Diagrama de fases experimental Fe-Sn-Zr. Nuevos resultados del corte isotérmico de 800 °C

ABSTRACT The Zr-based alloys are extensively applied in the field of nuclear technology. Alloyed with Sn and Fe, Zr is the main element in the zircaloy-type alloys, currently vastly used as structural elements and as containers of burnable elements in nuclear reactors. This ternary metallurgical system is also a component of more recently developed alloys such as Zirlo (USA). Although Zr is a major component in all of them, it is most important to know the phase diagrams of their components as best as possible. The Fe-Sn-Zr phase diagram has been systematically studied by our research team for many years. Considerable advancement has been made in the design of the phase diagram at 800°C, however, some regions in the Gibbs triangle are still unsolved. In order to evaluate these regions experimentally, a ternary alloy set was designed and prepared. These alloys were thermally treated at the chosen temperature for 2928 hours, and characterized by applying metallography techniques, X-ray diffraction and microanalysis. The presence of Y and Fe6Sn6Zr was confirmed, the presence of phase X” was verified, and 2- and 3-phase existence fields were determined. Finally, phase balance boundaries in the regions under study were traced, completing, to a great extent, the phase diagram for the isothermal cut analysed.

摘要 锆基合金在核技术领域应用广泛。以锆为主要组分、添加锡（Sn）与铁（Fe）合金化得到的锆锡合金（zircaloy-type alloys），是当前应用最为广泛的锆基合金体系，主要用作核反应堆的结构构件以及可燃毒物元件的封装容器。该三元冶金体系同时也是近年开发的Zirlo（美国）等新型合金的组成部分。尽管锆是所有此类合金的主要组分，但尽可能精准地掌握各组分的相图仍具有至关重要的意义。本研究团队多年来系统开展了Fe-Sn-Zr三元相图的研究工作，在800℃下的相图构建方面已取得显著进展，但吉布斯三角形（Gibbs triangle）内的部分区域仍未明确。为通过实验表征这些未明确区域，我们设计并制备了一组三元合金试样。将上述合金在选定温度下热处理2928小时后，采用金相技术、X射线衍射（X-ray diffraction）与微区分析手段对其进行了表征。实验确认了Y相以及Fe₆Sn₆Zr金属间化合物的存在，验证了X''相的存在，并确定了二相与三相共存区。最终，绘制了所研究区域的相平衡边界，在很大程度上完善了本次分析的等温截面相图。