中文摘要：

采用直径为4min和7min的试样对Al-4％Cu（质量分数，下同）合金进行定向凝固实验。研究表明：小直径试样温度梯度更高，但温度梯度变化幅度并未与试样直径比成线性比例。试样直径较小，胞／枝晶间距相应较小。获得直径为4min和7min试样一次枝晶间距与生长速率的关系，一次枝晶间距和生长速率、温度梯度的变化关系，且与理论值相符合；一次枝晶间距实验结果与TRIVEDI模型符合较好。

英文摘要：

Directional solidification experiment was carried out on Al-4%Cu（mass fraction） alloy with sample diameters of 4 mm and 7 mm. The results show that the sample with small diameter gets higher thermal gradient, the variation range of temperature gradient is not direct proportional to the ratio of diameters. Thin samples correspond to the smaller cellular and dendrite arm spacing. The variation of primary dendrite arm spacing for 4 mm and 7 mm sample in diameter with growth velocity and the relationship of primary dendrite arm spacing with growing velocity and temperature gradient are obtained. Both relationships agree with the theoretical model. The experimental result fit well with TRIVEDI model.