Orientation Dependence of Columnar Dendritic Growth with Sidebranching Behaviors in Directional Solidification: Insights
- PDF / 3,960,197 Bytes
- 13 Pages / 593.972 x 792 pts Page_size
- 31 Downloads / 184 Views
Orientation Dependence of Columnar Dendritic Growth with Sidebranching Behaviors in Directional Solidification: Insights from Phase-Field Simulations HUI XING, XIANGLEI DONG, JIANYUAN WANG, and KEXIN JIN In this study, a thin-interface phase-field model was employed to study the orientation dependence of the columnar dendritic growth with sidebranching behaviors in directional solidification. It was found that the dimensionless tip undercooling increases with the increase of misorientation angle for three pulling velocities. The primary spacing is found to be a function of misorientation angle, and the dimensionless primary spacing with respect to the misorientation angle follows the orientation correction given by Gandin and Rappaz (Acta. Metall. 42:2233–2246, 1994). For the analysis of the dendritic tip, the two-dimensional (2-D) form of the nonaxisymmetric needle crystal was used to determine the radius of the tilted columnar dendrite. Based on the definitions of open side and constrained side of the dendrite, the analysis of the width active sidebranches and the dendritic area in 2-D with respect to the distance from the dendritic tip was carried out to investigate the asymmetrical dendrite envelop and sidebranching behaviors on the two sides in directional solidification. The obtained prefactor and exponent with respect to misorientation angle are discussed, showing that the sidebranching behaviors of a tilted columnar dendritic array obey a similar power-law relationship with that of a free dendritic growth. https://doi.org/10.1007/s11663-018-1265-0 The Minerals, Metals & Materials Society and ASM International 2018
I.
INTRODUCTION
DENDRITES, originating from the instability of the solid-liquid interface, are the predominant microstructural features in the solidification of alloys, and their length scales and segregation patterns have a significant influence on the mechanical properties of the casting products.[1] Thus, understanding of the formation and evolution of dendritic growth as well as sidebranching has been of long standing interest in the scientific and technological fields. The interplay among the heat and mass diffusions, capillary effect, and fluid flow determines the evolution and formation of dendritic crystal grains and segregation patterns.[2,3] Directional solidification provides a well-established paradigm for competitive effects and resulting interface morphologies in nonequilibrium systems. In directional solidification, the alloy sample is
HUI XING, JIANYUAN WANG, and KEXIN JIN are with The Key Laboratory of Space Applied Physics and Chemistry, Northwestern Polytechnical University, Xi’an 710129, P.R. China. Contact email: [email protected] XIANGLEI DONG is with the College of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, P.R. China. Manuscript submitted July 31, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
pulled to grow at a pulling velocity of Vp through a fixed thermal gradient G. When the pulling velocity is above a critical value, the well-known Mullins–S
Data Loading...
