ФОРМУВАННЯ СТРУКТУРИ ТА ПІДВИЩЕННЯ МЕХАНІЧНИХ ВЛАСТИВОСТЕЙ КЕРАМІЧНИХ МАТЕРІАЛІВ НА ОСНОВІ НІТРИДУ КРЕМНІЮ ПРИ ВИСОКОТЕМПЕРАТУРНОМУ ДЕФОРМУВАННІ
The change of structure and properties of sintered materials Si <sub>3</sub>N <sub>4</sub>-5mas.%Y <sub>2</sub>O <sub>3</sub>-2mas.%Al <sub>2</sub>O <sub>3</sub>, Si <sub>3</sub>N <sub>4</sub>-5mas.%Y <sub>2</sub>O <sub>3</sub>-5mas.%Al <sub>2</sub>O <sub>3</sub>, at deformation on direct extrusion with degree of wringing 55 and 72 % within the temperature range 1750-1850 <sup>0</sup>С and pressures 20-30 MPa was investigated. After high temperature extrusion a structure from oriented along direction of deformation elongated grains of b - Si <sub>3</sub>N <sub>4</sub> is formed. The fracture toughness of obtained anisotropic structure in the directions perpendicular and parallel to direction of extrusion were at a rate of 11,5-12,0 MPа·m <sup>1/2</sup> and 7,5-7,8 MPа·m <sup>1/2</sup> accordingly. Hardness after extrusion increases on 1,0 GPa and it is at level 16,0 GPa. Keywords: silicon nitride, extrusion, microstructure, anisotropy, hardness, fracture toughness.