Magnesium Matrix Nanocomposites Research Articles

MgO-attached graphene nanosheet (MgO@GNS) reinforced magnesium matrix nanocomposite with superior mechanical, corrosion and biological performance

MgO-attached graphene nanosheet (MgO@GNS) reinforced magnesium matrix nanocomposite with superior mechanical, corrosion and biological performance

Hot deformation and processing map of in-situ graphene reinforced magnesium matrix nanocomposites

It is necessary to have a deep understanding of the deformation behavior of magnesium matrix nanocomposites to achieve precise control of components. In this work, the as-cast graphene reinforced magnesium matrix nanocomposites were produced by in-situ vapor-liquid reaction. The flow stress features of the nanocomposites were studied by isothermal compression. The constitutive equation and the processing map of nanocomposites were established under the given load conditions based on the stress-strain curve. The sample is in a stable processing state at a compression temperature of 350 ℃∼450 ℃ with a compression rate of 0.001 s−1 and a compression temperature of 350 ℃ with a compression rate of 0.01 s−1. Furthermore, graphene distributed within the grains facilitated the retention of high dislocation density, which increased the driving force of recrystallization. Recrystallized grains can be generated by the progressive rotation of subgrain due to grain boundary migration being inhibited by graphene. This work provides an important guideline for the optimization of deformation techniques of in-situ nanocomposites.

Toughening and strengthening of Cu-coated carbon nanotubes reinforced AZ61 magnesium matrix nanocomposites by improving interfacial bonding

Interfacial modification without damaging the structure of carbon nanotubes (CNTs) is urgently needed to improve the performance of CNTs reinforced metal matrix nanocomposites. To fabricate CNTs/AZ61 nanocomposite with strong interfacial bonding, copper-coated CNTs (0.15–2.4 vol%) and AZ61 powder were employed through the process of ball milling mixing, vacuum hot pressing and extrusion. The powder and nanocomposites were characterized by HRTEM, SEM, XRD and compressive test to study the distribution of reinforcements, microstructures, interfacial structure and compression behavior. During the high-temperature fabrication process, in-situ interfacial reactions occurred between Cu particles of CNTs and Mg, Al and Zn elements in AZ61 matrix. As a result, the formation of interfacial reaction phases, such as AlCu3, Al2Cu, Cu2Mg, CuMg2, Cu0.61Zn0.39 and MgAl2C2 phases, and their diffused and/or coherent interface significantly strengthen the interfacial bonding. With only 0.15 vol% CNTs, the work of fracture and compression strength of the composite are 40 % and 20 % higher than those of pure AZ61, respectively. The dominating toughening mechanisms are the load transfer role of scattered CNTs and fine-grain effect. The dominating strengthening mechanisms are thermal mismatch and Orowan strengthening.

Substructure Hardening and Twinning Suppression in Graphene Oxide‐Reinforced Magnesium Nanocomposites

The AZ31 magnesium matrix nanocomposites reinforced by 0, 1.2, 2.4 vol% graphene oxide (GO) nanoplatelets are thermomechanically fabricated through friction stir processing, and the influence of nanoplatelets on slip/twin activity is discussed in detail. The addition of GO significantly adjusts the characteristics of the developed substructure during the fabrication route and improves the matrix strength and work hardening rate in further mechanical loading. The presence of GO led to an increase in the length of low‐angle boundaries and higher dislocation storage in their vicinity can be found, highlighting the hardening effect of dislocation movements and increased flow stresses. The well‐defined developed substructure suppresses extension twinning leading to a twinning‐to‐slip deformation mode transition. Along with intensifying the substructure development, GO increases total intragranular strains developed during the fabrication and causes an improvement in the nanocomposites’ overall strength.

Influence of SiC nanoparticle contents on microstructural evolution and mechanical behavior of AZ91D magnesium matrix composites synthesised through a combination of a master pellet feeding technique and stir casting assisted by ultrasonic vibration

In this current study, an integrated approach involving a master pellet feeding technique and stir casting assisted by ultrasonic treatment processing was employed to fabricate AZ91D magnesium matrix nanocomposites reinforced with various concentrations of SiC nanoparticles (1.0, 1.5, and 2.0 wt%). The influence of the nanoparticle feeding method and the weight fraction of reinforcement on the microstructure and mechanical properties of AZ91D/SiC composites was thoroughly examined. The microstructural analysis revealed that the implementation of a master pellet feeding approach resulted in a relatively uniform dispersion of SiC nanoparticles within the primary α–Mg phase, whereas the original nanoparticle feeding method led to noticeable particle agglomeration in the microstructure. Additionally, with an increasing weight fraction of SiC nanoparticles, the primary α-Mg grain became finer and the β-Mg17Al12 intermetallic phase turned smaller. The hardness and tensile properties of AZ91D/SiC composites were significantly enhanced with increasing SiC contents. The addition of 2.0 wt% SiC reinforcements to the AZ91D magnesium alloy resulted in a maximal hardness increase of 41 %. Nevertheless, the ultimate tensile strength (UTS) and elongation (%EL) decreased when the SiC content exceeded 2.0 wt% due to the presence of increased porosity content and particle clusters in the microstructure. Notably, the AZ91D/1.5 wt% SiC composite exhibited promising tensile properties, with yield strength (YS), ultimate tensile strength (UTS), and elongation (%EL) values of 151 MPa, 192 MPa, and 4.54 %, respectively.

Deformation and failure behavior of heterogeneous Mg/SiC nanocomposite under compression

The heterogeneous magnesium (Mg) matrix nanocomposite with dispersed soft phase exhibits high strength and toughness. Herein, the deformation behavior and failure process were investigated to reveal the unique mechanical behavior of the heterogeneous microstructure under compression. The extensive plastic deformation is accompanied by the flattening and tilting of the soft phase, inhibiting strain localization and leading to strain hardening. Moreover, a stable crack multiplication process is activated, which endows high damage tolerance to the heterogeneous Mg matrix nanocomposites. The final failure of the composite is caused by crack coalescence in the shear plane along a tortuous path. The presence of dispersed soft phases within the hard matrix induces a noticeable change in mechanical response. Especially, the malleability of the heterogeneous Mg matrix nanocomposite is two and ten times higher than that of pure Mg and the homogeneous Mg matrix nanocomposite, respectively. The current study provides a novel strategy to break the trade-off between strength and toughness in metal matrix nanocomposites.

Improved strength and plasticity of magnesium matrix nanocomposites reinforced by carbonaceous nanoplatelets and micro-clusters

The uniform distribution of carbonaceous nanomaterials in a magnesium matrix composite can dramatically improve the strength without sacrificing ductility. In this work, graphene oxide (GO) reinforced AZ31 magnesium alloy matrix composites were fabricated using friction stir processing to achieve higher strength, toughness, and plasticity compared with the unreinforced condition. The composite microstructure consisted of individual GO nanoplatelets and GO micro-clusters, having different effects on the deformation behavior of the matrix. Texture analysis revealed that adding GO led to the activation of different twin types and variants during tensile deformation. In contrast, only one extension twin variant was dominant in the case of the unreinforced condition. In spite of the GO micro-clusters, the individual GO nanoplatelets cannot hinder the growth of twins. The GO micro-clusters inhibit twin growth, change the stress state in the parent grains, and provide a driving force for twin nucleation. The extensive twinning occurrence was followed by twin intersections and significantly enhanced the plasticity of the alloy by providing easy orientations for further basal slip.

Investigation on the machinability of TiN nano particulate reinforced magnesium matrix composite

In the present work, the machinability of magnesium matrix nanocomposite was investigated. The nanocomposite consists of pure Mg as matrix and TiN Nano particulate as reinforcement. The composite was fabricated through powder metallurgy process for three different compositions such as 1.5, 2.5 and 5% by weight of TiN Nano particulates. Machinability behavior of the nanocomposite was studied through milling process with process parameters, feed rate of 5, 10 and 15 mm/min, depth of cut of 0.15, 0.3 and 0.45 mm and spindle speed of end mill remain constant of about 2000 rpm. The performance measures considered in this study are cutting forces, material removal rate, surface roughness and tool tip temperature. The milling process was carried out at room temperature for normal atmospheric conditions. Poly crystalline diamond (PCD) coated solid carbide flat type end mill was used in the study. L27 orthogonal array was used to conduct the experiments. The results from the study revealed the fact that the performance measures like cutting force, tool tip temperature and surface roughness are significantly influenced by TiN Nano particulate in the composite, whereas the material removal rate is greatly influenced by the machining parameter feed rate. High hardness, heat resistance and excellent wear resistance of TiN Nano particulate resulted in the influence of the performance measures. Main effect plots and interaction plots were generated for the performance measures which was further followed by ANOVA and second order polynomial regression equation to test the level of significance with least error.

On the structure-properties relationship of amorphous and crystalline silica nanoparticles reinforced magnesium matrix nanocomposites

In this study, the structure-properties relationship of magnesium matrix nanocomposites was studied. Using an accumulative extrusion (AE) process, the matrix was reinforced by adding 0.25, 0.5 and 1 wt% crystalline and amorphous silica nanoparticles separately. The mechanical behavior of nanocomposite strips was investigated by hardness and uniaxial compression tests. The results indicated that the Mg/0.5%SiO2-Am had the best room temperature compressive properties. An increase of 28.5% in compressive yield strength after extrusion and 235% after annealing was measured. Ultimate compressive strength (UCS) was increased by 20% without reduction in the nanocomposite ductility compared to the pure magnesium strip. FESEM and OM were used for microstructural analysis and revealed no visible cracks or distinct defects between magnesium layers after AE passes. It is found from the EDS analysis that the reinforcement distribution after the AE process was uniform with few agglomerates. Texture analysis using X-ray diffraction and EBSD after the AE process for samples reinforced with 0.5 wt% of amorphous and crystalline silica nanoparticles indicated a negligible difference in the basal plane orientation of the monolithic and nanocomposite magnesium strips after the AE process along extrusion direction. On the other hand, increasing the basal plane peak intensity after annealing for the sample reinforced with amorphous silica compared to the sample reinforced with crystalline silica indicated a weakening of basal texture. Furthermore, the EBSD analysis showed that amorphous silica nanoparticles are more effective than crystalline silica in grain refinement.

Evading strength and ductility trade-off in an inverse nacre structured magnesium matrix nanocomposite

Mimicking nacre structure is an often-used strategy for developing materials which combine high strength and high toughness. Here, a novel strategy, named inverse nacre structure, is proposed where elongated and curled soft constituents are embedded in a matrix of hard constituent to form an ordered brick-and-mortar arrangement. This strategy is demonstrated in a particle reinforced metal matrix composite, using pure Mg as the soft phase and SiC nanoparticle reinforced Mg as the hard phase. The resulting nanocomposite yields high strength, and especially high tensile elongation which is five times that of the homogeneous counterpart. The superior comprehensive strengthening-toughening effect originates from the tailored inverse nacre structure which enables a stable microcrack-multiplication process by sufficiently promoting strain hardening so as to avoid any significant decrease in post-ultimate tensile strength. This strategy, while demonstrated here for the specific case of particle reinforced Mg, is not restricted to any particular material system but constitutes a generic pathway for the development of high-performance materials for engineering applications.

Tribological characterisation of magnesium matrix nanocomposites: A review

Magnesium matrix nanocomposites (Mg-MNCs) are high grade materials widely used in aerospace, electronics, biomedical and automotive sectors for high strength to weight ratio, excellent sustainability and superior mechanical and tribological characteristics. Basic properties of Mg-MNCs rely on type and amount of reinforcement and fabrication process. Current study reviews existing literatures to explore contribution of different parameters on tribological properties of Mg-MNCs. Effects of particle size and amount of different reinforcements like SiC, WC, Al2O3, TiB2, CNT, graphene nano platelets (GNP), graphite on tribological behaviour are discussed. Incorporation of nanoparticles generally enhances properties. Role of different fabrication processes like stir casting (SC), ultrasonic treatment casting (UST), disintegrated melt deposition (DMD), friction stir processing (FSP) on wear and friction behaviour of Mg-MNCs is also reviewed. Contributions of different tribological process parameters (sliding speed, load and sliding distance) on wear, friction and wear mechanism are also examined.

Reinforced AZ91D magnesium alloy with thixomolding process facilitated dispersion of graphene nanoplatelets and enhanced interfacial interactions

Magnesium matrix nanocomposites reinforced with graphene nanoplatelets (GNPs) additives have long been considered as exciting prospects among nanotechnology applications. Here, the thixomolding process, an extremely efficient dispersing technology, was applied to prepare AZ91D magnesium alloy- GNPs nanocomposites with different GNPs contents (0, 0.1, 0.3, 0.6, 0.9 and 1.2 wt%). The effects of screw rotate rate ( R S ) and injection velocity ( V I ) on microstructures, GNPs dispersibility and mechanical properties were investigated. The GNPs, fairly uniform dispersion in the nanocomposites, were incorporated in the α-Mg grains, not only in the grain boundaries. Strong bonding interfaces between GNPs and alloy matrix were established because of the formed MgO nanoparticles leading to the formation of Mg/MgO semi-coherency interface and MgO/GNPs interface. Compared with other previously reported results, a relatively higher overall efficiency was achieved in the prepared magnesium matrix nanocomposites. The developed technology has a potential for large-scale industrial production of not only thin-walled complex parts, but also thick-walled products such as automobile parts with complex structure.

Synergistic effects of hybrid (SiC+TiC) nanoparticles and dynamic precipitates in the design of a high-strength magnesium matrix nanocomposite

Novel nanocomposites based on an AZ91 magnesium alloy matrix reinforced with a hybrid mixture of SiC and TiC nanoparticles with different nanoparticle contents (0.5% and 1%, by mass fraction) were fabricated by semi-solid stirring followed by ultrasonic vibration. Microstructural analysis indicated that the hybrid nanoparticles were uniformly distributed in the nanocomposite. The morphology of the Mg17Al12-based eutectic phase changed from plate-like, in the as-cast AZ91 alloy, to lamellar in the as-cast nanocomposites. The tensile strength and micro-hardness of the nanocomposites were improved by increasing the fraction of nanoparticles in the composite. Following extrusion, the matrix grains in the nanocomposite were significantly refined. The extent of the grain refinement increased at higher mass fractions of the nanoparticle. This refinement was not only due to dynamic recrystallization, but also the synergistic pinning effects arising from both the externally added nanoparticles as well as dynamically precipitated Mg17Al12 particles. The nanoparticle additions led to increases in yield strength (YS), ultimate tensile strength (UTS) and elongation to failure (EL). The increase in YS was mostly attributed to the effects of grain refinement, with additional contributions from the influence of Orowan strengthening and thermal expansion effects. The values of both the work hardening rate (θ) and strain hardening exponent (n) increased with increasing fraction of nanoparticles. The high θ value in stage III was attributed to both grain refinement and weakening of the basal plane texture, while the high n value was mainly related to the increase in resistance to dislocation movement caused by pinning effects of the nanoparticles.

Nano-tribological behavior of graphene nanoplatelet–reinforced magnesium matrix nanocomposites

Abstract The corrosion resistance and wear resistance of metallic biomaterials are critically important for orthopedic hard-tissue replacement applications because the lack of such properties not only adversely affects their mechanical integrity but also allows the release of wear debris into the human body. In this study, the potential of zirconium (Zr) as an alloying element and graphene nanoplatelets (GNPs) as a nano-reinforcement material were investigated in relation to improving the tribological performance of pure magnesium (Mg). The GNPs–reinforced Mg matrix nanocomposites (MNCs) were fabricated using powder metallurgy. Results indicate that additions of 0.5 wt.% Zr and 0.1 wt.% GNPs to Mg matrices significantly improved the wear resistance by 89% and 92% at 200 µN load, 60% and 80% at 100 µN load, and 94% and 93% at 50 µN load, respectively, as compared to the wear resistance of pure Mg. The wear depth and coefficient of friction of the MNC containing 0.5 wt.% Zr and 0.1 wt.% GNPs (Mg0.5Zr0.1GNPs MNC) were considerably reduced as compared to pure Mg and Mg0.5Zr. Our results demonstrate that the Mg0.5Zr0.1GNPs MNC is promising for orthopedic applications in relation to its excellent tribological performance.

Magnesium matrix composite reinforced by nanoparticles – A review

Abstract Significant progress has been made in magnesium-based composites during recent decades, especially for the appearance of magnesium matrix composite reinforced by nanoparticles. The nanoparticles added not only exhibit a good strengthening effect, but also maintain the initial toughness of the matrix, effectively balancing the contradiction between the strength and plasticity in the traditional magnesium matrix composites. The magnesium matrix nanocomposites with excellent mechanical properties have pushed the development of magnesium matrix composites to a new stage. However, it is very difficult to disperse the nanoparticles in metal melt especially in magnesium melt which is different from other metal melts and dangerous during the cast processing. This means that the preparation of magnesium matrix nanocomposite is extremely challenging. Further, the magnesium matrix nanocomposites possess a distinctive characteristic in deformation behavior, strengthening and toughening mechanism due to their special size effect of nanoparticles. Accordingly, this review will focus on the new preparation technologies, deformation behavior, mechanical properties and strengthening and toughening mechanisms. The potential applications, development trends and future research ideas of magnesium matrix nanocomposite are also prospected.

Heterogeneous magnesium matrix nanocomposites with high bending strength and fracture toughness

Heterogeneous Mg matrix nanocomposites (Hetero-Mg-NCs) with different sizes/morphologies of soft phase were fabricated by planetary ball milling and subsequent hot-pressing sintering. The Hetero-Mg-NCs were subjected to non-notched and notched bending tests to investigate their bending behaviors. The results showed that high bending strength was successfully attained in the Hetero-Mg-NCs, especially the one with large soft phase exhibited a simultaneous improvement of bending strength and fracture toughness by 50% and 57.7%, respectively, compared with those of pure Mg. The fractography measurements revealed that the Hetero-Mg-NCs failed by a mixed-mode fracture. The abundant interfacial delamination cracks and micro-dimples were found in the Hetero-Mg-NC with large soft phase, indicating the enhancement of fracture toughness. By examining the crack propagation path, it was revealed that the Hetero-Mg-NC with large soft phase showed a longer zigzagging path, owing to the more profound crack tunneling, deflection and bifurcation phenomena. The results demonstrated that Mg–NCs with heterogeneous structure can simultaneously attain high strength and fracture toughness under bending loading.

Graphene Family Nanomaterial Reinforced Magnesium-Based Matrix Composites for Biomedical Application: A Comprehensive Review

Together with the enhancement of the load-bearing implant process for bone substitution and reproduction, an increasing requirement was observed concerning biodegradable magnesium and its alloys with lighter density and outstanding characteristics. Regardless of the current great potential of Mg utilization currently, the broader use of Mg alloys continues to be constrained by several natural causes, such as low resistance of corrosion, inadequate mechanical integrity during the healing process, and poor antibacterial performance. In this perspective, Mg-based composite encapsulated within graphene family nanomaterials (GFNs) such as graphene (Gr), graphene oxide (GO), graphene nanoplatelets (GNPs), and reduced graphene oxide (rGO) as reinforcement agents present great antibacterial activity, as well as cellular response and depicted numerous benefits for biomedical use. Magnesium matrix nanocomposites reinforced with GFNs possess enhanced mechanical properties and high corrosion resistance (low concentration graphene). It is worth noting that numerous elements including the production technique of the Mg-based composite containing GFNs and the size, distribution, and amounts of GFNs in the Mg-based matrix have a crucial role in their properties and applications. Then, the antibacterial mechanisms of GFN-based composite are briefly described. Subsequently, the antibacterial and strengthening mechanisms of GFN-embedded Mg-based composites are briefly described. This review article is designed to wrap up and explore the most pertinent research performed in the direction of Mg-based composites encapsulated within GFNs. Feasible upcoming investigation directions in the field of GFN-embedded Mg-based composites are discussed in detail.

Low cycle fatigue behavior of magnesium matrix nanocomposite at ambient and elevated temperatures

AZ31B alloy reinforced by 1.5 vol.% nano-sized Al2O3 particles has been subjected to fully-reversed strain-controlled uniaxial tension-compression cyclic loading at room temperature, 100 °C, and 200 °C. A combination of mechanical and magnetic stir casting methods followed by a hot-extrusion process was used to fabricate the composite material. Cyclic and fatigue behaviors of the composite were studied at the strain ranges of 0.8%–2.5%. The experimental results of the fatigue lives were used to assess and compare the life prediction capabilities of different existing strain-based and energy-based fatigue models. The results exhibited that the presence of the nano-sized reinforcing particles leads to a homogenously fine microstructure and slightly changes the texture of the composite extrusion, compared to the typical microstructure and texture of monolithic AZ31B extrusion. The cyclic behavior of the composite is altered from an asymmetric shape at room temperature to a symmetric one at 200 °C, resulting in reduction of mean stress. Unlike the room-temperature behavior, twinning and detwinning are not governing plastic deformation mechanisms at the elevated temperatures, especially at 200 °C. Cyclic softening occurs by increasing the temperature, in a manner similar to the monotonic tensile tests. Due to the strain-controlled loading and increasing the composite ductility at the elevated temperatures, the fatigue lives are comparable at the different temperatures. Finally, considering the results at all the temperatures, Jahed-Varvani (JV) as an energy-based model shows a more promising life prediction.

Damage behavior of heterogeneous magnesium matrix nanocomposites

Heterogeneous magnesium matrix nanocomposites (Hetero-Mg-NCs) exhibited excellent strength-toughness synergy, but their damage behavior and toughness mechanism lacked of investigation. Here, atomic force microscopy was first employed to characterize the microstructure evolution and damage behavior of the Hetero-Mg-NCs after indentation. The heterogeneous structure comprised of pure Mg areas (soft phase) and Mg nanocomposite areas (hard phase) was revealed by the electrostatic force microscopy. Furthermore, the surface morphology and cracks of the deformed area were investigated with high resolution. The results indicated the soft phase undertook most of the deformation and played an important role in capturing and blunting the crack.

Microstructural, mechanical and tribological characterization of vacuum stir cast Mg-4Zn/Si3N4 magnesium matrix nanocomposite

Stir casting route is a relatively easy, cheap and popular method to produce metal matrix composites. Vacuum stir casting method uses pressure values, which comes intermediate to the gravity and squeeze casting variants of the stir casting process. This article presents the mechanical properties, the microstructural and the wear characteristics of the as-cast nanocomposite of Magnesium. The Magnesium nanocomposite was produced by the vacuum stir casting process with Mg-4Zn alloy as the matrix and Si3N4 nanoparticles as the reinforcement. Microstructural characterization was carried out by optical microscopy and scanning electron microscopy. The results showed that the Mg-4Zn/Si3N4 nanocomposite possesses mechanical and wear properties comparable to other Mg-based materials reported in the literature.