基于团簇+连接原子模型的Fe-B-Si-Ta块体非晶合金的成分设计

COMPOSITION DESIGN OF Fe-B-Si-Ta BULK AMORPHOUS ALLOYS BASED ON CLUSTER+GLUE ATOM MODEL

依据团簇＋连接原子模型设计具有高玻璃形成能力的Fe-B-Si—Ta软磁块体非晶合金，以共晶点Fe83B17对应的共晶相Fe2B为基础．根据最大径向原子数密度和孤立度原则，得到以B为心的[B-B2Fe8】主团簇，结合理想非晶合金团簇式的电子浓度判据，构建出Fe-B二元非晶合金的理想团簇式[B—B2Fe8]Fe．为提升Fe—B二元合金的非晶形成能力，选择与Fe具有较大负混合焓的Si替代[B—B2Fe8]团簇的中心原子B，得到Fe-B-Si三元非晶合金的理想团簇式[Si—B2Fes]Fe．由于Ta与B和Si间具有较大的负混合焓，进一步以Ta替代[Si—B2Fe8]Fe团簇式中壳层位置的Fe原子，设计出[Si—B2Fe8-xTax]Fe四元非晶系列成分．结果表明，[Si-B2Fe8-xTax]Fe在x=0．4～0．7成分处均可形成直径为1．0min的非晶合金棒．其中，[Si—B2Fe7.4Ta0.6]Fe合金的非晶形成能力最佳，其非晶样品的约化玻璃转变温度磊为0．584，玻璃转变温度正为856K，过冷液相区宽度△Tx达33K．[Si-B2Fe8-xTax]Fe（x=0．4～0．7）块体非晶合金的Vickers硬度Hv随Ta的添加从1117HV（F0．4）上升到1154HV（x=0．7）．[Si—B2Fe7.6Ta0.4]Fe非晶合金具有良好的室温软磁性能，其饱和磁化强度Bs为1．37T,矫顽Hc垃为3．0A／m．

The structural and compositional features of amorphous alloys can be described by cluster-plus- glue atom model, which is an effective method for the composition design of amorphous alloys. In the Fe-B binary system, Fe2B phase is an intermetallic phase related to Fe83B17 eutectic point. Under the framework of the highest ra- dial number density and isolation principle, the local structure of Fe2B phase is characterized by a B-centered Ar- chimedean octahedral antiprism [B-B2Fe8] atomic cluster. Combined with the electron consistence criterion, the [B-B2Fe8]Fe （here the center and shell atoms are separated by a hyphen, a cluster is enclosed in square brackets, the glue atom is out square brackets） is then determined as an ideal cluster formula for Fe-B binary amorphous. To further enhance the glass-forming ability （GFA） of the alloy, the center B and shell Fe atoms in [B-B2Fes]Fe are re- placed with Si and Ta, respectively, due to their large negative enthalpy of mixing between Si-Fe and （B, Si）-Ta atomic pairs, and Fe-B-Si-Ta quaternary composition series, namely [Si-B2Fe8-xTax]Fe, are thus derived. The experimental results reveal that the bulk amorphous alloys with a diameter of 1.0 mm can be achieved for [Si-B2Fe8-xTax]Fe （x=0.4-0.7） compositions. Among them, [Si-B2Fe7.4Ta0.6]Fe （i.e. Fe70B16.67Si8.33Ta5, atomic frac- tion, %） is the best glass former, its glass transition temperature Tg, supercooled liquid region ATx and the re- duced glass transition temperatures Trg are 856 K, 33 K and 0.584, respectively. The Vickers hardness, saturation magnetization and coercivity of the [Si-B2Fe76Ta0.4]Fe （i.e. Fe71.67B16.67Si833Ta3.33） amorphous alloy are measured to be 1117 HV, 1.37 T, and 3.0 A/m, respectively. KEY WORDS cluster-plus-glue atom model, cluster formula, Fe-B-Si-Ta bulk amorphous alloy, magnetism