中文摘要：

采用定向凝固技术研究Al-4%Cu（质量分数）合金凝固界面形态和胞/枝晶间距调整。结果表明,在v=30μm/s低速时,枝晶通过竞争淘汰调整一次枝晶间距;在v=300μm/s高速时,枝晶通过尖端开裂而不是以往的三次枝生长调整间距。尖端半径与枝晶间距相互影响,在稳定枝晶间距范围内随枝晶间距的增加而增大。采用LMK理论进行分析,得到枝晶尖端开裂是尖端溶质浓度变化引起尖端半径发生变化。通过扩散模型建立了枝晶间距与凝固界面成分之间的关系,得出枝晶通过自动调节间距大小来降低成分过冷作用。

英文摘要：

The liquid/solid interface morphologies and cellular/dendrite spacing adjustment of Al-4%Cu （mass fraction） alloy were studied during directional solidification. The results show that the primary dendrite arm spacing adjustment mechanisms are overgrowth at low growth rate of v=30 μm/s, and dendrite tip splitting at higher growth rate as v=300 μm/s, which is instead of the growth of tertiary arm at higher growth rate. The tip radius interacts with primary dendrite spacing, and increases as primary spacing becoming larger in stable primary dendrite arm spacing. It is analyzed with LMK theory that the variation of dendrite tip concentration results in tip radius change, which leads to tip splitting. According to diffusion model, the relation of primary spacing and interface concentration is also obtained, and it shows that for dendrite it could reduce constitutional undercooling with adjusting primary spacing automatically.