Hybrid rolling additive manufacturing tailors gradient recrystallization and precipitation strengthening in Mg-Gd-Y-Zr alloy

Wire-arc additive manufacturing (WAAM) enables large magnesium-alloy components, but coarse grains, pores, and heterogeneous second phases restrict strength and ductility. This study compared Mg-9.54Gd-1.82Y-0.44Zr walls produced by WAAM and hybrid rolling additive manufacturing (HRAM) before and after T6 treatment. Interlayer rolling reduced porosity from 0.33% to 0.01% and stored deformation that promoted height-dependent recrystallization during subsequent deposition thermal cycles. At mid-height, HRAM refined the average grain size from 22.4 to 15.9 µm, while the upper region retained more deformed grains and higher hardness. In the as-deposited TD condition, HRAM increased the ultimate and yield strengths by 10.2% and 31.3% relative to WAAM while maintaining comparable elongation. After T6 treatment, paired EBSD and TEM/SAED characterization showed a smaller average grain size in HRAM-T6 than in WAAM-T6 (26.3 versus 32.5 µm) and confirmed intragranular β′ precipitates in both conditions. The precipitates observed in HRAM-T6 were finer in the examined TEM fields. HRAM-T6 achieved an ultimate tensile strength of 372.8 ± 3.8 MPa, a yield strength of 253.5 ± 3.0 MPa, and an elongation of 7.3% ± 2.1%, exceeding WAAM-T6 by 11.0%, 14.3%, and 82.5%, respectively. Sequential rolling and thermal exposure therefore combine densification, gradient recrystallization, and a modified aging response to improve the strength-ductility synergy of WAAM Mg-RE alloys.