Al Matrix Nanocomposites Research Articles

The role of twinning and stacking fault-induced plasticity on the mechanical properties of aluminum-lithium-graphene nanocomposites

In this study, the synthesis-structure-property relationship of graphene-reinforced Al matrix nanocomposites was investigated. The Al-Li-GNPs nanocomposite was synthesized to attain both high strength and good ductility. The incorporation of GNPs as a reinforcement in the Al-based matrix provided a nanocomposite structure for an integrated strengthening effect. To promote plasticity and maintain good ductility, the nanocrystalline Al matrix was alloyed with Li to reduce its stacking fault energy and promote additional deformation mechanisms. The compressive yield strength (CYS) increased from 88 MPa for the starting Al to 403 MPa for the Al-Li-GNPs nanocomposites with 1.0 wt% GNPs. Fracture analysis indicated that the synthesized nanocomposite exhibited a ductile nature and significant plastic deformation. Based on microscopic analysis, the enhanced strength of the Al-Li-GNPs nanocomposite was attributed to grain refinement, load transfer, and strain hardening. The good ductility, on the other hand, was attributed to dislocation slipping, the formation of stacking faults, and twinning.

Molecular dynamics simulations of tensile and creep-ratcheting behaviour of CNT reinforced columnar nanocrystalline Al nanocomposites

High-temperature cyclic loading is a major factor affecting the life of a structural component. In this study, the tensile and creep-ratcheting behaviour of three volume fractions of CNT-reinforced columnar nanocrystalline aluminium has been studied using hybrid potentials (EAM, AIREBO and LJ potentials) at two different stress ratios (R = 0.4, 0.6) and three different temperatures (T = 300 K, 467 K and 653 K). The aim is to determine the stress-strain curve, strain-time curve, overall dislocation density, dislocation types, and mainly the underlying deformation mechanisms of CNT-based NC Al matrix nanocomposites. Increasing the CNT volume fraction in the matrix has shown improved UTS values, enhanced dislocation annihilation rate, dissipation of the hysteresis loop energy, lower strain accumulation and higher time to fracture. The specimen fails quickly at higher temperatures which is depicted by the widening of the hysteresis loop. The predominant deformation mechanisms like grain boundary diffusion, widening, merging, sliding and rotations have been observed. Grain boundary diffusion drives the creep-ratcheting deformation behaviour under three temperatures and the misalignment has been noticed at the interaction of CNT-NC Al nanocomposite during the creep-ratcheting deformation at high temperature. The Shockley-partial and perfect dislocations have been determined to control the underlying deformation mechanism. The current work can serve as a keystone in the creep-ratcheting analysis of structural materials employed in high-temperature loading environments.

Advance processing of cluster-free CNT reinforced 6082 Al matrix nanocomposites: influence of mechanical milling and cryomilling

ABSTRACT In the present study, lightweight high-strength carbon nanotubes (CNTs) reinforced aluminium-based composite was fabricated through powder metallurgical processing. The effect of planetary milling and cryogenic assisted milling on the structure, morphology, mechanical properties, phase composition, and thermal stability of CNTs reinforced Al6082 Al nanocomposites powders was investigated using X-ray diffraction (XRD), scanning electron microscope (SEM)- Energy dispersive spectroscopy (EDS), transmission electron microscope (TEM), and indentation techniques. The CNTs in the Aluminium (AL) matrix were distributed uniformly after 50 h of milling. Further, the cryomilling of 50 h milled Aluminium matrix composites (AMC) decreases agglomeration even more and was successful in cleaving the nanotubes as well as minimising entanglements. The broadening of diffraction peaks suggests a reduction in the crystallite size (from ~36 to ~20 nm) and an increase in induced strain. Milled powders were consolidated through the hot-press and spark plasma sintering technique. The mechanical properties of these AMCs were evaluated through indentation for hardness (>250 HV) and compressive testing techniques. SPSed samples reported better properties in comparison to hot-pressed samples. It is discovered that post-CM of Mechanical Milling (MM) powder aids in overcoming issues related to the agglomeration of Al/CNT composites, and the goal to fabricate tangle-free CNT reinforced composite was achieved. Moreover, it showed enhanced mechanical properties with a maximum yield strength of 210 MPa and good synergy between strength and ductility.

The performance of ANFIS-PSO in optimization of Al matrix nanocomposites

The performance of ANFIS-PSO in optimization of Al matrix nanocomposites

Microstructure, Mechanical Properties, and Thermal Stability of Al-Al2O3 Nanocomposites Consolidated by ECAP or SPS from Milled Powders

Ultrafine-grained Al matrix nanocomposites, reinforced with Al2O3 nanoparticles, were produced from milled powders, either by equal channel angular pressing (ECAP), at room or high temperature, with or without back pressure, or by spark plasma sintering (SPS). Their microstructures, mechanical properties (compression, hardness, and sliding wear), and thermal stabilities (thermally induced softening and cracking) were compared, and the advantages and limitations of each process discussed on a scientific but also practical point of view. For the most successful set of process parameters, the yield stress in compression reached 380 MPa, the hardness, HV = 139, remained stable up to 500 °C, and the resistance to sliding wear was comparable to that of Al 5083, and better than that of Al 7075-T6. While the samples consolidated at high temperatures (by ECAP or SPS) showed a good thermal stability, those consolidated by ECAP at room temperature were prone to thermally induced softening and cracking, which was related to trapped and pressurized gases.

Ultrasound-Assisted Liquid-Phase Synthesis and Mechanical Properties of Aluminum Matrix Nanocomposites Incorporating Boride Nanocrystals.

Incorporating boride nanocrystals could significantly impact the mechanical properties of aluminum alloys. Molten salts synthesis offers opportunities to fabricate superhard boride nanoparticles, which can sustain the harsh conditions during the liquid-phase design of metallic nanocomposites. Here hafnium diboride-aluminum nanocomposites are unveiled from molten salt-derived HfB2 nanoparticles sequentially dispersed in aluminum by ultrasound treatment. The structure and size of the nanocrystals are retained in the final nanocomposites, supporting their high chemical stability. Semicoherent interfaces between the nanoparticles and the matrix are then evidenced by TEM, suggesting that the nanocrystals could promote heterogeneous nucleation of Al and then limit the Al grain size to ≈20µm. Nanoindentation measurements reveal significant grain boundary strengthening and grain refinement effects. It is finally shown that HfB2 nanoparticles also enable a decrease in matrix grain size and an increase in the hardness of the AlSi7 Cu0.5 Mg0.3 alloy. These proof-of-concept materials are paving the way to light-weight Al matrix nanocomposites doped by molten-salt synthesized nanoparticles.

A review of the mechanical performance of nanoparticles reinforced aluminium matrix nanocomposites

It is worth analysing the impact of nano-reinforcing on the aluminium (Al) matrix characteristics. Therefore, a critical evaluation of nano-sized reinforcements and their potential to resolve the key challenges of agglomeration, distribution, interfacial and structural reliability is imperatively pursuit to increase the reinforcement effectiveness of Al matrix nanocomposites (AMNCs).The analysis presents a concise yet substantial overview of the mechanical properties of nanoparticles reinforcements in the Al matrix and emphasizes the significant aspects of existing studies to reflect the basic problems and strengths of the fabricated AMNCs. Accounting for the facts of the reviewed literature, a comprehensive strategy with the ability to concurrently address all massive nano-reinforcing challenges is still to be developed. The future framework and a better outcome covering nano-reinforcement strategies are concluded.

Microstructural characterization and mechanical properties of in situ cast nanocomposites Al/TiC type

Al matrix nanocomposites reinforced with TiC particles have been successfully fabricated by self-propagating high-temperature reaction during casting from aluminium 1000 alloy and a mixture of powders of Ti, C and Al used as a moderator. The most important issue was to estimate the influence of moderator content on the microstructure. The microstructure of composites containing a lower amount of moderator (1% and 10%) consists of TiC particles, segregated mainly at grain boundaries of aluminium matrix, while a higher moderator content (>50%) allows to obtain materials with nearly homogenous distribution of TiC particles. Moreover, the elimination of brittle, additional phases e.g. TiAl3 and Al4C3, commonly observed in the Al/TiC composites, was evidenced. However, still small amounts of Ti3AlC and TiAl2.4Si0.6 phases that reduce the capacity of TiC were identified. The composites exhibit improved mechanical properties with regard to aluminium base alloy. The highest value of the relative increase of yield strength was found in the composite with 50% of moderator due to relatively small TiC particle size, well separated and uniformly distributed in the matrix.

Enhanced strengthening of Al–SiC nanocomposites containing a uniform dispersion of dense nanoparticles fabricated by a hybrid accumulative roll-bonding process

Al matrix nanocomposites reinforced by SiC nanoparticles were fabricated by a hybrid accumulative roll-bonding (HARB) process with ultrahigh rolling cycles. Experimental results showed that a highly uniform dispersion of SiC nanoparticles with a high volume fraction (up to 20%) in Al matrix can be achieved by HARB. The grains of Al matrix were refined into the size range of 180–740 nm, depending on the volume fraction of SiC. The as-prepared Al–SiC nanocomposites exhibited remarkably enhanced microhardness (maximum: 216 HV) and tensile strength (maximum: 603 MPa), both approximately 9 times those of the unreinforced matrix. The as-prepared Al–SiC nanocomposites also showed an excellent combination of strength and ductility as compared with other Al matrix composites. The enhanced strengthening of the nanocomposites can be attributed to the efficient contributions of various strengthening mechanisms owing to the uniform dispersion of dense SiC nanoparticles. The distinct strengthening effect due to coefficient of thermal expansion mismatch was evidenced and discussed.

Development of Aluminium-Nanoclay Composite by Using Powder Metallurgy and Hot Extrusion Process

It is well-known that Al matrix nanocomposites are always more expensive compared to conventional materials. In this study, the Al matrix composite containing montmorillonite Nanoclay reinforcement has been synthesized, which is cheaper and more abundant than other reinforcements. Powder metallurgy and extrusion process were employed for the production of the nanocomposite samples containing 0%, 1%, 2%, 6%, and 10% Nanoclay. Microstructural evaluations were carried out by using optical and scanning electron microscopy. Phase investigation was done by using X-ray diffraction and energy-dispersive X-ray spectrometer methods. Mechanical evaluations including macro- and micro-hardness, density evaluation, tensile and compression tests were also conducted. It was revealed that aluminium-clay nanocomposite properties were higher than the monolithic type. According to the obtained results, the addition of montmorillonite Nanoclay caused improvement of the mechanical properties, due to the mechanisms like Orowan and thermal expansion mismatch between reinforcement and the matrix. Thus, the ultimate tensile strengths of 1%, 2%, 6%, and 10% Nanoclay samples were increased about 31%, 46%, 62%, and 95%, respectively, than 0% Nanoclay specimen. The sample containing 2% Nanoclay represented the optimum properties which were the increase in hardness, tensile and compressive strengths about 63%, 46% and 53%, respectively. The increase in the Nanoclay content of the Al matrix changed the complete ductile fracture mode to the shear ductile type.

Optimization of the microstructure and mechanical properties of heterogeneous Al-Al2O3 nanocomposites

High-energy ball milling and hot-press sintering were employed to synthesize heterogeneous aluminum (Al) matrix nanocomposites reinforced by 5 vol.% alumina (Al2O3) nanoparticles. The heterogeneous structure was formed by the nonuniform distribution of Al2O3 nanoparticles in Al matrix, and it composed of an isolated irregular soft phase (pure Al) and a continuous hard phase (Al reinforced by Al2O3 nanoparticles). It was found that the size of soft phase is optimized with increasing ball milling time, resulting in an increase in the yield strength and ultimate strength, as well as retained failure strain. It is worth noting that the ultimate strength of heterogeneous Al nanocomposite with milling time of 20 h (referred to as Heter-20) reached 610 MPa under compression testing. In particular, the introduced soft phase exhibited severe plastic deformation and interface microcracks under compression, which led to higher failure strain (∼30% for Heter-20) and toughness compared to traditional homogeneous Al matrix composites. Furthermore, coexistence of brittle and ductile fractures was observed in the heterogeneous Al nanocomposites under quasi-static compression.

Fabrication of Al–Cu–Fe quasicrystal reinforced 6082 aluminium matrix nanocomposites through mechanical milling and spark plasma sintering

In the present investigation, attempts were made to study the effect of Al–Cu–Fe (40 vol%) quasicrystalline (QC) reinforcement on the structure, morphology and phase composition of 6082 Al matrix nanocomposites (AMCs) processed through mechanical milling (MM) and spark plasma sintering (SPS). The characterization of these MM and SPSed AMCs was done through X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM). The MM induces microstructural refinement of matrix and partial structural transformation of QC phase to Al13Fe4 approximant phase (a = 1.549 nm, b = 0.808 nm, c = 1.248 nm, α = β = 90°, γ = 107.72°; mC102; C2/m). The presence of (311111) diffraction peak of the QC phase in AMCs confirms the existence of face-centred QC phase even after 50 h of MM. The consolidation of Al-QC at 450 °C (723 K) and 550 °C (823 K) results in the fabrication of AMCs having a density of 2.921 and 3.319 g cm−3 respectively. The compressive yield strength and ultimate strength of these AMCs is ∼519 MPa and 639 MPa respectively. The enhancement in the mechanical properties may be attributed to strong interfacial bonding of the Al matrix and QC reinforcement due to interfacial reactions.

Development of Novel AlSi10Mg Based Nanocomposites: Microstructure, Thermal and Mechanical Properties

Al matrix nanocomposites are interestingly employed in the automotive, military, aerospace and electronics packaging industries. In this study, Graphene Nanoplatelets (GNPs) reinforced AlSi10Mg nanocomposites were produced via powder metallurgy. The effect of GNPs content on density, microstructure and mechanical characteristics of the AlSi10Mg/GNPs nanocomposites was investigated systematically. To this aim, AlSi10Mg/GNPs nanocomposites reinforced with 0.5, 1.0 and 2.0 wt.% of GNPs were produced by wet mixing method following by hot compaction at 600 °C. To evaluate the effect of GNPs on mechanical properties of the as-fabricated nanocomposite, Vickers hardness and tensile properties of composites analyzed at room temperature. According to the results, it was found that the fabrication of AlSi10Mg/GNPs nanocomposites is faced with several challenges such as agglomeration and non-uniform dispersion of GNPs that should be addressed to achieve the desirable thermal and mechanical properties. For instance, surprisingly, it is revealed that the mechanical and thermal properties of nanocomposites were deteriorated in the presence of a high quantity of GNPs (>1.0 wt.%), which can be attributed to the GNPs agglomeration and accordingly introduction of internal porosity in the nanocomposite. The relatively low fraction of GNPs can uniformly be dispersed in the matrix and improve the performance of the nanocomposite.

Microstructure and mechanical properties of Al matrix nanocomposites reinforced by different amounts of CNT and SiCW

This study aims to investigate the effect of carbon nanotube (CNT) and silicon carbide whisker (SiCW) reinforcements on mechanical properties of aluminum matrix composites. In this study, different amounts of CNT (0–5 wt%) and silicon carbide whiskers (0–5 wt%) were used for fabricating aluminum matrix composite samples. To distribute the reinforcements, aluminum powder and the reinforcements were mixed in a planetary ball mill with rotating speed of 120 rpm at different times (0.5, 1, and 2 h). The results showed that the optimum milling time is 1 h. Then samples were hot pressed under the pressure of 500 MPa at different times and temperatures. Scanning electron microscopy images of the samples fabricated by hot pressing showed that the optimum hot-pressing temperature is 550 °C. The effect of the type and the amount of reinforcement and hot-press time on density, hardness, yield strength, and compressive strength of the samples were also investigated. The results showed that, with decreasing the CNTs content (up to 0.5 wt %), the compression strength reaches a maximum (290 MPa), but with increasing CNTs content more than (0.5 wt%), it is degraded due to the agglomeration. In contrast, with increasing the SiCW content up to 3 wt%, the mechanical properties increases proportionally. The compression strength of the composite containing 3 wt% SiCW increased by 33.9% compared with the pure aluminum. Economically, it is preferred to use reinforcements that improve the properties at lower contents. As a result, CNT is a superior reinforcement in comparison with silicon carbide whiskers.

On the stability, microstructure, and mechanical property of powder metallurgy Al–SiC nanocomposites during similar and dissimilar laser welding

Aluminum matrix nanocomposites consolidated by powder metallurgy (P/M) have significant potential for practical applications in the aerospace and automotive industries considering their admirable strength to weight ratio and good corrosion resistance. Due to dimensional restrictions in traditional P/M manufacturing routes, similar and dissimilar joining would be essential to design complex structures, however, the stability of Al-matrix nanocomposites during joining process is a crucial issue. In this research, the stability of an Al-6 vol% (50 nm, ex-situ) SiC-2 vol% (15 nm, in situ) Al2O3 hybrid P/M nanocomposite was evaluated during laser joining in comparison to similar and dissimilar joints with commercially pure aluminum (AA1050 alloy). The processing parameters were optimized with a constant focus spot size of 200 μm, laser power of 4 kW, and travel speed of 8 m/min to achieve full-penetration joints. According to the experimental results, the similar P/M nanocomposite exhibited unstable behavior during laser welding due to the formation of porosity associated with clustering and void expansion near SiC nanoparticles. Hence, the fusion zone in both joint designs consisting of similar and dissimilar containing nanocomposite material became heterogeneous due to the presence of clusters and shrinkage micro-voids. The mechanical properties of weldments deteriorated considerably, with large fluctuations in the hardness profiles as well as low joining efficiency (<30%) and brittle fracture. Defects present in dissimilar welds were mainly located at the nanocomposite side.

Structural and mechanical properties of CeO2 reinforced Al matrix nanocomposites

Structural and mechanical properties of CeO2 reinforced Al matrix nanocomposites

Characterization of Carbon Nanotube Reinforced Aluminium Nano-composite using Field Emission Scanning Electron Microscope

Carbon nanotubes (CNT) is a promising fibrous materials for development of nanocomposite especially aluminium (Al) matrix nanocomposites as CNT exhibited extraordinary mechanical properties and high aspect ratios. The dispersion is the main factor for a quality CNT-Al nanocomposite that affects the uniformity in mixture leading to the enhanced mechanical and wear behaviour. The present study emphasizes on the characterization of carbon nanotube dispersion by means of field emission scanning electron microscope after synthetization of new nanocomposite. The mixing of the reinforcement and matrix powders was performed in ball mill for 2 hours at 250 rpm. The result shows the homogeneous distribution was observed from the experiment. The morphological characterization under FESEM provides insight features of CNT-Al nano-composite with the ball milling parameter on the sintering.

Influence of SiO2 nanoparticles on the microstructure and mechanical properties of Al matrix nanocomposites fabricated by spark plasma sintering

Abstract Al-SiO2 nanocomposite was produced using mechanical milling and spark plasma sintering (SPS) processes. In this research, the effects of ceramic nano size reinforcement on the microstructure and mechanical properties of the Al-SiO2 nanocomposite were investigated. Using electron microscopy, the microstructures of the primary powder and the produced composites were studied. Microhardness and tensile tests were also employed to study the mechanical properties of the composites. The results revealed a reduction in porosity as increasing the nanoparticles percentage up to 3 wt%. For higher reinforcing percentages the material's density reached the minimum (86% of the density of the composite with 3 wt% of reinforcing particles). EBSD was employed to study the microstructural evolution of the produced materials.

The effect of TiC:CNT mixing ratio and CNT content on the mechanical and tribological behaviors of TiC modified CNT-reinforced Al-matrix nanocomposites

In this study, a novel method was developed for surface modification of CNTs through a pressureless spark plasma sintering. TiC:CNT mixing ratio was changed in the range of 1:2–5:2 to find the optimum ratio. Thereafter, by changing the amount of nanotubes in the optimal mixing ratio (4:2), the effect of modified-CNT content (0.5–5 wt%) on the mechanical and tribological properties was investigated. The composite sample containing 1.5 wt% modified-CNT, with the mixing ratio of 4:2, showed the greatest properties. The results showed that microhardness, nanohardness and Young's modulus of the sample have the highest values of 97.61 HV, 0.93 GPa and 100.48 GPa, respectively. In addition, mean friction coefficient of 0.22 and wear weight loss of 7.4 mg were obtained for the composite.

Micromechanical study of elastic-plastic and thermoelastic behaviors of SiC nanoparticle-reinforced aluminum nanocomposites

Elastic-plastic and thermal expansion responses of aluminum (Al) matrix nanocomposites reinforced with silicon carbide (SiC) nanoparticles are investigated through a micromechanics analytical unit cell method. The formation of the interphase region between SiC nanoparticles and Al matrix is taken into account in the modeling of nanocomposites. The influences of some important parameters such as the thickness and material properties of the interphase, volume fraction and diameter of SiC nanoparticles on the elastic modulus, coefficient of thermal expansion (CTE) and elastoplastic stress-strain curve of the Al nanocomposites are studied in detail. The results clearly reveal high contribution of the interphase region to the overall mechanical and thermal behaviors of Al nanocomposites. It is found that when nanoparticle diameter is lower than about 150 nm, the decrease of SiC nanoparticle diameter leads to (i) an increment in mechanical properties both in the elastic and plastic regions and (ii) a reduction in CTE of the metal matrix nanocomposites. Also, the effect of interphase on the elastic modulus and CTE of Al nanocomposites becomes more important with the reduction of SiC nanoparticle diameter. Finally, the micromechanical model is employed to predict the elastoplastic behavior of SiC nanoparticle-reinforced Al nanocomposites subjected to multi-axial loading conditions in the presence and absence of the interphase region.