Interfacial Bonding of Al-Si/C Composites and Improvement of the Thermal Shock Resistance

The poor Carbon/Aluminum interfacial bonding and excessive difference in thermal expansion coefficients are the main factors for the performance failure of Carbon/Aluminum composites. C/Al-Si composites were prepared by pressure impregnation of carbon matrix with Al-Si alloys of different silicon element contents. The mechanism of the effect of silicon on improving the interfacial bonding, mechanical and electrical properties, and thermal shock resistance of the composites was investigated. The results showed that the mechanical strength and thermal shock resistance of the composites were proportional to the elemental silicon content, and the contact angle and porosity were inversely proportional to the mass fraction of silicon. When the mass fraction was 12 wt.%, the flexural strength was 1.49 times that of the unmodified composites and electrical conductivity of the composites were increased by 76.21% compared with the unmodified composites. The contact angle was reduced to 41°, and the flexural strength of the composites remained above 90% after thermal shock. This is because the generated silicon carbide layer formed between the interfaces can enhance the interfacial bonding, improve the impregnation rate, and reduce the thermal expansion difference, thus improving the overall performance of the C/Al-Si composites.