Computational Simulation of Localised Corrosion in Anodised AA 2099-T8 Aluminium-Lithium Alloy

The initiation of localised corrosion in anodised AA2099-T8 alloy is simulated by using Cellular Automata (CA) method. For CA simulation, the system consisting of corrosive electrolyte, porous anodic alumina film and alloy matrix is described as a 500×300 two-dimensional square lattice. Eight types of cells are defined to construct the cellular space, with the Von Neumann neighbourhood (four cells neighbourhood) being selected. The cellular space is constructed such that a void generated by oxidation of the high-copper-containing Al-Fe-Mn-Cu-Li particle exists in the porous anodic alumina film consisting of a porous layer and a barrier layer. It is suggested that localised corrosion is preferentially initiated in the void defect region in the porous anodic film, which is related to increased corrosion product diffusion rate in this region compared with diffusion in other regions of the porous layer.

Longitudinal pore alignment in anodic alumina films grown on polycrystalline metal substrates

A quantitative analysis of longitudinal pore alignment in anodic alumina films grown on polycrystalline metal substrates was performed on the basis of small-angle X-ray diffraction mapping. The very high sensitivity of the diffraction pattern to the orientation of the anodic alumina film allowed the average pore alignment within the irradiated area to be determined, with an accuracy better than 0.1°. It is shown that pores deviate from the orientation orthogonal to the metal surface by a small angle that is constant within a single-crystal grain. Strong correlation between the longitudinal pore alignment within the anodic alumina film and the grain structure of the aluminium substrate indicates the important role of the crystallographic orientation of the metal in the pore growth process.

Based on the DT-CWT Transformation Methods for 3D-Nanometer Roughness Rating Reference

This paper proposes the third generation wavelet--double tree complex wavelet (DT-CWT) transformation used in nanometer roughness rating, based on the explanation of the shortcomings of the current nanometer roughness rating reference and conventional three dimensional datum evaluations due to the insufficient study. The experiment got porous anodic alumina film as the object of surface roughness of nanotechnology study. Through the comparisons of the three generations of the wavelet reconstruction after the maximum reconstruction error, a conclusion can be made that the superiority of DT-CWT in application is very obvious, a result meeting the16% principle of the surface roughness rating on the bases of DT - CWT extracted datum to compute income parameters, which indicates the feasibility of this application to the extraction of the nano3-D roughness evaluation. Keywords: nanometer roughness;dual-tree complex wavelet;three dimensional datum