.8　%,　respectively.　The　self-closing　method　can　effectively　address　the　keyhole　retention　issue　in　VPPA　keyhole　welding.　By　using　this　method,　higher-quality　welds　with　better　microstructure　and　mechanical　properties　can　be　produced,　which　can　have　important　implications　for　various　industrial　applications,　and　in　applications　where　mechanical　properties　are　critical.　©　2023　The　Society　of　Manufacturing　Engineers