Mechanism of oxide adherence on Fe-25Cr-4Al (Y or Sc) alloys
Mechanism of oxide adherence on Fe-25Cr-4Al (Y or Sc) alloys
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DOI：
10.1007/bf02643050
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发表时间：
1972-06
期刊：
影响因子：
--
通讯作者：
J. Tien;F. Pettit
中科院分区：
文献类型：
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作者：
J. Tien;F. Pettit
氧化的Fe-25 Cr-4Al合金，一些含有少量的元素（钇或钪），强烈促进氧化物粘附，已受到广泛的结构研究扫描，复制和透射电子显微镜以及其他技术。Al 2 O3鳞片的形态细节，这对这些合金在高温氧化过程中发展，并在氧化物-基材界面的结构变化进行了讨论相对于氧化动力学和氧化物粘附。氧化皮生长到合金中的速率与细晶粒氧化皮的晶界下的氧扩散一致。钇和特别是钪的添加倾向于通过以氧化钇和氧化钪纵梁的形式提供快速扩散路径来增加氧化速率。更重要的是，形态学数据得出的结论是，不粘附的鳞片的spectament是由在氧化物-基体界面处的小空隙的分布。与这一结论一致，发现当不存在空隙时，氧化皮是牢固粘附的，就像钇或钪添加到合金中时的情况一样。据认为，这些合金添加促进氧化物粘附通过形成空位络合物与过量的空位或通过提供内部氧化物边界的多余空位，否则将在氧化物-衬底界面处冷凝，并形成负责氧化物spectrum的空隙的冷凝。空位汇的作用进一步证实，显示氧化物粘附促进Fe-25 Cr-4Al，在没有钇的钪，由分布的Al 2 O3颗粒。这一结果表明，已用于工程合金中用于强化目的的颗粒也可以促进氧化物粘附。形态数据也讨论了其他机制，已提出的氧化物粘附。
Oxidized alloys of Fe-25Cr-4Al, some containing small additions of elements (Yttrium or Scandium) which strongly promote oxide adherence, have been subjected to extensive structural studies by scanning, replication, and transmission electron microscopy as well as other techniques. The morphological details of the Al2O3scales, which develop on these alloys during high temperature oxidation, and the structural changes at the oxide-substrate interfaces are discussed with respect to oxidation kinetics and oxide adherence. The oxide scales grow into the alloys at rates consistent with the diffusion of oxygen down grain boundaries of the fine-grained scales. Yttrium and expecially scandium additions tend to increase oxidation rates by providing rapid diffusion paths in the form of yttria and scandia stringers. More importantly, the morphological data led to the conclusion that the spallation of nonadherent scale is caused by distributions of small voids at the oxide-substrate interface. Consistent with this conclusion, it is found that the oxide scale is tenaciously adherent when voids are absent, as is the case when yttrium or scandium is added to the alloy. It is maintained that these alloy additions promote oxide adherence by forming vacancy complexes with excess vacancies or by providing internal oxide boundaries for the condensation of excess vacancies, which would have otherwise condensed at the oxide-substrate interface and formed the voids responsible for oxide spallation. The role of vacancy sinks is further confirmed by showing that oxide adherence is promoted in Fe-25Cr-4Al, in the absence of yttrium of scandium, by a distribution of Al2O3particles. This result indicates that particles, which have been used in engineering alloys for strengthening purposes, can also promote oxide adherence. The morphological data are also discussed with respect to other mechanisms that had been proposed for oxide adherence.