Popov A. Structure formation and fracture toughness of composite ceramic materials with microinclusions of carbon.

The complex experimental study of hot pressed materials based on ТіВ2-ТіС- В4С system is carried out. Hot pressing of ТіС and В4С powders under the temperature interval 18000С?Т?21500С and pressure 20 - 40 MPa is shown to lead to TiB2 with carbon clusters phase formation. The cause of such structure appearance is the process of quasi-eutectic melting of TiC and В4С in local places of mutual contact accompanied by the chemical reaction of liquid TiB2 synthesis. This leads to superquick crystallization of titanium boride with C-clusters. A theoretical model for fracture toughness and destruction energy of matrix composite estimation is developed taking into account the crack front between places of delay bending possibility. It is shown, that inclusions with low Young modulus (blunting the crack tip) as well as inclusions which Young modulus is higher than that of matrix may strengthen the material. The size of low modulus inclusions should be larger than that of matrix and the size of high modulus inclusions should be smaller.