Tuning the Surface Characteristic of Al-Si Alloys and Its Impacts on the Formation of Micro Arc Oxidation Layers

Abstract

Aluminum Silicon (Al-Si) alloys are the most important among cast alloys and have widespread application. The β-Si phase is detrimental to the growth of micro arc oxidation (MAO) layers on Al-Si alloys. In this paper, the β-Si in the skin layer of different Al-Si alloys was removed by an acid etching pretreatment. Then, the impacts of different etching condition on their MAO process were investigated. Results show that, as etching time was prolonged, the Si content on the surface of Al-12 Si was decreased greatly (less than 0.5 wt.%), and the average size of pores left on the sample surface was increased gradually. This then led to the occurrence of some bigger and more drastic discharge sparks at the earlier oxidation stage. The corresponding layers had a higher ratio of Al2O3 and better corrosion resistance after 30 min of oxidation. Moreover, a 60 s etching pretreatment benefitted and boosted the growth rate and energy efficiency of layers on the Al-9 Si, Al-12 Si and Al-15 Si alloys. Such pretreatment was believed to be applicable to restrain the negative effects of Si on the MAO of different Al-Si alloys.

Characterization of the Anodic Film and Corrosion Resistance of an A535 Aluminum Alloy after Intermetallics Removal by Different Etching Time

“…An average roughness of the samples increased from 0.098 ± 0.025 µm at the beginning of etching to 0.744 ± 0.021 µm after 5 min of etching due to the surface chemical attack. This agrees well with previously reported increases in roughness with the etching time due to dissolution of Si on the surface of Al-Si alloys [31].…”

Plasma Electrolytic Oxidation (PEO) as a Promising Technology for the Development of High-Performance Coatings on Cast Al-Si Alloys: A Review

“…Another research also carried out an acid etching with the main aim of removing the detrimental β-Si phase contained in the skin layer of cast Al alloys with Si contents of 9 wt.%, 12 wt.%, and 15 wt.% [179]. The removal of the β-Si phase from the outermost region of the metallic substrates increased the coating growth rate and energy efficiency during early PEO stages.…”

Effect of process parameters on porosity defects in Al-Si alloy hot rolling

“…4004Al-Si alloy which uses silicon as the main alloying element exhibits good properties and is widely used in the automotive and air conditioning industries [1][2][3][4][5][6][7] ; it is also widely used in the aluminum foil manufacturing industry due to its advantages of good fluidity and low melting point. However, the high silicon content in the 4004 Al-Si alloy reduces the plastic deformation ability of the material, 8,9 results in defects such as porosity and loosening during casting, and these defects are magnified during the rolling process.…”