AMg-3.4Y-3.6Sm-2.6Zn-0.8Zr rare-earth magnesium alloy was fabricated via selective laser melting (SLM). The effects of various solution treatments and aging regimes on microstructural evolution, precipitate characteristics, and mechanical properties were systematically investigated through heat treatment experiments combined with scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive spectroscopy (EDS), with optimal heat treatment parameters identified. The results indicate that the as-SLM alloy has fine equiaxed grains (3.8 μm) consisting of an α-Mg matrix, a eutectic phase (Mg, Zn)3(Y, Sm), and Y2O3 oxides. The compressive yield strength (CYS), ultimate compressive strength (UCS), and strain of the as-built samples reach 406 MPa, 509 MPa, and 16.7%, respectively. Following solution treatment at 500 ℃ for 12 h, coarsening of the grains to 5.52 μmreduces the CYS to 381 MPa while increasing the UCS to 528 MPa. Quantitative EDS analysis reveals the maximum rare-earth (RE) element concentration within α-Mg. Solution treatment facilitates RE dissolution into the matrix and subsequent precipitation of dispersed RE-rich phases, whose

redistribution underpins the enhanced UCS from 509 MPa to 528 MPa, with favourable compressive strain retained at 16.4%.