The role of microstructural features on the electrical resistivity and mechanical properties of powder metallurgy Al-SiC-Al2O3 nanocomposites

Publication date: 15 September 2017
Source:Materials & Design, Volume 130
Author(s): F. Khodabakhshi, A. Simchi
There are many engineering applications in which composite materials are required to satisfy two or more criteria regarding physical and mechanical properties. In this article, Al-matrix nanocomposites reinforced with different volume fractions of SiC nanoparticles (~50nm; up to 6%) were processed by powder metallurgy (P/M) routes through mechanical milling and hot consolidation techniques. Microstructural studies showed that nano-metric Al2O3 particles with a size of ~20nm and volume fraction of ~2% were formed and distributed in the metal matrix, owing to the surface oxides breaking. Microstructural analysis also revealed that the size of cellular structure and the density of dislocations increased with the concentration of hard inclusions. However, the limit of deformability of the nanocomposite materials containing a high amount of nanoparticles (>4vol%) led to less densification upon hot consolidation stages deteriorating mechanical strength. It was shown that the formation of non-equilibrium grain boundaries with high residual stresses as well as scattering around nano-metric inclusions and dislocations influenced the electrical resistivity of the nanocompsites. A linear relationship between the concentration of hard inclusions, electrical resistivity and yield strength was found. This observation demonstrates the importance of substructure and microstructures on the physico-mechanical properties of metal matrix nanocomposites.

Graphical abstract

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