Sn含量对Zr-Sn-0.2Fe-0.1Cr合金高温蒸汽氧化行为的影响

Effect of Sn Content on High Temperature Steam Oxidation Behavior of Zr-Sn-0.2Fe-0.1Cr Alloys

摘要:

锆合金的高温蒸汽氧化行为是失水事故下需要重点关注的问题之一。为了研究Sn对锆合金高温蒸汽氧化行为的影响，开展了不同Sn含量的SH12(Zr-0.75Sn-0.2Fe-0.1Cr，wt.%)和Zr-4(Zr-1.5Sn-0.2Fe-0.1Cr)合金在模拟失水事故工况下1000，1050，1100和1200 ℃的高温蒸汽氧化试验。采用光学显微镜、电子探针、显微硬度计分析了氧化样品的显微组织以及氧化前后样品的显微硬度。结果表明：低Sn的SH12比高Sn的Zr-4合金的抗高温蒸汽氧化性能更好，这说明降低Sn含量可以改善锆合金的抗高温蒸汽氧化性能。氧化前，SH12合金的显微硬度低于Zr-4合金，而氧化后SH12合金基体的显微硬度明显高于Zr-4合金，与氧化后SH12合金基体中的氧含量高于Zr-4合金的结果相吻合，这说明Sn有抑制氧在Zr基体中扩散的作用。通过第一性原理计算，发现Sn容易与O结合，从而抑制了O在锆基体中的扩散，这合理解释了氧化后SH12合金中的氧含量比Zr-4合金高的原因。

Abstract:

The high-temperature steam oxidation behavior of zirconium alloys is one of the issues that need to be focused on under loss of coolant accident (LOCA). To study the effect of Sn on the high-temperature steam oxidation behavior of zirconium alloys, SH12(Zr-0.75Sn-0.2Fe-0.1Cr, wt.%) and Zr-4(Zr-1.5Sn-0.2Fe-0.1Cr) alloys with different Sn contents were used for high-temperature steam oxidation tests at 1000, 1050, 1100 and 1200 ℃, under simulated LOCA conditions. The microstructure of the oxidized samples and the microhardness of the samples before and after oxidation were analyzed by optical microscope, electron probe microanalyzer, and microhardness tester. The results show that SH12 with low Sn content has better oxidation resistance to high-temperature steam than Zr-4 alloy with high Sn. This indicates that reducing the Sn content can improve the oxidation resistance to high temperature steam of zirconium alloys. Before oxidation, the microhardness of the SH12 alloy is lower than that of the Zr-4 alloy, while after oxidation the microhardness of the SH12 alloy matrix is significantly higher than that of the Zr-4 alloy, which is consistent with the result that the oxygen content in the matrix of the SH12 alloy is higher than that of the Zr-4 alloy after oxidation. This indicates that Sn has the effect of inhibiting the diffusion of oxygen in the Zr matrix. Through first-principles calculations, it is found that Sn is easily combined with O, thereby inhibiting O diffusion in the zirconium matrix, which reasonably explains the higher oxygen content in the oxidized SH12 alloy compared to the Zr-4 alloy.