The Mg-3.5Zn-0.6Gd (at. %) alloy was prepared and homogenized at 673 K for 8 h, and then extruded at 523 K with an extrusion ratio of 9:1. The microstructure and mechanical properties of the extruded alloy have been investigated. Icosahedral quasicrystalline phase (I-phase) existed in extruded Mg-Zn-Gd-based alloys in two morphologies: (1) micron-scale I-phase formed in the solidification, (2) nano-scale ellipsoid-shape I-phase particles precipitated in the extrusion process. A definite orientation relationship and good atomic match between I-phase and α-Mg matrix were directly observed by conventional and high-resolution transmission electron microscopy (HRTEM), which contribute to the high tensile strength of 308 MPa and the large plasticity of 16.4%.
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