中文摘要：

利用微观组织相场法数值模拟技术,对Ni-Cu二元合金在温度梯度G=20K/cm条件下定向凝固的界面形态演化过程进行模拟仿真.基于均匀网格的有限差分法,采用C语言编制定向凝固晶体生长的相场法数值模拟程序,研究计算参数对凝固组织的影响,探讨定向凝固过程晶体的生长机制.研究结果表明：低的温度梯度条件下,初始平界面一旦失稳,快速形成胞状组织,在随后的演化过程中,侧向分支大量繁殖、尖端分裂,形成海藻状生长形态.因此,低温度梯度下二元合金定向凝固界面形态的转化形式为：平面状向胞状转变,最后转变为海藻状.

英文摘要：

Based on the numerical simulation technique of microscopic structure with phase-field method, the evolution of interface morphology of directionally solidified Ni-Cu binary alloy under constant thermal gradient G=20 K/cm is simulated in this paper. The finite difference method with uniform grid and C-Pro- gramming Code are used to compile the numerical simulation program of the growth of directionally solidi- fied crystal with phase-field method. The effects of computation parameters on solidified microstructure are studied and the mechanism of crystal growth in the process of directional solidification is explored. The investigation result indicates that, once the initial smooth solidification front was disrupted under the con- dition of low thermal gradient and became unstable, the cellular structures would occur immediately. In the subsequent process of evolution, a large number of side-branches propagate, and the cellular tips are split, forming seaweed-like growth morphology. So, the transition process of the solidification interface morphology in the process of directional solidification of binary alloy with low thermal gradient is as fol- lows： from flat form to cellular form to seaweed-like form.