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.

Corrosion Behavior, Microstructure and Mechanical Properties of Novel Mg-Zn-Ca-Er Alloy for Bio-Medical Applications

In this study, the effect of calcium (Ca) and erbium (Er) on the microstructure, mechanical properties, and corrosion behavior of magnesium-zinc alloys is reported. The alloys were prepared using disintegrated melt deposition (DMD) technique using the alloying additions as Zn, Ca, and Mg-Er master alloys and followed by hot extrusion. Results show that alloying addition of Er has significantly reduced the grain sizes of Mg-Zn alloys and also when compared to pure magnesium base material. It also has substantially enhanced both the tensile and the compressive properties by favoring the formation of MgZn2 type secondary phases that are uniformly distributed during hot-extrusion. The quaternary Mg-Zn-Ca-Er alloy exhibited the highest strength due to lower grain size and particle strengthening due to the influence of the rare earth addition Er. The observed elongation was a result of extensive twinning observed in the alloys. Also, the degradation rates have been substantially reduced as a result of alloying additions and it is attributed to the barrier effect caused by the secondary phases.

A Novel Method of Light Weighting Aluminium Using Magnesium Syntactic Composite Core

In this study, hybrid composite consisting of aluminium (Al) shell and magnesium/glass microballoon (Mg-20 wt.% GMB) syntactic composite core was fabricated in a shell-core pattern by combining powder metallurgy and disintegrated melt deposition (DMD) techniques. Physical, microstructural and mechanical properties of as-cast Al and Al/Mg-20GMB hybrid composite were examined. Approximately 13% reduction in density (with respect to aluminium) was realized through the use of a syntactic composite core. Microstructural investigations revealed reasonable interfacial integrity between aluminium shell and Mg-GMB core material and the presence of Al, Mg and GMB phases. The interface region showed a hardness of 109 ± 2 Hv in comparison to the hardness of Al shell region (68 ± 4 Hv) and Mg-20GMB core region (174 ± 5 Hv). In comparison to as-cast Al, the yield strength and ultimate compressive strength of the as-cast Al/Mg-20GMB hybrid composite increased by ~65.4% and ~60%, respectively. Further, the energy absorption under compressive loading for the Al/Mg-20GMB hybrid composite was ~26% higher compared to pure Al. This study validated that Al/Mg-20GMB hybrid composite with superior absolute and specific mechanical properties can be fabricated and used for weight critical applications.

Thermomechanical Processing of AZ31-3Ca Alloy Prepared by Disintegrated Melt Deposition (DMD)

Mg-3Zn-1Al (AZ31) alloy is a popular wrought alloy, and its mechanical properties could be further enhanced by the addition of calcium (Ca). The formation of stable secondary phase (Mg,Al)2Ca enhances the creep resistance at the expense of formability and, therefore, necessitates the establishment of safe working window(s) for producing wrought products. In this study, AZ31-3Ca alloy has been prepared by the disintegrated melt deposition (DMD) processing route, and its hot deformation mechanisms have been evaluated, and compared with similarly processed AZ31, AZ31-1Ca and AZ31-2Ca magnesium alloys. DMD processing has refined the grain size to 2–3 μm. A processing map has been developed for the temperature range 300–450 °C and strain rate range 0.0003–10 s−1. Three working domains are established in which dynamic recrystallization (DRX) readily occurs, although the underlying mechanisms of DRX differ from each other. The alloy exhibits flow instability at lower temperatures and higher strain rates, which manifests as adiabatic shear bands. A comparison of the processing maps of these alloys revealed that the hot deformation mechanisms have not changed significantly by the increase of Ca addition.

A New Method to Lightweight Magnesium Using Syntactic Composite Core

Light weighting of magnesium-based materials is crucial for its extensive use in transportation applications. Hybrid processing of these materials in a shell-core pattern can substantially improve the specific properties of magnesium. In the present study, the Mg/Mg-20GMB (glass microballoon) hybrid composite was prepared using a disintegrated melt deposition technique. Microstructural characterization and mechanical properties of the developed as-cast Mg/Mg-20GMB hybrid composite were investigated. Results revealed that a unified metallurgical interface was formed between the Mg-20GMB core material and the pure Mg shell. Energy dispersive X-ray spectroscopy (EDX) results confirmed the existence of Mg2Si as the secondary phase in the Mg-20GMB core material. The hybrid Mg/Mg-20GMB composite exhibited much superior compressive yield strength (↑71.6%), lower ultimate compressive strength (↓23.25%), and enhanced ductility (↑186.48%) when compared to as-cast pure magnesium.

ANALYSIS OF WEAR BEHAVIOR OF A NOVEL MAGNESIUM METAL–METAL COMPOSITE

The need of engineered materials with high strength to weight ratio was instrumental for the development of a novel magnesium metal–metal composite with the addition of titanium (reinforcement) and aluminum (alloying element) through disintegrated melt deposition technique. The X-ray diffraction analysis and scanning electron microscopy analysis used to explore the metallurgical insights of the developed magnesium metal–metal composite. Wear tests were carried out with pin-on-disc equipment by varying the input parameters load and sliding velocity over a sliding distance of 2000[Formula: see text]m. Wear was obtained as the output from the experiments, and the same was analyzed through Pareto analysis of variance, to identify the significant parameters. Also, a fuzzy logic-based model was developed to predict the wear behavior of the metal–metal composite. The wear mechanisms involved in the dry sliding wear behavior were analyzed through worn surface analysis and wear debris analysis.

Enhancing Properties of Aerospace Alloy Elektron 21 Using Boron Carbide Nanoparticles as Reinforcement

In this study, the effect of nano-B4C addition on the property profile of Elektron 21 (E21) alloys is investigated. E21 reinforced with different amounts of nano-size B4C particulates was synthesized using the disintegrated melt deposition technique followed by hot extrusion. Microstructural characterization of the developed E21-B4C composites revealed refined grains with the progressive addition of boron carbide nanoparticles. The evaluation of mechanical properties indicated a significant improvement in the yield strength of the nanocomposites under compressive loading. Further, the E21-2.5B4C nanocomposites exhibited the best damping characteristics, highest young’s modulus, and highest resistance to ignition, thus featuring all the characteristics of a material suitable for several aircraft applications besides the currently allowed seat frames. The superior mechanical properties of the E21-B4C nanocomposites are attributed to the refined grain sizes, uniform distribution of the nanoparticles, and the thermal insulating effects of nano-B4C particles.

Fe3O4 Nanoparticle-Reinforced Magnesium Nanocomposites Processed via Disintegrated Melt Deposition and Turning-Induced Deformation Techniques

Magnesium nanocomposites, with nano-scale ceramic reinforcements, have attracted a great deal of attention for several engineering and biomedical applications in the recent past. In this work, superparamagnetic iron oxide nanoparticles, Fe3O4, with their unique magnetic properties and the ability of being bio-compatible and non-toxic, are reinforced to magnesium to form Mg/(1, 2, and 3 wt %) Fe3O4 nanocomposites. These nanocomposites were fabricated using the conventional disintegrated melt deposition (DMD) technique followed by extrusion. Further, the materials were also processed using the novel turning-induced-deformation technique where the chips from turning process are collected, cold compacted, and hot extruded. The materials processed via the two techniques were compared in terms of microstructure and properties. Overall, the Mg/Fe3O4 nanocomposites, processed via both routes, exhibited a superior property profile. Further, the turning-induced deformation method showed promising results in terms of improved properties of the nanocomposites and serves as a great route for the recycling of metallic materials.

Preparation and Characterization of In Situ Carbide Particle Reinforced Fe-Based Gradient Materials by Laser Melt Deposition

To obtain the wear-resistant camshaft with surface rigidity and core toughness and improve the service life of camshaft, wear-resistant Fe-based alloy gradient material was prepared by laser melt deposition. The traditional camshaft was forged by 12CrNi2V. In this paper, four types of wear-resistant Fe-based powders were designed by introducing various content of Cr3C2 and V-rich Fe-based alloy (FeV50) into stainless steel powder. The results showed that the gradient materials formed a satisfactory metallurgical bond. The composition of the phases was mainly composed of α-Fe, Cr23C6, and V2C phases. The increasing of Cr3C2 and FeV50 led to transform V2C into the V8C7. The microstructures were mainly cellular dendrite and intergranular structure. Due to the addition of Cr3C2 and FeV50, the average microhardness and wear resistance of gradient materials were significantly better than that of 12CrNi2V. The sample with 8% V had the highest microhardness of 853 ± 18 HV, which was 2.6 times higher than that of 12CrNi2V. The sample with 6% V had the best wear resistance, which was 21 times greater than that of 12CrNi2V.