Additive manufacturing of novel aluminium matrix composites with enhanced strength and processability via boron nitride functionalization

• We investigate the addition of 0.3 wt % of BN nanoparticles to a custom Al alloy produced by PBF-LB. • The addition of BN promoted better flowability without compromising processability. • An extreme degree of grain refinement was observed when BN was added to the alloy. • Molten Al and BN reacted forming AlB 2 , which promoted heterogeneous nucleation. • The addition of BN granted the alloy a 40 % increase in yield strength. The present work systematically investigates the effects of BN nanopowder functionalization on the processability, microstructure and tensile response of the custom Powder Bed Fusion Laser Beam (PBF-LB) Al alloy ‘AMALLOY3D’. The results show that a minor addition of BN (0.3 % by weight) not only produces near fully dense parts (99.91 %), but is also paired with improved flowability, enhancing the overall processability. Electron backscatter diffraction (EBSD) analysis revealed the transformation to a fully equiaxed grain structure in the BN-functionalized material, resulting in a 40 % increase in yield strength. Energy dispersive spectroscopy using a scanning transmission electron microscope (STEM-EDS) was employed to reveal the intricate secondary phases’ arrangements. These observations coupled with the help of the CALPHAD approach led to the reconstruction of the solidification history of AMALLOY3D and the BN-functionalized material. The present study unravels the complex dynamics leading to the columnar-to-equiaxed transition in BN-reinforced AMCs, proving that such unique microstructures and exceptional tensile properties can be achieved without compromising PBF-LB processability.