Investigation of fatigue properties of zinc-aluminium based alloys

SUMMARY Investigation of Fatigue Properties of Zinc-Aluminum Based Alloys A series of ternary zinc-aluminum-copper and a quaternary zinc-aluminum-copper- silicon alloys were produced by permanent mould casting. Fatigue properties of these alloys were examined using a rotating beam fatigue testing apparatus which was designed and constructed for this work. As a result of this work, stress-number of cycles (S-N) curves or Wohler diagrams of these alloys were obtained. Fracture surfaces of the test samples were examined using both optical and scanning electron microscope (SEM). The S-N curves of these alloys found to be similar to each other showed an arrangement according to their strength values. For this reason, the fatigue life of these alloys were found to be increased with increasing aluminum content. Among the zinc- aluminum based alloys examined, the longest fatigue life was obtained from the ZnA140Cu2Sil alloy, which has the highest strength value, and the lowest fatigue life was obtained from the ZA-27 alloy which has the lowest tensile strength. It was also found that the fracture surfaces of zinc-aluminum based alloys obtained after fatigue testing, showed typical fatigue fracture surface characteristics and these alloys in general exhibited brittle fracture behaviour. The fatigue strength of zinc-aluminum based alloys was found to be higher than that of AlCu4Sil alloy, but CuZn20 brass exhibited superior fatigue behaviour than the zinc- aluminum based alloys. Key Words : Zinc-aluminum based alloys, fatigue strength, fatigue life and S-N diagrams. VI