Microscopic characterization on low cycle fatigue behavior at room temperature of Zircaloy-4 alloy with recrystallized microstructure

Low cycle fatigue (LCF) tests, with the total strain amplitude (Delta epsilon t/2) in the range of +/- (0.5-3.0%), were employed at room temperature on Zircaloy-4 (Zr-4) alloy with recrystallized microstructure, aiming to investigate its fatigue life, fatigue crack initiation and propagation mechanisms. Results indicated that the fatigue behavior of Zr-4 alloy followed Coffin-Mason relation with fatigue ductility exponent of 0.2426. Fractographic investigation of all mechanically tested specimens revealed that the fatigue specimen surface is the preferential crack initiation place. SEM observation on the crack propagation regions of fatigue specimens showed that a large number of fatigue striations distributed in the crack propagation regions. Further detailed investigation revealed that micro-crack growth rates can be quantitatively evaluated in terms of strain amplitude. (C) 2018 Elsevier B.V. All rights reserved.