REACTION SINTERING OF SHOCK-COMPRESSED TI+C POWDER MIXTURES

Shock compression was used to make dense compacts of Ti and C elementa l powder mixtures for subsequent reaction sintering in near-net form. The reaction sintering experiments were performed in an induction-heat ed hot press at temperatures below the melting point of Ti, with hold times of less than a few hours. The unique combination of defect state s and packing characteristics introduced during shock compression resu lts in significant enhancement in the solid-state chemical reactivity of the powder mixtures. Consequently, the reaction behavior of the pow ders is altered, and the reaction mechanism is dominated by solid-stat e diffusion, resulting in a microstructure reminiscent of solid-state processes. Reaction-sintered TiCx compacts, with bulk density in the r ange of 3.9 to 4.2 g/cm(3) (80 to 85 pct TMD of TiC), were produced in near-net form. The compacts had a highly re-fined microstructure (<6- mu m grain size) and microhardness in the range of 1360 to 1934 KHN. I n this article, reaction sintering mechanisms involving solid-state di ffusion in Ti + C powder mixture compacts will be described, along wit h characteristics of the titanium carbide produced by the combined sho ck modification and reaction sintering approach.