Effects of LaB6 content on microstructure and mechanical properties of TaC-LaB6 composites
Tantalum carbide (TaC)-based composites containing 0.1–30 mol% lanthanum hexaboride (LaB 6 ) were prepared by hot pressing at 1900 °C for 30 min under 30 MPa pressure. Effects of LaB 6 content on densification, microstructure and mechanical properties of the consolidated TaC-LaB 6 composites were investigated. Sinter-forge was performed to test creep resistance of the TaC-LaB 6 composites at temperatures up to 1950 °C. Addition of LaB 6 increased densification of the TaC-LaB 6 composites and the compositions with ≥1 mol% LaB 6 almost reached full densities. LaB 6 reacted with TaC and the Ta 2 O 3 impurity to form minor phases of TaB 2 , B 2 O 3 and C. Average size of the TaC grains in the consolidated composites showed a decrease trend with increase in the LaB 6 content. The TaC-LaB 6 composites with 1–2 mol% LaB 6 addition had relatively good flexural strength , Vickers hardness and fracture toughness with a value of 530 MPa, 15.6 GPa and 5.29 MPa m 1/2 , respectively. Addition of LaB 6 modified interfacial bonding strength of the TaC grains, hence increase in creep resistance under sinter-forge up to 1950 °C.
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