Zhou Yin, Ji Yunping, Li Yiming, Qi Jianbo, Xin Haohao, Ren Huiping
School of Materials and Metallurgy (School of Rare Earth), Inner Mongolia University of Science and Technology, Baotou 014010, China.
Inner Mongolia Autonomous Region Key Laboratory of Advanced Metal Materials, Baotou 014010, China.
Materials (Basel). 2022 Feb 12;15(4):1374. doi: 10.3390/ma15041374.
Rare earth (RE) inclusions with high melting points as heterogeneous nucleation in liquid steel have stimulated many recent studies. Evaluating the potency of RE inclusions as heterogeneous nucleation sites of the primary phase is still a challenge. In this work, the edge-to-edge matching (E2EM) model was employed to calculate the atomic matching mismatch and predict the orientation relationship between LaOS and γ-Fe from a crystallographic point of view. A rough orientation relationship (OR) was predicted with the minimum values of fr=9.43% and fd=20.72% as follows: [21¯1¯0]La2O2S∥[100]γ-Fe and (0003¯)La2O2S∥(002¯)γ-Fe. The interface energy and bonding characteristics between LaOS and γ-Fe were calculated on the atomic scale based on a crystallographic study using the first-principles calculation method. The calculations of the interface energy showed that the S-terminated and La(S)-terminated interface structures were more stable. The results of difference charge density, electron localization function (ELF), the Bader charges and the partial density of states (PDOS) study indicated that the La(S)-terminated interface possessed metallic bonds and ionic bonds, and the S-terminated interface exhibited metallic bond and covalent bond characteristics. This work addressed the stability and the characteristics of the LaOS/γ-Fe interface structure from the standpoint of crystallography and energetics, which provides an effective theoretical support to the study the heterogeneous nucleation mechanism. As a result, LaOS particles are not an effective heterogeneous nucleation site for the γ-Fe matrix from crystallography and energetics points of view.
作为钢液中非均匀形核位点的高熔点稀土（RE）夹杂物引发了近期的诸多研究。评估RE夹杂物作为初生相非均匀形核位点的效能仍是一项挑战。在本工作中，采用边到边匹配（E2EM）模型从晶体学角度计算原子匹配失配度，并预测LaOS与γ-Fe之间的取向关系。预测了一种粗略的取向关系（OR），其fr最小值为9.43%，fd最小值为20.72%，如下所示：[21¯1¯0]La2O2S∥[100]γ-Fe和(0003¯)La2O2S∥(002¯)γ-Fe。基于晶体学研究，使用第一性原理计算方法在原子尺度上计算了LaOS与γ-Fe之间的界面能和键合特性。界面能计算表明，S端终止和La(S)端终止的界面结构更稳定。差分电荷密度、电子局域函数（ELF）、巴德电荷和态密度（PDOS）研究结果表明，La(S)端终止的界面具有金属键和离子键，S端终止的界面表现出金属键和共价键特征。本工作从晶体学和能量学角度研究了LaOS/γ-Fe界面结构的稳定性和特性，为研究非均匀形核机制提供了有效的理论支持。结果表明，从晶体学和能量学角度来看，LaOS颗粒不是γ-Fe基体有效的非均匀形核位点。
