Fatigue Life Prediction in Aluminum Shape Castings

Increasing use of aluminum shape castings in automotive and aerospace industries has drawn great attention to fatigue properties of cast aluminum components. The fatigue resistance of aluminum castings strongly depends upon the presence of casting flaws and characteristics of microstructural constituents. The existence of casting flaws significantly reduces fatigue crack initiation life. In the absence of casting flaws, however, crack initiation occurs at the fatigue-sensitive microstructural constituents. Cracking and decohesion of large silicon and Ferich intermetallic particles and crystallographic shearing from persistent slip bands in the aluminum matrix play an important role in crack initiation. This paper reviews the latest understanding in fatigue crack initiation mechanisms in cast aluminum alloys and presents multi-scale fatigue (MSF) life models for aluminum castings that account for multi-scale casting flaws and microstructural constituents.