HIGH TEMPERATURE CYCLIC DEFORMATION BEHAVIOR OF AN ADVANCED AUSTENITIC STAINLESS STEEL (ALLOY 709)

摘要

Advanced structural materials are needed to improvethe efficiency, safety and reliability of next-generationnuclear reactors. Preliminary investigation onmechanical properties of a Fe-25wt.%Ni-20Cr austeniticstainless steel (Alloy 709) suggests it might be a potentialcandidate for Sodium-Cooled Fast Reactor. Hightemperature cyclic deformation behavior includingfatigue and creep-fatigue for the Alloy 709 is consideredfor design and safety purposes. Strain-controlled lowcyclefatigue tests were performed at strain amplitudesranging from 0.15% to 0.6% at 750°C in air followingASTM standard E2714–13, with a constant strain rate of2 × 10~(-3) s~(-1). In addition, different hold times of 1, 10, 30and 60 minutes were introduced at the maximum tensilestrain to investigate the effect of the creep damage on thefatigue-life at strain amplitude of 0.5% at 750 °C, while30 and 60 minutes were introduced at the maximumtensile strain at strain amplitude of 0.3% at 750 °C.During continuous cyclic loading, fatigue life is found todecrease with increase in strain amplitude, while thecreep-fatigue life is found to decrease with increasinghold time indicating rapid initiation and propagation ofcracks. The fractographs of the deformed samples arepresented and discussed.