Atomic-scale HAADF-STEM characterization of an age-hardenable Mg-Cd-Yb alloy

Herein, we present the first report of a high-density nanoblock Laves phase that can be directly precipitated in the Mg-Cd-Yb alloy, with peak-hardness increasing from 50.9 to 66.5 Vickers hardness (HV) during isothermal aging at 200 °C. Cs-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and energy dispersive X-ray spectroscopy (EDS) mapping results indicate that the nanoblock precipitate is a new, structured (Mg, Cd)2Yb ternary intermetallic compound, which has a C14 Laves structure (hcp, space group: P63/mmc, a = 6.28 Å, c = 10.14 Å). Additionally, the orientation relationship between the (Mg, Cd)2Yb precipitate and α-Mg matrix is determined to be (0001)p//(0001)α and [11¯00]p// [112¯0]α. This finding is expected to guide the future design of novel, high-strength, and corrosion resistant Mg-Cd alloys.