Structural study of eutectic Mg0.72Zn0.28 alloy II. Crystallization processes in the amorphous, liquid and undercooled states of the eutectic alloy Mg0.72Zn0.28
Structural study of eutectic Mg0.72Zn0.28 alloy II. Crystallization processes in the amorphous, liquid and undercooled states of the eutectic alloy Mg0.72Zn0.28
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DOI：
10.1016/0022-3093(89)90333-5
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发表时间：
1989-02
影响因子：
3.5
通讯作者：
P. Andonov;P. Chieux
中科院分区：
文献类型：
--
作者：
P. Andonov;P. Chieux
通过中子衍射实验原位观察了无序共晶合金Mg0.72Zn0.28在非晶态结晶以及液态和过冷熔体凝固过程中发生的结构变化。所获得的结构因子和径向分布函数使我们能够表明，通过快速液体淬火获得的非晶材料具有与液体或过冷熔体不同的瞬时结构。讨论了这种结构差异，并与之前发表的非晶合金实验进行了比较。我们的结果还根据以缺陷弛豫作为结构演化基础的理论模型进行了讨论。结构缺陷的运动和湮灭不足以解释局部原子重排。各种原子运动是必要的，这些运动主要涉及具有特殊协调的位置。无论初始无序状态如何，最终的原子排列始终是 Mg51Zn20 晶体；但是，根据初始状态和冷却速率（在液体的情况下），可以通过不同的方式实现晶序。
The structural changes which occur in the disordered eutectic alloy Mg0.72Zn0.28during the crystallization of the amorphous state and the solidification of the liquid and undercooled melt, are observed in situ by neutron diffraction experiments. The structure factors and the radial distribution functions which have been obtained allow us to show that the amorphous material, obtained by rapid liquid quench, has an instantaneous structure different from that of the liquid or undercooled melt. This structural difference is discussed and a comparison with the previously published experiments on the amorphous alloy is made. Our results are also discussed in the light of the theoretical model taking defect relaxation as a basis for structural evolution. Motion and annihilation of structural defects are not sufficient to explain the local atomic rearrangement. Various atomic movements are necessary which concern essentially the sites with peculiar coordination. Whatever may be the initial disordered state, the final atomic arrangement is always the Mg51Zn20crystal; but the approach to the crystalline order is achieved in different ways depending on the initial state and also on the cooling rate (in the case of the liquid).