凝固為相當重要之材料製程技術，大多數之金屬材料必須先熔化成液體，再利用鑄造之方式做出成品或半成品。材料的微觀組織會在凝固過程，決定各項性質之優劣。因此如何由不同之工作條件，如環境溫度、溫度梯度、外加物理場等，來控制材料於凝固過程的微觀組織型態，強化材料的性質，故凝固學為重要的研究領域。
方向性凝固，又稱定向凝固，對於金屬材料，就是人為地控制融熔金屬的結晶生長方向，以獲得結晶方向相近的柱狀晶，甚至單晶結構的凝固方法。電磁凝固是以電場或磁場控制凝固過程，為較新的研究領域。
本研究以錫-鉛合金（Sn-10wt％Pb）為研究材料，錫-鉛合金系統是典型的共晶系統，共晶系統中，加入另一成分金屬，熔點會降低，液相線經過最低溫度點成為共晶點。
本研究主要之研究方法有巨觀金相組織與微觀金相組織觀察，洛氏硬度試驗、截線法等。根據實驗結果，在磁場作用下凝固確實會影響材料的微結構。由硬度試驗的結果，可以證實方向性凝固之鑄件機械性質較傳統砂模鑄造的鑄件好。

Of all the processing techniques used in manufacturing materials, solidification is probably the most important one. Solidification affects the morphology control of microstructures, which directly influence the mechanical and physical properties.
The directional solidification process enables grain orientation to put in order along a specific direction. This process will decrease grain boundary (G.B.), which could improve mechanical properties of materials. The electromagnetic solidification process means the solidification process with the magnetic field or electric fields, and the electromagnetic solidification is a new research field.
In our study of sand mold casting and directional solidification, lead-tin (Sn-90wt%Pb) alloy is used as the casting material. The lead-tin alloy is a classic eutectic system, in which the alloy of eutectic composition has the lowest melting temperature. To analyse the solidification processes, we used Rockwell hardness test with HRL scale, metallographic observation, including macrostructure, microstructure with optical microscope, and calculate grain size with linear intercept method.
The casting process with a water-cooling copper chills, installed at the mold bottom, could induce the desired temperature gradient to make the casting grow directionally. According to the experimental results, hardnesses of directional solidification is higher than those of the sand-mold casting.

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