Casting defects vs durability: a sensitivity analysis on die cast aluminium alloy specimens and components

This paper summarises the results of a CRAFT project investigating the influence of casting defects on material properties for a high pressure die cast aluminium alloy. Defects consist in gas and shrinkage pores as well as cold fills, dross and alumina skins. Static and fatigue tests are run on standard specimens and production components. For the specimens, the influence is straightforward, while for components no significant difference was found between batches of components, judged as "acceptable" and "non acceptable" by the quality inspection within the foundry. Fatigue testing showed four different fracture regions; two corresponding to a region of high stress as indicated by a FEM simulation. For the other two regions of failure, voids or oxide layers of significant dimensions were observed on the fracture regions. These regions corresponded to regions of last solidification; moreover, for these regions, simulation of the casting process pointed out the presence of tensile residual stresses inside the cast components