The role of rare earth additions on low cycle fatigue behavior of a Mg-2Nd-1Y-0.1Zr-0.1Ca alloy

Abstract

The low-cycle fatigue behavior of an extruded, solution-treated Mg–2Nd–1Y–0.1Zr–0.1Ca alloy was investigated under fully reversed, strain-controlled loading at amplitudes of 0.4–0.8%. A multimodal characterization approach combining SEM, EBSD, FIB nanofabrication, STEM, and STEM-EDS was used to elucidate the influence of rare-earth (RE) elements on deformation mechanisms. The initial microstructure exhibited a RE texture with basal (0001) poles tilted ∼30–45° from the loading direction, promoting non-basal slip activity. Cyclic hardening was observed across all strain amplitudes, accompanied by increases in plastic strain amplitude and energy with increasing total strain. Site-specific STEM revealed that deformation was accommodated by basal ⟨a⟩ and pyramidal ⟨c + a⟩ slip. HAADF-STEM and center-of-symmetry analysis identified I₁ intrinsic stacking faults arising from ⟨c + a⟩ dislocation dissociation, along with dense fault aggregates in the postmortem microstructure. These findings provide new insight into the role of complex dislocation mechanisms in governing the cyclic response of rare-earth Mg alloys.