Interfacial Preparation And Structural Properties Of Reactive Melt Infiltration C/C-SiC-ZrC Matrix Composites

C/C-SiC-ZrC composites have broad application prospects in the direction of hypersonic aircraft,but the C/C-SiC-ZrC composites prepared by reactive melt infiltration still have serious fiber damage and slightly poor mechanical properties.There are few studies on its influence on mechanical properties.In this paper,300 nm PyC interface,PyC/SiC interface,and 100 nm,300 nm,and 800 nm（PyC+SiC）co-deposited interfaces were introduced into the carbon fiber needle punched preform,and the C/C-SiC-ZrC composites were prepared by reactive melt infiltration method.The distribution of（PyC+SiC）co-deposited interface on the preform was statistically analyzed,the protective effect of different interfaces in reactive infiltration was discussed,and the influence of interface type and interface thickness on the mechanical properties of composites was studied.The main conclusions of the paper are as follows:（1）Three kinds of interfaces prepared by CVI method have uniform distribution and obvious characteristics.The ceramic phase distribution of the C/C-SiC-ZrC composites formed by reactive melt infiltration is uniform and the porosity is low.（2）The distribution law of the（PyC+SiC）interface on the preform was calculated,and the results show that the（PyC+SiC）interface on the preform has a thicker surface layer and a slightly thinner distribution characteristic in the middle.With the increase of preparation time,the thickness gradient of the（PyC+SiC）co-deposited interface becomes larger,and the interface thickness gradient at the corner of the preform is higher than that at the center of the preform,and the growth rate of the interface increases with the increase of preparation time.（3）The protective effect of different interfaces in the infiltration process was studied.The results show that the PyC interface can only play a protective role by reacting with the melt to consume the melt;The SiC grains in the（PyC+SiC）co-deposition interface physically block the melt and provide nuclei for SiC growth,which makes it easier to form a continuous SiC layer at the interface,and the protective effect is enhanced;The continuous SiC layer in the PyC/SiC double-layer interface has the best protection effect,but the thermal fusion of the SiC layer caused by the erosion of SiC by Zr at high temperature and the temperature increase caused by the reaction at the interface is the reason for the damage to the interface layer.（4）The fracture mechanism of the composites with different interface types and the effect of the interface types on the mechanical properties of the composites were studied.The results showed that the interface debonding of PyC mainly occurred between the interface and the CVI PyC.（PyC+SiC）co-deposited interface debonding mainly occurred between the interface and the fiber,and the bilayer interface debonding mainly occurred between the layers.With the 300 nm-thickness interface,the flexural strength and fracture toughness of the bilayer interface composite reached 208.58 MPa and 8.04 MPa m^1/2,and the flexural strength and fracture toughness of the composite with the（PyC+SiC）co-deposited interface reached 162.80 MPa and 6.21MPa·m^1/2,which are better than the composites with PyC interface prepared by the same process.（5）The effect of interface thickness on the mechanical properties of composites was studied,and the results showed that with the increase of（PyC+SiC）co-deposited interface thickness,the interface bonding performance decreased,and the flexural strength and fracture toughness of the composites showed a trend of increasing first and then decreasing.When the interface thickness is 300 nm,the composite has the best mechanical properties.50 Figures,14 Tables,77 References...