Abstract:In this paper, the fatigue properties of Zr705 alloy in original state and ultrasonic rolling state after pre-corrosion in 1mol/L LiOH solution, 3.5% NaCl solution and 5% HCl solution for 30 days were studied. The results show that the corrosion degree of the original Zr705 alloy is the most serious in 3.5% NaCl solution, followed by 5% HCl solution and the least in 1mol/L LiOH solution. This is related to the different corrosion mechanism of Zr705 alloy in different media: when Zr705 alloy is in LiOH solution, mainly O2- and OH- participate in the corrosion reaction, while Li+ does not participate in the corrosion reaction, but is adsorbed on the pore wall of oxide film and the grain boundary of ZrO2 to accelerate the corrosion; When Zr705 alloy is in NaCl solution, a large amount of Cl- plays a leading role in the corrosion reaction. When Zr705 alloy is in HCl solution, both H+ and Cl- participate in the corrosion process of Zr705 alloy in HCl solution. USRP-Zr705 alloy is more easily corroded than the original Zr705 alloy because of the high density dislocation defects in the surface gradient structure. After immersion corrosion treatment, the fatigue life of the original Zr705 alloy decreased obviously, which was mainly caused by corrosion damage on the surface of the sample during immersion corrosion. After immersion corrosion treatment, the fatigue life of USRP-Zr705 sample in 1mol/L LiOH solution is higher than that of the original Zr705 alloy, but it is lower in 3.5% NaCl solution and 5% HCl solution. There is a competitive relationship between the corrosion environment and the surface gradient structure on the fatigue properties of zirconium alloys: when the corrosion medium is weak, the surface gradient structure is the main factor affecting the fatigue properties of zirconium alloys. When the corrosive medium is strong, the surface gradient structure is still the main factor affecting the fatigue properties of the alloy under high stress cyclic loading. Under low stress cyclic loading, corrosion environment is the main factor affecting the fatigue properties of the alloy.