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The structurization and properties of O 3 nanocomposites consolidated by electric-discharge sintering are examined. TiN-AlN composites with a relative density of about 98 to 99% are produced. Their structure is not homogenous and consists of TiN and AlN grains of about 200 nm in size. There are also large spherical grains of titanium nitride of 2 to 10 μm. This effect is probably caused by microdischarges between particles of the conducting phase and subsequent meltback of the interacting surfaces. The effect of yttrium oxide additives on the material structure and properties is investigated. It is shown that TiN-AlN composites consolidated by electric-discharge sintering have high hardness (HV ~ 25 GPa) and fracture toughness (K 1c ~ 6 MPa · m 1/2 ).Ceramics based on refractory compounds show excellent operating properties (high melting temperature, hardness, wear resistance, and stability). This is why they are widely applied in engineering, transportation, aerospace, and power industries.The research efforts made in the last decades show that nanostructuring a consolidated material based on refractory compounds can improve its mechanical characteristics by 20 to 40%. The paper [1] demonstrates that ceramics based on titanium nitride become harder by 18-20 to 30 GPa if grain sizes are reduced from several microns to 30 nm.Unconventional approaches are needed to develop nanostructured materials since it is quite a contradictory task to produce a dense material with grain growth being inhibited. Electric-discharge sintering (EDS) is a promising technique to consolidate nanopowders. It offers a high consolidation rate and use of a protective environment and pressure to enable rapid and complete compaction and minimize the grain growth [2-6]. EDS permits wide variation in the strength (from 0.1 to 1000 A) and type (direct, alternating, or both) of the current flowing through the material, i.e., current-induced treatment conditions can be widely changed [5][6][7][8][9]. However, experimental data are still needed to find out how to activate microdischarge-induced sintering of powder materials, which remains a hypothetical problem.The technique is known to be used to consolidate nanopowders of metals, refractory nitrides, and carbonitrides [3, 4, 10]. EDS of the titanium nitride powder in [3] has resulted in a 98%-dense material, with sintering lasting for more than 5 min and temperature being higher than 1600°C.The paper [3] examines EDS and hot pressing of nanostructured powders of titanium carbonitride with grains of 100 to 200 nm in size. A material with a density of 95% of the theoretical value was produced at 1600 to 1800°C and holding time of 1 min. The material sintered had grains of 500 nm (EDS) and 3 μm (hot pressing) in size. Therefore, electric-discharge sintering is a promising consolidation technique that retains the grain nanostructure.In terms of electric-discharge sintering, a heterophase TiN-AlN system is of interest since titanium nitride is a conductor and aluminum nitride is a dielectric. EDS-in...

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