ZnxAl100-x合金快凝过程中微结构演变特性的分子动力学模拟

采用分子动力学方法对液态Zn_xAl_100-x（x=25,50,75）合金的快速凝固过程进行了模拟,并通过键型指数与原子团类型指数表征和分析了凝固过程中熔体微观结构的演变特性.结果表明,在冷速1×10¹²K/s下,3种成分的Zn-A1合金都形成了以1551键对和二十面体（12 0 12 0 0 0）基本原子团为主体的非晶结构,并且在玻璃转变温度T_g附近熔体中1551键对和二十面体基本原子团的数目最多;随Zn含量增加,合金玻璃转变温度T_g、非晶形成能力和化学短程序参数降低.对应不同成分的合金,Zn和A1呈现不同程度的偏聚与团簇化趋势.

MOLECULAR DYNAMICS SIMULATION ON THE EVOLUTION OF MICROSTRUCTURES OF LIQUID ZnxAl100-x ALLOYS DURING RAPID SOLIDIFICATION

A molecular dynamics simulation of the rapid solidification process of liquid Zn_xAl_100-x（x=25,50,75） alloys has been performed,and their microstructural evolutions have been analyzed by means of bond-type index method of Honeycutt-Andersen（H-A） and cluster-type index method.Results show that at the cooling rate of 1×10¹² K/s all rapid solidified alloys are amorphous structures with majority of 1551 bond-type and icosahedronal basic cluster of（12 0 12 0 0 0）. In the rapid solidification process,a peak of the number of 1551 bond-type and icosahedronal basic cluster is demonstrated to exist at the special point corresponding to the glass transition temperature （T_g） of alloys.T_g,the glass forming ability（GFA） and the chemical short-range order(P_csro) drop with the increase in content of Zn of Zn_xAl_100-x（x=25,50,75） alloys.Segregation and clustering of Zn and Al atoms in molten and rapid solidified alloys are also detected by Pcsro and visualization analysis.