本研究主要是探討凝固冷卻條件對A390鋁合金的顯微組織及
機械性質的影響。實驗採用三種不同厚度平板配合不同尺寸的冒口
與冷激鐵以獲得不同的冷卻參數。
實驗結果顯示，鑄件加大冒口尺寸可降低孔洞率，對鑄件偏析
現象有改善。增大冷激鐵寬度，可以降低中、厚板鑄件的孔洞率，
提高抗拉強度與硬度，細化初晶矽，改善鑄件偏析現象，但對薄板
鑄件影響較小。
鑄件孔洞率與補充效率因子和溫度梯度的相關性較高。初晶矽
尺寸與凝固指數和補充效率因子的相關性較高。偏析現象與中、厚
板鑄件的冷卻速率和補充效率因子的相關性較高。
鑄件的孔洞率與初晶矽和抗拉強度有較大的相關性，對硬度、
伸長率的相關性較低。鑄件抗拉強度與補充效率因子和凝固指數的
相關性較高，與溫度梯度的相關性較低。鑄件伸長率的實驗數據紊
亂與冷卻參數幾乎無關，但厚板鑄件的伸長率比薄、中板鑄件都大。
鑄件硬度與溫度梯度和補充效率因子相關性較高。若考慮板厚因素，
中、厚板鑄件與冷卻參數的相關性都很高。

The effects of solidification cooling conditions on microstructures and mechanical properties of the A390 aluminum alloy were studied in this research. The cooling parameters were varied substantially by employing various plate thickness and different riser and chill dimensions.
The results of this study show that the increasing of the riser size of casting will decrease the porosity and modify the segregation. Meanwhile,increasing the size (dimension, width) of chills can lower the porosity and advance the strength of tensile and hardness of middle, thick plate casting, the smaller of primary silicon, and improve the segregation. But the affect to the thin plate castings is lighter.
The correlation of porosity with feeding efficiency factor and temperature gradients is higher. The correlation of primary silicon with freezing index and feeding efficiency factor is higher. In the phenomenon of segregation, the thick plate castings is higher correlated with cooling rates and feeding efficiency factor.
The strength of tensile is higher correlated with porosity and primary silicon than the hardness and elongation. Meanwhile, the strength of tensile is higher correlated with feeding efficiency factor and freezing index than the temperature gradients.
The elongation is almost none correlated with cooling parameters but that of thick plate is larger than thin and middle plate. The hardness of castings is higher correlated with temperature gradients and feeding efficiency factor. But considering the factor of plate's thickness, the middle and thick plate is highly correlated with cooling parameters.