钆含量对Fe-B-Nb-Gd非晶合金磁学性能和氧化机制的影响规律

Influence of gadolinium content on magnetic property and oxidation mechanism of Fe-B-Nb-Gd metallic glass

研究了Gd含量对(Fe_(73)B_(22)Nb_(5))_(100–x)Gd_(x)(x=0,0.5,1.0,1.5,2.0)合金非晶形成能力、热稳定性和磁学性能的影响规律,并对比分析了非晶氧化机制.通过添加Gd元素,合金的原子尺寸差超过13%,构型熵增大了30%,提升了合金的非晶形成能力.随着Gd含量的增大,过冷液相区范围达到73 K,热稳定性得到明显增强.Gd元素导致合金局部各向异性受到限制,准位错偶极子型缺陷密度降低.这有效减少了阻碍磁畴壁旋转的钉扎位点,提高合金软磁性能.此外,Gd元素使得非晶在氧化过程中对温度的变化更为敏感,达到最大氧化速率的温度降低了15 K,但是并未恶化其抗氧化性能.Gd原子受结合能影响向表层迁移,形成的富Gd氧化物填充了表层缺陷,占据了大量顶部空间,合金表面附近的结构更加致密.这种结构减少了氧原子通过微观组织界面进行扩散的通道,有助于增强抗氧化性能.

In this work,we use the rapid solidification technique to prepare five kinds of metallic glasses with different Gd content,and investigate in depth the influences of Gd content on the amorphous formation capability,thermal stability,and magnetic properties of(Fe_(73)B_(22)Nb_(5))_(100-x)Gd_(x)(x=0,0.5,1.0,1.5,2.0) alloys.By comparing the microstructural morphology and solute distribution of oxidation products before adding Gd and those after adding Gd,the amorphous oxidation mechanism is analyzed systematically.With the addition of Gd,the atomic size difference of the alloys exceeds 13%,and the configuration entropy increases from 7.27 kJ/(mol·K)to 9.44 kJ/(mol·K).The glass-forming ability of the alloy is significantly improved.The increase of Gd content can increase the glass transition temperature of the alloy to 864 K,and the undercooled liquid region can reach 73 K,significantly enhancing the thermal stability of the metallic glasses.The Gd limits the local anisotropy of the alloy and reduces the density of quasi-dislocation dipole defects.This can effectively reduce the pinning sites that hinder the rotation of magnetic domain walls,thereby improving the soft magnetic property.By comparing with the metallic glasses without Gd,only 2%(atomic percentage)Gd can reduce the coercivity by 8%.Moreover,the Gd makes the metallic glasses more sensitive to temperature variation in the oxidation process,and the temperature of the maximum oxidation rate is reduced by 15 K.However,their antioxidant performance does not deteriorate.The Gd atoms are influenced by binding energy and migrate to the surface,forming Gd-rich oxides.They fill surface defects and occupy a large part of the top space,leading to the structure becoming more compact near the surface.This structure reduces the channels for oxygen atoms to diffuse through the microstructure interface,which helps to improve antioxidant capability.This work provides a new approach for designing high performance Fe-based metallic glasses.