Akihisa Inoue

Abstract:

Multicomponent alloys have attracted definitely increasing interest for the last three decades since the first synthesis of multicomponent bulk metallic glasses (BMGs) by copper mold casting in 1990. The multicomponent alloys reported to date are classified to BMGs, BMG composites, high entropy (HE) BMGs and HE alloys. When we focus on engineering applications, the most widely commercialized alloys are BMGs. Their BMGs are roughly classified into nonmagnetic Zr-based and ferromagnetic Fe-based types. The former type is typically composed of Zr-Al-Ni-Cu and Zr-Al-Ni-Cu-(Ti,Nb) systems and the latter type is Fe-Cr-(P,B,C,Si), Fe-(Cr,Nb)-P-B and Fe-(Cr,Nb)-(P,B,Si) systems. The commercialization articles have been usually produced by die casting from liquid for the Zr-based BMGs, while the Fe-based glass-type alloys have been produced by high-pressure gas atomization or ultrahigh water atomization. The former BMGs have been used as various structural materials such as casing, housing, pin spring, hinge, clinic instruments, ratch cover writing tools, precise gears, knives, optical mirrors, sporting goods and ornaments, etc., while the latter glassy powders are used to produce soft magnetic composite (SMC) by mixing with resin et al. The SMCs exhibit unique soft magnetic properties with the features of low core losses, good high-frequency permeability characteristics and high electrical resistivity in high-frequency range from 100 kHz to 5 MHz. High glass-forming ability enables the mass production of good spherical glassy powders over the whole particle size range even by low-cost water atomization process. Owing to their unique production process and good soft magnetic properties, the SMCs have been used as high performance of inductors and reactors with low core losses even in a high frequency range up to 3 MHz in various kinds of fields such as smartphone, smartwatch, tablet-type computer, notebook PC, DC/DC converter, point of load power supply, digital camera, automobile AV equipment, car navigation system and RFID sheet, etc. Thus, Zr- and Fe-based BMGs are expected to increase academic and technological interests as functional materials in recent information communication technology owing to the unique properties that cannot be obtained for ordinary crystalline structural and magnetic materials.