Estimation on Nodular Corrosion Resistance of LWR Cladding by Magnetic Method

虽然已报道的β相是添加了铁、铬、镍等添加剂的过饱和固溶体，但我们发现，β淬火后的Z-4合金处于超顺磁性状态，其中含有极小的铁磁性金属间化合物析出物，小到几纳米，用通常的方法检测不到。在Zircaloy-2的情况下，相可能是类似于Zircaloy-4的状态，但不能被称为超顺磁性状态，因为负责的析出物是非磁性的。添加Nb的Zircaloy也被发现是由直径约10 nm的铁磁性金属间化合物的析出物引起的超顺磁性状态。金属间化合物为四元系(Zr_&lt；1-x&gt；Nb_x)(Fe_&lt；1-y&gt；Cr_y)_2和(Zr_&lt；1-x&gt；Nb_x)Fe_2和Zr(Fe_&lt；1-x&gt；最后，对经淬火或炉冷等不同条件处理的锆-4合金样品进行了堆外腐蚀试验，温度范围分别为β相和β相+α相。研究发现，处于超顺磁性状态的Zircaloy-4β淬火材料具有抗“球状腐蚀”的腐蚀性能。

Although the beta-phase has been reported to be a supersaturated solid solution with additives, such as iron, chromium, nickel, and so forth, we have found that Zircaloy-4 after beta-quench is in a superparamagnetic state which contains ferromagnetic intermetallic precipitates so small a few nm that they can not be detected by usual methods. In the case of Zircaloy-2, the phase may be a similar state to Zircaloy-4, but can not be called a superparamagnetic state because of the nonmagnetism of the responsible precipitates.Zircaloy with additive of niobium was also found to be in a superparamagnetic state caused by the precipitates with about 10nm in diameter of ferromagnetic intermetallic compounds. The intermetallic compounds are a quaternary (Zr_<1-x>Nb_x) (Fe_<1-y>Cr_y)_2 as well as (Zr_<1-x>Nb_x) Fe_2 and Zr (Fe_<1-x>Cr_x)_2.Finally, the out of pile corrosion test was performed on the samples of Zircaloy-4, which were heat-treated under the various conditions, such as quenching or furnace-cooling from the temperatures in the temperature range of beta-phase and beta-phase plus alpha-phase of Zirconium. It was found that beta-quench materials of Zircaloy-4 which is in the superparamagnetic state have a corrosion resistant property for "nodular corrosion".