Stress corrosion resistance of Nd/Gd-modified Mg–Zn–Mn biomagnesium alloys in Hank's solution

The premature failure of biodegradable magnesium alloys under the combined action of mechanical stress and physiological corrosion severely limits their clinical application. To address this, Gd- and Gd + Nd-modified Mg–Zn–Mn (ZM30) alloys, namely ZM30-1Gd and ZM30-1Gd-1Nd (containing approximately 1 wt% each of Gd and Nd), were fabricated via hot extrusion. Microstructural characterization revealed that Gd addition and Gd + Nd co-addition significantly refined the grain structure and transformed the dominant secondary phase from Mg 7 Zn 3 to the more stable W-phase (Mg 3 RE 2 Zn 3 , where RE = Gd or Nd). Electrochemical tests in Hank's solution demonstrated enhanced corrosion resistance after microalloying, and slow strain rate tensile tests in Hank's solution showed that the stress corrosion cracking susceptibility index of ZM30-1Gd-1Nd was reduced to 47.19%, compared with 64.58% for ZM30. Concurrently, the elongation to failure increased from 3.2% to 8.8%, and fractographic analysis indicated clear suppression of the corrosion-induced crack propagation. These results indicate that the ZM30-1Gd-1Nd alloy offers improved stress corrosion cracking resistance and bone-matched mechanical properties, making it a promising candidate for next-generation biodegradable orthopedic implants.