Fatigue deformation mechanism of weakly textured Zircaloy-4 alloy

Cyclic softening during fatigue, under a total strain range of less than 1.6%, was observed in an annealed Zircaloy-4 alloy with a weak texture. The experimental results showed that the rotation of grains oriented favorably for easy slip on a prism plane results in cyclic softening due to decreasing friction stress as cumulative plastic strain increases. In the later stage of fatigue, the second and third prism slip systems are also activated, increasing the density of dislocations and jogged dislocations, causing an increase in back stress. A mechanistic model of grain rotation during fatigue is proposed.