热处理对C/ SiC 复合材料拉伸性能的影响

对等温化学气相渗透法(ICVI)制备的C/SiC复合材料进行热处理,利用声发射(AE)技术对热处理前后C/SiC试样拉伸过程声发射累积能量进行分析,通过SEM进行微结构观察。结果表明:界面层较薄的C/SiC试样经1 500℃热处理后拉伸强度与初始强度相近,经1 700和1 900℃热处理后拉伸强度显著提高,其断裂应变随着热处理温度升高而大幅提高,弹性模量却呈现下降趋势;界面层较厚的C/SiC试样经1 500和1 700℃热处理后拉伸强度变化不大,断裂应变显著提高,弹性模量逐渐降低,经1 900℃热处理后拉伸强度和断裂应变开始下降,而弹性模量变化较小。热处理可以显著提高C/SiC的韧性,在拉伸过程中的断裂功和声发射累积能量均显著增加。界面层较薄的C/SiC断裂模式从脆性逐渐向韧性转变,而界面层较厚的C/SiC热处理后韧性进一步提高。

Effects of Heat Treatment on Tensile Properties of C/ SiC Composite

C/ SiC composites fabricated by isothermal chemical vapor infiltration were heat treated. Acoustic emission (AE) was introduced to analyze the variations of AE accumulative energy during monotonic tensile test. The microstructures were examined by scanning electronic microscope (SEM). The results indicate that, for the thin interlayer C/SiC, its tensile strength is close to the initial one after heat treatment at 1 500 , but tensile strengths of the compositescan be increased after heat treatment at 1 700 and 1 900. With the increase of heat treatment temperature, tensile stresses increase significantly and modulus decrease gradually. For the thick interlayer C/ SiC, tensile strengths have little changes and tensile stresses increase obviously but modulus decrease gradually after heat treatment at 1 500 and 1 700, while tensile strength and strain begin to decrease but modulus has little change after the same heat treatment at 1 900. Heat treatment remarkably improves the toughness of C/ SiC composites. The fracture work and AE accumula tive energy increase obviously after heat treatment. For the composites with thin interlayer, the fracture mechanism varies from brittle mode to toughness one, and for the composites with thick interlayer, the toughness is further enhanced.