Abstract: Laser powder bed fusion (LPBF) additive manufacturing of zinc (Zn) offers promising advantages for biodegradable metal bone implants, including tailorable microstructures, controllable porous structures, and appropriate degradation rates. However, the layer-by-layer construction during LPBF often leads to microstructural and performance anisotropy within metallic materials. In this work, the anisotropic mechanical and degradation properties of pure Zn processed using LPBF were comprehensively investigated for the first time. Specifically, the influence of microstructural characteristics on the mechanical and degradation properties of LPBF-processed Zn in both horizontal and vertical planes was revealed, while the underlying deformation mechanisms in different planes were illustrated. The results demonstrated that the horizontal plane exhibited higher mechanical strength compared to the vertical plane, with ultimate tensile strength of 123.6 and 107.86 MPa, respectively, significantly surpassing that of the traditionally cast counterpart (52.7 MPa). Importantly, abundant deformation twins coupled with infrequent microbands and pyramidal 〈c + a〉 slip systems activated during tensile loading along the vertical plane enabled multiple deformation modes, which sustained durable work hardening ability while delaying plastic instability, resulting in extraordinary plasticity (elongation of 14.2 %). Additionally, synergistic effects between high-density grain boundaries including low-angle grain boundaries and pre-existing dislocations promoted the stable presence of a passive film along the horizontal plane, thus exhibiting relatively low corrosion sensitivity. Furthermore, the LPBF-processed Zn also demonstrated favorable biological activity and osteogenic potential. These findings provide valuable insights into multiple mechanisms underlying anisotropy in mechanical and degradation properties of laser additively manufactured Zn-based materials.

Key words: Zinc, Laser powder bed fusion, Anisotropy, Mechanical properties, Degradation behaviors