Jia Peng, Wang En-Gang, Han Ke
Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819, China.
National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA.
Materials (Basel). 2016 Nov 4;9(11):899. doi: 10.3390/ma9110899.
In contrast with amorphous alloys, nanocrystalline soft magnetic materials show improved thermal stability and higher soft magnetic properties. The nanocrystalline soft magnetic composites are usually fabricated by partially crystallizing from parent amorphous alloys. This paper reports our experimental observation on the sequence of crystallization in metallic glass under a high magnetic field (HMF). An application of a HMF to bulk metallic glass (BMG) of [(FeCo)BSi]Nb₄ prioritizes the precipitation of α-(Fe,Co) phase separated from the subsequent precipitation of borides, (Fe,Co)B₆, upon isothermal annealing at a glass transition temperature. Furthermore, it was observed that, through the annealing treatment under a HMF, a soft magnetic nanocomposite, in which only α-(Fe,Co) phase uniformly distributes in amorphous matrix, was achieved for boron-bearing BMG. The promotion of the α-Fe or (Fe,Co) phase and the prevention of the boride phases during the isothermal annealing process help to produce high-quality soft magnetic nanocomposite materials. The mechanism by which a HMF influences the crystallization sequence was interpreted via certain changes in Gibbs free energies for two ferromagnetic phases. This finding evidences that the annealing treatment under a HMF is suitable for enhancing the soft magnetic properties of high B content (Fe,Co)-based bulk amorphous and nanocrystalline materials.
与非晶合金相比，纳米晶软磁材料具有更好的热稳定性和更高的软磁性能。纳米晶软磁复合材料通常是通过母体非晶合金的部分晶化来制备的。本文报道了我们在高磁场（HMF）下对金属玻璃结晶顺序的实验观察。在玻璃化转变温度下进行等温退火时，对[(FeCo)BSi]Nb₄块状金属玻璃（BMG）施加高磁场会优先析出α-(Fe,Co)相，随后再析出硼化物(Fe,Co)B₆。此外，观察到，通过在高磁场下进行退火处理，对于含硼BMG可获得一种软磁纳米复合材料，其中仅α-(Fe,Co)相均匀分布在非晶基体中。在等温退火过程中促进α-Fe或(Fe,Co)相并抑制硼化物相有助于制备高质量的软磁纳米复合材料。通过两个铁磁相的吉布斯自由能的某些变化来解释高磁场影响结晶顺序的机制。这一发现证明，在高磁场下进行退火处理适用于提高高硼含量（Fe,Co）基块状非晶和纳米晶材料的软磁性能。
