FATIGUE BEHAVIOR OF ADVANCED SPRAY CASTING 7075 ALUMINUM ALLOY

A spray casting 7075 alloy with Zn, Mg, Zr,… as dispersoid forming elements has been studied at aging temperature of 120°C. Tensile properties of the alloy at room temperature are higher than that of many high strength aluminum alloys. (Sy = 685 MPa, Su = 698 MPa, after 8hr aging at 120°C). General fatigue behavior (S-N curves) of heat-treated alloy (8hr/120°C) was studied. Endurance limit of the alloy at N = 1.8×106 is 228 Mpa, which is better than that of many traditional aluminum alloys. SEM fractography of fractured fatigue samples showed that the subsurface coarse intermetallic particles are the main source of fatigue crack initiation. Fatigue crack propagation mechanism is dominant transcrystalline mode for low aging temperature and time (8 hr/120°C) but in higher aging temperature regime (3 hr/150°0C) this mechanism changes to intergranular mode.