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在Zr-0.7Sn-1.07Nb-0.32Fe-0.08Cr(T5)合金中添加不同含量Bi制备成T5+x Bi(x=0.1,0.3,0.5,质量分数,%)合金,用静态高压釜腐蚀试验研究了T5+x Bi合金在400℃/10.3 MPa过热蒸汽中的耐腐蚀性能。用TEM和SEM分别观察了合金的显微组织和氧化膜断口形貌。结果表明:当添加的Bi含量?0.3%时,合金中只检测到了密排六方结构的Zr(Nb,Fe,Cr)2第二相;当Bi含量达到0.5%时,合金中除了析出大量的Zr(Nb,Fe,Cr)2第二相外,还发现少量正交结构的Zr Bi2型Zr(Bi,Fe,Sn)2和结构未确定的Zr-Nb-Bi-Fe-Cr-Sn第二相。这说明Bi在T5+x Bi合金中固溶在α-Zr基体中的最大含量(CBi)为:0.3%?CBi?0.5%(质量分数);Bi的添加促进了T5合金中原来固溶在α-Zr基体中的Sn以第二相形式析出。当添加的Bi含量?0.3%时,耐腐蚀性能得到一定程度的改善,而添加0.5%Bi后耐腐蚀性能反而降低。结合显微组织分析结果可以说明:固溶在α-Zr基体中的Bi可改善合金的耐腐蚀性能,而合金中析出含Bi和Sn的第二相后又会降低合金的耐腐蚀性能。
T5 + x Bi (x = 0.1, 0.3, 0.5, mass fraction,%) alloys were prepared by adding different amounts of Bi to Zr-0.7Sn-1.07Nb-0.32Fe-0.08Cr (T5) The corrosion resistance of T5 + x Bi alloy in 400 ℃ / 10.3 MPa superheated steam was studied. TEM and SEM were used to observe the microstructure and oxide film fracture morphology. The results show that only Zr (Nb, Fe, Cr) 2 second phase with hexagonal close packed hexagonal structure is detected when Bi content is added to 0.3%. When Bi content reaches 0.5% Zr (Nb, Fe, Cr) 2 and Zr-Nb-Bi-Fe-Cr-Sn Two-phase. This shows that the maximum content of Bi in the T5 + x Bi alloy solution in the α-Zr matrix (CBi) is: 0.3% · CBi · 0.5% (mass fraction); the addition of Bi promotes the original solution of T5 alloy in Sn in the α-Zr matrix precipitates in the second phase. When the content of Bi added is 0.3%, the corrosion resistance can be improved to a certain degree, but the corrosion resistance decreases with the addition of 0.5% Bi. Combining with the results of microstructure analysis, it can be concluded that the Bi dissolved in the α-Zr matrix can improve the corrosion resistance of the alloy, while the precipitation of the second phase containing Bi and Sn in the alloy will reduce the corrosion resistance of the alloy.