退火温度对Hi-Nicalon SiC纤维微观结构及力学性能的影响

EFFECTS OF TEMPERATURE ON MICROSTRUCTURE EVOLUTION AND MECHANICAL PROPERTIES OF HI-NICALON SiC FIBERS

Hi-Nicalon碳化硅纤维是一种作为高温下应用的陶瓷基复合材料的增强体。研究温度对Hi-Nicalon碳化硅纤维微观结构及力学性能 的影响对于Hi-Nicalon碳化硅纤维的改进和应用具有重要意义。在氩气流的保护下,Hi-Nicalon碳化硅纤维分别在1400,1600℃和1800℃ 保温10h进行了退火处理。然后利用高分辨透射电子显微镜和X射线衍射分析方法对其经不同温度退火处理后纤维的微观结构进行表征,并用 电子单纤维强力机测定其拉伸强度。研究结果表明:随着退火温度的升高,βSiC晶粒不断长大;堆垛层错不断形成;游离碳堆垛层数和长度都 随之增加,排列也趋于规整。拉伸强度也随着退火温度的升高而降低,经1800℃保温10h退火处理后的纤维的平均强度下降到了1.0GPa。

Hi-Nicalon silicon carbide fibers are mainly used as the reinforcement of the ceramic-matrix composites served for high temperature. Effects of temperature on the microstructure evolution and mechanical properties of Hi-Nicalon silicon carbide fibers were investigated, which are very important for the improvement and application of the material. Hi-Nicalon silicon carbide fibers were annealed at 1400, 1600°C and 1800°C for 10 h in an argon flow, respectively. Their microstructure was characterized by high resolution transmission electron microscope and X-ray diffraction, and the tensile strength was determined by a monofilament tensile testing machine. The results indicate that with the increasing of annealing temperatures the grain size of β-SiC is increased, the stacking faults are formed gradually and organization of the free carbon phase is increased. In addition, the tensile strength decreases with the increase of annealing temperatures. The mean strength of the fibers reduces to 1.0 GPa after annealed at 1800°C for 10 h.