Effect of 0.5 wt% LaB6 on microstructure and properties of PBF-LB-fabricated 10SiC/AlSi10Mg composites

Powder Bed Fusion-Laser Beam (PBF-LB) technology not only overcomes the challenges of composition control and complex processing in traditional SiC/Al composite fabrication, but also enables the rapid production of lightweight, structurally complex, and highly customized components. This study explores the effects of introducing 0.5 wt% LaB<inf>6</inf> into 10SiC/AlSi10Mg composites on their microstructure, stress distribution, and mechanical properties. The results show that the addition of LaB<inf>6</inf> significantly promotes grain refinement, achieving a 49.2% reduction in grain size, a 45.7% increase in the proportion of high-angle grain boundaries, and a 137.8% increase in the proportion of grains in a low stored dislocation density (grain orientation spread, GOS < 2°). During the PBF-LB process, LaB<inf>6</inf> and SiC undergo partial decomposition, and La, Si, and C atoms diffuse into the melt pool. Upon solidification, coral-shaped nano Si clusters and in-situ precipitated Al<inf>4</inf>C<inf>3</inf> phase form. LaAlSi<inf>2</inf> phases precipitate in the heat-affected zone (HAZ) of the as-built composites. After 400 °C-1.5 h heat treatment, high-density precipitation of spherical LaAlSi<inf>2</inf> phase and submicron Si particles is observed. Therefore, compared to the 10SiC/AlSi10Mg composite, the 0.5LaB<inf>6</inf>-10SiC/AlSi10Mg composite exhibits superior mechanical properties after heat treatment. It has a tensile strength of 348.69 MPa, a yield strength of 219.88 MPa, and an elastic modulus of 84.9 GPa, with a yield ratio of 0.63. This indicates excellent mechanical properties and a high potential for engineering applications.