等通道轉角擠壓鎂鈣合金之原子層沉積奈米氧化膜之特性研究

本研究利用等通道轉角擠壓加工和原子層沉積技術來提升鎂鈣合金之機械性質與抗腐蝕特性，並針對等通道轉角擠壓加工處理後，鎂鈣合金微觀組織之改變對於後續原子層沉積所製備之二氧化鋯薄膜的影響做進一步分析與探討。首先將擠製態鎂鈣合金利用等通道轉角擠壓作二次加工後，鎂鈣合金晶粒大小從原先的5.02微米縮小至1.48微米。鎂鈣合金之材料特性中，其加工前後之表面硬度提升約10維氏硬度，並且由於鎂鈣介金屬化合物變得細小且均勻，使得腐蝕行為變得更加均勻。此外，利用原子層沉積技術在擠製態鎂鈣合金表面上沉積200週期之二氧化鋯薄膜，能使腐蝕電流密度由9.39 × 10^-5安培/公分^2下降至4.67 × 10^-7 安培/公分^2。通過X光繞射儀、穿透式電子顯微鏡和X光光電子能譜儀觀察與比較二氧化鋯薄膜於等通道轉角擠壓加工前後鎂鈣合金上的微結構和缺陷差異，以及利用奈米刮痕測試與電化學方法了解二氧化鋯薄膜的機械性質與腐蝕保護性質。實驗結果發現二氧化鋯薄膜均勻沉積在鎂鈣合金上且其厚度約為18奈米，此外成長於經等通道轉角擠壓加工之鎂鈣合金的二氧化鋯薄膜具有更高的結晶度，結構為緻密的四方晶系，能提供較好的腐蝕保護效果，使腐蝕電流密度降低至1.34 × 10^-7 安培/公分^2。最後，鎂鈣合金於等通道轉角擠壓加工前後表面特性分析結果顯示，鎂鈣合金在加工後表面天然氧化物組成之改變有利於後續製備原子層沉積之二氧化鋯薄膜，在腐蝕保護性上具有正向的影響。

關鍵字

鎂鈣合金；等通道轉角擠壓；原子層沉積；二氧化鋯薄膜；腐蝕保護

並列摘要

In this study, equal channel angular pressing and atomic layer deposition were used to improve the mechanical properties and corrosion resistance of magnesium calcium alloy, and the effect of change in microstructure of magnesium calcium alloy after equal channel angular pressing on the zirconia film deposited by atomic layer deposition was further analyzed and discussed. Firstly, the grain size of extruded magnesium calcium alloy was reduced from 5.02 μm to 1.48 μm after equal channel angular pressing for secondary processing. In the material properties of magnesium calcium alloy, the surface hardness after processing increased by about 10 hv, and the magnesium calcium intermetallic compounds became finer and more uniform, which making the corrosion behavior more uniform. In addition, using atomic layer deposition to deposit 200 cycles of zirconia thin film on the surface of extruded magnesium calcium alloy, the corrosion current density could be decreased from 9.39 × 10^-5 A/cm^2 to about 4.67 × 10^-7 A/cm^2. The microstructure and defects of zirconia thin film on magnesium calcium alloy before and after equal channel angular pressing were observed and compared by X-ray diffraction, transmission electron microscope and X-ray photoelectron spectroscopy, and the mechanical properties and corrosion protection properties of zirconia thin film were measured by nanoscratch test and electrochemical methods. The experimental results showed that the zirconia film was uniformly deposited on the magnesium calcium alloy and its thickness was about 18 nm. In addition, the zirconia film grown on the equal channel angular pressed magnesium calcium alloy had higher crystallinity, and the structure was dense tetragonal system, which could provide better corrosion protection property, so that the corrosion current density was reduced to 1.34 × 10^-7 A/cm^2. Finally, the analysis results of surface characteristics of magnesium calcium alloy before and after equal channel pressing showed that the change of native oxide composition on the surface of magnesium calcium alloy after processing, which was helpful for the subsequent deposition of zirconia film by atomic layer deposition, and had a positive effect on corrosion protection.

並列關鍵字

magnesium calcium alloy ； equal channel angular pressing ； atomic layer deposition ； zirconia thin film ； corrosion protection

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