Mechanical properties of Zr-2.5Nb porous structures with different porosities produced by electron beam powder bed fusion.

Abstract

Additive manufacturing enables the fabrication of porous metallic lattices with complex architectures. However, porous structures fabricated from conventional materials such as Ti-6Al-4V may exhibit limited ductility under certain loading conditions, motivating the exploration of alternative alloys. In this work, Zr-2.5Nb porous structures with a wide range of tailored porosities (64.4%-86.5%) were fabricated via electron beam powder bed fusion (EB-PBF). By adjusting the single-spot energy input, target porosities were systematically achieved, enabling a dedicated investigation of the porosity-property relationship. Mechanical properties were evaluated on samples within the porosity range of 64.4%-76.8%. Comprehensive mechanical evaluations (compression, bending, and tension) revealed that porosity serves as the dominant design variable: decreasing the porosity from 76.8% to 64.4% substantially enhanced the elastic modulus (0.81 to 2.36 GPa), compressive yield strength (21.9 to 64.7 MPa), bending yield strength (35.7 to 81.6 MPa), and tensile yield strength (14.0 to 45.9 MPa). These values fall within the range of human cancellous bone, suggesting potential relevance to bone replacement applications, though direct biological validation is required. Notably, the EB-PBF fabricated Zr-2.5Nb structures exhibited progressive compressive yielding without strut fracture, indicating sustained energy absorption capacity. The mechanical responses under all three loading modes were fitted using the Gibson-Ashby model, revealing a strong power-law dependence on relative density (exponents 2.19-2.54), which provides a quantitative framework for predicting mechanical behavior across the investigated porosity range. These results demonstrate that relative density governs the mechanical performance of EB-PBF Zr-2.5Nb porous lattices, establishing a porosity-centric design foundation for load-bearing orthopedic implants.