Abstract
The brown or grayish-white color films were prepared by the micro-arc oxidation (MAO) method on in-situ TiB2/7050Al composites using these alkaline electrolytes with/without KMnO4 as an additive. The microstructure, elemental composition, chemical state and corrosion behavior have been investigated by the microstructure characterizations and electrochemistry measurements on the MAO films comparatively. The results indicated that a brown film was obtained via adding KMnO4 into the alkaline electrolyte. The coloration mechanism of the brown color can be ascribed to the existence of MnO inside the film. Furthermore, the initiation of corrosion to the Al composite was intensively hindered by the brown MAO film. Compared with the Al substrate and grayish-white film, the brown MAO film exhibited the elevated corrosion potential and reduced corrosion current. Therefore, the brown film has presented an optimized corrosion resistance for the composite.
Highlights
Al matrix composites (AMCs) are extensively developed and exhibited some superior properties, including high specific strength [1,2,3,4,5,6], good ductility [7,8], superior fatigue limit [9] and elevated modulus [2,10,11]
It is known that the grains are equiaxial in the normal direction-transverse direction (ND-TD) plane
The rest TiB2 particles are randomly dispersing into the grains (Supported by Figure 2c)
Summary
Al matrix composites (AMCs) are extensively developed and exhibited some superior properties, including high specific strength [1,2,3,4,5,6], good ductility [7,8], superior fatigue limit [9] and elevated modulus [2,10,11]. The corrosion resistance and color unity of AMCs often fails to satisfy the design and application demands, which limits their further practices. The surface treatment is always applied to enhance the corrosion resistance for long-term service, wear resistance, decoration and hardness for Al-based materials. The surface appearance treatment of AMCs has drawn intensive interests, because the color has played a crucial part both in the decorative properties and functional applications (i.e., medical identification/optical absorption/spacecraft application [15]). For Al alloys, Li et al [19] prepared a black
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