Al-based composites reinforced with ceramic particles formed by in situ reactions between Al and amorphous SiNxOy

Abstract

This work combines two approaches to the creation of high-strength heat-resistant Al-based materials: dispersion hardening and stabilization of nanosized Al grains by grain-boundary precipitates. For this, the amorphous SiNxOy phase (1, 2, 3, 4, 5, and 10 wt%) was used as a reactive additive to the Al nanopowder. The Al-SiNxOy composites were obtained by a combination of high-energy ball milling and spark plasma sintering. Chemical reactions between a-SiNxOy and Al led to the formation of nanoscale AlN, Al2O3, and SiO2 phases located at the Al grain boundaries and inside the metal matrix with a bimodal size distribution: approximately 50–150 and 3–10 nm. Compared to unreinforced Al, the addition of 3% SiNxOy increased hardness by 464%, tensile strength by 103% (25 °C), 84% (300 °C), and 86% (500 °C), compressive strength by 200% (25 °C), 164% (300 °C), and 192% (500 °C), and impact wear resistance by 33–46%. TEM microstructure analysis after deformation revealed the types of defects and helped to elucidate the deformation and strengthening mechanisms. The obtained results are important for the development of Al-based composites capable of operating in an extended temperature range.