Abstract:In order to solve the problem that boron carbide (B4C) is difficult for sintering densification and poor toughness, the B4C-LaB6 composite ceramics were fabricated via rapid hot press sintering at 2 000 ℃ and 30 MPa with B4C and lanthana (La2O3) as raw materials. The effects of additive La2O3 content on the microstructures and mechanical properties of B4C-LaB6 composite ceramics were investigated, and the toughening mechanism of LaB6 was studied. The results show that the B4C-LaB6 composite ceramics with w(La2O3)=3% have better comprehensive mechanical properties, the relative density, Vickers hardness, bending strength, and fracture toughness reach 99.51%, 36.56 GPa, 547.43 MPa, and 4.18 MPa∙m1/2, respectively. LaB6 refines the grain, and improves the relative density and fracture toughness of the B4C-LaB6 composite ceramics. The toughening mechanism of LaB6 is related to crack deflection and grain cracking.
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