| Popis: |
The cermet charge in the Al‒Al2O3 system was obtained by mechanical processing (MP) in a planetary ball mill of aluminum powder of the industrial grade PAP-2 (GOST 5494‒95), consisting of flake particles of submicron thickness with a coating of stearin. Depending on the MP modes used, 4 types of charge were obtained, the bulk density of which varied from 0,33 to 1,1 g/cm3. For all types of charge, the synthesis of the α-Al2O3 phase was observed as a result of the exothermic reaction of the interaction of air oxygen with the surface of aluminum particles during the MP. It is also possible to form boehmite and gibbsite when the activated surface of Al particles interacts with atmospheric water vapor. The local X-ray spectral analysis (EDX) was used to detect X-ray amorphous carbon in the composition of the charge, the appearance of which is associated with the impact- shearing effect of grinding bodies, leading to the nucleation of X-ray amorphous carbon inclusions due to the termal destruction of stearin. The maximum bending strength of the sintered cermet was 550 MPa. This cermet is characterized by a discrete fracture: the formation of dimples as a result of the shear of layered packets under the action of tangential stresses. The revealed mechanisms cermet’s fractures allow us to establish the optimal modes of MP of powder compositions for obtaining various constructional elements from them. |
