添加Al 对MSI 制备C/ C-SiC 复合材料组织和力学性能的影响

以聚丙烯腈( PAN) 基炭纤维(Cf ) 针刺整体毡为预制体, 用化学气相渗透(CVI) 法制备炭纤维增强炭基体(C/ C) 的多孔坯体, 采用熔融渗硅(MSI) 法制备C/ C-SiC 复合材料, 研究了渗剂中添加Al 对复合材料组织结构和力学性能的影响。结果表明: C/ C 坯体反应溶渗硅后复合材料的物相组成为SiC 相、C 相及残留Si 相。随着渗剂中Al 量的增加, 材料组成相中的Al 相也增加而其它相减少; SiC 主要分布在炭纤维周围, 残留Si 相分布在远离炭纤维处, 而此处几乎不含Al ; 当渗剂中Al 量由0 增加到10 %时, 复合材料的抗弯强度由116. 7 MPa 增加到175. 4 MPa , 提高了50. 3 % , 断裂韧性由5. 8 MPa·m1/2增加到8. 6 MPa·m1/2 , 提高了48. 2 %。Al 相的存在使复合材料基体出现韧性断裂的特征。 

Influence of adding Al on the microstructure and mechanicalproperties of C/ C-SiC composites fabricated by MSI

C/ C-SiC composites were fabricated by molten silicon infilt ration (MSI) to C/ C preforms prepared bychemical vapor infilt ration (CVI) . The influences of adding Al in molten Si infilt rating agent on the microst ructureand mechanical properties of the composites was studied. The result s show that the composites fabricated by infiltrating Si into C/ C preforms contain SiC , C and residual Si phases. With the increasing of the amount of adding Al inthe agent , the amount of Al phase in the composites increases and the amount s of other phases such as SiC and Siphase decrease. SiC phase dist ributes around the carbon f iber , and Si phase exist s far away from the carbon f iberwhere there is nearly no Al phase. The bending st rength and the f racture toughness increase with the increase of theamount of adding Al. When the amount of Al increases from 0 to 10 % , the bending st rength increases from 116. 7MPa to 175. 4 MPa and the f racture toughness from 5. 8 MPa·m1/2 to 8. 6 MPa·m1/2 , that is , by 50. 3 % and 48. 2 %respectively. The Al phase makes the f racture mechanism of the composite become toughness f racture.