The　real-time　evolution　of　the　deformation　and　strain　field　of　non-heat-treatable　aluminum　alloy　5754　and　heat-treatable　aluminum　alloy　6061　resistance　spot　welding　joints　during　the　lap　shear　test　was　extracted　using　the　digital　image　correlation　(DIC)　technique.　The　strain　competition　phenomenon　between　the　nugget　and　its　peripheral　metal　was　quantitatively　analyzed　by　applying　2D　and　3D　DIC　analyses.　The　quantitative　data　show　the　tensile　strain　concentrated　in　the　peripheral　metal　of　the　AA5754-O　joint,　which　fractured　in　the　pull-out　mode.　In　comparison,　a　significant　shear　strain　appears　in　the　nugget　of　the　AA6061-T6　joint,　leading　to　its　fracture　in　the　interfacial　failure　mode　during　the　lap　shear　test.　The　phase　evolution　of　the　nugget　was　analyzed　using　the　thermodynamics　database　JMatPro,　which　was　further　used　to　calculate　the　local　strength　of　the　joints.　The　results　indicate　that　the　nugget　strength　of　AA5754　is　223　MPa,　the　nugget　strength　of　AA6061　is　178　MPa,　and　the　heat-affected　zone　(HAZ)　strength　of　AA6061　is　263　MPa.　By　inputting　the　local　strength　data,　the　calculated　result　of　the　analytical　load-bearing　competition　model　is　in　accordance　with　the　experimental　data　of　the　lap　shear　test.