Mechanical grinding method was employed to prepare FeCoNiSi_xAl_0.4 high entropy alloy powders, which present a simple solid solution structure (FCC and BCC). After annealing at 673 K, a large amount of BCC phase precipitate and a small amount of CoFe₂O₄ phase generate. The change of crystal structure may lead to an increase in M_s (from 100.3 emu g⁻¹ to 124.2 emu g⁻¹) and a decrease in H_c (from 107 Oe to 59.5 Oe for FeCoNiSi_0.3Al_0.4). The silica content has a significant effect on the electromagnetic parameters of the as-milled and as-annealed alloy powders, presenting the trend of first increase and then decrease. And the dielectric constant is obviously improved after annealing (e.g. from 8.48 to 11.21 and from 0.15 to 2.84 for the ε′ and ε′′ of FeCoNiSi_0.3Al_0.4 at 18 GHz, respectively), while the permeability is reduced. Compared with those of the as-milled samples, the μ′ of as-annealed FeCoNiSi_xAl_0.4 (x = 0.1, 0.3, 0.4) remain unchanged or even increase due to the formation of CoFe₂O₄. Meanwhile, the relative content of the precipitated BCC to FCC for FeCoNiSi_0.3Al_0.4 enhance with the annealing temperature increase from 573 K to 773 K, and then reduce. And the ε′ and μ′ at 2 GHz present the same trend as the content ratio (A_BCC/A_FCC), while the ε′′ improve obviously after annealing, corresponding to the elevation of conductivity.

中文翻译：

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基于 FeCoNiSixAl0.4 高熵合金粉末的可调谐晶体结构改善电磁性能的新机制†

采用机械研磨法制备了FeCoNiSi _x Al _0.4高熵合金粉末，其具有简单的固溶体结构（FCC和BCC）。在673 K退火后，大量的BCC相析出和少量的CoFe ₂ O ₄相生成。晶体结构的变化可能导致M _s增加（从 100.3 emu g ^-1到 124.2 emu g ^-1）和H _{c减少（对于 FeCoNiSi 0.3} Al _0.4，从 107 Oe 到 59.5 Oe）。二氧化硅含量对球磨态和退火态合金粉末的电磁参数有显着影响，呈现先增加后降低的趋势。退火后介电常数明显提高（例如，FeCoNiSi _0.3 Al _0.4在 18 GHz 时的ε '和ε ''分别从 8.48 提高到 11.21 和 0.15 提高到 2.84 ），同时磁导率降低。_{由于CoFe 2} O ₄的形成，退火后的FeCoNiSi _x Al _0.4 ( x = 0.1, 0.3, 0.4)的μ '与研磨样品相比保持不变甚至增加. 同时，FeCoNiSi _0.3 Al _0.4析出的BCC与FCC的相对含量随着退火温度从573 K升高到773 K而升高，然后降低。并且2GHz时的ε ′和μ ′与含量比（ A _BCC / A _FCC）呈现相同的趋势，而退火后的ε ′′明显提高，对应于电导率的提高。