Development and industrialization of Zr- and Fe-based bulk metallic glasses and light metal-based metastable alloys

Since the first synthesis of a bulk metallic glass (BMG) in 1990, a number of studies on the clarification of alloy composition, glass-forming ability (GFA), structure, thermal stability and mechanical, physical, magnetic and chemical properties have been carried out for BMGs, with the aim of using as practical materials in our society. As a result, Zr-based BMGs in Zr-Al-Ni-Cu-based system were commercialized for the first time as sporting goods in 1998, followed by the practical uses of watch parts and micro-gear motor parts etc. However, Zr-based BMGs could not gain vast application state for many years up to 2015. In 2016, the full automation type die mold casting machine was established, leading to the achievement of the mass production of Zr-based BMGs. Nowadays, Zr-based BMGs have been commercialized as structural materials in a variety of application fields. On the other hand, ferromagnetic Fe-based BMGs were synthesized for the first time in 1995. Their BMGs also exhibit higher GFA, better magnetic softness and higher electrical resistivity which cannot be obtained for Fe-based amorphous alloys prepared by melt spinning. Owing to their useful properties for Fe-based BMGs as well as the easy formation of spherical glassy powders by water atomization, Fe-based BMGs have opened up a new industrialization field called as soft magnetic composites (SMC) which are essential for the mass production of advanced high-performance information-communication technology instruments. Based on the knowledge on the high GFA for Fe-based BMGs, a new type of nanocrystalline soft magnetic alloys with high Bs above 1.7 T as well as good mass production ability from liquid was also developed and commercialized in 2015. This paper reviews the development history, fundamental properties and wide application fields for structural Zr- and soft magnetic Fe-based BMGs as well as novel nanocrystalline Fe-based soft magnetic alloys.