Effect of the Microstructure on the Corrosion Resistance of Zr-Sn-Nb Alloy
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摘要: 将两种Zr-Sn-Nb合金样品分别进行1000℃-0.5 h、1000℃-0.5 h/560℃-10 h、1000℃-0.5 h/冷轧/560℃-10 h和750℃-0.5 h、750℃-0.5 h/560℃-10 h、750℃-0.5 h/冷轧/560℃-10 h的不同处理后,研究它们的显微组织和在350℃、16.8 MPa、0.04 mol·L~(-1)LiOH水溶液中的耐腐蚀性能。结果表明:在所采用的上述变形及热处理条件中,以750℃-0.5 h/冷轧/560℃-10 h处理后样品的耐腐蚀性能最好。其原因在于:经此处理后,基体αZr中固溶的Nb含量较低,βZr分解后获得了细小尺寸分布的βNb(含Fe)第二相粒子,后者对改善耐腐蚀性能尤为重要。但当合金中含有Cr时,因Cr和Fe首先与Zr形成Zr(FeCr)_2第二相,减少了βNb粒子中的Fe含量,而使耐腐蚀性能变坏。样品在最终560℃加热处理之前的冷轧变形可促进βZr分解时的形核,是获得细小尺寸βNb的必要措施。
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关键词:
- Zr-Sn-Nb合金 ,
- 耐腐蚀性能 ,
- 第二相 ,
- 显微组织
Abstract: The specimens of Zr-Sn-Nb alloy with two different composition were treated in different ways as 1 000 ℃-0. 5 h, 1 000℃-0. 5 h/560 ℃-10 h, 1 000 ℃-0. 5 h/C. R. (cold rolling)/560 ℃-10 h and 750 ℃-0. 5 h, 750 ℃-0. 5 h/560 ℃-10 h, 750℃-0. 5 h/ C. R. /560 ℃-10 h, respectively. Their microstructures were examined by transmission electron microscopy (TEM), and the corrosion resistance was investigated with autoclave tests in 0. 04 mol · L-1 LiOH aqueous solution at 350 ℃, 16. 8 MPa. It shows that the corrosion resistance of specimens treated by 750 ℃-0. 5 h/C. R. /560 ℃-10 h is the best among all specimens treated in different ways in present study. A lower niobium concentration in solid solution in αZr matrix and a uniform distribution of fine αNb (containing iron) particles are important factors for improving the corrosion resistance significantly, especially, the later one is more important. Chromium, if it is contained in the alloy, will go with iron to form Zr(FeCr)2 second phase particles at first, then the cor- rosion resistance decreases due to the depletion of iron in the βNb fine particles. The cold deformation before the final annealing at 560℃ plays an important role in obtaining fine βNb particles because which can promote the nucleation during the *Zr decomposition.-
Keywords:
- Zr-Sn-Nb alloy ,
- corrosion resistance ,
- secondary phase ,
- microstructure
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