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Creep Behaviors of Stress-Relieved and Annealed Zr-1Nb-0.7Sn-0.1Fe Nuclear Cladding Tubes at Intermediate Temperatures

In order to explore the possibility of enhanced creep resistance by grain size control, creep tests of stress-relieved and annealed Zr-1Nb-0.7Sn-0.1Fe cladding tubes were carried out at intermediate temperatures. The creep rate decreased significantly with increase of grain size from ~1.2 μm to 4 μm with annealing. The stress exponent was observed to be in the range of 5.0~6.5 for both stress-relieved and annealed Zr-1Nb-0.7Sn- 0.1Fe, suggesting that the dislocation climb is the rate controlling creep mechanism. It was shown that not only the creep rate decreased but also creep life increased in the annealed Zr-1Nb-0.7Sn-0.1Fe, suggesting the grain size control may provide an effective way to enhance the creep resistance in Zr alloys for nuclear application.