Effect of Gd on microstructure, mechanical properties, and corrosion behavior of as-homogenized Mg−8Li−3Al−2Zn−0.2Zr alloy

The microstructure observation, tensile test, electrochemical measurement, and corrosion morphology characterization were conducted to study the effect of Gd on the microstructure, mechanical properties, and corrosion behavior of as-homogenized Mg−8Li−3Al−2Zn−0.2Zr (LAZ832−0.2Zr) alloy. The addition of trace Gd can improve the mechanical properties of as-homogenized LAZ832−0.2Zr alloy by refining the microstructure, reducing the content of AlLi softening phase, and forming Al2Gd strengthening phase. Meanwhile, the addition of trace Gd can weaken the microgalvanic corrosion between matrix phase and AlLi phase, inhibit the galvanic corrosion between α-Mg phase and β-Li phase, and result in the formation of dense oxide film containing Gd2O3, thereby improving the corrosion resistance of the alloy. When the Gd content is 1.0 wt.%, the alloy shows the best comprehensive properties with the ultimate tensile strength of 189.8 MPa, elongation of 42.3%, and corrosion rate (determined by hydrogen evolution) of 0.86 mm·a−1.