过冷度和耦合系数对枝晶生长速度及形貌的影响

Effects of Super-cooling Degree and Coupling Coefficient on Dendrite Growth Rate and Morphology

采用耦合溶质场、温度场的相场模型,对金属镍凝固过程中枝晶生长进行模拟,研究了过冷度和耦合度对枝晶生长速度及形貌的影响。结果表明:过冷度和耦合度比较小时,整个枝晶形貌近似球形,枝晶生长速度随着过冷度和耦合度的增加而增加,主枝的增长速度优于其他方向,整个枝晶由开始近似球形慢慢变为星形;随过冷度继续增大,主枝的生长优势慢慢消失,出现更多侧枝,整体形貌又开始向球形过渡,直至第二侧枝速度赶上主枝,第三侧枝则完全消失。

The dendrite growth of nickel solidification process was simulated by the phase-field model coupling with solute field and temperature field, and the effects of super-cooling degree and coupling coefficient on dendrite growth rate and morphology were investigated. The results show that the dendrite morphology approximates sphere when the super-cooling degree and coupling coefficient is small. The dendrite growth rate increases with the increase of super-cooling degree and coupling coefficient. The main branch growth rate is faster than the other direction, and the dendrite morphology slowly begin to become star from sphere. Along with the super-cooling degree continues to increase, the main branch growth advantage disappears and more lateral branches appear, the dendrite morphology begin to become spherical. Until the second lateral branch catch up with the main branch rate, the third lateral branch has completely disappeared.