title: Degenerate seaweed to tilted dendrite transition and their growth dynamics in directional solidification of non-axially oriented crystals: a phase-field study.
abstract: We report the results of a phase-field study of degenerate seaweed to tilted dendrite transition and their growth dynamics during directional solidification of a binary alloy. Morphological selection maps in the planes of (G, Vp) and (ε4, Vp) show that lower pulling velocity, weaker anisotropic strength and higher thermal gradient can enhance the formation of the degenerate seaweed. The tip undercooling shows oscillations in seaweed growth, but it keeps at a constant value in dendritic growth. The M-S instability on the tips and the surface tension anisotropy of the solid-liquid interface are responsible for the formation of the degenerate seaweed. It is evidenced that the place where the interfacial instability occurs determines the morphological transition. The transient transition from degenerate seaweed to tilted dendrite shows that dendrites are dynamically preferred over seaweed. For the tilted dendritic arrays with a large tilted angle, primary spacing is investigated by comparing predicted results with the classical scaling power law, and the growth direction is found to be less sensitive to the pulling velocity and the primary spacing. Furthermore, the effect of the initial interface wavelength on the morphological transition is investigated to perform the history dependence of morphological selection.
authors.affiliation: The Key Laboratory of Space Applied Physics and Chemistry, Northwestern Polytechnical University, Xi'an, 710129, P.R. China.
authors.forename: Hui
authors.initials: H
authors.lastname: Xing
authors.affiliation: The Key Laboratory of Space Applied Physics and Chemistry, Northwestern Polytechnical University, Xi'an, 710129, P.R. China.
authors.forename: Xianglei
authors.initials: X
authors.lastname: Dong
authors.affiliation: The Key Laboratory of Space Applied Physics and Chemistry, Northwestern Polytechnical University, Xi'an, 710129, P.R. China.
authors.forename: Hongjing
authors.initials: H
authors.lastname: Wu
authors.affiliation: The Key Laboratory of Space Applied Physics and Chemistry, Northwestern Polytechnical University, Xi'an, 710129, P.R. China.
authors.forename: Guanhua
authors.initials: G
authors.lastname: Hao
authors.affiliation: The Key Laboratory of Space Applied Physics and Chemistry, Northwestern Polytechnical University, Xi'an, 710129, P.R. China.
authors.forename: Jianyuan
authors.initials: J
authors.lastname: Wang
authors.affiliation: The Key Laboratory of Space Applied Physics and Chemistry, Northwestern Polytechnical University, Xi'an, 710129, P.R. China.
authors.forename: Changle
authors.initials: C
authors.lastname: Chen
authors.affiliation: The Key Laboratory of Space Applied Physics and Chemistry, Northwestern Polytechnical University, Xi'an, 710129, P.R. China.
authors.forename: Kexin
authors.initials: K
authors.lastname: Jin
mesh_terms: D016880:Anisotropy; D003461:Crystallography; D008956:Models, Chemical; D012624:Seaweed