Outstanding fatigue performance of Mg-Gd-Zn-Zr alloy enriched with SFs rather than LPSO Structure

• RE-Mg enriched with LPSO structure or SFs. • SFs-enriched Mg shows outstanding fatigue strength. • Solute strengthening improves the fatigue resistance of Mg nanolayers. Both solute-segregated long-period stacking ordered (LPSO) structure and stacking faults (SFs) are essential in strengthening rare-earth (RE) Mg alloys. Herein, LPSO-enriched Mg and SFs-enriched Mg are fabricated and comparably investigated for fatigue performances. During fatigue, the Mg nanolayers between LPSO lamellae or SFs act as the gliding channels of dislocations. However, SFs-enriched Mg exhibits outstanding fatigue strength due to solute strengthening within Mg nanolayers. Solute strengthening is assumed to contribute to the local accumulation of basal dislocations and the activation of non-basal dislocations. Dislocations are restricted locally and cannot glide long distances to specimen surfaces, which mitigates fatigue-induced extrusions and slip markings, ultimately leading to an increase in fatigue strength. These findings guide the development of RE-Mg alloys towards a synergy between high tensile and high fatigue performances.