Fe-RE(Y、La和Ce)合金中相稳定性和固溶度的第一性原理研究

First-principles study of phase stability and solubility in Fe-RE (Y, La and Ce) alloys

摘要:

合金元素的固溶度对于新型合金的设计和合金动力学过程的研究具有重要的作用。本文利用密度泛函理论,计算了Fe-RE二元化合物的基态,确定了Fe-Y和Fe-Ce体系的稳态和亚稳态结构。计算结果表明,Fe-Y的稳定结构为Fe₁₂Y.tI26、Fe₁₇Y₂.hP38和Fe₂Y.cF24,Fe-Ce的稳定结构为Fe₁₇Ce₂.hP38、Fe₁₉Ce₅.hR24和Fe₂Ce.cF24。基于稀格子气统计热力学理论,利用第一性原理计算得到了稀土元素在α-Fe中随温度变化的固溶度曲线。结果显示,稀土Y、La和Ce元素在α-Fe中的固溶度为S_La>S_Ce>S_Y,这一趋势对应于三者在α-Fe中的溶解形成焓关系H_sol(La)< H_sol(Ce)< H_sol(Y).

关键词:固溶度; Fe-RE; 稳定结构; 第一性原理

Abstract:

The solubility limit of elements plays a crucial role in alloy designing, as well as in the understanding of kinetic processes in alloys. Using first-principles calculations, we calculated the ground states of Fe-RE compound, and predicted the stable and metastable structures of Fe-Y and Fe-Ce. The results indicate that the stable structures for Fe-Y compounds are Fe₁₂Y.tI26, Fe₁₇Y₂.hP38 and Fe₂Y.cF24, and those for Fe-Ce binary are Fe₁₇Ce₂.hP38, Fe₁₉Ce₅.hR24 and Fe₂Ce.cF24. Based on the statistical-thermodynamic theory of dilute lattice gas, we presented a systematic series of calculations of the solubility limits of RE in α-Fe as a function of temperature. It is found that the solubilities are sorted in the following order: S_La>S_Ce>S_Y, correspond to the trend in the solubility formation enthalpies: H_sol(La)< H_sol(Ce)< H_sol(Y).

Key words:solubility; Fe-RE; Stable structure; First-principles