硼化钛对无压烧结碳化硼结构和性能的影响

Effect of Titanium Boride on Microstructure and Properties of Boron Carbide by Pressureless Sintering

利用无压真空烧结炉,选用C和Si作为烧结助剂,将不同含量的TiB2作为第二相添加到B4C基体中,在不同温度下进行无压烧结制备出B4C–Ti B2复相陶瓷。研究了B4C–TiB2成分配比和烧结温度对复相陶瓷微观结构和力学性能的影响,以及B4C–TiB2复相陶瓷的增韧机理。结果表明:当烧结温度为2200℃、Ti B2含量为30%时,所制复相陶瓷的致密度及综合力学性能最高,致密度为94.59%,洛氏硬度、抗弯强度和断裂韧度分别为87.62、182 MPa、3.97 MPa·m1/2;TiB2颗粒能有效的钉扎晶界,抑制B4C晶粒的长大,起到细晶强化的作用,TiB2和叠层状石墨相阻碍了裂纹扩展,提高复相陶瓷的断裂韧性。

B4C–TiB2 multi-phase ceramics were prepared in a pressureless vacuum sintering-furnace at different temperatures with TiB2 added into B4C matrix as a second phase substance,and C and Si as sintering aids.The density,hardness,bending strength and fracture toughness of the samples were determined.The influences of composition ratio of B4C–TiB2 and sintering temperature on the microstructure and mechanical properties of the multiphase ceramics were investigated by X–ray diffraction,energy dispersive spectroscopy and scanning electron microscopy.The toughening mechanism of ceramics was discussed.The results show that the optimum density and comprehensive mechanical properties of the multiphase ceramics(i.e.,the relative density of 94.59%,the Rockwell hardness of 87.62,the bending strength of 182 MPa,and the fracture toughness of 3.97 MPa·m1/2 can be obtained at a sintering temperature of 2200℃and TiB2 content of 30%.The TiB2 particles can effectively nail the grain boundary,inhibit the growth of B4C grains and play a role in fine-grain strengthening.The TiB2 and laminated graphite phase hinder the crack growth,thus improving the fracture toughness.