Effect of casting imperfections on the fatigue properties of aluminum-silicon casting alloys.

摘要

Energy is the single most critical factor facing the world today. The automotive industry has taken a giant step forward in reducing the weight of the car by replacing cast and malleable iron castings with aluminum castings. Aluminum-silicon casting alloys find extensive applications in this sector, due to their high strength-to-weight ratio which improves the performance and fuel economy. Aluminum sand, die, and permanent mold castings are critically important in engine construction, where engine block, pistons, cylinder heads, intake manifolds, crankcases, carburetors, brake valves and callipers join innumerable components in car design importance.; Five Al-Si casting alloys with silicon contents ranging from 7 to 17% were selected for this study: hypoeutectic LP PM319-F, A356-T6 and C354-T6 alloys and hypereutectic AE425 and PM-390 alloys, all used extensively in automotive applications. The aim of this work was to investigate the effect of casting defects on the fatigue properties of these alloys by correlating the sample fatigue life with the defect that initiated the fatigue crack, and to characterize these defects (i.e., porosity, oxide films, slip bands, etc.) by their critical role in affecting the fatigue life. Porosity was investigated in terms of the pore size at the sample fracture surface and its location i.e. near the edge or close to the interior. The effect of hot isostatic pressing (HIPping) on the fatigue life of C354-T6 alloy was also studied and the behavior of HIPped and non-HIPped samples compared. (Abstract shortened by UMI.)