Effect Of Rolling Process On Electrochemical Corrosion Behavior Of Zirconium Alloys

Zirconium alloy(Zr)is widely used as fuel cladding material for light water reactors and boiling water reactors.In recent years,the severity of nuclear reactor accident has been concerned by the society.At the same time,because nuclear reactors need higher fuel consumption and longer life,higher requirements are put forward for material properties related to nuclear field.Zirconium alloy material is used as reactor safeguard line and radiation barrier,and its performance is always the research focus in this field.At present,the research of zirconium alloy materials mainly focuses on the influence of alloy composition and deformation rate of hot and cold rolling on microstructure and properties.The effect of rolling direction on microstructure change and corrosion resistance of zirconium alloy is still lacking.In this paper,two Zr-Sn-Nb alloys with different composition ratios are used as experimental materials,the alloy plates required for the experiment are prepared by high vacuum arc melting system,ultra-high temperature box-type electric furnace and double-roll mill.The prepared alloy sheet is in the hot rolled fully annealed state.Then,cold rolling in the Rolling direction,cross cold rolling and cold rolling in the Transverse direction were applied through the double-roll mill.Finally,the cold-rolled sample was vacuum recrystallization annealed in a box-type electric furnace.As a result,the cold rolling and cross cold rolling in different directions samples are obtained.After being kept at 700℃ for 30 min in a box-type electric furnace,hot rolling in Rolling direction,cross hot rolling and hot rolling in Transverse direction were used in a twin-roll mill to obtain hot rolling and cross hot rolling samples in different directions.The microstructures of the hot and cold rolled samples obtained by rolling in different directions were characterized and analyzed by means of X-ray diffractometer,Micro hardness tester,Electron backscatter diffractometer and other characterization techniques.After that,the electrochemical corrosion behavior of the sample was experimentally analyzed with the help of an Electrochemical workstation,and the resistance of zirconium alloy sheets rolled in different directions at room temperature and high temperature was discussed and analyzed by Tafel curve and impedance spectroscopy.Scanning electron microscopy was used to magnify the surface morphology after electrochemical corrosion and analyze the corrosion products.The elements of the corroded surface were analyzed by energy dispersive spectrometer.The results show that cross cold rolling can weaken the texture orientation of zirconium alloy sheet,with random orientation distribution and fine grain distribution.For cold rolling,cross cold rolling has the best corrosion resistance.Taking zirconium B as an example,the corrosion rate of cross cold rolling is 11 times less than that of Rolling direction and 43 times less than that of Transverse direction.The corrosion process of cold rolling along Transverse direction produces thick oxide film,poor surface finish and worst corrosion resistance.For hot rolling,the texture orientation of cross hot rolling and Transverse direction hot rolling is weakened,the C axis of <0001> base plane deviates from the ND direction,the orientation distribution is random,the grain size is small,and the fine grains are scattered.The dynamic recrystallization degree of cross rolling is high and the deformation matrix is dispersed and refined,and the recrystallization degree exceeds 80%.The hot rolling along Rolling direction is mainly deformed matrix,and the deformed microstructure is more than 60%.The corrosion resistance of cross hot rolling is the best.Taking zirconium alloy B as an example,the corrosion rate of cross hot rolling is 10 times smaller than that of hot rolling along Rolling direction and 4.8 times smaller than that of hot rolling along Transverse direction.In this paper,some rules which have theoretical guiding significance for improving production and processing technology of zirconium alloy are obtained.