Effect of Surface Treatment on the Thermal Properties of Magnesium–Rare Earth Alloys

Abstract

To enhance the mechanical properties, ignition resistance, corrosion resistance, and oxidation resistance of magnesium, elements such as lithium, manganese, zinc, and rare earth elements are added into magnesium, and the surface treatments are also applied. The addition of elements and surface treatments will affect the thermal properties of magnesium alloys. However, less attention has been paid on this field, which limits the accurate prediction of temperature and thermal stress distribution in engineering applications. In this study, for the comparison between magnesium–rare earth alloys treated with micro-arc oxidation and chemical oxidation, the thermal conductivity, specific heat capacity, and thermal expansion coefficient were measured from room temperature to 500 °C, respectively. Additionally, the phase transition temperature, ignition temperature, and combustion heat were also determined. The variations of various thermal properties with temperature were obtained, and the results showed that the maximum deviations in thermal conductivity, phase transition temperature, specific heat capacity, and thermal expansion coefficient between the magnesium–rare earth alloys treated with micro-arc oxidation and chemical oxidation were 9 %, 0.04 %, 16.21 %, and 2.53 %, respectively. Both the micro-arc oxidation and chemical oxidation surface treatment could improve the ignition temperature of the magnesium–rare earth alloys at least 49 °C. The results of this study demonstrate that surface treatments effectively enhance the ignition resistance of magnesium alloys, but the effect on other thermal properties varies. In addition, accurate thermal property measurements play a crucial role in optimizing the thermal design of components made from magnesium alloys.