Mechanical Property And Corrosion Resistance Of Zr-702

Zirconium and zirconium alloys have been widely applied in the nuclear power and chemical industry due to lots of good characterizations,such as moderately comprehensive mechanical properties,low neutron absorption cross-section,excellent corrosion resistance against high temperature water,high thermal conductivity and suitable hydrogen absorption kinetics,etc.This paper focused on the basic mechanical property and corrosion resistance of commercial purity zirconium Zr-702 sheet,which is of theoretical significance and industrialized application value.The mechanical tests consisted of uniaxial tests and biaxial tests.The uniaxial tests included monotonic tensile and cyclic tensile tests.Biaxial tension with stress ratio of 1:1 or 2:1 was conducted on the cruciforms with different initial basal texture intensity.The electron backscattered diffraction(ebsd)was employed to indicate the deformation mechanisms of specimens under uniaxial and biaxial tension.Scanning Electron Microscope(SEM)was applied to analyze the fatigue fracture.The experimental results show that Zr-702 sheet with strong basal texture,when tensioned along rolling or transverse direction,the tensile strength showed slight difference.The deformation mechanisms of the slip lines on the uniaxial tensile specimen were determined by calculating the Schmidt factor and contrasting the critical resolved shear stress for each deformation mechanism.It indicates that there was little twinning when the specimen was monotonically tensioned,and prismatic slip dominated the deformation mechanism.After biaxial tension,the texture intensity of the specimen with a strong basal texture was weakened significantly and no twins came out,there existed an obvious preferred orientation for the prismatic plane,dislocation dominated the deformation mechanism.However,there came up a lot of twins after biaxial tension on the specimen with weaker basal texture and twinning was the dominant deformation mechanism.Cyclic testing result shows that larger stress amplitude induced pronounced ratcheting strain accumulation.The cyclic fracture embodied the ductile characteristic.This paper combined the monotonic tension with online corrosion.As-received,hydrided and annealed specimens were used to perform the tests.Lithium hydroxide solution was employed as the corrosive solution as it is the main component of the PWR coolant.Monotonic tension was performed both in air and under online-corrosion.Ultra-field-depth 3-D microscopic system was employed to measure the morphology and size of the corrosion pits and hydirde morphology.The SEM was applied to analyze the monotonic tensile fracture of non-hydirded and hydrided specimens.EBSD was utilized to define the deformation mechanism for hydirded specimen.Electro chemical technique was used to contrast the electrochemical corrosion resistance of three kinds of samples.The main conclusions are obtained that the strength slightly increased and the plasticity decreased after hydrided,tensile fracture of specimens transformed from ductile fracture to ductile-brittle fracture,and hydriding aggravated the corrosion.The strength and plasticity declined significantly when tensioned in the corrosive solution compared with that tested in air.However,Zr-702 holds high corrosion resistance generally.