Effect of Temperature and Fluid Flow on Dendrite Growth During Solidification of Al-3 Wt Pct Cu Alloy by the Two-Dimensional Cellular Automaton Method CHENG GU, YANHONG WEI, RENPEI LIU, and FENGYI YU A two-dimensional cellular automaton–finite volume model was developed to simulate dendrite growth of Al-3 wt pct Cu alloy during solidification to investigate the effect of temperature and fluid flow on dendrite morphology, solute concentration distribution, and dendrite growth velocity. Different calculation conditions that may influence the results of the simulation, including temperature and flow, were considered. The model was also employed to study the effect of different undercoolings, applied temperature fields, and forced flow velocities on solute segregation and dendrite growth. The initial temperature and fluid flow have a significant impact on the dendrite morphologies and solute profiles during solidification. The release of energy is operated with solidification and results in the increase of temperature. A larger undercooling leads to larger solute concentration near the solid/liquid interface and solute concentration gradient at the same time-step. Solute concentration in the solid region tends to increase with the increase of undercooling. Four vortexes appear under the condition when natural flow exists: the two on the right of the dendrite rotate clockwise, and those on the left of the dendrite rotate counterclockwise. With the increase of forced flow velocity, the rejected solute in the upstream region becomes easier to be washed away and enriched in the downstream region, resulting in acceleration of the growth of the dendrite in the upstream and inhibiting the downstream dendrite growth. The dendrite perpendicular to fluid flow shows a coarser morphology in the upstream region than that of the downstream. Almost no secondary dendrite appears during the calculation process. DOI: 10.1007/s11663-017-1060-3 Ó The Minerals, Metals & Materials Society and ASM International 2017 I. INTRODUCTION DENDRITE microstructure, the most commonly observed during the solidification process, is closely associated with the final properties of welding and casting products. [1–4] The dendrite growth is a complex physical process significantly influenced by heat and solute transfer as well as fluid flow during solidification. To improve mechanical performance of the final prod- ucts, it is valuable to study the key factors affecting the evolution of dendrites. Experimental tests are great useful methods for the examination of solidification microstructure. Sal- loum-Abou-Jaoude et al. [5] carried out the in situ and real time observations of the equiaxed grain motion during directional solidification of Al-10 wt pct Cu under static magnetic field by means of synchrotron X-ray radiography. Shevchenko et al. [6] investigated the direc- tional bottom–up solidification of Ga-25 wt pct In alloys by using the X-ray radioscopic technique and chose three experiments for examining the effect of natural and forced convection on the growth behavior of the Indium dendrites. Murphy et al. [7] presented experimental results of near-isothermal equiaxed solidification on the Al-Cu system performed in situ with laboratory-based radiog- raphy. All of the preceding research shows that the advances achieved in compact microfocus X-ray source and detector technology have made solidification exper- iments possible. However, these works mainly focused on directional solidification, and the experiments were performed with many conditions limited, which made it hard to obtain the dynamic evolution of microstructures under the condition of elevated temperature, especially under that of welding solidification, where the various temperature fields and flow fields appear. With the improvement of computer technology and the advancement of material science in recent years, numerical simulation of microstructure evolution during solidification has led to great achievements. [8–12] Dong and Lee [9] applied a combined cellular automaton-finite CHENG GU, YANHONG WEI, RENPEI LIU, and FENGYI YU are with the College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China. Contact email: nuaaliurenpei@126.com Manuscript submitted May 22, 2017.