Influence of Anodizing Conditions on The Mechanical Properties of Anodic Alumina Films Fabricated in Sulphuric Acid

Abstract

The hardness and elastic modulus for the anodic films formed on high purity aluminium are investigated by nano-indentation and micro-hardness techniques. Micro-hardness investigation is revealed that the film hardness reduces as the distance increases from aluminium/film interface due to the chemical degradation in the outer region of the film during anodizing process, which increases with rise of the anodizing time and temperature. Moreover nano-indentation is shown that the hardness and elastic modulus for hard films are relatively independent of the selected anodizing conditions, with respective values of ~ 5.6 ± 0.40 GPa and ~

110.8 ± 6 GPa. However, for films fabricated at 20 C˚, the hardness and elastic modulus increases linearly with rise of current density and with reduction of anodizing time. This reduction of hardness and elastic modulus with increased anodizing time indicates the role of chemical degradation which is promoted by increased temperature.