Crystallization behaviour in a new multicomponent Ti 16.6 Zr 16.6 Hf 16.6 Ni 20 Cu 20 Al 10 metallic glass developed by the equiatomic substitution technique

A new amorphous Ti16.6Zr16.6Hf16.6Ni20Cu20A110 alloy has been developed using the novel equiatomic substitution technique. Melt spinning Ti16.6Zr16.6Hf16.6Ni20Cu20A110 forms an amorphous phase with a large supercooled liquid region, ΔT=70°C. After isothermal annealing within the supercooled liquid region for 3 h at 470°C, the amorphous alloy crystallizes to form a fine-scale distribution of 2-5 nm nanocrystals, and the supercooled liquid region increases to ΔT=108°C. Atomic-scale compositional analysis of this partially crystalline material using a three-dimensional atom probe (3DAP) is unable to detect any compositional difference between the nanocrystals and the remaining amorphous phase. After annealing for 1 hr at 620°C, the amorphous alloy crystallizes to form 20-50nm equiaxed grains of a hexagonal-type C14 Laves phase with lattice parameters a = 5.2Aring and c = 9.0 Aring. 3DAP analysis shows that this Laves phase has a composition very close to that of the initial amorphous phase, suggesting that the alloy crystallizes via a polymorphic rather than a primary crystallization mechanism, despite the complexity of the alloy composition.