Research Progress and Application Prospect of Fe-based Soft Magnetic Amorphous/Nanocrystalline Alloys

Research Progress and Application Prospect of ferro-based soft magnetic amorphous/nanocrystalline alloys reviewed the discovery and development history of soft magnetic amorphous alloys, introduced the important contributions of relevant basic research achievements and technological progress to the development and industrial application of ferro-based soft magnetic amorphous/nanocrystalline alloys, and pointed out the challenges and development direction in the development and application of ferro-based soft magnetic amorphous alloys. The corresponding author of the above work is Professor Yao Kefu of the School of Materials Science, Tsinghua University.

①Fe base soft magnetic amorphous alloy

In 1960, Gubanov theorized that the band structure of electrons was mainly determined by the short atomic program, that is, the ferromagnetism was generated by the exchange coupling of adjacent atoms, thus predicting the ferromagnetism of Fe-based amorphous alloys. This provides a theoretical basis for the possibility of ferromagnetism in ferro-based amorphous alloys.

In 1967, Duwez et al. prepared Fe80P12.5C7.5 amorphous alloy by quench cooling method. The ferro-based amorphous alloy is a typical soft magnetic amorphous alloy, although the coercivity is slightly higher. This result not only confirmed Gubanov's theoretical analysis results experimentally, but also attracted many researchers to the basic research and application research of Fe based soft magnetic amorphous materials.

② Development history of ferro-based soft magnetic amorphous alloys

The appearance of alloy melt spin quenching technology has brought opportunities for the development of Fe-based amorphous alloys, triggered the first upsurge in the basic and application research of Fe-based amorphous materials, and made the research of Fe-based soft magnetic amorphous alloys develop rapidly.

In the 1970s, researchers developed many new Fe based soft magnetic amorphous materials based on melt rotation quenching technology, and found that most of them have better soft magnetic properties. Another important finding is that the coercivity of soft magnetic amorphous alloy can be significantly increased by the internal stress introduced in the process of preparation. The coercivity of soft magnetic amorphous alloy can be significantly reduced by eliminating the structural inhomogeneity and internal stress generated in the process of preparation. The reduction of coercivity can reduce the hysteresis loss of soft magnetic amorphous alloy. The results show that the excellent soft magnetic properties of Fe-based soft magnetic amorphous alloys are due to the long disordered arrangement of atoms, and the factors such as composition, structural uniformity and internal stress have important effects on the soft magnetic properties of amorphous alloys. These research results provide a theoretical basis for the application of Fe-based soft magnetic amorphous alloys.

In 1979, Allied Signal developed the plane-flow casting technology to produce a wide strip, and established a continuous strip manufacturing company in 1982. Soft magnetic amorphous alloys entered the era of industrialization and commercialization. In 1984, four transformer manufacturers in the United States demonstrated practical amorphous distribution transformers with amorphous cores at the IEEE Conference, which culminated in the development of applications of ferro-based soft magnetic amorphous alloys.

In 1988, Yoshizawa et al. developed Fe73.5Si13.5B9Nb3Cu1 amorphous alloy by adding a small amount of Cu and Nb to FeSiB alloy, which was registered as FINEMET, and then developed FINEMET series amorphous nanocrystalline alloys. FINEMET alloys combine the high magnetic sensitivity of Fe-based amorphous alloys with the high permeability, low loss and low cost of cobalt-based amorphous alloys. The invention of ferro-based soft magnetic nanocrystalline alloy is a breakthrough in soft magnetic amorphous alloy materials, which pushes the research and development of ferro-based amorphous alloy to a new climax -- namely, opens the second upsurge of research and application of soft magnetic amorphous/nanocrystalline alloy.

After FINEMET soft magnetic nanocrystalline alloy came out, Hitachi Metal company quickly realized industrialization. In 1992, German company VAC began to introduce nanocrystalline alloys to replace cobalt-based amorphous alloys. Especially in network interface equipment, nanocrystalline magnetic cores were widely used to make interface transformers and digital filter parts. In 1998, Suzuki et al. developed FeZrB amorphous nanocrystalline biphase alloy system with high iron content and registered it as NANOPERM alloy. In 2006 Ogawa and others developed an iron-based amorphous alloy called HB1; In 2009, Makino et al. developed Fe-Si-B-P-Cu system, and the iron-based soft magnetic amorphous/nanocrystal alloy system was registered as NANOMET. The emergence of HB1 and NANOMET greatly encouraged researchers and led to the third research boom in ferro-based soft magnetic amorphous alloys, which led to the research boom in high Bs soft magnetic amorphous/nanocrystalline alloys.

At present, the amorphous alloy that has been widely used in engineering is still FeSiB ferro-based soft magnetic amorphous alloy used in the manufacture of transformer core. The brand in China is 1K101, and the corresponding brand abroad is METGLAS 2605SA1 alloy.

The research and development and application of ferro-based soft magnetic amorphous alloy began in 1976 and has taken an independent road. In 2016, China's production capacity of amorphous strip was about 140,000 tons, and the actual output was about 113,000 tons, exceeding 100,000 tons for the first time. The actual output of Antai, Yunlu and other enterprises reached or approached 30,000 tons. China has become a major producer of ferro-based soft magnetic amorphous/nanocrystalline alloy strips and related products in the world.

At present, according to the market demand, special soft magnetic amorphous/nanocrystalline alloy materials are being developed to further expand the application field. At the same time, we also aim at high frequency, high efficiency and energy saving motors and other high-end products, develop high performance soft magnetic amorphous/nanocrystalline alloy materials and related products processing and manufacturing core technology, to meet the needs of the market and the development of high-tech field.

(3) Challenges and development directions of ferromagnetic amorphous/nanocrystalline alloys

Although ferro-based soft magnetic amorphous/nanocrystalline alloys with low coercivity, high effective permeability and low iron loss have obvious advantages over traditional soft magnetic materials in many applications, there are still many challenges.

At present, the main challenges and development directions of ferro-based soft magnetic amorphous/nanocrystalline alloys are as follows:

(1) The brittleness of amorphous alloys

Ferro-based soft magnetic amorphous alloys, especially nanocrystalline alloys, have problems of low ductility and high brittleness. It is necessary to further study the factors affecting ductility and explore ways to improve ductility to ensure safety in use.

(2) The saturation magnetic sensitivity Bs is still low, and the comprehensive magnetic performance still needs to be further improved

It is necessary to further study the new process or the alloy with better technology, so that the alloy has high saturation magnetic sensitivity, low coercivity and high permeability, that is, to obtain the ferro-based soft magnetic amorphous alloy or amorphous/nanocrystalline alloy with excellent comprehensive soft magnetic properties.

(3) Lack of efficient processing technology of amorphous alloy

Amorphous alloy/nanocrystalline alloy due to high hardness, brittleness, processing is difficult, processing efficiency is not high. It is necessary to study the factors affecting the machining performance of soft magnetic amorphous/nanocrystalline alloy, and explore the technical methods to improve the machining efficiency and guarantee the machining quality.

(4) Develop soft magnetic amorphous/nanocrystalline alloy system to meet different requirements

Different industrial products have very different requirements on the magnetic properties of soft magnetic amorphous alloy, so it is necessary to develop a variety of soft magnetic amorphous/nanocrystalline alloy systems to meet the needs of different products in different application fields.