A combined experimental and ab initio molecular dynamics study on a novel B-based B50Sm10Co40 amorphous alloy

A novel B based B50Sm10Co40 amorphous alloy was fabricated by melt-spinning technique. The crystallization temperature, Vickers hardness, and Young's modulus of the alloy are 1068 K,15.2 GPa, and 230 GPa, respectively, much higher than those of a Co-based Co65Sm10B25 amorphous alloy in the same system. Ab initio molecular dynamics simulation based on density-functional theory indicates that the short-range order of the B50Sm10Co40 amorphous alloy is dominated by B-centered tri-capped trigonal prisms (TTPs) and bi-capped square Archimedean antiprisms, whereas the Co65Sm10B25 alloy mainly contains B-centered TTPs and Co-centered distorted icosahedral-like polyhedra, and the fraction of the TTPs is lower than that in the B50Sm10Co40. The dense-packed B-centered prism-type clusters with a high proportion of stable B-B covalent bonds reduce the atomic diffusivity and mobility, and increase the resistance to crystallization and shear transformation, which contribute to the high thermal stability and hardness/modulus of the B-based B50Sm10Co40 amorphous alloy. (C) 2021 Elsevier B.V. All rights reserved.