Impact of graphene on properties of LA141 Mg–Li alloy micro-arc oxidation coating

The low hardness and poor corrosion resistance of magnesium–lithium alloys limit their application in critical components. To improve their performance, this study investigates the LA141 magnesium–lithium alloys using micro-arc oxidation technology and incorporating different concentrations of graphene particles to prepare composite coating layers, with a base electrolyte solution of silicate–phosphate composite salt. The results indicate that the addition of graphene promotes the micro-arc oxidation process. As the concentration of graphene increases, the micro-arc oxidation voltage first rises and then decreases, resulting in an overall higher voltage compared with the undoped samples. The thickness and hardness of the coating layers exhibit an initial increase followed by a decrease, while surface roughness initially decreases and then increases. At a concentration of 3 g/l, the coating demonstrates optimal density and roughness, achieving a microhardness of 343.6 HV. X-ray diffraction analysis reveals that the main phase components of the doped coating include Mg, Li, and Mg2SiO4. The increase in coating thickness and reduction in pore quantity significantly enhance corrosion resistance, with the best performance observed at a concentration of 3 g/l. In conclusion, the addition of graphene can effectively improve the performance of the LA141 magnesium–lithium alloys.