冷却速率对液态金属Zn快速凝固过程中微观结构的影响

Effect of Cooling Rates on Microstructures during Solidification Process of Liquid Metal Zn

用分子动力学模拟方法研究了六种不同冷却速率对液态金属Zn凝固过程微观结构的影响.采用双体分布函数g(r)曲线、平均原子总能量、Honeycutt-Andersen(HA)键型指数法和原子团类型指数法(CTIM-2)对凝固过程中微观结构的变化进行了分析.结果表明,冷却速率对微观结构的转变有决定性影响,当冷却速率为1×1014、5×1013、2×1013、1×1013、5×1012K·s-1时,系统形成以1551、1541、1431键型为主体的非晶态结构;当冷却速率为1×1012K·s-1时,系统形成以1421、1422键型为主或以密排六方(hcp)基本原子团(1200066)和面心立方(fcc)基本原子团(12000120)共存的部分晶态结构.同时发现,在形成非晶的五个系统中,玻璃化转变温度Tg随着冷速的降低而降低.

A simulation study was performed for the effects of six different cooling rates on microstructure during solidification of liquid metal Zn adopting molecular dynamics method. The pair distribution function g（r） curves, the total energy per atom, the bond-type index method and the cluster-type index method （CTIM-2） were used to analyze the variations of microstructure during the solidification process. The results showed that the cooling rate played a critical role in the microstructure transitions. As the cooling rate being 1×10^14, 5×10^13, 2×10^13, 1 ×10^13, 5×10^12 K ·s^-1, the amorphous structures would be formed with 1551, 1541 and 1431 bond-types as the main body in the system. As the cooling rate being 1×10^12 K·s^-1, a part of crystal structure would be formed, in which the hcp and fcc basic cluster structures with 1421 and 1422 bond-types coexisted as the main body. At the same time, it was found that the glass transition temperature Tg would be decreased with the cooling rate slowing down.