Imaging the atomic configuration of defects in laves phase MgNi2 using 4D-STEM

Laves phases are promising candidates for high-temperature structural materials, with their mechanical properties strongly influenced by defect structures. In this study, the atomic configurations of defects in the Laves phase MgNi₂ were systematically investigated using four-dimensional scanning transmission electron microscopy (4D-STEM). Combined multislice simulations and experimental results validated the robustness of Center-of-Mass (CoM) imaging based on 4D-STEM for simultaneously resolving both heavy and light elements in MgNi₂ under varying sample and instrument parameters. We conducted a detailed analysis of planar faults and dislocations in MgNi₂ using 4D-STEM. Our findings revealed that the hexagonal planar faults, formed via relative sliding of adjacent regions, are characterized by nickel deficiency. Additionally, the atomic structure of dislocations in regions containing non-basal stacking faults suggests a synchroshear deformation mechanism. These results demonstrate the effectiveness of 4D-STEM in probing complex defect structures in intermetallic materials, offering critical insights into their deformation behavior.