Significant Improvement of Mechanical and Corrosion Properties of As‐Cast Mg‐9Gd‐3Y‐0.5Zr‐9Li Alloy by a High‐Temperature Short‐Time Heat Treatment

A one‐step high‐temperature short‐time heat treatment at 510°C was applied to an as‐cast Mg‐9Gd‐3Y‐0.5Zr‐9Li alloy. This treatment achieved simultaneous improvement in mechanical strength and corrosion resistance. During treatment, the continuous reticular eutectic phase transformed into a discontinuous distribution, while numerous spherical and chain‐like Mg ₃ RE nanoprecipitates (40–300 nm) formed within grains. After 4 h of heat treatment, the alloy exhibited peak mechanical properties: yield strength increased by 32.76% (from 116 to 154 MPa) and ultimate tensile strength by 43.06% (from 144 to 206 MPa). These improvements are attributed to precipitation strengthening. Concurrently, the corrosion rate decreased dramatically from 33.27 mm/year (as‐cast) to 4.00 mm/year, with the lowest corrosion current density of 7.55 × 10 ⁻⁵ A/cm ² . Scanning Kelvin probe force microscopy revealed that microstructural homogenization, including Mg ₃ RE phase refinement and compositional uniformity of the α/β matrix, reduced micro‐galvanic corrosion effects. This study demonstrates that simple heat treatment can effectively overcome the strength‐corrosion tradeoff in Mg‐RE‐Li alloys, offering a promising strategy for developing high‐performance magnesium alloys.