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arXiv 1910.09660cond-mat.mtrl-scicond-mat.stat-mech
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第一性原理集团变分法研究X-Al-Ti(X:Fe,Co,Ni)合金中B2和L21有序相的形成

Origin of the Phase Separation into B2 and L21 Ordered Phases in the X-Al-Ti (X: Fe, Co, and Ni) Alloys from the First-principles Cluster Variation Method

Ryo Yamada, Tetsuo Mohri

摘要:

采用团簇变分法(CVM)分析了X-Al-Ti(X:Fe,Co,Ni)合金中从单一B2有序相到B2和L2 $_1$两个有序相的相分离行为,并从能带结构计算得到了相互作用能。对X-$_2$-Al-$_{2-x}$-Ti-$_x$($0 \leq x \leq 2$)合金采用了CVM的立方近似,限制了X原子固定在$γ$ -亚晶格上的L2 $_1$有序结构的$α$ -和$β$ -亚晶格上的Al和Ti原子之间的交换.研究了B2和L2 $_1$结构的相稳定性,并确定了赝二元区XAl-XTi的相图。B2和L2 $_1$相的两相区域,即相分离行为,成功地产生在Co和Ni-Al-Ti合金系统,而没有相分离预测在Fe-Al-Ti合金。Co-和Ni-Al-Ti合金中相分离的起源分别归因于机械不稳定性和机械不稳定性与不同对的化学排斥的组合。

英文摘要:

The phase separation behaviors from the single B2 ordered phase into the two separate B2 and L2$_1$ ordered phases in the X-Al-Ti (X: Fe, Co, and Ni) alloys are analyzed using the cluster variation method (CVM) with the interaction energies evaluated from the electronic band structure calculations. The cubic approximation of the CVM is employed for the X$_2$Al$_{2-x}$Ti$_x$ ($0 \leq x \leq 2$) alloys limiting an interchange between Al and Ti atoms on the $α$- and $β$-sublattices of the L2$_1$ ordered structure with the X atoms fixed on the $γ$-sublattice. The phase stabilities of the B2 and L2$_1$ structures are examined, and the phase diagrams at the pseudo-binary section, XAl-XTi, are determined. The two-phase regions of B2 and L2$_1$ phases, i.e., phase separation behavior, are successfully produced in both Co- and Ni-Al-Ti alloy systems, whereas no phase separation is predicted in the Fe-Al-Ti alloy. The origin of the phase separation in the Co- and Ni-Al-Ti alloys is, respectively, attributed to the mechanical instability and the combination of mechanical instability and chemical repulsions of unlike pairs.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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