Unexpectedly achieving high strength in a low rare-earth magnesium alloy via low-temperature extrusion

Obtaining high strength in low-RE-alloyed Mg alloys (RE < 6 wt%) remains a huge challenge so far. In this work, we fabricated a novel high-strength and low-RE-alloyed Mg-3Yb-0.6Zn-0.4Zr (wt%) alloy using the conventional extrusion at low temperature, which breaks through the stereotypical "fewer RE, lower strength" wisdom. The microstructure of the alloy and mechanical properties were examined with optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Instron testing machine. This alloy exhibits a high tensile yield strength of 410 MPa and a favorable elongation of 7.8%, outperforming the majority of traditional high-strength Mg-Gd-Y(-Zn)-Zr extrusion alloys with high RE additions, at least 12 wt%. The high yield strength of the alloy is closely associated with the synergistic effect of submicron recrystallized grains and highly-textural hot-worked grains containing numerous dynamic precipitates and residual dislocations, rather than the widely-considered age-hardening in those heavy RE containing Mg alloys. This work provides an important reference for the development of high-performance extruded Mg alloys with low RE solutes. (c) 2025 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.