Preparation, structure and properties of digoride’s solid solutions (Hf1 – хTaх)B2

Abstract

Porous sinters of solid solutions were obtained from the elements by the SHS method and then crushed in a ball mill to a fraction of d50 < 10 µm. Single-phase (Hf1 – хTах)B2 solid solutions with a wide range of compositions were obtained by a hot pressing. Detailed investigations of structure and properties were carried out. The plotted lattice parameters vs. solid solution stoichiometry diagrams confirmed the Vegard’s law. SEM, TEM, and EDX structural analysis demonstrated the existence of a HfВ2 – TaB2 single-phase solution region. The structure of samples (lamellas) of (Hf0.8Ta0.2)B2 and (Hf0.6Ta0.4)B2 solid solutions was analyzed by TEM. It has been established that with an increase in the content of tantalum, the size of subgrains decreases to 0.2 – 1 µm. This correlates with the CSR size determined by the X-ray diffraction method. Studies of mechanical properties of single-phase solid solutions have shown that (Hf0.8Ta0.2)B2 and (Hf0.6Ta0.4)B2 possessed extremely high hardness of 63–70 GPa and elastic modulus of 550 – 587 GPa. Electrical resistance dependence on temperature was investigated, values of heat capacity, thermal diffusivity and thermal conductivity coefficients were determined in a wide range of (Hf 1 – xTax)B2 solid solution compositions.