Amorphous phase formation, spinodal decomposition, and fractal growth of nanocrystals in an immiscible Hf-Nb system studied by ion beam mixing and atomistic modeling

Journal Article · Tue Apr 15 00:00:00 EDT 2008 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.2912718· OSTI ID:21137176

Tai, K P; He, X; Liu, B X ^[1]

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1. Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

In the equilibrium immiscible Hf-Nb system characterized by a positive heat of formation, five Hf-Nb metallic glasses with overall compositions of Hf{sub 84}Nb{sub 16}, Hf{sub 65}Nb{sub 35}, Hf{sub 45}Nb{sub 55}, Hf{sub 38}Nb{sub 62}, and Hf{sub 20}Nb{sub 80} are obtained by ion beam mixing with properly designed Hf-Nb multilayered films, suggesting a glass-forming composition range of 16-80 at. % of Nb. For the special case of Hf{sub 45}Nb{sub 55} located at the ridge point on the convex free energy curve, dual-glass phases are formed at a dose of 2x10{sup 15} Xe{sup +}/cm{sup 2}, which results from a spinodal decomposition of the expected Hf{sub 45}Nb{sub 55} amorphous phase. With increasing irradiation dose, fractal growth of nanocrystals (around 20 nm) appears in the major glass phase and the dimension is determined to be from 1.70 to 1.84 within a dose range of (4-7)x10{sup 15} Xe{sup +}/cm{sup 2}. In atomistic modeling, a n-body Hf-Nb potential is first constructed with the aid of ab initio calculations. Applying the constructed potential, molecular dynamics simulations using the hcp and bcc solid solution models, reveals an intrinsic glass-forming range to be within 15-83 at. % of Nb, which is compatible with the ion beam mixing experiments. Moreover, the formation of the metallic glasses and the fractal growth in association with the amorphous spinodal decomposition are also discussed in terms of the atomic collision theory and cluster-diffusion-limited-aggregation model.

• OSTI ID: 21137176
• Journal Information: Journal of Applied Physics, Vol. 103, Issue 8; Other Information: DOI: 10.1063/1.2912718; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AMORPHOUS STATE
ATOM COLLISIONS
BCC LATTICES
CRYSTAL GROWTH
DECOMPOSITION
FORMATION HEAT
FRACTALS
FREE ENERGY
HAFNIUM ALLOYS
HCP LATTICES
INTERMETALLIC COMPOUNDS
ION BEAMS
MOLECULAR DYNAMICS METHOD
NANOSTRUCTURES
NIOBIUM ALLOYS
RADIATION DOSES
SIMULATION
SOLID SOLUTIONS
THIN FILMS
XENON IONS