Porosity Characterization with X-ray CT and its Effects on Tensile Properties of Die Cast Magnesium Alloy

Porosity is one of the most typical defects in high pressure die castings, induced mainly by entrapped air or shrinkage of solidified material. Porosity is very detrimental to material mechanical properties. The pore sizes and morphology are highly dependent on the casting process, gating design and product geometry. It is very challenging to characterize and quantify the porosity distribution due to the complex three-dimensional morphology and large number density. In this study, a comprehensive porosity analysis was conducted for cast-to-size samples of high pressure die casting Magnesium AE44 alloy. Three different approaches are evaluated including metallography image analysis, SEM observation of the fracture surface, and X-ray computed tomography. The correlation of porosity characteristics among different approaches is established. The effects of porosity distribution on the tensile properties are also discussed.