Contents lists available at ScienceDirect Journal of the European Ceramic Society journal homepage: www.elsevier.com/locate/jeurceramsoc Original Article Microstructures and mechanical properties of B 4 C-TiB 2 -SiC composites fabricated by ball milling and hot pressing Qianglong He, Aiyang Wang, Chun Liu, Weimin Wang ⁎ , Hao Wang, Zhengyi Fu The State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China ARTICLE INFO Keywords: B 4 C-TiB 2 -SiC composites Ball milling Hot pressing Microstructure Mechanical properties ABSTRACT B 4 C-TiB 2 -SiC composites were fabricated via hot pressing using ball milled B 4 C, TiB 2 , and SiC powder mixtures as the starting materials. The impact of ball milling on the densification behaviors, mechanical properties, and microstructures of the ceramic composites were investigated. The results showed that the refinement of the powder mixtures and the removal of the oxide impurities played an important role in the improvement of densification and properties. Moreover, the formation of the liquid phases during the sintering was deemed beneficial for densification. The typical values of relative density, hardness, bending strength, and fracture toughness of the composites reached 99.20%, 32.84 GPa, 858 MPa and 8.21 MPa m 1/2 , respectively. Crack de- flection, crack bridging, crack branching, and microcracking were considered to be the potential toughening mechanisms in the composites. Furthermore, numerous nano-sized intergranular/intragranular phases and twin structures were observed in the B 4 C-TiB 2 -SiC composite. 1. Introduction Boron carbide (B 4 C) is named “black diamond” as its hardness is only inferior to that of diamond and cubic boron nitride. Owing to its low density (2.52 g/cm 3 ), high Young’s modulus, high melting point, good chemical stability, and excellent neutron absorption ability, B 4 C has been applied in cutting tools, light-weight armor, and nuclear in- dustry [1–3]. Nevertheless, its relatively low fracture toughness (2–3 MPa m 1/2 ) and poor sinterability owing to the existence of strong covalent bonds and low self-diffusion coefficient are the main obstacles for its widespread applications [4,5]. The addition of hard and light particles is considered to be an ef- ficient method to improve the sinterability and mechanical properties of boron carbide simultaneously. Accordingly, TiB 2 and SiC are the ideal choices as additives for B 4 C matrix because the addition of TiB 2 and SiC can preserve the high hardness and low density of B 4 C, and simultaneously enhance the sinterability and various other properties [6–9]. Furthermore, TiB 2 has good electrical conductivity, which can allow the composite to be easily machined via electrical discharge machining, and SiC has a low thermal expansion coefficient, high thermal conductivity, and high-temperature oxidation resistance, which can maintain the stability of the composite in a high-temperature environment [10–12]. Therefore, the B 4 C-TiB 2 -SiC (BTS) composite has the potential to possess an excellent combination of the properties of each component. The binary composites B 4 C-TiB 2 and B 4 C-SiC were investigated by many researchers, but the ternary composite B 4 C-TiB 2 -SiC was seldom studied, to the best of the author’s knowledge. In order to obtain finer starting material powders, many researchers adopted the in-situ synthesis method [13–18], but there are some drawbacks to this ap- proach: (1) Only a fraction of the phases in the composites were in situ produced and the others still originated from the commercial coarse powders; (2) The ratio of each phase depends on the chemical reaction, which cannot be adjusted according to the requirements. In the present study, finer powder mixtures were obtained via ball milling treatment, and subsequently hot pressing was used to fabricate B 4 C-TiB 2 -SiC composites with fine grains. 2. Experimental 2.1. Materials Commercially available B 4 C powder (D 50 = 2.5 μm, Jingangzuan Boron Carbide Co., Ltd., Mudanjiang, China), TiB 2 powder (D 50 = 8.0 μm, Dandong Chemical Research Institute Co., Ltd., Dandong, China) and SiC powder (D 50 = 0.5–0.7 μm Shanghai Aladdin Biochemical Technology Co., Ltd., Shanghai, China) were used as the raw materials. The characteristics of the raw material powders, in- cluding mean particle size, specific surface area, oxygen content and certain metal impurities content are shown in Table 1. https://doi.org/10.1016/j.jeurceramsoc.2018.02.020 Received 22 December 2017; Received in revised form 10 February 2018; Accepted 12 February 2018 ⁎ Corresponding author. E-mail address: shswmwang@whut.edu.cn (W. Wang). Journal of the European Ceramic Society xxx (xxxx) xxx–xxx 0955-2219/ © 2018 Elsevier Ltd. All rights reserved. Please cite this article as: He, Q., Journal of the European Ceramic Society (2018), https://doi.org/10.1016/j.jeurceramsoc.2018.02.020