Icosahedral symmetry, fragility and stability of supercooled liquid state of metallic glasses
Icosahedral symmetry, fragility and stability of supercooled liquid state of metallic glasses
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DOI：
10.1051/metal/2011077
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发表时间：
2012
影响因子：
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通讯作者：
M. Shimono;H. Onodera
中科院分区：
文献类型：
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作者：
M. Shimono;H. Onodera
材料的脆性应该与过冷液态下形成的局部结构有关。特别是，在金属玻璃的情况下，二十面体有序形成被认为起着重要作用。为了阐明金属玻璃过冷液态下局部结构形成与弛豫行为（或脆性）之间的关系，对一个简单的二元合金模型进行了分子动力学模拟，在该模型中我们可以改变原子尺寸比。从模拟结果中，我们发现二十面体团簇存在于过冷液态中，并在玻璃化转变附近的强过冷状态以及玻璃态下形成中程网络结构。我们还发现，随着原子尺寸差异的增加，簇的数量密度也增加。因此，由于二十面体团簇的丰富性，在原子尺寸差异较大的系统中，计算出的脆性参数取较低的值。
The fragility of materials should be related to a local structure formed in supercooled liquid states. Especially, in the cases of metallic glasses, the icosahedral order formation is considered to play an important role. To clarify the relation between the local structure formation and the relaxation behavior (or fragility) in the supercooled liquid states of metallic glasses, molecular dynamics simulations were performed for a simple model of binary alloys, in which we can change the atomic size ratio. From the simulation results, we found that the icosahedral clusters exist in supercooled liquid states and form a medium-range network structure in strongly supercooled regime near the glass transition as well as in the glassy states. We also found that the number density of the clusters increases as the atomic size difference increases. Consequently, the calculated fragility parameter takes a lower value in a system with larger atomic size difference due to the richness of the icosahedral clusters.