Fatigue behavior of Magnox AL80 and irradiation effect on fatigue properties

Bending fatigue tests were carried out at room temperature on Magnox AL80 of different grain size specimens as well as on welded specimens. Also, the structure of the surface of the fatigue fractured specimens was examined. The fatigue strength of the fine-grained specimens was much larger than that of the coarse-grained. The fatigue behavior of the welded specimens was not appreciably different from that of the fine-grained specimens, although the S-N curves for these specimens were slightly different. In the fine-grained specimens, the fatigue cracks nucleated in the slip striations within the grains and propagated intergranularly for the most part. In the coarse-grained specimens the cracks propagated along slip bands within the grains or along the grain boundaries. The irradiation effect on the fatigue properties of Magnox AL80 was also investigated. The fatigue resistance of the fine-grained specimens, including the welded specimens, was lowered by irradiation to an exposure of 1 × 10¹⁷nvt when tested at high stress levels; conversely, that of coarse-grained specimens was raised. (author)