<p>Formability is the ability of a material to undergo plastic deformation without being damaged. In sheet metal forming, materials are known to experience deformation in biaxial stretch mode. In order to simulate the common failure strains in sheet metal forming process, numerous formability test methods can be used. A material’s formability can be altered in several ways, one of which is post-weld heat treatment. In this study, the effect of post-weld heat treatment on the formability of aluminum alloy 6061 and SAE1020 mild steel tailor welded blanks fabricated by friction stir welding was evaluated using limiting dome height test. It was found that the specimens which underwent post-weld heat treatment recorded a lower springback and higher value of plane strain, indicating a better formability. The improved formability is attributed to microstructural homogenization, defects elimination, residual stresses relieve and IMC layer growth control from the post-weld heat treatment process.</p>