The Influence of Casting Defects on the Fatigue of SiCp/AI MMCs

摘要

The high cycle fatigue behavior of a cast SiC particle-reinforced aluminum composite, Duralcan F3D20S, has been studied. The material, which contains about 20 vol.% of SiC particles with an average size of 15 μm, has been examined in the following two conditions: (a) in the as-cast condition after high-pressure die casting and (b) after hot isostatic pressing (HIP). Somewhat surprisingly, there were no significant differences between the high cycle fatigue lives of as-cast and HIP 'd specimens. While porosity limited the fatigue lives in all cases, surface porosity was found to be more deleterious to fatigue life than internal pores of the same size. Primarily as a result of this factor, the HIP 'd specimens, which retained small porosity on the subsequently machined surface, did not exhibit improved fatigue lives. Particle-free regions rich in Cu and Ni contents were also present and, when present in the vicinity of porosity, contributed to crack initiation, reducing fatigue life.