Cu熔体中原子团簇在凝固过程中的演变规律分子动力学模拟

用分子动力学模拟研究了Cu熔体以不同速率冷却微观结构的演变规律.结果表明,冷却速率在10^12.6K/s到10^14.5K/s之间时,Cu熔体凝固后形成了非晶体与晶体的混合体;Cu熔体中的原子团簇、临界晶核及凝固后晶体的结构均是由hcp和fcc结构层状镶嵌排列构成,这说明Cu凝固后形成的层状镶嵌结构起源于形核阶段;冷却速率小于10^13.3K/s时,Cu层状镶嵌结构中具有fcc结构的原子数多于hcp结构的原子数,而冷却速率大于10^13.3K/s后,hcp结构的原子数多于fcc结构的原子数;Cu非晶基体中晶态结构原子团簇的尺寸小于临界晶核尺寸时,虽然用HA键型指数法能确定出一定数量晶态结构原子键对的存在,但径向分布函数反映不出其晶态结构的特征.

MOLECULAR DYNAMICS SIMULATION OF THE ATOM CLUSTER EVOLUTION IN COPPER MELT DURING SOLIDIFICATION PROCESS

The structure evolution of atom cluster in copper melt and the microstructure of solidificated copper during the solidification process were investigated by using the molecular dynamics simulation method.It was found that the solidificated structure is composed of crystal phase and amorphous phase when the cooling rate is ranged from 10^12.6 to 10^14.5 K/s.All the structures of the growing crystal,the critical nuclei and the atom cluster in copper melt are the layer mosaic structure constructed by fcc and hcp structure,which indicates that the layer mosaic structure of copper originates from the nucleation.When the cooling rate is lower than 10¹³³ K/s,the atom number of hcp structure in the layer mosaic structure in the amorphous matrix is less than that of fcc structure,but when the cooling rate is higher than 10^13.3 K/s,the atom number of fcc structure in the layer mosaic structure is less than that of hcp structure.When the size of the atom cluster with the crystalline structure in copper melt is smaller than the critical size of the homogenous nucleation huclei,radial distribution function cannot reflect out the feature of crystalline structure though the HA bond-type index have confirmed the presence of a certain number of atom bond of crystalline structure.