Hard rhenium-boron-cobalt amorphous alloys with a wide supercooled liquid region

Novel Re-B-Co amorphous alloys with compositions of Re65−xB35Cox (at%, x=25, 30, 35, 40, 45, and 50) were fabricated by single-roller melt spinning. These alloys were found to exhibit a clear glass transition phenomenon. The width of supercooled liquid region (ΔTx) is in the range of 52-71 K. Such a large ΔTx allows us to produce amorphous alloy bulks by thermoplastic forming. The Vickers hardness is up to 19.10 GPa for the Re40B35Co25 alloy, which is close to that reported for some hard covalent crystals. Thus, the present alloys with a combination of large ΔTx and high hardness are expected to be used as a new type of structural materials. Furthermore, the relationships of hardness with glass transition temperature and Young's modulus were also discussed.