Microstructure, mechanical properties, and corrosion behavior of Mg-xDy binary alloys: Optimization of dysprosium content for enhanced performance

The effects of varying dysprosium (Dy) contents (1, 3, 5, 7, 9 wt.%) on the microstructural evolution, mechanical performance, and corrosion behavior of pure magnesium (Mg) were systematically examined. Mg-xDy binary alloys were prepared by vacuum arc melting and copper mold cooling. Microstructural analysis revealed a dendritic morphology across all samples, attributed to varying cooling rates. According to the compression test results, the Mg-7Dy alloy exhibited the optimal mechanical response, showing a compressive yield strength of 112.1 MPa and an ultimate compressive strength of 297.5 MPa, due to solid solution strengthening, grain refinement, and second-phase strengthening. A comprehensive evaluation of corrosion behavior was conducted by integrating electrochemical analyses with immersion testing. Results from potentiodynamic polarization and electrochemical impedance spectroscopy demonstrated that the Mg-1Dy alloy exhibited the highest corrosion resistance, characterized by a low corrosion current density of 0.029 mA/cm 2 and a high polarization resistance of 479.68 Ω·cm 2 . The formation of a protective Dy 2 O 3 surface film inhibited corrosion. However, excessive Dy additions resulted in increased Mg 24 Dy 5 formation, a cathodic phase accelerating α-Mg matrix corrosion. Performance curves, combining experimental results and existing literature, illustrated the relationship between Dy content (0−20 wt.%) and the mechanical and corrosion properties of Mg-Dy alloys. This research highlighted the complex interplay between Dy content, microstructure, and the resulting properties.