Fe+Cr及Si含量对Zr-4合金耐腐蚀性能的影响

Effect of Fe+Cr and Si Contents on Corrosion Resistance of Zircaloy-4

为了优化国产Zr-4合金的耐腐蚀性能,在420℃、10.3 MPa的高温高压水蒸气加速腐蚀条件下,研究了合金元素Fe+Cr以及杂质元素Si对国产Zr-4合金耐腐蚀性能的影响。结果表明:在美国材料实验学会(ASTM)规定的Fe+Cr含量范围内(0.28 wt%~0.37 wt%,wt%表示质量分数),Fe+Cr含量越高,析出的第二相数目越多、尺寸越大,越有利于材料耐腐蚀性能提升。在420℃水蒸气中腐蚀126 d后,当Fe+Cr含量从0.28 wt%增加到0.37 wt%时,Zr-4合金的腐蚀增重降低约30%。Zr-4合金在1100℃淬火时,当Si含量低至10 mg/kg时,形成粗大的平行板条结构;而增加Si含量到100 mg/kg后,析出的细小Zr_(3)Si为α相提供形核位置,使得组织中出现网篮结构和细小的平行板条结构。网篮结构能促使组织中第二相分布更均匀弥散,因此,高Si含量的Zr-4合金表现出更优良的耐腐蚀性能。

In order to optimize the corrosion resistance of domestic Zr-4 alloy,the effects of alloying element Fe+Cr and impurity element Si on the corrosion resistance of domestic Zr-4 alloy were studied under the accelerated corrosion condition of high temperature and high pressure steam at 420℃and 10.3 MPa.The results show that within the range of Fe+Cr content specified by ASTM(0.28 wt%-0.37 wt%,with wt%representing mass percentage),the higher the Fe+Cr content,the larger the number and size of the precipitated second phases,which is beneficial to the improvement of the corrosion resistance of the material.When the content of Fe+Cr increases from 0.28 wt%to 0.37 wt%,the corrosion weight gain of Zr-4 alloy decreases by about 30%after 126 d of corrosion in steam at 420℃.When the Si content of Zr-4 alloy is as low as 10 mg/kg during quenching at 1100℃,the coarse parallel-plate structure is formed.When the Si content is increased to 100 mg/kg,the precipitated fine Zr_(3)Si provides nucleation sites forαphase,which leads to the appearance of basketweave structure and fine parallel-plate structure in the microstructure.The basketweave structure can promote the distribution of the second phase in the structure to be more uniform and diffuse,so the Zr-4 alloy with high Si content shows better corrosion resistance.