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。電磁凝固是以電場或磁場搭配控制參數來控制凝固過程，此技術較為複雜的研究領域。
本研究是以方向性凝固製備錫鉛合金，使用不同濃度之錫鉛合金(Sn-10wt.%Pb)、(Sn-37wt.%Pb)以及(Sn-60wt.%Pb)作為研究材料，施加強力磁鐵所產生的磁場效應研究凝固過程。透過不同的控制參數實驗出六種不同之實驗組別，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。
實驗結果分析可知，含鉛量越高，其硬度值越小。以有無施加磁鐵之部分加以說明，觀察橫切面之金相組織，可以發現有施加磁鐵之組別，其硬度值會比無施加磁鐵之組別還大，原因是有施加磁鐵之組別受到強力磁鐵之影響，使內部晶粒尺寸細化，而整體之硬度值上升之現象。探討密度值之大小，純鉛之密度高於純錫之密度，因此在分析不同濃度之錫鉛合金時，含鉛濃度越高之錫鉛合金，其密度較高，熔點與沸點也會上升。

This study prepared tin-lead alloy for directional solidification, using tin-lead alloy (Sn-10wt.%Pb)、(Sn-37wt.%Pb) and (Sn-60wt.%Pb) of different concentrations as the research materials, with used the magnetic field effect by the application of a strong magnet to study the solidification process. Through six different experimental cases with different control parameters, the study is to analysis the macro metallographic structure and micro metallographic structure, cooling curve, temperature gradient, growth rate, grain size and hardness value etc.

The analysis of experimental results shows that the hardness value is smaller when the lead concentration is higher. Explain whether the magnet is applied or not. Observing the metallographic structure of the cross-sectional, it can be found that the hardness value of the case with themadnet applied is higher than the case without magnet. The reason is that the case with magnet applied receives strong magnetic field. The influence of the magnet makes the internal grain size refinement and the overall hardness value increases.

Discuss the density value. The density of pure lead higher than pure tin. Therefore, when analyzing the different concentrations of tin-lead alloy, the density and the melting point and boiling point is higher when the lead concentration is higher.

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