<p>Entrained defects formed during the preparation of semi-solid slurries significantly limit the application of rheocasting in lightweight components. Effectively controlling these defects remains a critical challenge. This study investigates the closure of porosity defects under varying levels of deformation using parallel plate compression. Microstructures and defects were characterized using optical microscopy (OM), scanning electron microscopy (SEM), and X-ray computed tomography (XCT). The mechanisms for closing porosity defects were analyzed through a combination of tensile testing and numerical simulation. Results indicate that both the defect area and area fraction progressively decrease as the compression level increases. The grain shape factor initially rises before, experiencing a decline, which is accompanied by significant grain refinement under conditions of high strain. While mechanical properties generally improve with deformation, they exhibit a decline at 80&#xa0;pct compression strain due to defect clustering. Numerical simulations indicate that increased strain enhances the closure of porosity defects, while higher strain rates impede this process. The initial size of the porosity defects has a limited effect on the closure process; however, their morphology plays a critical role in the closing behavior. Specifically, porosity defects with complex shape demonstrate a slower closing rate. This study offers novel insights into the mechanisms of porosity defect closure in semi-solid slurries subjected to compression.</p>