Analysis of intermetallic particles in Mg-12Â wt.%Zn binary alloy using transmission electron microscopy

Three distinct intermetallic particles with sizes ≥ 1 μm, ~ 100 nm and ~ 5 nm were found in the α-Mg matrix and identified as Mg21Zn25 (trigonal structure with the R3¯c space group and lattice parameters a = 2.578 nm and c = 0.876 nm), Mg51Zn20 (orthorhombic structure with the Immm space group and lattice parameters a = 1.408 nm, b = 1.449 nm, c = 1.403 nm) and MgZn2 (hexagonal structure with the P63/mmc space group and lattice parameters a = 0.522 nm, c = 0.857 nm), respectively. The structure of the Mg21Zn25 and MgZn2 phases was confirmed based on the precession-assisted electron diffraction tomography data, and the existence of Mg21Zn25 is discussed in detail. MgZn2 nanoparticles have the preferential shape and orientation relationship toward the α-Mg matrix. Mg51Zn20 nanoparticles with sizes of 10-50 nm were also discovered in the Mg21Zn25 particles, which form a eutectic compound Mg21Zn25 + Mg51Zn20.