Fe50Cu50合金熔体相分离过程的分子动力学模拟

摘要

Molecular dynamics simulation based on the newly developed embedded atom method has been performed to explore the microstructure of liquid Fe50Cu50 alloy. The results show that coordination numbers (CNs) of Fe-Fe and Cu-Cu for Fe50Cu50 melt gradually increase with relaxation time increasing, and they are 9.9 and 9.3 respectively as the liquid is in an equilibrium state; while the CN of heterogeneous atomic pairs Fe-Cu gradually decreases, and it is about 4.6. The correlation length (CL) extracted from Bhatia-Thornton (B-T) structure factor increases with relaxation time increasing. Both CN and CL indicate that the Fe50 Cu50 melt exhibits liquid-liquid (L-L) phase separation. The interconnected type of structure can be observed in the Fe50Cu50 melt at the early stage, then the heterogeneous atomic pairs separate gradually with time going by, the Fe-rich and Cu-rich structure are formed, which shows the characteristics of spinodal decomposition. By comparison, the atom snapshot of Fe75Cu25 melt is also visualized in the paper, and the finding indicates that the smaller number difference between Fe atom and Cu atom may lead to the stronger L-L phase separation, as a result of shorter time to reach stable layer-like structure. Our studies mentioned above characterize L-L phase separation of metallic liquid on the atomic scale.%基于镶嵌原子势，采用分子动力学模拟的方法探讨了Fe50Cu50合金熔体在1823 K下液-液相分离过程。结果发现：熔体中同类原子配位数随弛豫时间的延长逐渐增大，而异类原子配位数逐渐减少；由Bhatia-Thornton结构因子SCC(q)获得的相关长度随时间的变化也呈现出明显的递增趋势，表明该合金熔体在该温度下发生了液-液相分离。原子轨迹的可视化显示结果发现，相分离的初期，体系呈明显的网络状组织，随时间的延长，异类原子逐渐分离，最终形成富Fe和富Cu的相分离组织，符合调幅分解特征。与Fe75Cu25合金熔体的相分离过程对比发现， Fe与Cu原子数目相差越小，相分离行为越剧烈，形成稳定分层结构所需的时间越短。以上研究从原子尺度上表征了金属熔体的相分离过程。