Processing–microstructure–property relationships in Mg-Gd-Y-Zr alloys mechanical, electrochemical and tribological performance - A review

Magnesium–rare-earth (Mg–RE) alloys, predominantly Mg-Gd-Y-Zr compositions, have attracted significant attention for high-performance structural applications because they offer a better strength-to-weight ratio, thermal stability, and corrosion resistance than conventional magnesium alloys. Precipitation hardening increases markedly when gadolinium (Gd) and yttrium (Y) are combined, while zirconium (Zr) serves as an effective grain refiner, thereby enhancing mechanical properties and microstructural stability. Thermomechanical processing, solidification parameters, and cooling rate influence the formation of intermetallic phases, eutectic content, and grain size. Heat treatment processes, particularly solutionizing (T4 condition) followed by ageing (T6 condition) are essential for strengthening through precipitation mechanisms, as they promote the development of metastable precipitates such as β′′, β′, β 1 and β. A homogeneous microstructure and the presence of stable precipitates that inhibit fracture initiation and propagation lead to improved fatigue performance. Electrochemical behaviour, such as oxidation and corrosion, is strongly influenced by the alloy composition and microstructure. Hardness, microstructural integrity, and the formation of protective oxide layers during sliding are the main factors governing the wear behavior of Mg-Gd-Y-Zr alloys. Improved hardness and stable intermetallic phases enhance wear resistance, whereas oxidative wear is more prevalent under dry sliding conditions. These integrated properties make them preferred for high-temperature structural applications in the automotive and aerospace industries. This review presents significant findings on the design and optimization of magnesium-rare earth alloys by precisely analyzing how alloying composition and processing techniques influence microstructural development and associated characteristics.