Microstructure evolution and performance of B4C–NdB6 composites fabricated by in situ hot pressing

Abstract

AbstractB4C–NdB6 composites were fabricated by in situ hot pressing at different temperatures (1950–2150°C) with B4C and Nd2O3 (2–4 wt%) as raw materials. The microstructure evolution of the composites with sintering temperature and Nd2O3 content was studied in detail, and the influence of pressure on the sintering of B4C with different contents of Nd2O3 was also investigated. The performance of the fabricated composites was researched and the toughening mechanism was discussed. The results indicate that Nd2O3 can react with B4C to form the thin‐sheet intermediate products (Nd(BO2)3, Nd2CO5) first, which then transform to band‐shaped NdB6. Pressure can reduce the distance of B4C and Nd2O3, accelerating the mass transfer and contributing to the formation of NdB6. NdB6 and intermediate products are first in agglomerate structure at 1950°C, and then the agglomerates are broken to form dispersive micron and submicron NdB6 at 2000°C by the synergistic function of pressure, diffusion at high temperature, and liquid phase sintering. NdB6 can enhance the densification owing to the bonding function. Excessive Nd2O3 content leads to residual pores, and excessive temperature (2150°C) results in the coarsening of phases. The coexistence of transgranular and intergranular fracture of NdB6 promote the fracture toughness.