非惰性铸造气氛提高Fe基软磁合金非晶形成能力的机理研究

Fe-based metallic glasses (MGs) with high glass forming ability (GFA) and high saturation magnetization (Bs) are essential to make electromagnetic components microminiaturize and preparation simplify. To improve the GFA and diminish heterogeneous nucleation site, the strategies of high vacuum and high pure argon as casting atmosphere are suggested to be adopted. However, based on our previous work, it was found some non-inert casting atmospheres could significantly enhance the GFA of some Fe-based MGs without deteriorating their Bs, which is contrary to the classic heterogeneous nucleation theory. In this project, the influence of non-inert casting atmospheres on the GFA of some Fe-based MGs will be investigated, the characteristics in composition of those alloys whose GFA can be improved by non-inert casting atmospheres will be summarized, and the underlying mechanism will be explored. Also, the characteristic relation between GFA and the casting atmosphere are expected to be established at atomic, thermodynamic and kinetic levels, and the procedure “magnetic properties-components-casting atmosphere-GFA” for soft magnetic Fe-based MGs with high performance could be realized, which are expected to provide theoretical basis for the alloy design and technical guidance for the industrialization of the amorphous alloys.

兼具高非晶形成能力和高饱和磁感应强度的Fe基非晶合金是促进电磁元件向制备简单化和体积微型化方向发展的重要软磁材料。为了提高其非晶形成能力，减少异质形核点，人们通常采用高真空技术和高纯惰性氩气铸造气氛。然而，在预研过程中，我们却发现一反常现象：一些非惰性铸造气氛(比如氧气)，在不降低合金饱和磁感应强度的情况下，还能大大提高某些Fe基合金的非晶形成能力。这显然与经典非均匀形核理论相悖。本项目拟研究非惰性铸造气氛对Fe基软磁合金非晶形成能力的影响规律，归纳能被非惰性铸造气氛提高非晶形成能力的合金的成分特点，阐明非惰性铸造气氛提高合金非晶形成能力的本质。从原子、热力学及动力学层次上建立合金非晶形成能力与铸造气氛的特征关系，实现高性能Fe基非晶软磁合金的“磁性—成分—铸造气氛—非晶形成能力”的科研思路，为今后兼具高非晶形成能力与高饱和磁感应强度的Fe基软磁非晶合金的成分设计和制备提供理论依据与指导。

兼具高非晶形成能力和高饱和磁感应强度的Fe基非晶合金是促进电磁元件向制备简单化和体积微型化方向发展的重要软磁材料。为了提高其非晶形成能力，减少异质形核点，人们通常采用高真空技术和高纯氩气作为铸造气氛。然而，我们却发现一些非惰性铸造气氛(比如O2)，在不降低合金饱和磁感应强度的情况下，还能大大提高某些Fe基合金的非晶形成能力。这与经典的非均匀形核理论相悖。在这种情况下，本项目首先研究了Ar、N2、air和O2对Fe基软磁合金非晶形成能力的影响规律，发现了不同气氛对Fe76Si9B10P5，Fe76Si8B10P5Mo1，Fe77Mo2P10C4B4Si3和[(Fe0.8Co0.2)0.75B0.2Si0.05]96Nb4合金临界厚度的提高幅度不同。然后，归纳了能被非惰性铸造气氛提高非晶形成能力的合金的成分特点，发现非惰性气氛能够提高Fe76Si9B10P5，Fe76Si8B10P5Mo1，Fe77Mo2P10C4B4Si3等含P合金的临界直径，而不能够提高[(Fe0.8Co0.2)0.75B0.2Si0.05]96Nb4不含P合金的临界直径，确定了P为气氛敏感元素。最后，发现气氛虽然可以改变合金的临界直径，但是几乎不影响合金的热力学性能与磁性能，不改变合金的体成分，然而却显著减少了Fe基合金的表面偏析的P含量；通过对含P合金晶化特性的分析以及Fe76Si9B10Px合金系的热力学、黏度、表面张力的测量，发现非惰性气氛是通过提高合金表面张力来减少形核率、抑制表面晶化而提高合金非晶形成能力的，从而阐明了非惰性铸造气氛提高Fe基合金非晶形成能力的本质，建立了高性能Fe基非晶软磁合金的“磁性—成分—铸造气氛—非晶形成能力”的关联，为今后兼具高非晶形成能力与高饱和磁感应强度的Fe基软磁非晶合金的成分设计和制备提供了理论依据与指导。