• The 18R-LPSO phases appeared in the as-deposited samples, with a maximum volume fraction of about 1.43%. • The formation mechanism of 18R-LPSO during WAAM was clarified. • At an ICT of 90 s, the as-deposited sample reached a peak UTS of about 259.7 MPa along the BD. Rational interlayer cooling time management emerges as a critical yet underexplored parameter for controlling microstructural evolution and mechanical performance in wire-arc additive manufacturing (WAAM) of rare-earth magnesium alloys. The present work systematically investigates, through integrated experiment and simulation, how varying cooling intervals (45–180 s) affect grain morphology, phase precipitation, and tensile properties in CMT-WAAM fabricated Mg-Gd-Y-Zn-Zr components. Repetitive thermal cycling during deposition induces solid-state transformations, notably promoting the formation of long-period stacking ordered (18R-LPSO) phases. The phases volume fractions were determined by quantitative metallography, reach a maximum of 1.43 % at a cooling time of 120 s and a minimum of 0.41 % at 45 s. Microstructural characterization reveals a characteristic bimodal grain structure comprising alternating coarse (15–35 µm) and fine (5–12 µm) equiaxed grains, with average sizes ranging from 11.32 ± 5.35 µm (180 s) to 15.62 ± 6.94 µm (45 s). Mechanical testing demonstrates strength-ductility trade-off: samples with 90 s cooling duration exhibit peak ultimate tensile strength (259.7 ± 12.7 MPa) and yield strength (224.3 ± 2.5 MPa), while 120s-cooled samples display superior elongation (8.5 ± 0.54 %) but reduced strength. These findings establish interlayer cooling time as an effective microstructural engineering tool for tailoring mechanical properties in WAAM-processed Mg-RE alloy systems through controlled thermal management.
Li et al. (Wed,) studied this question.