发表机构
Merrimack College; Mendelan LLC（梅里马克学院; 门德兰有限责任公司）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过第一性原理热力学计算，揭示了回收Nd2Fe14B磁体中Zr和B在晶界共偏聚的机制，为理解ZrB2析出和晶界稳定化提供了理论依据。
AI 中文摘要
晶界化学性质对Nd2Fe14B永磁体的矫顽力和热稳定性至关重要，尤其是在回收磁体中，硬磁相的恢复本身并不能恢复晶间微观结构。我们近期的实验研究表明，在回收过程中，尽管整体Zr浓度仅约为0.1 at.%，但纳米级ZrB2析出物可以在晶界和三叉晶界处出现，这些析出物与晶界稳定化和抑制晶粒粗化有关。在此，我们使用自旋极化密度泛函理论并加入Hubbard修正（DFT+U）来确定这种优先局域化背后的原子级热力学。一组系统的成分匹配的体相/晶界DFT+U超胞提供了跨晶界化学性质的共同关联电子描述。我们比较了Nd2Fe14B体相和晶界环境中的B、Zr、Dy以及类ZrB2局域构型。过量B在晶界处被强烈稳定化，而Zr也表现出对界面区域的独立热力学偏好。当Zr和B以类ZrB2构型结合时，晶界偏好得以保留，表明随着Zr-B配位的发展，界面仍然是有利的。这些结果确立了Zr和B在ZrB2形成之前共局域化的热力学路径。磁态分析进一步表明，所有比较的结构都保持在相同的高矩Fe亚晶格区域内，并且晶界局域缺陷对归一化磁化强度的扰动通常小于其基体对应物。因此，计算为Zr-B化学偏聚在晶间区域以及这种晶界局域态如何支持高矫顽力回收Nd-Fe-B磁体所需的微观结构稳定性提供了第一性原理解释。
英文摘要
Grain-boundary chemistry is central to the coercivity and thermal stability of Nd2Fe14B permanent magnets, particularly in recycled magnets where recovery of the hard-magnetic phase does not by itself restore the intergranular microstructure. Our recent experimental study showed that nanoscale ZrB2 precipitates can emerge at grain boundaries and triple junctions during recycling despite an overall Zr concentration of only about 0.1 at.%, where they are associated with boundary stabilization and suppression of grain coarsening. Here we use spin-polarized density-functional theory with a Hubbard correction (DFT+U) to determine the atomistic thermodynamics underlying this preferential localization. A systematic set of composition-matched bulk/grain-boundary DFT+U supercells provides a common correlated-electron description across boundary chemistries. We compare B, Zr, Dy, and ZrB2-like local configurations in bulk and grain-boundary environments of Nd2Fe14B. Excess B is strongly stabilized at the boundary, while Zr also shows an independent thermodynamic preference for the interfacial region. When Zr and B are combined in a ZrB2-like configuration, the boundary preference is retained, indicating that the interface remains favorable as Zr-B coordination develops. These results establish a thermodynamic pathway for the co-localization of Zr and B prior to ZrB2 formation. Magnetic-state analysis further shows that all compared structures remain within the same high-moment Fe-sublattice regime, and boundary-localized defects generally perturb the normalized magnetization less than their matrix counterparts. The calculations therefore provide a first-principles explanation for why Zr-B chemistry concentrates at intergranular regions and how such boundary-localized states can support the microstructural stability required for high-coercivity recycled Nd-Fe-B magnets.
