The effect of cooling rates on hereditary characteristics of icosahedral clusters in rapid solidification of liquid Cu56Zr44 alloys
DD Wen and P Peng and YQ Jiang and ZA Tian and RS Liu and KJ Dong, JOURNAL OF NON-CRYSTALLINE SOLIDS, 388, 75-85 (2014).
A molecular dynamics simulation is performed to investigate the influence of cooling rates gamma on the hereditary characteristics of icosahedral clusters during the rapid solidification of liquid Cu56Zr44 alloys. The analysis from an extended cluster-type index method based on the H-A bond-type index shows (12 0 12 0 0 0 0 0 0 0) standard icosahedra and (12 0 8 0 0 0 2 2 0 0) as well as (12 2 8 2 0 0 0 0 0 0) defective icosahedra play a key role in the formation of Cu56Zr44 glassy alloys. With the increase of cooling rates gamma, the glass transformation temperature T-g rises, but the clustering degree towards icosahedra descends in the rapidly solidified solid. An inverse tracking of atom traces reveals the icosahedral clusters at 300 K mainly originate from the configuration heredity below T-g, and the perfect heredity is dominant among perfect, core and segmental heredity modes. Relative to (12 0 8 0 0 0 2 2 0 0) and (12 2 8 2 0 0 0 0 0 0) defective icosahedra, (12 0 12 0 0 0 0 0 0 0) standard icosahedra are of high structural stability and large heredity ability, and their descendible efficiencies and heredity behaviors vary with gamma In the case of high gamma, not only the descendible fractions f(i) of icosahedral clusters above T-g are enlarged, but also their initial descendible temperatures T-onset in the super-cooled liquid region are elevated. As a result, icosahedral medium-range orders (IMROs) can be easily formed and grown in the super-cooled liquid. Therefore, a big T-rg = T-g/T-m of Cu56Zr44 alloys at high gamma can be attributed to the ascent of T-onset caused by increasing gamma to some extent. (C) 2014 Elsevier B.V. All rights reserved.
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