Abstract Influence of applied electric field on atom diffusion behavior and mechanism for W/NiFe interface in diffusion bonding of Steel/NiFe interlayer/W by spark plasma sintering was studied using the first-principles calculations. The result indicates that applied electric field reduces d-orbital electron concentrations of W atom and Ni atom effectively, and then weakens W-W metallic bonding/Ni-Ni metallic bonding and Nisp-W metallic bonding/Wsp-Ni metallic bonding for W/NiFe diffusion interface, which decides the vacancy formation energy and solute atom migration energy. Therefore, the diffusion activation energy composed by vacancy formation energy and solute atom migration energy was reduced and leading to the increasing interfacial atom diffusion coefficient. Moreover, because W atom is more susceptible to applied electric field due to the smaller stability of d-orbital electrons than Ni atom, the decline degrees of W-W and Nisp-W metallic bonding strength are larger than those of Ni-Ni and Wsp-Ni metallic bonding strength. Therefore, the accelerating effect for Ni atom diffusing into W slab is larger than W atom diffusing into NiFe slab on W/NiFe interface, presented as that the diffusion activation energies for them decrease by 0.37 eV and 0.07 eV, and the diffusion coefficients at 1400 K increase by 26.72 times and 2.23 times, respectively.

中文翻译：

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外加电场对原子扩散行为的影响以及W/NiFe界面在Steel/NiFe中间层/W通过火花等离子烧结扩散键合的机理

摘要 采用第一性原理计算，研究了外加电场对原子扩散行为的影响以及W/NiFe界面在放电等离子烧结Steel/NiFe中间层/W扩散结合过程中的作用机制。结果表明，外加电场有效地降低了 W 原子和 Ni 原子的 d 轨道电子浓度，从而削弱了 W/NiFe 扩散的 WW 金属键/Ni-Ni 金属键和 Nisp-W 金属键/Wsp-Ni 金属键界面，它决定了空位形成能和溶质原子迁移能。因此，由空位形成能和溶质原子迁移能组成的扩散活化能降低，导致界面原子扩散系数增加。而且，由于 d 轨道电子的稳定性比 Ni 原子小，W 原子更容易受到外加电场的影响，因此 WW 和 Nisp-W 金属键合强度的下降程度大于 Ni-Ni 和 Wsp-Ni 金属键合强度的下降程度力量。因此，在 W/NiFe 界面上，Ni 原子扩散到 W 板中的加速作用大于 W 原子扩散到 NiFe 板中的作用，表现为它们的扩散活化能分别降低 0.37 eV 和 0.07 eV，扩散系数在 1400 K 分别增加了 26.72 倍和 2.23 倍。