| The corrosion and microstructural characteristics with heat treatment of Zircaloy-4 alloy were investigated for the specimens heated in the temperature range of α, α+β and β. The microstructures of specimens heated in the α, α+β and β range showed the equiaxed α, the mixed type of equiaxed and widmansta¨tten structure, and widmanstatten structrue, respectively. As the annealing temperature increased, the volume fraction and size of precipitates decreased. Mini autoclave tests were carried out at steam temperature of 500℃ and steam pressure of 1500psi to investigate the effect of annealing temperature and annealing time on the corrosion resistance of Zircaloy-4 alloy. It was observed that the corrosion resistance of β-heat treated specimen was higher than that of α-heat treated specimen. From combining the present results with other works, it is suggested that the nodular corrosion occur in the local region where alloying elements are depleted. |
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