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以B4C、TiO2、酚醛树脂和金属Si为原料,通过两步反应控制制备出B4C-SiC-Si-TiB_2复合材料,并利用XRD、SEM、材料电子拉伸机等手段研究TiB_2含量对复合材料相组成、显微组织和力学性能的影响。结果表明:复合材料由BxC、B12(C,Si,B)3、SiC、Si和TiB_2等相组成,游离Si填充在均匀分布的BxC、Si C和TiB_2等相的空隙处。随着复合材料中TiB_2含量的增加,硬度和抗弯强度逐渐增加、断裂韧性先增加后稍微降低,当TiB_2含量为20%(质量分数)时,复合材料的硬度、抗弯强度和断裂韧性分别为22.53 GPa、445 MPa和4.5 MPa·m1/2。复合材料中各相之间的热膨胀系数失配导致的裂纹偏转作用是提高复合材料断裂韧性的主要原因。复合材料的断裂方式主要为穿晶断裂和沿晶断裂的混合断裂方式。
B4C, TiO2, phenolic resin and metal Si were used as raw materials to prepare B4C-SiC-Si-TiB2 composites by two-step reaction. The effects of TiB2 content on the composites phase were studied by XRD, SEM, Composition, microstructure and mechanical properties. The results show that the composite material is composed of BxC, B12 (C, Si, B) 3, SiC, Si and TiB 2 phases, and the free Si is filled in the pores of uniformly distributed BxC, SiC and TiB_2 phases. With the increase of TiB2 content, the hardness and flexural strength increase gradually, the fracture toughness increases first and then decreases slightly. When TiB2 content is 20% (mass fraction), the hardness, flexural strength and fracture toughness of composites are respectively 22.53 GPa, 445 MPa and 4.5 MPa · m1 / 2 respectively. The crack deflection caused by the thermal expansion coefficient mismatch between the various phases in the composite is the main reason for improving the fracture toughness of the composite. The fracture modes of composites mainly include the mixed fracture mode of transgranular fracture and intergranular fracture.