In Situ Synthesis of Ti₅Si₃ Matrix Nanocomposites Reinforced with Nanoparticles by High‐Energy Mechanical Alloying

Abstract In the present work, in situ TiN/Ti₅Si₃ nanocomposite powder was prepared by high‐energy mechanical alloying of a Ti and Si₃N₄ powder mixture via the following route: 9Ti + Si₃N₄ = Ti₅Si₃ + 4TiN. Constitution phases and microstructural features of the milled powders at different milling times were studied by XRD, SEM, and TEM. The operative formation mechanisms behind the microstructural developments were disclosed. It showed that the original Si₃N₄ and Ti constituents demonstrated two different reaction mechanisms during milling, i.e., a progressive mechanism of Si₃N₄ (≤20 h) and a speedy mechanism of Ti (≤10 h). The morphologies of the milled composite powders experienced a successive change: pre‐refining – coarsening – re‐refining on increasing the applied milling time. The variation of the operative mechanisms was ascribed to the existence/exhaustion of the ductile Ti constituent in the milling system due to the nonoccurrence/initiation of the in situ reaction. The 20 h milled powder was the typical nanocomposites featured by the nanocrystalline Ti₅Si₃ matrix reinforced with in situ TiN nanoparticles. The grain sizes of the in situ formed Ti₅Si₃ and TiN phases were generally ≤15 nm, exhibiting coherent interfacial structure between reinforcement and matrix.