621.762 Oxide composite Al 2 O 3 -ZrO 2 (Y 2 O 3 ) powders containing 50 and 70 vol.% Al 2 O 3 , are deposited from salt solutions. The surface area of the deposited powders exceeds 75 m 2 /g. It is established that the α-Al 2 O 3 and t-ZrO 2 (Y 2 O 3 ) matrix has an effect on stepwise crystallization of α-Al 2 O 3 and the powder production history on the sinterability of oxide composites. Ceramics based on Al 2 O 3 -ZrO 2 (Y 2 O 3 ) composite powder containing 20 vol.% titanium carbonitride are hot pressed to be used as a cutting tool. The microstructure and mechanical properties of the ceramics are analyzed. The best mechanical properties are shown by ceramic samples sintered at 1550°C at 35 MPa: bending strength 950 MPa, fracture toughness 10.1 MPa ⋅ m 1/2 , and hardness 18.0 GPa. The performance and lifetime of cutting tools based on these ceramics are tested according to GOST 26613-85.
The paper demonstrates the possibility to control the degree of tetragonal zirconia stabilization, microstructure and physical and mechanical behavior of Al2O3 -ZrO2(Y2O3) ceramic composite. Control is exerted via the process variables during deposition synthesis of nanosized composite powders from hydroxide salts, and their subsequent heat treatment and consolidation. Morphology features of nanosized powder systems and microstructures of the consolidated nanostructured materials were characterized by BET surface are measurements, scanning electron microscopy (both standard and HR), and large-angle X-ray diffraction. Correlations are established between microstructure parameters, physical and mechanical behavior of composite ceramics and a degree of stabilization of tetragonal ZrO2.
The dependence of wall thickness of hollow ceramic raw body formed by hot casting under the action of centrifugal forces on casting mode is explored. The phenomenon of thickening and thinning of the walls on adjacent octants of spheroid received by simultaneous rotation around the vertical and horizontal axes is experimentally discovered and theoretically explained. Ill. 5. Ref. 7. Tab. 3.
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