Mechanical properties and fatigue behavior of vacuum-assist die cast AlMgSiMn alloy

Aluminum die castings are often used as non-structural parts of automobile, in order to apply aluminum die castings as high-duty structural components, the fatigue behavior and mechanical properties of die casting (DC) and vacuum die casting (VDC) Al-Mg-Si-Mn samples are studied. Results indicate that ultimate tensile strength, yield strength and elongation of VDC samples (331 MPa, 210 MPa and 4.4% respectively) are superior to those of DC samples (321 MPa, 205 MPa and 3.9% respectively). Fatigue lives of the VDC and DC samples are similar to each other, while the fatigue life of the VDC samples is less scattered than those of DC samples. Slope of da/dN-ΔK curve of the VDC samples (2.824) is slightly smaller than that of DC samples (3.692). Vacuum assistance improves the fatigue resistance and the detrimental effect of Fe-bearing particles is eliminated. In addition, porosity, oxide inclusion and ductile deformation are responsible for the crack initiation and transgranular fracture is the dominant crack propagation mechanism.