SEDL / STP / STP1023-EB / STP18883S

Magnetic Study of Zircaloy

Miyake, C
Associate professor and Master of Engineering candidate, Faculty of Engineering, Osaka University, Osaka,

Takamiya, T
Associate professor and Master of Engineering candidate, Faculty of Engineering, Osaka University, Osaka,

Pages: 11    Published: Jan 1989

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Abstract

Although the β-phase has been reported to be a supersaturated solid solution with a small amount of elements, such as iron, chromium, nickel, and so forth, it was found that the phase of Zircaloy-4 after heat treatments above 830°C quenching and 1030°C annealing is in a superparamagnetic state which contains particles of Zr(Fe^1-xCr^x)² so small (10 to 20 Å) that they can not be detected by usual methods. The β-phase of Zircaloy-2 may be in a similar state to Zircaloy-4 but can not be called a superparamagnetic state because of nonmagnetism of responsible precipitates. In order to give a deeper understanding of “nodular corrosion,” magnetic measurements of susceptibility and magnetization were carried out on Zircaloy-2 and -4 before and after heat treatments at 0.1 to 1 T from temperature of liquid nitrogen to room temperature. Magnetization curves at temperature of liquid nitrogen for Zircaloy-4 correspond closely to the calculated Langevin function. After heat treatments above 900°C, magnetization for Zircaloy-4 increases more than three times. This means that the amount of small particles of ferromagnetic precipitates is increased by heat treatments.