In-situ chemical reaction mechanism and non-equilibrium microstructural evolution of (TiB₂ + TiC)/AlSi10Mg composites prepared by SLM-CS processing

The preparation of aluminum matrix composites (AMCs) by laser additive manufacturing (AM) technology has become an important means of improving performance of aluminum alloys. In this work, a novel in-situ synthesis method of selective laser melting combined combustion synthesis (SLM-CS) was used to prepare dual-phase reinforced AMCs. The feasibility of a B₄C–Ti combustion synthesis reaction system to produce TiB₂ and TiC ceramics by selective laser melting (SLM) was verified. AlSi10Mg alloy matrix composites with dual reinforcements were then fabricated by SLM, and systematic qualitative and quantitative phase analysis was carried out. The calculation results of the graphical-extrapolation method show that the lattice constant of α-Al matrix phase in the composites increases from 0.40466 nm to 0.40528 nm. The effects of a series of reactants with different chemical element composition ratios on the characteristics of melting process and non-equilibrium solidification microstructure were studied. The preliminary principles of the combustion chemical reaction under the rapid and continuous laser scanning were concluded from the theory and experiments results. In terms of mechanical properties, an appropriate amount of ceramic particles results in a significant improvement in the microhardness and elastic modulus, and yet composites prepared with a mixture powder amount greater than 0.7 wt % witnessing a clear drop in the tensile strength as well.