BCC枝晶生长原子堆垛过程的晶体相场研究

Investigation of atom-attaching process of three-dimensional body-center-cubic dendritic growth by phase-field crystal model

通过在自由能泛函中引入各向异性参数得到了一个基于高斯内核的改进晶体相场模型,并采用该模型研究了体心立方结构(BCC)枝晶生长的原子堆垛过程.结果表明,在BCC由正十二面体平衡形貌演化为枝晶组织过程中,形核位置经历了由面心({110}面)到尖端(?100?取向)的转移,进而发生界面失稳形成枝晶组织;枝晶生长过程中,新的固相原子首先在枝晶尖端附近形核,并快速向尖端及根部生长,枝晶尖端被新原子完全包覆后将再次诱发液相原子附着形核及生长;随初始液相密度的增加,固-液界面移动速率增加,速率系数的各向异性也增强.

On the basis of the Gaussian kernel phase field crystal model （PFC）, we propose a modified PFC model. The atom-attaching process of three-dimensional body-center-cubic （BCC） dendritic growth is examined by using the modified PFC model. Our simulations indicate that in the process of the morphology evolution from regular dodecahedron to dendrite shape, the nucleation position of new layer is transferred from the center of {110} planes into the region of{110}plane near the？100？tips, and then the BCC dendritic morphology is obtained. In the process of dendritic growth, first, new solid atom absorption takes place near dendrite tips, then liquid atoms start to grow up on the existing solid phase rapidly. After the dendrite tips are completely occupied by new atoms, new nuclei begin to form again. Increasing the initial atom density n will increase the velocity coe？cient C and the anisotropy of C.