Intrinsic quasi-isotropic tensile properties of powder bed fused–laser beam TiB₂/AlMgScZr composites

In the study, a 1.5 % TiB₂ nanoparticle containing AlMgScZr composites was fabricated by the powder bed fused–laser beam (PBF-LB) at different scanning speeds, where near-fully dense, crack-free high-strength samples were obtained at a scanning speed of 500 mm/s. Systematic tensile testing reveals quasi-isotropic tensile properties: uniform elongation values are comparable between horizontal and building directions, while tensile strength differential remains 2 %. Microstructure characterization revealed that the printed samples exhibit columnar/equiaxed bimodal grain structures. The TiB₂ particles in the matrix serve as nucleation sites engulfed by solidification fronts, enabling grain refinement. TiB₂ further promotes the precipitation and thus increases the volume fraction of the Al₃Sc and Al₃Zr phase during PBF-LB fabrication. These Al₃Sc and Al₃Zr precipitates further promote the nucleation of fine equiaxed grains. Consequently, equiaxed grains obstruct columnar grain epitaxial growth, suppressing fiber texture development. The bimodal grain structure of weakly textured columnar grains and randomly oriented equiaxed grains contributes to the overall weak fiber texture and thus quasi-isotropic tensile properties of TiB₂/AlMgScZr.