凝固是指在溫度降低時，物質由液態轉變成固態之過程。而在凝固過程中，會因為不同之濃度、溫度與冷卻條件等控制參數，會形成不同的巨觀及微觀結構以及決定各項之物理性質與化學性質，並可以運用在各種領域當中。
方向性凝固，又稱為定向凝固，使金屬材料利用人為控制融熔金屬的結晶成長方向，得到結晶方向相近的柱狀晶，並更進一步獲得單晶結構的凝固方法。
本研究是以方向性凝固製備鋁銅合金，使用不同濃度之鋁銅合金(91.5wt.%Al-6wt.%Cu-0.6wt.%Bi-0.7wt.%Fe)、(90wt.%Al-5wt.%Cu-1.2wt.%Mn-1.2wt.%Si-0.8wt.%Mg-0.7wt.%Fe)以及(91wt.%Al-4wt.%Cu-2wt.%Mg-1wt.%Mn-0.5wt.%Si-0.5wt.%Fe)作為研究材料。透過不同的控制參數實驗出九種不同之實驗組別，分析巨觀及微觀金相組織、冷卻曲線、溫度梯度、成長速率、晶粒尺寸及硬度值等。

Solidification is a process in which a substance changes from a liquid state to a solid state when the temperature drops. In the solidification process, different control parameters such as concentration, temperature and cooling conditions will result in different macroscopic and microscopic structures and determine various physical and chemical properties, which can be applied in various fields.

Directional solidification, also known as directional solidification, is a method of solidification in which the crystallization direction of the molten metal is artificially controlled to obtain columnar crystals with similar crystallization direction and further single crystal structure.

In this study, Al-Cu alloys were prepared by directional solidification using different concentrations of Al-Cu alloys (91.5wt.%Al-6wt.%Cu-0.6wt.%Bi-0.7wt.%Fe), (90wt.%Al-5wt.%Cu-1.2wt.%Mn-1.2wt.%Si-0.8wt.%Mg-0.7wt.%Fe)and( 91wt.%Al-4wt.%Cu-2wt.%Mg-1wt.%Mn-0.5wt.%Si-0.5wt.%Fe) were used as study materials. Nine different experimental groups were experimented with different control parameters to analyze the macroscopic and microscopic metallographic organization, cooling curves, temperature gradient, growth rate, grain size and hardness values.

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