Investigation of the thermophysical properties of the oxide layer formed by microarc oxidation on Al-Si alloy

Abstract

The results of the experimental study of the thermophysical properties of the coating formed by microarc oxidation (MAO) on an aluminum-silicon alloy AK12D are presented. The description of the research methodology, including the formation of the MAO-layer on the surface of laboratory samples and the study of their structure, composition and of thermophysical properties are given. The thermal conductivity of the coating was investigated by two methods: steady state and laser flash method. The tests were performed within the temperature range of 50-400°C. The obtained results showed that the coating have a rather low thermal conductivity (λ= 1.32…52 W/(m·K) at 100°C). It is shown that a wealth of mullite (up to 60%) does not lower the thermal conductivity of the coating. It is assumed that the basic factors affecting the thermal conductivity of the oxide layer are small-scale porosity, crystallite sizes and amorphous phase.