成形压力对SiC/TiB2复合材料组织与性能的影响

基于熔融Si浸渗法制备出较致密的SiC/TiB₂复合材料, 并研究了坯体成形压力对SiC/TiB₂复合材料致密度、相组成、显微组织和力学性能的影响。实验结果表明, 复合材料由TiB₂、SiC和Si相组成。SiC/TiB₂复合材料的显微组织特征为: TiB₂相和SiC相均匀分布, 游离Si填充在TiB₂相和SiC相的空隙处, 且形成了连续相。随成形压力的增大, 复合材料中游离Si含量降低, TiB₂颗粒尺寸减小, 复合材料的力学性能先增加后降低。坯体最佳成形压力为200 MPa, 对应SiC/TiB₂复合材料的体积密度、开口气孔率、抗弯强度、断裂韧性和维氏硬度分别为3.63 g/cm³、0.90%、(354±16) MPa、(6.8±0.2) MPa·m^1/2和(21.0±1.1) GPa。

Effect of Forming Pressure on Microstructure and Mechanical Properties of SiC/TiB2 Composites

SiC/TiB₂ composites were fabricated by infiltration of molten silicon (Si) into porous preforms containing titanium diboride (TiB₂) and free carbon (C) at 1550℃ for 30 min. And the influences of forming pressure on the phase compositions, microstructure, density and mechanical properties of SiC/TiB₂ composites were investgated. It is found that forming pressures have significant influence on the microstructure and mechanical properties of SiC/TiB₂ composites. XRD results show that the composites consist of TiB₂, SiC and Si phases. The microstructure analysis show that the TiB₂ and SiC phases distribute in the composite uniformly, with free Si fills in the continuous gaps between TiB₂ and SiC phases. TiB₂ particle size and volume fraction of free Si both decrease with the increase of forming pressures. The mechanical properties of SiC/TiB₂ composites are improved initially and then deteriorated with the increase of forming pressures. Under the optimal pressure of 200 MPa, Vikers-hardness, flexural strength and fracture toughness of the obtained SiC/TiB₂ composite are (21.0±1.1) GPa, (354±16) MPa and (6.8±0.2) MPa·m^1/2, respectively. The open porosity and bulk density of the obtained SiC/TiB₂ composite prepared at 200 MPa forming pressure are 0.90% and 3.63 g/cm³.