The performance of aluminium-matrix composites with nanometric particulate Si-N-C reinforcement

Aluminium-matrix composites reinforced with nanomatric Si-N-C particles (Si-N-C/Al) were fabricated by a powder-metallurgy process. X-ray diffraction, metallography, tensile, dynamic compression and high-temperature creep tests were used to characterize the microstructure and mechanical properties of these composites. The results showed that the tensile strength of the 1 vol. % Si-N-C/Al composite is equivalent to that of the 15 vol. % SiCp(3.5 mu m)/Al composite. However, the tensile properties of the Si-N-C/Al composite deteriorated considerably with increasing particle content owing to the clustering of particles. The creep resistance of the 1 vol. % Si-N-C/Al composite was at least two orders of magnitude higher than that of the 15 vol. % SiCp(3.5 mu m)/Al composite. Furthermore, the 1 vol. % Si-N-C/Al composite exhibited an apparent stress exponent ranging from 15.7 to 23.0 and an apparent activation energy of 248 kJ/mol. The creep data of the composite was rationalized by using the substructure-invariant model with a stress exponent of 8 together with a threshold stress. The dynamic compression tests indicated that the strength and strain hardening rate of the 1 vol. % Si-N-C/Al composite increase significantly with increasing the strain rate from 10(-3) s(-1) to 10(3) s(-1). (C) 1999 Elsevier Science Ltd. All rights reserved.