Structural aspects of metallic glasses
Structural aspects of metallic glasses
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DOI：
10.1557/mrs2007.124
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发表时间：
2007-08-01
期刊：
影响因子：
5
通讯作者：
Kelton, Kenneth F.
中科院分区：
文献类型：
--
作者：
Miracle, Daniel B.;Egami, Takeshi;Kelton, Kenneth F.
最近的一个结构模型协调了金属玻璃中共存的随机性、短程有序和中程有序这三个明显相互冲突的特征。在这个有效的团簇堆积模型中，短程有序可以用有效堆积的溶质中心团簇来描述，产生十几个已建立的原子团簇，包括二十面体。在金属玻璃中观察到的二十面体短程有序的偏好与有效的原子堆积的主题是一致的，并且进一步受到以溶剂为中心的团簇的青睐。在溶质-溶质回避的驱动下，中期有序是在重叠、渗透(通过连接的路径)、准等价团簇空间中的组织产生的。这些团簇的立方结构和二十面体结构与测量的中程有序性一致。涨落电子显微镜等新技术现在提供了更详细的中程有序实验研究，以便与模型预测进行比较。有效的团簇堆积模型中的微观自由体积能够代表实验和计算结果，显示出从亚原子到原子水平的自由体积复合体。自由体积将静态结构模型与扩散和变形等动态过程联系起来。处理“自由”和“反自由”微观体积和原子协调运动的新方法显示了对结构弛豫的复杂动力学建模的希望，例如玻璃化转变。提出了统一静态和动态结构视图的下一步工作。
A recent structural model reconciles apparently conflicting features of randomness, short-range order, and medium-range order that coexist in metallic glasses. In this efficient cluster packing model, short-range order can be described by efficiently packed solute-centered clusters, producing more than a dozen established atomic clusters, including icosahedra. The observed preference for icosahedral short-range order in metallic glasses is consistent with the theme of efficient atomic packing and is further favored by solvent-centered clusters. Driven by solute-solute avoidance, medium-range order results from the organization in space of overlapping, percolating (via connected pathways), quasi-equivalent clusters. Cubic-like and icosahedral-like organization of these clusters are consistent with measured medium-range order. New techniques such as fluctuation electron microscopy now provide more detailed experimental studies of medium-range order for comparison with model predictions. Microscopic free volume in the efficient cluster packing model is able to represent experimental and computational results, showing free volume complexes ranging from subatomic to atomic-level sizes. Free volume connects static structural models to dynamic processes such as diffusion and deformation. New approaches dealing with "free" and "anti-free" microscopic volume and coordinated atomic motion show promise for modeling the complex dynamics of structural relaxations such as the glass transition. Future work unifying static and dynamic structural views is suggested.