A CaCO₃ coating with good anticorrosion and adhesion performance was fabricated via ultrasound-assisted chemical conversion on AZ41 magnesium alloy, with a water-bath treated coating as a control. The coating formed on AZ41 mainly consists of an outer CaCO₃ layer and an inner (Ca, Mg)CO₃ layer. Surface characterizations were carried out to obtain the morphology and the chemical composition, mechanical tests were also adopted to assess the hardness and the adhesion of the coating prepared. Afterwards, the long-term corrosion resistance was investigated via electrochemical methods in the chloride-containing Portland cement system. Results show that the ultrasound-assisted coating exhibits higher mechanical properties. In addition, the corrosion resistance of the ultrasound-assisted coating is also higher than that of the bare AZ41 alloy and the water-bath treated coating. This could be due to the formation of a much more compact CaCO₃ coating on AZ41 Mg alloy, which is mainly benefit from the assistance of the ultrasound. Ultrasound accelerates the nucleation of CaCO₃ crystals and assists the removal of hydrogen bubbles. Additionally, corrosion mechanism was suggested and discussed for the CaCO₃ coating.

This work studied the microstructure, mechanical properties and damping properties of Mg_95.34Ni₂Y_2.66 and Mg_95.34Zn₁Ni₁Y_2.66 alloys systematically. The difference in the evolution of the long-period stacked ordered (LPSO) phase in the two alloys during heat treatment was the focus. The morphology of the as-cast Mg_95.34Ni₂Y_2.66 presented a disordered network. After heat treatment at 773 K for 2 hours, the eutectic phase was integrated into the matrix, and the LPSO phase maintained the 18R structure. As Zn partially replaced Ni, the crystal grains became rounded in the cast alloy, and lamellar LPSO phases and more solid solution atoms were contained in the matrix after heat treatment of the Mg_95.34Zn₁Ni₁Y_2.66 alloy. Both Zn and the heat treatment had a significant effect on damping. Obvious dislocation internal friction peaks and grain boundary internal friction peaks were found after temperature-dependent damping of the Mg_95.34Ni₂Y_2.66 and Mg_95.34Zn₁Ni₁Y_2.66 alloys. After heat treatment, the dislocation peak was significantly increased, especially in the alloy Mg_95.34Ni₂Y_2.66. The annealed Mg_95.34Ni₂Y_2.66 alloy with a rod-shaped LPSO phase exhibited a good damping performance of 0.14 at ε=10⁻³, which was due to the difference between the second phase and solid solution atom content. These factors also affected the dynamic modulus of the alloy. The results of this study will help in further development of high-damping magnesium alloys.