Abstract: Titanium-silicon (Ti-Si) alloy system shows significant potential for aerospace and automotive applications due to its superior specific strength, creep resistance, and oxidation resistance. For Si-containing Ti alloys, the sufficient content of Si is critical for achieving these favorable performances, while excessive Si addition will result in mechanical brittleness. Herein, both physical experiments and finite element (FE) simulations are employed to investigate the micro-mechanisms of Si alloying in tailoring the mechanical properties of Ti alloys. Four typical states of Si-containing Ti alloys (solid solution state, hypoeutectoid state, near-eutectoid state, hypereutectoid state) with varying Si content (0.3-1.2 wt.%) were fabricated via in-situ alloying spark plasma sintering. Experimental results indicate that in-situ alloying of 0.6 wt.% Si enhances the alloy's strength and ductility simultaneously due to the formation of fine and uniformly dispersed Ti₅Si₃ particles, while higher content of Si (0.9 and 1.2 wt.%) results in coarser primary Ti₅Si₃ agglomerations, deteriorating the ductility. FE simulations support these findings, highlighting the finer and more uniformly distributed Ti₅Si₃ particles contribute to less stress concentration and promote uniform deformation across the matrix, while agglomerated Ti₅Si₃ particles result in increased local stress concentrations, leading to higher chances of particle fracture and reduced ductility. This study not only elucidates the micro-mechanisms of in-situ Si alloying for tailoring the mechanical properties of Ti alloys but also aids in optimizing the design of high-performance Si-containing Ti alloys.

Key words: Titanium alloy, Spark plasma sintering, Micro-scale deformation behavior, Mechanical property tailoring, Computational modeling