| 摘要: | 本研究主要在探討加熱持溫過程中，鋁合金對氧化膜生長與分解的影響。實驗試片以「三明治形式」製成，分為上部試片、中間夾層、下部試片等三層。上部試片合金成份分別為純鋁(99.999%)、商用純鋁(99.82%)、Al-7%Si、Al-13%Si、Al-0.5%Mg、A356.2、A356.2-high Sr等七種；中間夾層是鋁表面在高溫下所成長生成的氧化膜；下部試片為純鋁(99.999%)。將上、下部試片結合，放入氬氣保護氣氛下的加熱爐中，從室溫加熱至750℃後作持溫的時間變化(12、15、20分鐘)，以比較合金成份及時間的變化對氧化膜生長與分解的影響。 實驗結果證實在高溫(610℃)自然成長的氧化膜為γ-Al2O3。由於受高溫鋁液的滲入、侵蝕，氧化膜會被分解，散開於鋁基地內；持溫時間加長，氧化膜被侵蝕、分解更嚴重，最後上、下部試片會完全融合一起。 對於合金成份的影響：實驗試片含有Si元素時，Si會吸附於氧化膜(氧化鋁)上，且有些Si會隨鋁液擴散進入膜內；試片中含有Mg元素時，Mg隨鋁液擴散進入氧化膜內並迅速與Al2O3反應結合；試片含有Sr、Si、Mg元素時，Sr擴散至共晶Si上，阻礙Mg擴散並遲緩(或隔絕)和氧化膜反應結合。若試片中Si的含量提高，Si吸附於氧化膜上的量會顯著增加，並延緩高溫鋁液的滲入氧化層內、增加鋁液侵蝕分解氧化膜的時間，使得中間夾層的氧化膜在高溫持溫下會生長，使氧化層增厚。 The purpose of the study is aimed at investigating the difference of growth and decomposition of aluminum oxide film affected by aluminum alloys during adding heat and holding temperature. Experimental specimens are made by “sandwich type”, divided into up-specimen, middle layer and down-specimen. The alloys used in the up-specimen are pure Al (99.999%), commercial pure Al (99.82%), Al-7%Si alloy, Al-13%Si alloy, Al-0.5%Mg alloy, A356.2 alloy, A356.2-high Sr alloy, respectively. Middle layer is oxide films grown on Al surface at high temperature. Down-specimen is pure Al (99.999%). Make up-specimen and down-specimen combine, and place the specimen in heat furnace under argon atmosphere. The heat furnace heats from room temperature to 750℃ and then holds temperature, and then the specimen is holded by change of time (12,15,20 minutes) to compare with growth and decomposition of oxide films affected by alloy components and change of time. Experimental results prove that growing oxide films naturally at high temperature (610℃) is γ-Al2O3. Because permeated and corroded by Al liquid，aluminum oxide is decomposed and scatters Al substrates. When holding time increases, aluminum oxide is corroded and decomposed more seriously, and finally up-specimen and down-specimen fuse together. For effects of alloy components: the specimen includes Si element, Si adheres to oxide films(Al2O3) and several Si diffuse into films by Al liquid. The specimen includes Mg element, Mg diffuses into oxide films by Al liquid, combines with and react to films rapidly. The specimen includes Sr, Si, and Mg elements, Sr diffuses into eutectic Si and hinders which Mg diffuses into and combines with oxide films. If Si quantity in the specimen increases, the amounts of Si adhering oxide films increase obviously. Further, the action delays which Al liquid permeates aluminum oxide, and increases corroded and decomposed time of aluminum oxide. Therefore, oxide in the middle layer grows at high holding temperature and thickens. |
