Spark plasma sintering mechanisms and microstructural evolution of U3Si2–Al

The high uranium density and good thermal conductivity render U 3 Si 2 -Al an excellent candidate fuel for research reactors. Spark plasma sintering (SPS) offers significant advantages in fabricating fine-grained metal matrix composites. Currently, systematic research into SPS mechanisms and microstructural evolution for U 3 Si 2 -Al remains insufficient. In this study, U 3 Si 2 -Al dispersion fuel pellets were synthesized via SPS at 423K–753K using Al powder, which realized no interface reaction, fine-grained structure, uniform dispersion, and controllable porosity. Comparative experiments with pure Al were conducted under identical sintering conditions to clarify U 3 Si 2 influence mechanisms. Integrated microstructural characterization revealed distinct densification mechanisms between U 3 Si 2 -Al and pure Al. Notably, an abrupt interfacial reaction occurs between 763K and 773K, producing U(Al, Si) 3 . At 200 MPa, U 3 Si 2 particles exhibit extensive systematic fracturing along force chain directions. Apparent activation energy (Q) and stress exponent (n) were determined, utilizing the Helle-Granger model.During the SPS pre-pressurization stage, U 3 Si 2 -Al undergoes rapid densification via particle rearrangement. This stage accomplishes most density improvement, significantly compressing the densification window for subsequent heating and holding phases. From the initial state to 82% TD, Q and n values gradually increase to 183kJ⋅mol -1 and 2, respectively.