Effect of Temperature and Thermal Stress on Micropores and Cracks in Aluminum Alloy Film During Micro-Arc Oxidation

Abstract

In this paper, COMSOL Multiphysics software was used to simulate the micro-arc oxidation of 7075 aluminum alloy, so as to study the influence of temperature and thermal stress on the micropores and cracks in the process of micro-arc oxidation. The results show that: The high temperature and high-pressure environment at the discharge channel leads to the eruption of molten oxide at the discharge channel and the formation of irregular micropores on the surface of the oxide film. The reason for the formation of cracks is that the thermal stress around the discharge channel and in the corner region of the film layer is much larger than the tensile strength of the Al2O3 film layer, in which case the material will have local plastic deformation or cracks. The larger the temperature gradient span near the discharge channel is, the larger the thermal stress will be, resulting in larger diameter of micropores on the surface of the film, more irregular shape, and even bigger defects due to the penetration of cracks. Because the crack region has a relatively low resistivity, it is easier to generate a dense spark discharge, so the crack region has a denser distribution of micropores.