Enhanced Strength and Ductility in Magnesium Matrix Composites Reinforced by a High Volume Fraction of Nano- and Submicron-Sized SiC Particles Produced by Mechanical Milling and Hot Extrusion.

Kamrani Kamrani,Hübler Hübler,Fleck Fleck,Ghasemi Ghasemi

doi:10.3390/ma12203445

Kamrani Kamrani, Hübler Hübler + Show 2 more

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https://doi.org/10.3390/ma12203445

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Abstract

In the present study, Mg nanocomposites with a high volume fraction (10 vol %) of SiC particles were fabricated by two approaches: mechanical milling and mixing, followed by the powder consolidation steps, including isostatic cold pressing, sintering, and extrusion. A uniform distribution of the high content SiC particles in a fully dense Mg matrix with ultrafine microstructure was successfully achieved in the mechanically milled composites. The effect of nano- and submicron-sized SiC particles on the microstructure and mechanical properties of the nanocomposites was evaluated. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), and X-ray diffractometry (XRD) were used to characterize microstructures of the milled and mixed composites. Mechanical behavior of the Mg composites was studied under nanoindentation and compressive loading to understand the effects the microstructural modification on the strength and ductility of the Mg/SiC composites. The mechanical properties of the composites showed a significant difference regarding the size and distribution of SiC particles in the Mg matrix. The enhanced strength and superior ductility achieved in the mechanically milled Mg composites are mainly ascribed to the effective load transfer between matrix and SiC particles, grain refinement of the matrix, and strengthening effects of the nano- and submicron-sized SiC particles.

Highlights

The combination of magnesium (Mg) with ceramic particles results in materials with innovative and multifunctional properties such as low density, high specific stiffness, strength, and damping capacity
The mechanically milled nanocomposite, M10Sn, showed a great enhancement, in strength and in elongation, as compared to the mechanically milled submicrocomposite, M10Sμ. This suggests that, the plasticity is not reduced by SiC nanoparticle addition, the compressive strength can be retained for prolonged periods
The results of mechanical properties determined at the macro- and nanoscale show that the mechanical milling process, as well as the addition of nanoparticles, can simultaneously improve both the strength and the elongation of Mg matrix composites reinforced by a high volume fraction of nanometer-sized particles

Summary

Introduction

The combination of magnesium (Mg) with ceramic particles results in materials with innovative and multifunctional properties such as low density, high specific stiffness, strength, and damping capacity. While the addition of micron size ceramic particles improves strength significantly, it usually deteriorates the ductility due to the brittle nature of the particles. Reducing the size of the ceramic particles to the submicron- or nano-meter regime is a promising strategy to produce composites with high strength and ductility [4,5,6,7], as has, for instance, been shown for Mg composites reinforced by 1.1 vol % Al2 O3 nanoand submicron particles [8]. A significant increase in ductility from 4.2% to 12.0% was observed when nano-Y2 O3 particles (0.66 vol %) were added to pure Mg [9]. Ferguson et al [10] collected the available experimental data for Mg nanocomposites in the reported literature and analyzed the contribution of the primary strengthening mechanisms of the nanoparticles, such as the Orowan

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