Cheng H, Lü Y J, Chen M
Department of Engineering Mechanics, Tsinghua University, Beijing 100084, People's Republic of China.
J Chem Phys. 2009 Jul 28;131(4):044502. doi: 10.1063/1.3184614.
The interdiffusion processes in liquid Al-Cu and Ni-Cu alloys are studied by using molecular dynamics simulation method. The Maxwell-Stefan (MS) diffusivities are calculated over a wide composition range with both the Green-Kubo method and the Darken relation. Comparisons show that the Darken relation predicts well the MS diffusivity for Ni-Cu alloy, while overestimates the value for Al-Cu alloy, especially in the medium concentration region. Based on the calculated MS diffusivities and the activities of the alloys, the Fickian interdiffusivities are predicted. The results show strong dependences on the compositions of the alloys. In addition, the Fickian interdiffusivities of Al(60)Cu(40) and Ni(50)Cu(50) melts as a function of undercooling are estimated, which is proved to be beneficial in improving the quantitative predictions of dendrite growth velocity in solidification.
采用分子动力学模拟方法研究了液态Al-Cu和Ni-Cu合金中的互扩散过程。利用格林-库博方法和达肯关系在较宽的成分范围内计算了麦克斯韦-斯蒂芬（MS）扩散系数。比较表明，达肯关系能很好地预测Ni-Cu合金的MS扩散系数，而对Al-Cu合金的值则有高估，尤其是在中等浓度区域。基于计算得到的MS扩散系数和合金的活度，预测了菲克互扩散系数。结果表明，其强烈依赖于合金的成分。此外，还估算了Al(60)Cu(40)和Ni(50)Cu(50)熔体的菲克互扩散系数随过冷度的变化关系，这被证明有利于改进凝固过程中枝晶生长速度的定量预测。
