Becker C A, Olmsted D, Asta M, Hoyt J J, Foiles S M
Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA.
Phys Rev Lett. 2007 Mar 23;98(12):125701. doi: 10.1103/PhysRevLett.98.125701. Epub 2007 Mar 21.
In dendritic solidification, growth morphologies often display a pronounced sensitivity to small changes in composition. To gain insight into the origins of this phenomenon, we undertake an atomistic calculation of the magnitude and anisotropy of the crystal-melt interfacial free energy in a model alloy system featuring no atomic size mismatch and relatively ideal solution thermodynamics. By comparing the results of these calculations with predictions from recent phase-field calculations, we demonstrate that alloying gives rise to changes in free-energy anisotropies that are substantial on the scale required to induce changes in growth orientations.
在枝晶凝固过程中，生长形态通常对成分的微小变化表现出显著的敏感性。为了深入了解这一现象的起源，我们在一个不存在原子尺寸失配且具有相对理想溶液热力学的模型合金体系中，对晶体 - 熔体界面自由能的大小和各向异性进行了原子尺度计算。通过将这些计算结果与近期相场计算的预测结果进行比较，我们证明合金化会导致自由能各向异性发生变化，这种变化在诱导生长取向改变所需的尺度上是相当大的。
