Microstructures and Mechanical Properties of In Situ Al2O3/Al-Si Composites Fabricated by Reaction Hot Pressing (original) (raw)

2014, Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science

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 deflection, 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. 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, including mean particle size, specific surface area, oxygen content and certain metal impurities content are shown in Table 1.