Properties Of Metal Matrix Nanocomposites Research Articles

Reduced Graphene Oxide Nanosheets Decorated with Copper and Silver Nanoparticles for Achieving Superior Strength and Ductility in Titanium Composites.

Graphene and its derivates are extensively applied to enhance the mechanical properties of metal matrix nanocomposites. However, their high reactivity with a metal matrix such as titanium and thus the limited strengthening effects are major problems for achieving high-performance graphene-based nanocomposites. Herein, reduced graphene oxide nanosheets decorated with copper or silver (i.e., Cu@rGO and Ag@rGO) nanopowders are introduced into Ti matrix composites using multiple processes of one-step chemical coreduction, hydrothermal synthesis, low-energy ball milling, spark plasma sintering, and hot rolling. The Cu@rGO/Ti and Ag@rGO/Ti nanocomposites exhibit significantly enhanced strength with superior elongation to fracture (846 MPa-11.6 and 900 MPa-8.4%, respectively, basically reaching the level of the commercial Ti-6Al-4V titanium alloy), which are much higher than those of the fabricated Ti (670 MPa-7.0%) and rGO/Ti composites (726 MPa-11.3%). Furthermore, fracture toughness values of the M@rGO/Ti composites are all significantly improved, that is, the highest KIC value is 34.4 MPa·m1/2 for 0.5Cu@rGO/Ti composites, which is 20.28 and 51.5% higher than those of monolithic Ti and 0.5rGO/Ti composites, respectively. The outstanding mechanical properties of Ag@rGO/Ti and Cu@rGO/Ti composites are attributed to the effective load transfer of in situ formed TiC nanoparticles and the formation of interfacial intermetallic compounds between the rGO nanosheets and Ti matrix. This study provides new insights and approach for the fabrication of metal-modified graphene/Ti composites with a high performance.

Advances in graphene reinforced metal matrix nanocomposites: Mechanisms, processing, modelling, properties and applications

Graphene has been extensively explored to enhance functional and mechanical properties of metal matrix nanocomposites for wide-range applications due to their superior mechanical, electrical and thermal properties. This article discusses recent advances of key mechanisms, synthesis, manufacture, modelling and applications of graphene metal matrix nanocomposites. The main strengthening mechanisms include load transfer, Orowan cycle, thermal mismatch, and refinement strengthening. Synthesis technologies are discussed including some conventional methods (such as liquid metallurgy, powder metallurgy, thermal spraying and deposition technology) and some advanced processing methods (such as molecular-level mixing and friction stir processing). Analytical modelling (including phenomenological models, semi-empirical models, homogenization models, and self-consistent model) and numerical simulations (including finite elements method, finite difference method, and boundary element method) have been discussed for understanding the interface bonding and performance characteristics between graphene and different metal matrices (Al, Cu, Mg, Ni). Key challenges in applying graphene as a reinforcing component for the metal matrix composites and the potential solutions as well as prospectives of future development and opportunities are highlighted.

Laminate analogy approach for the effective elastic properties of metal matrix nanocomposites filled with randomly dispersed graphene nanoplatelets

In this study, the laminate analogy technique is utilized to calculate the elastic properties of metal matrix nanocomposites filled with graphene nanoplatelets. The graphene nanoscale fillers are the most commonly used form of graphene inclusions, which are mostly considered to be disk-shaped. With the help of the Eshelby tensor, the effects of three different shapes of graphene inclusions on the mechanical response are examined. Combining layers of metal matrix composite lamina reinforced by uniformly dispersed graphene inclusions, which are aligned differently in each layer, the metal matrix nanocomposite is simulated. In each lamina, the Mori–Tanaka micromechanical method is employed to calculate the effective elastic properties. Given the fact that the inclusions are aligned, the change in the principal axis of each laminate from the global axis does not affect the Mori–Tanaka results thus resulting in an equivalent laminate composite. Then, classical laminate theory is implemented to obtain the elastic modulus of the equivalent laminate composite. The results obtained from this analytical model are compared with experimental data and a good agreement can be found between them. Two factors are observed to play a critical role in the final results; (i) the number of layers and (ii) the geometrical features of the graphene inclusions. An equivalent laminate composite with few layers acts as a composite material with anisotropic properties, and the increase of the number of layers will cause the isotropic behavior in the equivalent laminate composite. By increasing the aspect ratio, the effective elastic modulus of the nanocomposite exhibits a near-linear growth.

Dynamic behavior of particulate metal matrix nanocomposite plates under low velocity impact

The main purpose of this work is to investigate low velocity impact behavior of metal matrix nanocomposite plates reinforced with silicon carbide nanoscale particles. First, a micromechanical model is proposed to predict the effective mechanical properties of metal matrix nanocomposites. Two features of the nanocomposite microstructure affecting the elastic properties, including agglomerated state of silicon carbide nanoparticles and size factor, are taken into account in the micromechanical simulation. Then, finite element method is used to analyze the time histories of contact force and center deflection of silicon carbide nanoparticle-reinforced metal matrix nanocomposite plates. Several detailed parametric studies are accomplished to explore the influence of volume fraction, diameter and dispersion type of silicon carbide nanoparticles, spherical impactor velocity and diameter, plate dimensions, as well as different boundary conditions on the dynamic response of metal matrix nanocomposite plates. The presented approach accuracy is verified with the available open literature results displaying a clear agreement. The results indicate that adding the silicon carbide nanoparticles into the metal matrix materials leads to a reduction in plate center deflection and an increase in contact force between the plate and projectile. Moreover, it is found that the nanoparticle agglomeration dramatically decreases the contact force and increases the center deflection of metal matrix nanocomposite plates.

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

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.

Shape effects on nanoparticle engulfment for metal matrix nanocomposites

Obtaining a uniform dispersion of the nanoparticles and their structural integrity in metal matrix is a prominent obstacle to use the intrinsic properties of metal matrix nanocomposites (MMNCs) to the full extent. In this study, a potential way to overcome the scientific and technical barrier of nanoparticle dispersion in high performance lightweight MMNCs is presented. The goal is to identify the shape and size of Al2O3 nanoparticle for its optimal dispersion in Al matrix. Critical velocity of solidification is calculated numerically for spherical, cylindrical and disk-shaped nanoparticles using an analytical model which incorporates drag force, intermolecular force and inertia effect. The results show that it is possible to reduce the critical solidification velocity for nanoparticle capture by 6 times with proper shape modification.

Study on Mechanical Properties and Wear Behavior of LM6 Aluminum/Nano Al<sub>2</sub>O<sub>3</sub> Composites

In thepresent study, preparation and characterization of LM6 (A413) aluminum alloy reinforced with nanoalumina powder (Al2O3) is investigated. Al2O3 nanopowder reinforced LM6 (A413) aluminum alloy Metal Matrix nanoComposites (MMNCs) were prepared by stir casting method. The distribution of reinforcement of alumina nanoparticles in LM6 (A413) aluminum alloy were observed with a scanning electron microscopy (SEM). The effect of Al2O3 nanoparticles on mechanical properties of MMNCs were investigated. The wear behavior of MMNCs against hardened steel under dry sliding condition was evaluated on friction wear tester. The results revealed that the inclusion of 2.5% weight fraction alumina nanopowders into LM6 (A413) aluminum alloy enhanced the hardness, impact strength and wear resistance compared with reinforcement of 1, 1.5, 2.5, 5% weight fraction alumina nanopowders. However, the better tensile strength is achieved with 1.5% weight fraction reinforcement in the composites.

Mechanical Properties of Metal Matrix Nanocomposites Synthesized by Selective Laser Melting Measured by Depth Sensing Indentation Technique

This work presents an investigation of basic mechanical properties (hardness, Young modulus) of metal matrix composites (MMC) reinforced with non-oxide ceramic nanoparticles by means of nanoindentation measurements. The evaluated materials were manufactured by selective laser melting (SLS/M). As a matrix 316L stainless steel and as a reinforcing phase TiC nanoparticles were used. The influence of nanoscale reinforcement on the mechanical properties of MMC manufacturing with SLS/M process was examined. In this case statistical evaluation of hardness and Young modulus based on nanoindentation data was performed.

Dimensional analysis and scaling in mechanical mixing for fabrication of metal matrix nanocomposites

For a successful enhancement of mechanical properties of metal matrix nanocomposites, a homogeneous nanoparticle dispersion and distribution in the solidified metal is required. Mechanical mixing can be used for initial break-up of agglomerates, and its study can be simplified with dimensional analysis. Using this technique, mixing time and vortex height were assessed while varying fluid properties, impeller angle, and angular speed. Three relevant dimensionless numbers were recognized: the Reynolds (Re), Froude and Galilei (Ga) numbers. Based on blade and impeller shaft angles, a modified Froude number (Fr*) was defined. These parameters were calculated experimentally, varying angular speed from 200 to 1000rpm for three different impeller angles: 0°, 15° and 30°. This procedure was performed with three fluids: water, and two aqueous glycerin solutions (25% and 50% by volume). Digital images were taken and processed to measure vortex height. Mixing time was measured for water at 0° impeller angle, angular speed ranging from 200 to 1200rpm. Results showed an optimal dimensionless mixing time with respect to Re. A linear relationship was found between dimensionless vortex height and Fr*. The first had a second order polynomial relationship with the product ReFr*, regardless of impeller angle. This relationship, together with the Ga, specific for each fluid, allows scaling the results to other fluids such as molten pure aluminum. This study allows experimenting in simpler systems that involve transparent fluids, room temperature and low cost, to then elaborate a prediction of vortex height in fluids where measurements are difficult and costly, such as molten metals.