Influence of severe plastic deformation on intermetallic particles in Mg-12Â wt.%Zn alloy investigated using transmission electron microscopy

The microstructural evolution of the α-Mg matrix and the Mg21Zn25, Mg51Zn20 and MgZn2 was analyzed using bright field imaging, selected area electron diffraction, high-resolution transmission electron microscopy and high-angle annular dark field imaging in scanning mode. The plastic deformation process influenced the α-Mg matrix and each type of intermetallic particle. The α-Mg matrix consisted of two types of areas. The first type of area had a highly deformed structure, and the second type of area had a partially recrystallized structure with an average grain size of approximately 250 nm. The Mg21Zn25 microparticles exhibited distinct forms in the α-Mg matrix that were characterized as a single-crystalline form, a nano-crystalline form and a broken up form. No evidence of Mg51Zn20 nanoparticles within the α-Mg matrix was found in the microstructure, which indicates their dissolution or phase transformation during the deformation process. MgZn2 nanoparticles exhibited different behavior in both types of α-Mg matrix. Two orientation relationships toward the highly deformed α-Mg matrix were observed; however, there was no relationship toward the partially recrystallized α-Mg matrix. Additionally, the growth of the MgZn2 nanoparticles was different in the two types of α-Mg matrix. The Mg51Zn20 nanoparticles inside Mg21Zn25 microparticles exhibited a distinct behavior within the single-crystalline or nano-crystalline form of the parent Mg21Zn25 microparticles. The Mg21Zn25 + Mg51Zn20 eutectic compound was confirmed for both forms of the parent Mg21Zn25 microparticles, and the growth of Mg51Zn20 nanoparticles is discussed.