冷速对Cu10Ag90合金凝固结构的影响

The effect of cooling rate on solidification structure of CuAg alloy

通过分子动力学对液态Cu10Ag90合金在四种冷速条件下进行快速凝固模拟.结果显示,1×10^(10)和1×10^(11)K/s下系统的平均原子能量分别在750 K和650 K发生突变,冷速越低最终平均原子能量越低;1×10^(12)和1×10^(13)K/s的双体分布函数第二峰出现分裂,表明结构处于非晶态.从1×10^(11)K/s开始出现尖锐小峰,表明此冷速开始出现晶化现象,1×10^(10)K/s下分裂的峰更加尖锐明显,说明体系形成结晶度较高的晶体结构;1×10^(10)和1×10^(11)K/s下系统凝固后晶体结构含量由高到低分别为fcc,hcp,bcc.冷速越低晶体结构数目越多,系统的有序度更高,结构熵越低.

The rapid solidification of Cu10Ag90 alloy is investigated under four cooling rates by molecular dynamics(MD) simulation.The result shows that the average atomic energies suddenly change at 750 K and 650 K under 1 ×10^(10),1 ×10^(11) K/s,respectively.The lower cooling rate gets,the lower final average atomic energy.The second peaks at the cooling rates of 1 ×10^(12) and 1 ×10^(13) K/s split into two sub-peaks,indicating that amorphous structure has been formed.There are many sharp major peaks in pair distribution function curves from the cooling rate of 1 ×10^(11) K/s,demonstrating the existence of the crystalline microstructures.With the rise of sharp major peaks,the crystallinity of structure goes up under the cooling rate of 1 ×10^(10) K/s.The number of fcc,hcp,bcc crystal clusters have been formed in order at the cooling rates of 1 ×10^(10) and 1 ×10^(11) K/s.As cooling rate decreases,the order degree gets higher and the structural entropy becomes lower due to the more crystal clusters.