LAUSR

The effects of Wand Mo power additives during spark-plasma sintering of compositions at compression force 60 MPa at 1200 – 1600°C on the phase composition, microstructure, crystalline-phase grain size, relative density, linear shrinkage, physicomechanical properties, and the linear correlation of the elasticity modulus and fracture toughness of mullite–ZrB2–β-SiC–TaC samples were studied. The synthesized ZrB2, β-SiC, and TaC powders were characterized by extensive crystallization of ZrB2, β-SiC, and TaCcub, respectively. Sintered samples withWand Mo powder additives showed extensive mullite formation and more active crystallization of β-SiC, (Zr, Ta)B, C, β-WC, and β-WB than (Ta, Zr)C, B, β-MoC, β-MoB, and MoB2 at 1200 – 1600°C. The microstructure of the sample with the Mo additive at 1500°C was more uniformly and densely sintered and crystalline; contained fewer pores and weakly sintered areas; and was more reinforced at the boundaries of oxide-free oxide and oxide-free crystalline phases. This sample had characteristically smaller grain sizes of the crystalline phases at 1400 – 1600°C and showed uniform growth of the relative density, linear shrinkage, and physicomechanical properties; higher crack resistance (with propagation of microcracks along a meandering path), and a better linear correlation of the elasticity modulus and fracture toughness at 1200 – 1600°C.