Kinetics of Nonisothermal Pressure Sintering of Zirconium Diboride Powder with Additives of Boron and Chromium Carbides in Vacuum

The analysis of the experimental data on the kinetics of nonisothermal pressure sintering of zirconium diboride-based powder mixtures with the addition of boron and chromium carbides in vacuum showed a division of the sintering temperature mode into low-temperature and hightemperature areas. The division is clearly observed when the temperature increases at a rate of 20°C/min. In low-temperature area, the densification occurs slowly and hardly depends on the temperature. In high-temperature area, the viscous flow of the matrix of the porous material is controlled by the power-law creep of the matrix forming the porous body with an activation energy of 394 kJ/mol. Twofold increase in heating rate leads to acceleration of low- and high-temperature strain of the matrix and increase in the apparent activation energy to 581 kJ/mol, indicating the series engagement of additional mechanisms of material flow. The investigation of structure and properties of materials has showed that the formation of new boron–carbide phases and eutectic that disappears during sintering activates the densification of the porous material. It is found out that under low pressure nonisothermal sintering, a superplasticity phenomenon can occur, which results in the densification of the porous body to the virtually non-porous state.