本研究主要探討Al-6Zn和Al-6Zn-2Mg合金試片的熱成長氧化膜分析，目的在於了解鋅對鋁合金氧化膜的影響，所以採用仿7系列鋁合金成份來研究，實驗利用乾磨的方式將試片研磨至P2000號砂紙，在空氣和氮氣氣氛下，將試片置於加熱爐內500℃持溫後觀察氧化膜的相變化。使用熱重分析儀(TGA)來量測試片氧化膜重量的改變，再用低掠角X-ray判定氧化膜可能的化合物，以及SEM、ESCA、EPMA等儀器分析。 從實驗結果得知Al-6Zn合金在空氣氣氛中的氧化膜表層以致密的γ氧化鋁為主，內層的γ氧化鋁則和鋅反應形成Zn spinel，並且有鋅顆粒散佈在氧化膜上面。Al-6Zn-2Mg合金當中鎂的氧化物自由能比鋁氧化物還低，所以表面為氧化鎂和Mg spinel組成的氧化物為主並且結構較為鬆散，而γ氧化鋁位於鎂氧化層和基材之間，以及有鋅顆粒在表面的散佈。 在氮氣氣氛當中，鋅原子不容易形成氮化鋅，所以Al-6Zn氮氣中的試片以AlN以及因表面吸附的氧與基材的鋁反應形成的γ氧化鋁為主，而Al-6Zn-2Mg氮氣中的試片表面主要為鋁和鎂的氮化物，產生的Mg3N2化合物會與基材中的鋁反應持續產生AlN造成重量的改變。 The purpose of this study is analyzing the thermal-formed oxide on aluminum alloys and effect of Zinc in the oxide film. Two materials, Al-6Zn、Al-6Zn-2Mg were used in this study. All surface of the sample were dry polished by SiC paper from P400 to P2000. The sample were set in quartz furnace then heated at 773K for different time spans in dry air and nitrogen gas. Thermo-gravimetric analysis was used to measure the weight change of oxide film. Samples were discussed according to XRD、SEM、ESCA、EPMA analysis. Experimental result show that the oxide film of Al-6Zn alloy comprised γ-alumina in top layer and Zn spinel in inter layer. The γ-alumina reacted with Zinc transformed to Zn spinel .There are metallic Zinc on the Al-6Zn sample oxide film surface. The main consists of Al-6Zn-2Mg oxide film were magnesium oxide and Mg spinel, because of magnesium oxide Gibbs-free energy lower than the alumina. Magnesium oxide film possessed of loose structures. The alumina located at region near the interface between magnesium oxide film and substrate. This sample have metallic Zinc in oxide film too. Because of the Zinc is difficult to form Zinc nitride in the nitrogen gas, so that Al-6Zn sample weight change is due to the formation of AlN and γ-alumina. Al-6Zn-2Mg sample surface was formed by aluminum nitride and magnesium nitride in the nitrogen gas, Mg3N2 contact with substrate Al and form AlN, and this chain reaction will cause the sample weight change.
