A　novel　twin-wire　co-molten-pool　gas　tungsten　arc　welding　(GTAW)　technique　was　developed　in　this　study,　enabling　the　weld　to　achieve　an　optimal　deformation-induced　martensitic　transformation　(DIMT)　response　sensitivity.　This　leads　to　a　synchronous　increase　in　both　the　tensile　strength　and　ductility　of　the　AISI　630　weld.　Digital　image　correlation　(DIC)　and　electron　backscatter　diffraction　(EBSD)　analysis　indicate　that,　during　the　tensile　process,　the　fully　austenitic　AISI630　twin-wire　co-molten-pool　weld　(filled　with　ER2209　and　ER310　wire)　transforms　into　a　dual-phase　microstructure　consisting　of　both　austenite　and　martensite.　The　DIMT-induced　strain　hardening　can　uniformly　and　extensively　propagate　throughout　the　entire　weld,　resulting　in　exceptionally　high　tensile　strength　and　static　toughness.　©　2024　Elsevier　B.V.