Barvitskyi P. Regularities of forming the structure of shock-resistant materials based on refractory borides in the thermobaric sintering conditions

The actual scientific and technical problem connected with establishment of regularities of structure formation of refractory-borides-based composite materials on (-AlB12, AlB12C2, AlB12C2–TiB2, B4C, B4C–SiC) in thermobaric conditions (30 MPa and 2 GPa, in the temperature range 1200-2200 С) has been solved, resulting in the development of new lightweight impact-resistant materials for personal protective equipment, protection of helicopters and aircrafts, where the weight of protective elements is one of the determining factors, as well as structural ceramics for nuclear power plants, abrasive nozzles, ceramic bearings, friction pairs operating in aggressive environments, etc. The study of the regularities of C, TiC and SiC additives influence on the structure and properties of materials based on -AlB12 and B4C allowed to create composites with mechanical characteristics that exceed or are at the level of hot-pressed boron carbide, with following compositions:(1) B4C–22 wt.% SiC (with approximate stoichiometry B3.64CSi0.01 of matrix phase and SiC1.07 of inclusions) specific density  = 2.63 g/cm3, with Vickers microhardness HV (49 N) = 34.6 ±0.5 GPa, fracture toughness K1с (49 N) = 5,4 MPam1/2, K1с (with three-point bending) = 7.4 MPam1/2, bending strength Rbm = 474 MPa, compressive strength Rcm = 1878 MPa and ultimate tensile strength Rm = 386 MPa, logarithmic decrement  = 1,45 % and Young's modulus E = 521 GPa; (2) AlB12C2–22 wt.% TiB2–4 wt.% Al2O3 (with approximate stoichiometry Al0.17B4.55C2O0.04N0.21 – matrix phase and TiB2.58C0.8Al0.02 and Al2O3.79B2.04C0.8 inclusions) with  = 3.2 g/cm3, HV (49 N) = 37.7 ±6.7 GPa, K1с (49 N) = 6.9 ±0.6 MPam1/2, KIс (by three-point bending) = 6.1 MPam1/2, Rbm = 646 MPa, Rcm = 1143 MPa, Rm = 515 MPa,  = 1,44 % and with Young's modulus E = 509 GPa. A high level of mechanical properties was achieved due to the formation of solid solutions. The results are confirmed by the Test Reports from the FMI of the NAS of Ukraine and the STC "Composite Materials" at IPM NAS and by two patents of Ukraine.