Spark plasma sintering of Ti‐25at%Si targets: densification mechanisms, phase evolution, and reaction sintering kinetics

Abstract Ti‐Si targets are used in cutting tool coatings and semiconductor gate dielectrics. This study investigated densification mechanisms, phase evolution, and reactive sintering kinetics of Ti‐25at%Si targets fabricated by spark plasma sintering using blended Ti and TiSi ₂ powders. Significant shrinkage was observed between 600°C and 900°C with minor solid‐state reactions. At 1000°C, reactions intensified, promoting further densification. The creep model determines the stress exponent ( n ) and apparent activation energies, revealing the transition from a grain boundary diffusion‐dominated densification mechanism under high effective stress ( n = 1.5, activation energy 108 ± 4 kJ/mol) to a dislocation‐climb‐assisted densification mechanism under low effective stress ( n = 3, activation energy 205 ± 14 kJ/mol). Transmission electron microscopy confirms dislocation climb, while grain boundary diffusion is supported by the formation of new phases (such as Ti ₅ Si ₃ ) generated through diffusion reactions. The Johnson–Mehl–Avrami kinetic equation was used to fit the reactive sintering experimental data around 1000°C, yielding an Avrami exponent of 1.16 ± 0.15, indicating that the reaction proceeds via two‐dimensional nucleation and growth. The activation energy for Ti ₅ Si ₃ formation, calculated using the Arrhenius equation, is 60 ± 7 kJ/mol, which is lower than the 205 kJ/mol obtained from the direct reaction between Ti and Si.