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

Abstract

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.