Effect of Annealing Temperature on the Corrosion Resistance of Zirconium Alloy
The effect of annealing temperature on the microstructure and second-phase particles of cold-rolled industrial zirconium alloy plate was studied by means of annealing microstructure and second-phase particle observation,electrochemical corrosion test and corrosion morphology analysis.It is found that the microstructure of the plate after annealing at 470℃is mainly deformed microstructure,and its electro-chemical corrosion resistance is the worst.After annealing at 500℃and above,a completely recrystallized microstructure is formed in the plate,where the number and size of second-phase particles have a signifi-cant influence on the corrosion resistance of zirconium alloy in nitric acid medium.At the annealing temper-ature of 500℃,the number and size of second-phase particles precipitated from zirconium alloy are small.At the annealing temperature of 550℃,the number and size of second-phase particles in the alloy increa-ses.When the annealing temperature rises to 600℃,the number of second-phase particles in the alloy changes little,but the size coarsens obviously.The sample annealed at 600℃has low self-corrosion poten-tial Ecorr,its passivation film is repeatedly broken down and repaired,and there are the most corrosion pits with relatively large size on the surface of the sample.Coarse second-phase particles are preferentially cor-roded in nitric acid medium,so it is necessary to control the low annealing temperature while the formation of completely recrystallized microstructure is ensured,to obtain fine second-phase particles and then im-prove the corrosion resistance of zirconium alloy in nitric acid.In this experiment,the zirconium alloy sam-ple annealed at 500℃has fine second-phase particles with small number and the best corrosion resistance.
zirconium alloysecond-phase particleelectrochemical corrosionpolarization curvecorrosion morphologyannealing temperature
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