Fatigue Properties Of Squeeze, Semisolid And Gravity Diecast Al-Si-Mg Alloy

Fatigue endurance properties are reported for squeeze, semisolid and gravity diecastings as measured with axially loaded polished specimens. Fatigue cracks were initiated from oxide defects in the squeezecast castings and from both oxide defects and shrinkage pores in the semisolid and gravity castings. Despite differences in the microstructures and in the defect populations in the squeeze and semisolid castings, their fatigue properties were similar. The fatigue properties of the gravity diecastings were inferior to the other two types. Previous reports that the fatigue properties of semisolid castings are inherently superior to those of other types of castings may be in error. Measurements of the sizes and types of the defects that initiate fatigue are reported.