本研究加熱不同鋁合金形成熱合氧化膜，並採用三明治融合試片法來探討氫及融合時氧化膜分解對氣孔成核的影響。試驗中所採用的材料有純度達99.999wt%的純鋁靶材及矽含量為1.2wt%與7.6wt%的鋁矽合金，試片切割成10mm × 10mm × 6mm的尺寸後使用乾磨方式研磨試片表面至P2000號砂紙。 試片於前處理完成後，將純鋁試片置於610℃持温25小時以及鋁-1.2矽置於570℃持温25小時以生成熱合氧化膜。生長完熱合氧化膜的試片分別與純鋁、鋁-7.6矽試塊進行三明治試片融合20分鐘，待爐冷至室溫後觀察融合後試片介面。 在純鋁/純鋁氧化膜/純鋁試片融合後的介面上可觀察到的不同的凹孔，其中曲率半徑最大可達14.82μm，接觸角為164.7°。於鋁-7.6矽/純鋁氧化膜/純鋁三明治融合試片介面觀察到凹孔的最大曲率半徑為7.89μm，但是接觸角卻有約20°的變動範圍，由於試片內的矽會在高溫時與氧化膜及鋁液反應生成矽或氧化矽，介面上的氣袋在成長時受其影響造成氣袋受力的動態不平衡而形成微氣泡脫離介面上浮，因此使得相同曲率半徑的氣袋可能產生接觸角達20°的變化範圍。鋁-1.2矽所生長的氧化膜結構鬆散且不具微通道，氧化膜在三明治試片融合時容易分解，形成氣袋附著氧化膜顆粒而懸浮於熔液中。 純鋁/純鋁氧化膜/純鋁融合試片會於氧化膜介面上形成氣袋；而純鋁/鋁-1.2矽氧化膜/鋁-1.2矽三明治融合試片會形成微氣孔懸浮於熔並殘留在凝固後的試片中。 The present study investigated the influence of hydrogen and thermally-formed oxide layer on the foundation of air pocket and micro-bubble. High purity aluminum (99.999 wt.%) and Al-XSi alloy (X=1.2 wt% and 7.6 wt%) were used in this study. The cube samples were prepared in size 10 mm × 10 mm × 6 mm and polished by P400 to P2000 abrasive papers. These cube samples were moved to the muffle furnace and then heated to 610℃ and 570℃ for pure aluminum and aluminum-silicon alloys, respectively. Two different cube were heated for 25 hrs to develop thermally-formed oxide film. After sandwich samples(Al/oxide film/Al, Al-7.6Si/ oxide film/Al, Al/oxide film/Al-1.2Si) were fused in the muffle furnace, the sample were sectioned to observe the air pocket on the interface of fusion. The radius of curvature and contact angle of air-pore on the interface were increased. The maximum contact angle and curvature of radius for air pocket in the pure aluminum sandwich specimen interface was 164.7° and 14.82μm. From SEM observation, no micro-bubble has been trapped in the top cube sample. Silicon changed the surface tension of liquid aluminum and the wetting condition between liquid aluminum and oxide film, the maximum curvature of radius were reduced to 7.89μm and the variation of contact angle was about 20° , from 143° to 164°. Micro-bubble trapped in the top sample has been observed. The structure of Al-1.2Si thermally-formed oxide layer was loose. The sandwich sample show no(or few) apparent air-pocket on the interface of fusion. However, micro-bubble along with inclusion has been observed in the cube sample.
