中文摘要：

在主要树突手臂间距和样品直径之间的关系为 Al-4%Cu (集体部分) 在方向性的团结期间被学习合金。主要树突间距以给定的生长率与样品直径的减少被减少，这被显示出。由 regressing 在主要树突手臂间距和生长率之间的关系，主要树突手臂间距遵循 461.76v ? 0.53， 417.92v ? 0.28 并且 415.83v ? 0.25 为 1.8， 3.5 和 7.2 公里的样品直径分别地。为不同样品直径的主要树突间距，生长率和热坡度遵循 28.77v ? 0.35G ? 0.70， 23.17v ? 0.35G ? 0.70 并且 23.84v ? 0.35G ? 0.70 分别地。他们都与理论模型 1=kb 历久不渝 ? a1G ? b1，和 b1/a1=2。由与古典模型一起分析试验性的结果， KURZ 鱼模型与更弱的 thermosolute 传送对流在更小的样品直径为主要树突间距适合，这被显示出。而 TRIVEDI 模型对描述主要树突合适，用一条更大的直径武装间距(d > 2 公里) 在传送对流应该被考虑的地方。

英文摘要：

The relationship between primary dendrite arm spacing and sample diameter was studied during directional solidification for Al-4%Cu （mass fraction） alloy. It is shown that primary dendrite spacing is decreased with the decrease of the sample diameter at given growth rate. By regressing the relationship between primary dendrite arm spacing and the growth rate, the primary dendrite arm spacing complies with 461.76v-0.53, 417.92v-0.28 and 415.83v-0.25 for the sample diameter of 1.8, 3.5 and 7.2 mm, respectively. The primary dendrite spacing, growth rate and thermal gradient for different sample diameters comply with 28.77v -0.35G-0.70, 23.17v-0.35G-0.70 and 23.84v-0.35G-0.70, respectively. They are all consistent with the theoretical model λ1 =kbv-a-a1G-b1, and b1/a1=2. By analyzing the experimental results with classical models, it is shown that KURZ-FISHER model fits for the primary dendrite spacing in smaller sample diameters with weaker thermosolute convection. Whereas TRIVEDI model is suitable for describing primary dendrite arm spacing with a larger diameter （d〉2 mm） where convection should be considered.