化学气相渗透法制备2.5D浅交弯联SiCf/SiC复合材料的结构与力学性能

Microstructure and mechanical properties of 2.5D curved shallow-crossing linking SiC_f/SiC composites fabricated by chemical vapor infiltration

采用化学气相渗透(chemical vapor infiltration,CVI)方法,在具有2.5D浅交弯联结构的SiC纤维管状编织体上预沉积SiC-PyC-SiC多层界面(PyC即Pydrolytic carbon,热解碳),再利用CH_3SiCl_3-H_2-Ar体系对其进行化学气相渗透SiC增密,制备管状SiC_f/SiC复合材料,研究SiC_f/SiC复合材料的物相组成、微观结构、轴向压缩、径向压溃以及环向拉伸等力学性能及其断口形貌。结果表明:SiC_f/SiC复合材料主要由SiC纤维、SiC-PyC-SiC复合界面以及SiC基体组成。SiC-PyC-SiC复合界面中,PyC界面厚度为400~500 nm,SiC界面厚度为700~800 nm,SiC基体主要为β-SiC相。SiC_f/SiC复合材料的密度为2.50~2.58 g/cm^3,开孔率为7.70%~9.10%,轴向抗压强度为53.2 MPa,径向压溃强度为38.18 MPa。轴向压缩时表现为与水平方向成45°方向的剪切破坏,径向压溃时表现为形成4个塑性铰后发生分瓣破坏,断口处明显观察到纤维拔出现象,但拔出不长,表现出"假塑性"特征。SiC_f/SiC复合材料的环向抗拉强度为12.8 MPa,其断口相对较平整,纤维拔出不明显,表现为脆性破坏。

The tubular SiCf/SiC composite materials were prepared by depositing SiC-PyC-SiC multi-interlayers on the SiC fibers with 2.5D curved shallow-crossing linking structure densified with SiC matrix using CH3SiCl3-H2-Ar system by chemical vapor infiltration(CVI).The phase composition,microstructure,axial compression,radial crushing and circumferential tension and fracture morphology of SiCf/SiC composites were investigated.The results show that SiCf/SiC composites are mainly composed of SiC fiber,SiC-PyC-SiC multi-interlayers and SiC matrix.In the SiC-PyC-SiC multi-interlayers,the thickness of PyC interlayers is 700?800 nm,the thickness of SiC interface is 400-500 nm,and SiC matrix is mainlyβ-SiC phase.After densification,the density of SiCf/SiC composites is 2.50-2.58 g/cm3,and the porosity is 7.70%-9.10%.The axial compressive strength of SiCf/SiC composites is 53.2 MPa,and the radial crushing strength is 38.18 MPa.Compression is expressed as a shear failure in the 45°direction with the horizontal plane while it is broken into pieces during crushing test.The fiber pull-out phenomenon can be observed obviously at the fracture,but the pull-out is not long and exhibits a typical pseudo ductility feature.The circumferential tensile strength of SiCf/SiC composites is 12.8 MPa.The fracture is relatively flat,and the phenomenon of fiber pull-out is not obvious,which indicates that it is brittle fracture.