Microstructure and tensile properties of TIB2-reinforced Al-2618 thin walls produced by laser powder bed fusion

This study focuses on enhancing the processability and mechanical properties of the Al-2618 Al alloy by functionalizing powder with TiB2. Four different methods have been used to add TiB2 particles to the Al alloy powder: i) low-pressure plasma, ii) low-energy and iii) high-energy mechanical mixing, and iv) pre-alloying by gas-atomization. Comprehensive characterization of composite powders was conducted, followed by Laser Powder Bed Fusion (LPBF) manufacturing of samples. High-density printed composites were achieved with all powder feedstocks, with homogeneous dispersion of TiB2 and absence of cracks. Borides effectively promoted heterogeneous nucleation of α-Al phase, suppressing epitaxial growth and leading to a fine equiaxed microstructure. Upon preliminary study on different heat-treatment routes (T6 and T5), tensile tests aided by Digital Image Correlation (DIC) have been performed to assess the mechanical properties. Results show significant enhancements in yield and ultimate strengths post-heat treatments. Despite lower ductility, pre-alloyed powder exhibited superior mechanical performance due to nano-metric TiB2 formation.