Tuning the microstructure and strength of Mg–RE alloys through the rare-earth elements

Abstract Magnesium (Mg) and its alloys have significant attention due to their lower density, higher specific strength, and favorable casting characteristics, making them ideal for lightweight structural applications. However, their broader utilization is hindered by limitations in heat resistance and mechanical strength. This study investigates the effects of microstructure on mechanical performance of three Mg-based rare earth (RE) alloys, focusing on the role of RE elements gadolinium (Gd) and erbium (Er) in enhancing material performance through precipitation. The microstructure and strengthening mechanism of the Mg–RE alloys have been studied, and it is found that eutectics phases are primarily dispersed at grain boundaries. An increase in RE contents from 9.0 weight percent (wt%) to 12.5 wt% leads to enhance the volume fraction of eutectic phase. The microstructure of solution-treated alloys indicates that the eutectic phase is dispersed, with a minor fraction of undissolved cubic-shaped particles exhibiting non-homogenous distribution within the matrix. Furthermore, the aging response and mechanical performance of the studied Mg–RE alloys demonstrate that the RE elements could remarkably improve the performance of Mg–RE alloys. The results illustrate that the peak-aged Mg–10Gd–2.5Er–0.5Zr alloy exhibits the most robust mechanical performance. The ultimate tensile strength (UTS) and yield strength (YS) are approximately 245 ± 2.3 MPa and 330 ± 4.2 MPa, respectively, with an elongation (EL) of 2.0 ± 0.6%. The marked increase in the mechanical performance at the peak-aged state is mainly attributed to β′ precipitates. Graphical abstract