Electrochemical and microstructural study of oxide films formed electrochemically at microcrystalline al‐fe‐v‐si alloys
Electrochemical and microstructural study of oxide films formed electrochemically at microcrystalline al‐fe‐v‐si alloys
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微晶 Al-Fe-V-Si 合金电化学形成氧化膜的电化学和微观结构研究
DOI：
10.1002/jemt.1070310405
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
D. Tessier
中科院分区：
文献类型：
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作者：
S. Thomas;V. Birss;And D. STEELE;D. Tessier
冶金技术的一个新进展是快速凝固技术在铝合金生产中的应用。FVS 0812是一种微晶铝基合金，由8重量% Fe、1重量% V和2重量% Si组成。它是一种两相合金，由Ca。在基本上纯的Al基体中的27体积%的近似球形的富Fe-V-Si弥散体。然而，这种先进材料和其他相关合金的高强度、低密度特性尚未实现，部分原因是合金无法形成厚的、粘附的、耐磨的外表面氧化膜，这是通过常规阳极氧化方法在常规铝合金上容易实现的特征。目前的研究涉及812合金氧化膜生长的电化学研究，具体目标是寻求对氧化膜生长问题的起源的理解，并最终提出在这种材料上形成厚而稳定的氧化膜的替代方法。在这项研究中使用的技术包括电化学方法，如循环伏安法和电化学阻抗谱。通过透射电子显微镜（TEM）的超薄切片标本的关键信息已获得。实验最初在中性硼酸盐溶液中进行，以表征在该环境中形成的致密阻挡氧化膜，并且预期存在于在正常硫酸阳极氧化介质中形成的多孔氧化膜下方。在硼酸盐溶液中，电化学结果暗示氧化膜厚度小于随后通过TEM工作所看到的厚度，这表明812合金处的阻挡膜可以被其外表面处的非常细的孔中的溶液渗透（通过常规TEM不可分辨），或者被捕获在氧化膜中的分散质导致在合金表面上形成不同的氧化膜厚度。在硫酸溶液中，Fe和V在阳极氧化期间从812合金中发生溶解。阻抗和TEM研究表明，在812合金表面的阻挡膜的情况下。而且，厚的氧化物覆盖层具有比在Al处形成的更曲折和更开放的孔结构，并且氧化物膜也比其应该薄得多。有人建议，没有一个屏障氧化膜表明，硫酸阳极氧化介质是过于积极的氧化膜形成在812合金，导致过度溶解和不良的氧化膜的质量。© 1995 Wiley利斯公司
A recent advance in metallurgical technology has been the application of rapid solidification techniques to Al alloy production. FVS0812 is the designation given to a microcrystalline Al‐based alloy consisting of 8 wt% Fe, 1 wt% V and 2 wt% Si. It is a two‐phase alloy, consisting of ca. 27 vol percent of approximately spherical Fe‐V‐Si‐rich dispersoids in an essentially pure Al matrix. The high strength, low density properties of this advanced material, and other related alloys, have not yet been realized, however, due, in part, to the inability of the alloy to form a thick, adherent, abrasion‐resistant outer surface oxide film, a feature readily achieved at conventional Al alloys by normal anodizing methods. The present research has involved an electro‐chemical study of oxide film growth at the 812 alloy, with the specific goals being to seek an understanding of the origin of the oxide film growth problem and ultimately to propose alternative approaches to the formation of a thick, stable oxide film at this material. The techniques used in this research have included electrochemical methodologies such as cyclic voltammetry and electrochemical impedance spectroscopy. Crucial information has been obtained through transmission electron microscopy (TEM) of ultramicrotomed specimens. Experiments were carried out initially in neutral borate solutions to characterize the compact barrier oxide film formed in this environment and expected to be present beneath the porous oxide film formed in the normal sulfuric acid anodizing medium. In borate solutions, the electrochemical results implied oxide film thicknesses which were less than seen subsequently by TEM work, suggesting either that the barrier film at the 812 alloy can be penetrated by solution in very fine pores (not resolvable by conventional TEM) at its outer surface or that dispersoids trapped in the oxide film cause differential oxide film thicknesses to develop across the alloy surface. In sulfuric acid solutions, dissolution of Fe and V occurs from the 812 alloy during anodization. Both impedance and TEM studies reveal the absence of a barrier film at the 812 alloy surface. Also, the thick oxide overlayer has a tortuous and more open pore structure than formed at Al and the oxide film is also substantially thinner than it should be. It is suggested that the absence of a barrier oxide film indicates that the sulfuric acid anodizing medium is too aggressive for oxide film formation at the 812 alloy, resulting in excessive dissolution and poor oxide film qualities. © 1995 Wiley‐Liss, Inc.