Functionally graded structure of a nitride-strengthened Mg₂Si-based hybrid composite

The ex-situ incorporation of the secondary SiC reinforcement, along with the in-situ incorporation of the tertiary and quaternary Mg₃N₂ and Si₃N₄ phases, in the primary matrix of Mg₂Si is employed in order to provide ultimate wear resistance based on the laser-irradiation-induced inclusion of N₂ gas during laser powder bed fusion. This is substantialized based on both the thermal diffusion- and chemical reaction-based metallurgy of the Mg₂Si–SiC/nitride hybrid composite. This study also proposes a functional platform for systematically modulating a functionally graded structure and modeling build-direction-dependent architectonics during additive manufacturing. This strategy enables the development of a compositional gradient from the center to the edge of each melt pool of the Mg₂Si–SiC/nitride hybrid composite. Consequently, the coefficient of friction of the hybrid composite exhibits a 309.3% decrease to –1.67 compared to –0.54 for the conventional nonreinforced Mg₂Si structure, while the tensile strength exhibits a 171.3% increase to 831.5 MPa compared to 485.3 MPa for the conventional structure. This outstanding mechanical behavior is due to the (1) the complementary and synergistic reinforcement effects of the SiC and nitride compounds, each of which possesses an intrinsically high hardness, and (2) the strong adhesion of these compounds to the Mg₂Si matrix despite their small sizes and low concentrations.