Reinforced Aluminum Matrix Nanocomposites Research Articles

Evaluation of Elastic Properties of Graphene Nanoplatelet Reinforced Aluminum Matrix Nanocomposites

Evaluation of Elastic Properties of Graphene Nanoplatelet Reinforced Aluminum Matrix Nanocomposites

Machine-learning-assisted microstructure–property linkages of carbon nanotube-reinforced aluminum matrix nanocomposites produced by laser powder bed fusion

Abstract In this study, the cellular microstructural features in a subgrain size of carbon nanotube (CNT)-reinforced aluminum matrix nanocomposites produced by laser powder bed fusion (LPBF) (a size range between 0.5–1 μm) were quantitatively extracted and calculated from scanning electron microscopy images by applying a cell segmentation method and various image analysis techniques. Over 80 geometric features for each cellular cell were extracted and statistically analyzed using machine learning techniques to explore the structure–property linkages of carbon nanotube reinforced AlSi10Mg nanocomposites. Predictive models for hardness and relative mass density were established using these subgrain cellular microstructural features. Data dimension reduction using principal component analysis was conducted to reduce the feature number to 3. The results showed that even AlSi10Mg nanocomposite specimens produced using different laser parameters exhibited similar Al–Si eutectic microstructures, displaying a large difference in their mechanical properties including hardness and relative mass density due to cellular structure variance. For hardness prediction, the Extra Tress regression models showed a relative error of 2.47% for prediction accuracies. For the relative mass density prediction, the Decision Tress regression models showed a relative error of 1.42% for prediction accuracies. The results demonstrate that the developed models deliver satisfactory performance for hardness and relative mass density prediction of AlSi10Mg nanocomposites. The framework established in this study can be applied to the LPBF process optimization and mechanical properties manipulation of AlSi10Mg-based alloys and other additive manufacturing newly designed alloys or composites.

Evolution of Microstructure, Texture and Mechanical Properties for Multilayered Al Matrix Composites by Accumulative Roll Bonding.

Carbon nanotubes (CNTs) reinforced aluminum matrix nanocomposites were fabricated by Accumulative Roll Bonding (ARB). The surface morphologies, mechanical properties, grains texture and orientation of the Al/CNTs nanocomposites were characterized, and the mechanisms and influences of CNTs contents and ARB cycles on the mechanical performance and grain textures of Al/CNTs were investigated and revealed. The strength of the composites rose with increase of the CNTs content, and the ARB cycles showed a 26% improvement when the CNTs content varied from 0 to 1 volume percent (vol.%). The increase in the mass fraction of the carbon nanotubes made the grain distribution in the Al/CNTs nanocomposite samples more diffuse. Besides, the stable texture of the hot rolled crystal grains on the α orientation are constantly turning to {011}< 011> with the mass fraction of the reinforcing phase increased.

In situ synthesized nano-Al4C3 reinforced aluminum matrix composites via friction stir processing

The strength-ductility trade-off problem of carbon nanotube (CNT) reinforced aluminum matrix nanocomposites (AMNCs) restricts its further application. Hence, we report the fabrication of nano-Al 4 C 3 reinforced AMNCs through friction stir processing (FSP) on CNT/Al composites which can simultaneously elevate the ductility of the composite and maintain the original strength. The microstructure evolution and the dispersion of reinforcement are investigated. Tensile tests show that the elongation of the Al 4 C 3 /Al composites fabricated via FSP at a rotation rate of 800 rpm increased by 1.6 times than that of CNT/Al composite and the yield strength retained 95%. The improvement of the mechanical properties is due to the strong Al 4 C 3 –Al interface, homogeneous dispersion, nano size, and dynamic recrystallization during FSP. Grain refinement and Orowan strengthening are the main strengthening mechanisms of Al 4 C 3 /Al composites. This research shares an approach to preparing a nano-Al 4 C 3 reinforced aluminum matrix composite with well strength and outstanding ductility.

Directed energy deposition of CNTs/AlSi10Mg nanocomposites: Powder preparation, temperature field, forming, and properties

Recently, research of carbon nanotubes (CNTs) doping reinforced aluminum matrix nanocomposites has drawn significant attention. In this study, we conducted annular beam directed energy deposition (DED) experiments using CNTs/AlSi10Mg composites, prepared using a new procedure to improve the laser absorptivity of AlSi10Mg. The effect of the dispersant on CNTs adsorption and that of CNTs adsorption on temperature field, microstructure evolution, formability, and properties were clarified experimentally. The results show that CNTs exhibit good dispersion and adsorption in pure N-methyl pyrrolidone (NMP). Further, grains in the DED track were refined as the CNTs content increased, micro-hardness and laser absorptivity also improved. High-quality thin walls of 0.5- wt%-CNTs/AlSi10Mg were successfully formed, demonstrating that the new DED method for the preparation of CNTs/AlSi10Mg metal matrix nanocomposites is viable, expanding the potential application scenarios of composite material structures.

Microstructure and wear characterization of carbon nanotubes (CNTs) reinforced aluminum matrix nanocomposites manufactured using selective laser melting

Aluminum matrix composites are attractive in aerospace and automobile industry due to its low density, high strength and high corrosion resistance. Additive manufacturing methods such as selective laser melting enable the fabrication of such composites with a complex geometry, and the processing of novel, customized, tailored hybrid materials with unique hierarchical microstructures across multiple length scales. However, the microstructure evolution, wear resistance, frictional behavior under different fabrication and operation conditions of such composites still need to be explored. This study aims to fill the research gap in microstructure evolution and wear characterization of SLM-produced CNTs reinforced aluminum matrix nanocomposites. The surface characteristics, density, wear groove morphology, and surface damages in wear tests were examined. It was determined with SEM/EDS that the major phases of SLM-processed CNTs/Al-based nanocomposites were Al9Si and Si. These phases formed during the SLM process within the composites changed their wear behavior drastically. The wear surfaces were undergoing severe plastic deformation and progressive pitting. The wear rate of CNTs/AlSi10Mg nanocomposites specimens is about 33% lower than that of AlSi10Mg specimens. The higher wear resistance of the CNTs/AlSi10Mg nanocomposites specimens with shallow and narrow wear groove is attributed to the CNTs reinforcement induced higher surface hardness and also the unique hierarchical microstructure of the nanocomposites. The results showed that the SLM-produced CNTs reinforced aluminum matrix nanocomposites have good potentials to be an alternative to pure AlSi10Mg counterparts in terms of hardness, strength, frictional and wear behavior.

Application of a novel method for fabrication of graphene reinforced aluminum matrix nanocomposites: Synthesis, microstructure, and mechanical properties

In this study, the graphene reinforced aluminium matrix nanocomposite is fabricated through the combination of high energy ball milling (HEBM) and molecular level mixing (MLM) processes followed by spark plasma sintering (SPS) method. FTIR, XRD and FESEM analyses revealed that Cu/RGO nanocomposite was well synthesized by the MLM method with a uniform distribution of Cu nanoparticles on RGO surface. XRD and Raman spectroscopy showed that no Al4C3 phase was formed during the manufacturing process, but Al2Cu fine particles precipitated during the SPS treatment which were smaller in size and more uniform in distribution when RGO was used as reinforcement according to TEM analysis. Grain refinement of the nanocomposites was also investigated in the presence of RGO by EBSD method. The results showed that with increasing RGO content from 0 to 1 wt %, the coarse grained microstructure changed to bimodal microstructure. In addition, the mean grain size decreased from 3.9 to 1.6 μm, and dislocation density increased significantly with the increased RGO content. The SPS process also resulted in a nearly fully dense nanocomposite with a relative density higher than 99%. The investigation of mechanical properties of the sintered nanocomposite indicated an improvement of 79, 49 and 44% of yield strength, ultimate strength, and Vickers hardness, respectively, for only 1 wt % graphene containing nanocomposite in comparison to the unreinforced Al–4Cu alloy.

Regulation of interface between carbon nanotubes-aluminum and its strengthening effect in CNTs reinforced aluminum matrix nanocomposites

Carbon nanotubes (CNTs) are popular as the chosen reinforcement to achieve excellent mechanical and functional performance in aluminum matrix nanocomposites (AMNCs). However, the key bottleneck problems restrict the strengthening effect using CNTs in AMNCs due to the dispersion homogeneity of CNTs, the distinct differences in physical properties, poor wettability and interface bonding between CNTs and aluminum matrix. This study aims to address these key issues by introducing a continuous SiC nano layer on CNTs surface synthesized from carbon-silicon reaction, acting as a compatibility transition layer prior to mixing with aluminum powders. The results clearly show that the SiC cladding layer provides a good wettability and strong interfacial bonding between CNTs and aluminum matrix, and the interfacial reaction between CNTs and aluminum matrix could be effectively regulated. It is also conducive to reducing the mass density difference and specific surface energy, improving the dispersion of CNTs in matrix. Those factors make a strong contribution to the strengthening effect of CNTs enforcement by achieving high load transfer efficiency. The AMNCs reinforced by this new CNTs/SiC composite powder show clear improvement of mechanical performance without compromising in ductility and electrical conductivity, as compared to AMNCs reinforced by only CNTs or SiC.

Laser additive manufacturing of carbon nanotubes (CNTs) reinforced aluminum matrix nanocomposites: Processing optimization, microstructure evolution and mechanical properties

In this study, a laser-based additive manufacturing route of selective laser melting (SLM) was applied to fabricate carbon nanotubes (CNTs) reinforced Al-based nanocomposites with tailored microstructures and excellent mechanical properties. The densification behavior, microstructure features and mechanical properties were investigated and the relationship between process and property was established. The results showed that the applied laser power and scan speed were the governing factors of the densification behavior of SLM-processed Al-based nanocomposites. SLM processing of 0.5 wt.% CNTs/AlSi10Mg nanocomposite powder led to the formation of three typical microstructures including the primary Al9Si cellular dendrites decorated with fibrous Si, the in situ Al4C3 covered on CNTs, and the precipitated Si inside the cellular grains. As the optimal SLM processing parameters of laser power of 350 W and scan speed of 2.0 m/s were applied, the fully dense SLM-processed CNTs/Al-based nanocomposites exhibited high microhardness of 154.12 HV0.2, tensile strength of 420.8 MPa and elongation of 8.87%, due to the formation of high densification and ultrafine microstructure. The grain refinement effect, Orowan looping system and load transfer are considered as three strengthening mechanisms occurred simultaneously during tensile tests, leading to excellent mechanical properties of SLM-processed CNTs/Al-based nanocomposites.

Effects of energy input during friction stir processing on microstructures and mechanical properties of aluminum/carbon nanotubes nanocomposites

Carbon nanotubes reinforced aluminum matrix nanocomposites were fabricated by friction stir processing. Raman spectroscopy, scanning electron microscope, transmission electron microscopy and tensile tests were used to characterize microstructures and mechanical properties of the nanocomposites. Effects of energy input during friction stir processing on microstructures and mechanical properties of the nanocomposites were investigated. It was found that the grain of aluminum matrix in the nanocomposites was coarsened slightly with the increase of energy input. Microstructure analysis showed that carbon nanotubes were successfully incorporated into aluminum matrix by friction stir processing and well bonded interfaces between the carbon nanotubes and aluminum matrix were formed. However, the carbon nanotubes dispersion and mechanical properties of the nanocomposites fabricated with different energy inputs were quite different, in which better carbon nanotubes dispersion and higher tensile strength could be obtained by applying higher energy input during the fabrication process. By applying the highest energy input, the tensile strength of the nanocomposite was 53.8% higher than that of the unreinforced aluminum. Meanwhile, the elongation of the nanocomposite was 31.2%, which showed an excellent ductility. The strengthening mechanisms were the synergy of Orowan looping, load transfer and grain refining. The present findings may provide the guidance on the optimization of the processing parameters during friction stir processing for fabricating the high performance aluminum/CNTs nanocomposites.

Structural and Mechanical Properties of Amorphous Si3N4 Nanoparticles Reinforced Al Matrix Composites Prepared by Microwave Sintering

The present study focuses on the synthesis and characterization of amorphous silicon nitride (Si3N4) reinforced aluminum matrix nanocomposites through the microwave sintering process. The effect of Si3N4 (0, 1, 2 and 3 wt.%) nanoparticles addition to the microstructure and mechanical properties of the Al-Si3N4 nanocomposites were investigated. The density of Al-Si3N4 nanocomposites increased with increased Si3N4 content, while porosity decreased. X-ray diffraction (XRD) analysis reveals the presence of Si3N4 nanoparticles in Al matrix. Microstructural investigation of the nanocomposites shows the uniform distribution of Si3N4 nanoparticles in the aluminum matrix. Mechanical properties of the composites were found to increase with an increasing volume fraction of amorphous Si3N4 reinforcement particles. Al-Si3N4 nanocomposites exhibits higher hardness, yield strength and enhanced compressive performance than the pure Al matrix. A maximum increase of approximately 72% and 37% in ultimate compressive strength and 0.2% yield strength are achieved. Among the synthesized nanocomposites, Al-3wt.% Si3N4 nanocomposites displayed the maximum hardness (77 ± 2 Hv) and compressive strength (364 ± 2 MPa) with minimum porosity level of 1.1%.

Effect of aluminum carbide interphase on the thermomechanical behavior of carbon nanotube/aluminum nanocomposites

The objective of this work is to investigate the coefficient of thermal expansion of carbon nanotube reinforced aluminum matrix nanocomposites in which aluminum carbide (Al4C3) interphase formed due to chemical interaction between the carbon nanotube and aluminum matrix is included. To this end, the micromechanical finite element method along with a representative volume element, which incorporates, carbon nanotube, interphase, and aluminum matrix is employed. The emphasis is mainly placed on the effect of Al4C3 interphase on the coefficient of thermal expansion of aluminum nanocomposites with random microstructures. The effects of interphase thickness, carbon nanotube diameter, and volume fraction on the thermomechanical response of aluminum nanocomposite are discussed. The results reveal that the effect of Al4C3 interphase on the coefficient of thermal expansion of the aluminum nanocomposites becomes more significant with (i) increasing the coefficient of thermal expansion volume fraction, (ii) decreasing the coefficient of thermal expansion diameter, and (iii) increasing the interphase thickness. It is clearly observed that the coefficient of thermal expansion varies nonlinearly with the carbon nanotube diameter; however, it decreases linearly as the carbon nanotube volume fraction increases. Furthermore, the axial and transverse coefficient of thermal expansions of aligned continuous and discontinuous carbon nanotube-reinforced aluminum nanocomposites with Al4C3 interphase are predicted. Also, the presented finite element method results are compared with the available experiment in the literature, rule of mixture, and concentric cylinder model results.

A novel strengthening effect of in-situ nano Al2O3w on CNTs reinforced aluminum matrix nanocomposites and the matched strengthening mechanisms

Nano alumina whiskers (Al2O3w) were in-situ synthesized in carbon nanotubes (CNTs) reinforced aluminum matrix nanocomposites (AMNCs) which were fabricated by flake powder metallurgy (P/M). To study the strengthening effect of nano Al2O3w on CNTs reinforced AMNCs and clarify the strengthening mechanisms, the microstructures and mechanical properties of AMNCs are investigated. It is found that CNTs-Al2O3w reinforcements have a significant hybrid strengthening effect on tensile strength due to their uniform dispersion and good interfacial bonding with Al matrix. The strengthening mechanisms of CNTs-Al2O3w reinforcements are considered as a sum of load transfer, grain refinement, thermal mismatch and Orowan looping theory. The experimental strengths of AMNCs containing 0.25 and 0.5 vol% CNTs are well matched with the theoretical values calculated by the strengthening mechanisms. And the differences between them are less than 2.9%, which is highly effective for predicting the mechanical properties of CNTs-Al2O3w reinforced AMNCs. The predicted values indicate that load transfer mechanism from both CNTs and Al2O3w is dominant, improving UTS of 0.5CNTs reinforced flake AMNCs (228 MPa) by more than 79.5% in comparison with pure Al.

Microstructure and synergistic-strengthening efficiency of CNTs-SiCp dual-nano reinforcements in aluminum matrix composites

In this study, reinforcements of carbon nanotubes (CNTs) and silicon carbide particle (SiCp) in CNTs-SiCp reinforced aluminum matrix nanocomposites (AMNCs) are studied. The tensile strength of 0.5CNTs-0.5SiCp/Al increase by 94% compared with pure Al reaching 247 MPa, it also has a lifting of 14% and 56% compared with 1.0CNTs/Al and 1.0SiCp/Al. CNT-SiCp reinforcements have the synergistic enhancement effect of 1 + 1 > 2 in tensile strength. It is found that SiCp as a dispersed particle around CNTs can inhibit and delay the pulling out and peeling of CNTs to further enhance the strengthening effect of CNTs by pinning effect. Between CNTs and Al matrix, there is a nano-scale reaction transition layer which improves the mechanical properties of AMNCs by strengthening the interfacial bonding. The existences of SiCp inhibit the excessive reaction of the interface, when the tensile strength of AMNCs increases compared with pure Al, the elongation and conductivity have similar maintaining.

Graphene Reinforced Aluminum Matrix Nanocomposites

Graphene Reinforced Aluminum Matrix Nanocomposites

Effects of CNTs content and milling time on mechanical behavior of MWCNT-reinforced aluminum nanocomposites

Mechanical behavior of multi-walled carbon nanotubes (MWCNTs) reinforced aluminum matrix nanocomposites was evaluated microstructurally and mechanically using density measurement, Vickers hardness test and nanoindentation. Nanocomposites containing 1, 2 and 5 wt% of CNTs were synthesized with a combination of ball milling and powder metallurgy routes to investigate the effects of CNTs content and milling time on mechanical properties of the nanocomposites. Findings revealed that milling time plays an important role in the dispersion of MWCNTs within the Al matrix and subsequently in the mechanical properties of nanocomposites. Hardness and Young's modulus of the nanocomposites were improved significantly with increasing CNTs content and where a homogenous dispersion of CNTs was obtained. Bulk densities of composites were found to decrease with increasing CNTs content at a constant milling time but increased with increasing the milling time at a constant amount of CNTs.

Preparation of SiC Nano-particulates Reinforced Aluminum Matrix Nanocomposites by High Intensity Ultrasonic Cavitation Process

The present investigation attempts to evaluate the effect of high intensity ultrasonic cavitation on dispersing the SiC nanoparticles in aluminum 6061 melt. Aluminum melt with various volume percentages of SiC nanoparticles was ultrasonically processed by dipping the ultrasonic horn into the melt. SEM and EDS study with elemental mapping validates the uniform distribution of SiC nanoparticles in the Al matrix. Compared to the un-reinforced alloy matrix and conventional composites, the mechanical properties of the nanocomposites, including tensile strength and hardness improved quite significantly as the particle volume percentage increased. The nanocomposites show better ductile properties as compared to the conventional composites. To understand the effect of ultrasonic vibrations on processing the nanocomposites, the nanocomposite was processed at three amplitudes and the results are presented. Ultrasonic cavitation based fabrication process proved as a better alternative to the conventional stir casting route to disperse the nano ceramic particles in molten alloys.

Fabrication of silicon carbide reinforced aluminum matrix nanocomposites and characterization of its mechanical properties using non-destructive technique

The SiC nanoparticulate reinforced Al matrix composites (with 2.5–12.5vol%) were successfully fabricated by employing high energy ball milling with cold-pressing and sintering technology at 550°C for 1h. Microstructures and nanoparticulate distribution were analyzed with scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM). Mechanical property and hardness were studied using pulse echo overlap (PEO) method as a non-destructive technique. Microstructure analysis showed that the nanocomposites contained only α-Al and SiC phases with clean interface of thickness ∼1.5nm, and preserved nano-grained network structure. The SiC nanoparticulates were distributed uniformly in a metal matrix, and neither voids nor cracks were detected at the interface of Al/SiC. Besides, there was no reaction product has been found at the interface. Accordingly, the mechanical properties of composites reinforced by SiC nanoparticulates were significantly improved, while the Poisson's ratio of nanocomposites was retained. This was mainly due to the stronger interfacial bonding derived from direct mechanical interlocking between the adjacent component surfaces.

Fabrication and evaluation of mechanical and tribological properties of boron carbide reinforced aluminum matrix nanocomposites

In this study, fabrication and characterization of bulk Al–B 4C nanocomposites were investigated. B 4C nanoparticles were mixed with pure Al powder by ball milling to produce Al–B 4C powder. Al–B 4C powders containing different amounts of B 4C (5, 10 and 15 wt.%) were subsequently hot pressed to produce bulk nanocomposite samples. Consolidated samples were characterized by hardness, compression and wear tests. Results showed that the sample with 15 wt.% B 4C had the optimum properties. This sample had a value of 164 HV which is significantly higher than 33 HV for pure Al. Also, ultimate compressive strength of the sample was measured to be 485 MPa which is much higher than that for pure Al (130 MPa). The wear resistance of the nanocomposites increased significantly by increasing the B 4C content. Dominant wear mechanisms for Al–B 4C nanocomposites were determined to be formation of mechanical mixed layer on the surface of samples.