非晶材料的热膨胀系数和声子谱测量与纳米晶成形机制的关联

Formation Mechanism of Nanocrystalline Related to Thermal Expand Coefficient and Generalized Phonon Spectra in Amorphous

用熔体快淬法制备的非晶态合金经退火处理可形成纳米晶合金,其形成机制至今仍是研究的热点。国外纳米晶成形机制研究主要集中在添加元素在晶核的形成和长大过程中的作用等方面。本工作认为纳米晶的形成有着更深层的原因,结合长期以来关于因瓦合金的热膨胀系数和声子谱测量,以及最近纳米软磁材料的声子谱研究,指出非晶态合金中的声子软化现象反映出原子间的相互作用力减弱,非晶合金体系处于结构松散状态,非晶合金的这种结构不稳定性才是造成其在晶化初期易于爆发式大量形核,并进一步形成均匀分布的纳米晶的主要原因。

Since the successful development of nanocrystalline alloys by means of annealing amorphous alloys which were prepared by rapid quenching from the melt, the formation mechanism of nanocrystalline microstructures has been one of the most interesting subjects. According literatures, it has been intensively studied on the effect of additive elements in the process of nucleation and growth. In this paper, the formation mechanism of nanocrystalline microstructure was investigated by means of the thermal expand coefficient and GPS （generalize phonon spectra） in various amorphous materials, including invar amorphous alloys and nanocrystalline soft magnetic materials. Those amorphous alloys which are favorable for the formation of nanocrystalline microstructure appear a phonon softening phenomenon, which indirectly indicates that the interaction forces decrease between atomics and these alloys appear a characteristic of structural instability. It is suggested that the structural instability of amorphous alloys increase the nucleation rate which is favorable for the formation of the homogeneous nanoscale grain structure.