Effects Of Heat Treatment On Fatigue Property Of Rolled AZ80 Magnesium Alloy

Magnesium alloy, as structural material, is subjected to cyclic loading action in the process of using, and fatigue failure becomes the main failure form of Magnesium alloy under the long-term cyclic loading action. Only a comprehensive grasp of the fatigue performance data magnesium alloys under different circumstances, can we avoid accidents and get a better theoretical basis for magnesium alloy product design and improvement.In this paper, AZ80 magnesium alloy after different heat treatment, through room temperature mechanical performance test, hardness test, fatigue test, microstructure observation, scanning, spectroscopy and XRD experiments, on the analysis of experimental data and results, we reached the following conclusions:(1) T4 treatment has little effect on the hardness of AZ80 magnesium alloy. Both T5 and T6 treatment can increase the metal hardness values.T6 treatment is particularly significant for improving the hardness values. Compared with the state of rolling, it improves 42%.(2) After T4 treatment, both the tensile strength and yield strength of AZ80 magnesium alloy decreases, but the elongation increases; After T5 and T6 treatment, both the tensile strength and yield strength of alloy increase,the elongation decreases.(3) In the process of fatigue cycles, four states’ AZ80 magnesium alloys have emerged cyclic hardening phenomenon; under the higher strain amplitude conditions, heat treatment can improve the fatigue life of AZ80 magnesium alloy; under the higher strain amplitude conditions, four different states’ AZ80 magnesium alloy will show a significant asymmetry in tension and compression.(4) with obvious cracks observed from fatigue specimens’ surface, the direction of the cracks and axial tension and compression is perpendicular to each other; fatigue cracks are produced on the fatigue specimens’ surface, and there are multiple crack sources; the fatigue cracks extend with transgranular manner, and fatigue fractures show a significant cleavage fracture characteristics where the presence of secondary cracks can be seen; fatigue strips are obvious fatigue brittle strips.(5) Magnesium alloys of the heat treatment will have a dissolution and precipitation of the second phases. Through the analysis of XRD, in the AZ80 magnesium alloy, the second phases are mainly Al12Mg17, remaining small amount of AlMn, Mg0.97Zn0.03, and MgAlZn. The morphologies of second phases are elongated morphology, box-shaped, round, oval, and relatively small needle-like shape.