摘要:
从电子层面系统研究Fe-Cr-Al合金氧化膜的形成机理,杂质硫对氧化膜黏附性的影响,稀土元素在改善氧化膜黏附性方面的作用,揭示合金氧化的物理本质.研究表明氧使Al在合金表层的环境敏感镶嵌能最低,促使Al原子从合金内部向合金表面扩散,最终在合金表面偏聚.由于氧与Al间的亲和力较大,氧原子易与Al结合生成Al_2O_3保护膜.杂质S在基体/氧化膜界面的环境敏感镶嵌能较低,可通过扩散偏聚在基体/氧化膜界面,削弱氧化膜与合金基体的结合力.当合金中加入Y后,Y易与S结合形成稳定的硫化物,阻碍S向基体/氧化膜界面的偏聚,显著提高氧化膜的黏附性,提高合金抗高温氧化能力.
Abstract:
The formation mechanism of the oxide film on Fe-Cr-Al aHoy, the effects of sulfur on the adhesion of the oxide film, and the role of RE element Y on the improvement of the oxide film adhesion were systematically studied on an electronic level, so that the physical nature of oxidation of the alloy was revealed. The results show that Al atom (compared with Cr or Fe atom) has the lowest environment-sensitive embedding energy when O atoms are present on the ahoy surface, thus leading to an outward diffusion of Al atoms from the interior of the alloy, and hence to the segregation of Al atoms on the ahoy surface. Oxygen atoms are easy to combine with Al atoms to form Al_2O_3 oxide films on the alloy surface due to its high affinity with Al atoms. The impurity S has a lower environment-sensitive embedding energy on the interface between the Al_2O_3 oxide film and the ahoy matrix than within the alloy matrix, suggesting that S can diffuse (segregate) to the interface. S atoms segregated on the interface weakens the cohesion of Al_2O_3 oxide film with the ahoy matrix. Y is easy to combine with sulfur to form a stable sulfide within the interior of the ahoy matrix, which inhibits the diffusion of sttffur to the Al_2O_3 oxide film/matrix interface. Y added into the ahoy can thus markedly increase the adhesion of the oxide film with the alloy matrix, and significantly improve the high-temperature oxidation resistance of the alloy.
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