中文摘要：

材料的微观组织结构对材料的性能具有决定性的作用,而凝固过程中横向限制的存在则会直接影响晶体微观结构的演化过程。利用非等温的相场模型,以纯金属Ni为研究对象,模拟了其在横向挡板限制下的微观组织演化过程,研究不同形状横向挡板对不同初始枝晶间距枝晶演化过程的影响,讨论挡板形状对枝晶间距的调整作用。结果表明：横向限制的存在会明显改变晶体的生长和发育过程,且不同形状横向挡板的限制均会对枝晶间距产生显著的影响：上三角形挡板对枝晶间距的改变最明显;下三角形及矩形的横向限制对枝晶间距具有一定的控制作用,即对于不同初始间距枝晶绕过这两类挡板后具有基本相同的重新发育模式,枝晶间距只与挡板尺寸有关,与初始枝晶间距关系不大;不同尺寸梯形挡板对于枝晶间距具有完全不同的调整作用,通过调整梯形挡板尺寸比例可以有效实现改变枝晶间距的作用。因此,在凝固过程中引入不同性质的横向限制可以有效地实现枝晶间距调整。

英文摘要：

The mechanical properties of materials are strongly dependent upon their microstructures, and the lateral constrains in presence of melt have a significantly effect on the microstructure evolution. A non-isothermal phase-field model for pure metal was implemented to simulate the microstructure evolution in the presence of lateral constrains of different shapes during the solidification of pure Ni, in order to study the effect of lateral constrains on the dendritic spacing changes caused by these lateral constrains. The results indicate that lateral constrains have a direct influence on the dendrite development, and the lateral constrains of different shapes can lead to different influences on the dendrite arm spacing changes. The constrains of triangle with sharp corner at the bottom has the most significant influence on the dendrite spacing changes, and rectangle and triangular constrains with its sharp corner above show a controlling effect on the dendrite arm spacing, that is, the dendrite growth of different primary arm spacings has the same developing manner with these two kinds of lateral constrains, the new developing dendrite arm spacing is determined by the shape of constrains, and has less relationship with its primary arm spacing. When the lateral constrain of trapezoid is introduced, the dendrite arm spacing can be determined by changing the size of the hemline of constrains. Therefore, the lateral constrains in the solidification process can significantly change the dendrite arm spacing.