純鋁材具有良好的散熱性與抗腐蝕性，常被使用於汽車散熱器之相關工件上，然而散熱器內部工件接合使用硬銲製程，製程過程的熔融液相會往接合點附近工件的晶界穿隧，造成銲接點弱化和工件可靠度發生問題。本實驗利用摩擦攪拌製程（friction stir process, FSP）局部加工的優點，且攪拌材經高溫加熱處理後晶粒粗大化現象，得到具有局部粗大化之純鋁材，未來可應用於欲銲接的位置，以減少改善液相沿晶界穿隧之問題，又能保留整體工件之強度。本研究選用商用1050純鋁材，透過改變摩擦攪拌製程轉速與加熱處理的參數以獲得不同晶粒徑的粗大化晶粒，並探討粗大化材料的拉伸性質，以了解於後續加工可能產生之問題，最後利用浸鍍試驗模擬硬銲製程，觀察液相穿隧之情形。
研究結果顯示，低轉速之攪拌材晶粒粗大化臨界溫度相對較低。而粗大化現象先行發生在攪拌區上表面，隨加熱處理時間的增加，粗大化所涵蓋的範圍增加。於晶粒徑變化的部分，固定加熱時間下，粗大化晶粒的平均晶粒徑隨加熱處理溫度上升而下降；固定加熱溫度下，粗大化晶粒的平均晶粒徑隨加熱處理時間增加先下降，但後續持溫時間增加平均晶粒徑之變化趨緩。
此外，本實驗分別取拉伸方向平行/垂直攪拌進給方向兩種試片，探討晶粒粗大化對拉伸性質的影響。拉伸方向平行攪拌進給方向之試片，延性與強度皆隨著平均晶粒徑的上升而下降，且粗大化後之延性因為單位體積內之晶粒少，維持持續變形的滑移系統少，延性值偏低；拉伸方向垂直攪拌進給方向之試片，平行部包含粗大化晶粒與相對較小之晶粒（經同樣加熱條件之基材部分），其延性隨著粗大晶粒徑的增加而下降，由金相圖可觀察到粗細晶粒徑不匹配處為變形量較大之區域，且斷裂位置在靠近晶粒徑不匹配處的粗晶。
於模擬硬銲製程的浸鍍實驗，可觀察到粗大化之攪拌材浸鍍於ADC12鋁合金熔融液也會有穿隧現象，若與未粗大化材料的浸鍍結果比較，因粗大化後晶界比例較少，發生液相穿隧的路徑少，液相穿隧現象因此改善。

Commercial pure aluminum is widely used for car heat exchanger due to its excellent heat dissipation and high corrosion resistance. The joint process of workpieces in heat exchanger is brazing. However, in some cases the brazing may cause the penetration on the workpieces around joint point by melting metal along grain boundary. This phenomenon may worsen the joint part and lead to some reliability problems. Thus, in order to coarsen the grains of the material to improve the liquid phase penetration and not decrease the strength, friction stir process (FSP) is conducted based on the advantage of partial modification and heat treatment-induced grain coarsening. In this research, Commercial pure aluminum 1050 was used to obtain diverse coarse grain sizes by changing the rotational rate of FSP and parameters of heat treatment. Then, The tensile properties of coarse grain samples were investigated to clarify the problems from subsequent processing. Finally, dipping was chosen to replace the brazing to observe the liquid phase penetration.
The results reveal that the lower rotational rate of FSP is, the lower critical temperature of the grain coarsening is. Furthermore, the grains coarsen initially occur on the top of stir zone and then extend to other regions with increasing heating time. There are two variations in grain size. The first one is that the average coarse grain size decrease with increasing the temperature in the fixed heat treatment time. The other is that the average coarse grain size decrease with time in the fixed heat treatment temperature. Then, the average grain size may become steady in the subsequent duration time.
In the tensile test, two kinds of samples, with feeding direction parallel to the tensile direction and perpendicular to the tensile direction, were used to discuss the grain coarsening effect on tensile property. The strength and ductility for the parallel samples decreased with increasing average grain size. Great decrease in ductility resulted from less grains and slip system maintaining deformation in tensile process. The perpendicular samples contain coarse grains and fine grains, and their ductility decreased with increasing coarse grain size. And the crack phenomenon occurred in the coarse grain near the incompatibility of the grain size.
In the dipping test, the result shows that if the number of grain boundary became less by grain coarsening, the penetration of the melting ADC12 aluminum alloy can be improved.

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