The stability range of primary spacing of the tilted dendritic arrays in directional solidification has been studied by quantitative phase-field simulations. Results show that both the real growth direction and morpho...The stability range of primary spacing of the tilted dendritic arrays in directional solidification has been studied by quantitative phase-field simulations. Results show that both the real growth direction and morphological shapes of dendritic arrays change with the primary spacing for different misorientation angles(θ0). It has been found that the lower limit of primary spacing is independent of θ0, but the upper limit of primary spacing is strongly influenced by that. The two kinds of tertiary branching instabilities result in different behaviors of the variation of the upper limit with misorientation angle for different pulling velocities.展开更多
In this paper,we introduce different forms of mobility into a quantitative phase-field model to produce arbitrary Ehrlich-Schwoebel(ES)effects.Convergence studies were carried out in the one-side step-flow model,which...In this paper,we introduce different forms of mobility into a quantitative phase-field model to produce arbitrary Ehrlich-Schwoebel(ES)effects.Convergence studies were carried out in the one-side step-flow model,which showed that the original mobility not only induces the ES effect,but also leads to larger numerical instability with increase of the step width.Thus,another modified form of the ES barrier is proposed,and is found to be more suitable for large-scale simulations.Model applications were performed on the wedding-cake structure,coarsening and coalescence of islands and spiral growth.The results show that the ES barrier exhibits more significant kinetic effects at the larger deposition rates by limiting motions of atoms on upper steps,leading to aggregation on the top layers,as well as the roughening of growing surfaces.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.61078057 and 51172183)the Natural Science Foundation of Shaanxi Province in China(Grant No.2012JQ8013)+1 种基金the Fundamental Research Funds for the Central Universities(Grant Nos.3102014KYJD026 and JC20120246)the grant from the Program of New Staff and Research Area Project of NPU(Grant No.13GH014602)
文摘The stability range of primary spacing of the tilted dendritic arrays in directional solidification has been studied by quantitative phase-field simulations. Results show that both the real growth direction and morphological shapes of dendritic arrays change with the primary spacing for different misorientation angles(θ0). It has been found that the lower limit of primary spacing is independent of θ0, but the upper limit of primary spacing is strongly influenced by that. The two kinds of tertiary branching instabilities result in different behaviors of the variation of the upper limit with misorientation angle for different pulling velocities.
基金The National Natural Science Foundation of China(Grant Nos.61078057,61471301,51172183,51402240 and 51471134)The NPU Foundation for Fundamental Research(Grant No.JC20120246)+2 种基金The National Science Foundation of Shaanxi Province,China(Grant No.2012JQ8013)The Doctorate Foundation of Northwestern Polytechnical University(Grant No.CX201325)The Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20126102110045)
文摘In this paper,we introduce different forms of mobility into a quantitative phase-field model to produce arbitrary Ehrlich-Schwoebel(ES)effects.Convergence studies were carried out in the one-side step-flow model,which showed that the original mobility not only induces the ES effect,but also leads to larger numerical instability with increase of the step width.Thus,another modified form of the ES barrier is proposed,and is found to be more suitable for large-scale simulations.Model applications were performed on the wedding-cake structure,coarsening and coalescence of islands and spiral growth.The results show that the ES barrier exhibits more significant kinetic effects at the larger deposition rates by limiting motions of atoms on upper steps,leading to aggregation on the top layers,as well as the roughening of growing surfaces.
