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Magnesium is a lightweight metal that holds great potential in automotive, aerospace and biomedical applications. Magnesium when incorporated with nanoparticles, exhibits simultaneous improvements in mechanical, tribological and biological properties without altering its density. This article presents a short review and analysis of mechanical (tensile and compressive), ignition, damping, tribological and in vitro degradation (corrosion and biocompatibility) behaviour of magnesium- based nanocomposites. Owing to the flexibility in tailoring for multiple applications, powder metallurgy routes are being explored to target unique microstructures, novel compositions and high performance in magnesium-based nanocomposites. The mechanical and in vitro study of magnesium nanocomposite synthesized by powder metallurgy route demonstrates improved strength, controlled degradation and good biocompatibility. The article also proposes a powder metallurgy route incorporating hybrid microwave sintering as a promising environment-friendly technique to develop magnesium nanocomposites for biomedical applications.

Aims: The primary aim of this research is to understand the effects of type of nanoparticles on the microstructure and mechanical properties of Mg-based hybrid nanocomposites. For this reason, new Mg-based hybrid nanocomposites containing 2.2 vol.% Ti and 1.1 vol.% nano-Al2O3 or nano B4C particles were synthesized and their properties were studied in comparison with Mg-Ti and pure Mg. Background: Magnesium with excellent weight-saving potential is ideal for automotive and aerospace applications. But its use in pure Mg is restricted due to inherent limitations such as poor absolute strength, elastic modulus, deformability, and corrosion susceptibility. While most of these limitations can be circumvented by the judicious addition of micron-sized ceramic reinforcements, ductility is often compromised. One of the promising ways for ductility enhancement involves the use of nano-length scale reinforcements. Similar ductility improvements were also reported when hybrid reinforcements were introduced into the Mg matrix. While the role of hybrid reinforcement preparation, the particle size distribution, and volume fraction of hybrid reinforcements were studied extensively in the past, no detailed investigation on the effects of type of nanoparticles has been conducted so far. Objective: The objectives of this research include the successful synthesis and property characterization of Mg-based hybrid nanocomposites containing hybrid (Ti+Al2O3 or Ti+B4C) reinforcements. Result: While both hybrid nanocomposites displayed fine grains when compared to pure Mg and Mg-Ti, there was no noticeable difference between the grain size distribution profiles of Mg- (Ti+Al2O3) and Mg-(Ti+B4C) hybrid composites. The results of property measurements indicated an improvement in dimensional stability, indentation, tension, and compression properties of Mg due to the addition of either individual Ti or hybrid (Ti+Al2O3) or Mg-(Ti+B4C) particles. Among the hybrid composites, Mg-(Ti+B4C) containing hybrid (Ti+B4C) reinforcement exhibited a better combination of strengths and ductility. While the inherent strengthening contribution from B4C and Al2O3 reinforcements resulted in slightly different strength properties, the ductilization benefits of boron compounds enhanced the tensile fracture strain of Mg-(Ti+B4C). Conclusion: Since the particle size distribution and volume fraction of (Ti+Al2O3) and (Ti+B4C) are similar, the difference in strength values between Mg-(Ti+Al2O3) and Mg-(Ti+B4C) can be attributed to the matrix strengthening contribution from reinforcement type.

In this work Al-ZnO-Y2O3 hybrid composites were fabricated utilizing powder metallurgy and hybrid microwave sintering approach from the powder blend of Al, ZnO and Y2O3. Depth sensing nano-indentat...

Magnesium is an ideal candidate for biodegradable implants, but the major concern is its uncontrollable degradation for application as a biomaterial. The in vitro corrosion and cytotoxicity of Mg‐0.4Ce/ZnO2 (magnesium nanocomposites) were studied to determine its suitability as a biodegradable material. The polycrystalline nature of Mg‐0.4Ce/ZnO2 was assessed using an optical microscope. The hydrophobic nature of Mg‐0.4Ce/ZnO2 was determined by contact angle measurements. The corrosion resistance of magnesium nanocomposites was tested in phosphate buffer solution (PBS) and it was improved by the gradual deposition of a protective layer on its surface after 48 h. The cytotoxicity of Mg‐0.4Ce/ZnO2 was evaluated by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay and calcium deposition by Alizarin red staining using sarcoma osteogenic (Saos2) cells. The haemocompatibility test of Mg‐0.4Ce/ZnO2 showed 30% haemolysis, which is higher than the safe value for biomaterials, and cell viability was reduced after 24 h in comparison with control groups. The calcium deposition by sarcoma osteogenic cells showed a brick red colour deposition in both the control group and Mg‐0.4Ce/ZnO2 after 24 h. The preliminary degradation results of Mg‐0.4Ce/ZnO2 showed good corrosion resistance; however further improvement is needed in haemolysis and cytotoxicity studies for its use as a biodegradable material for orthopaedic applications.

As one of the lightest metallic materials, magnesium is considered as a promising replacement for aluminum, titanium, and steel. However, lightweight energy-saving magnesium and magnesium alloys suffer from poor ductility (5% to 8%) due to their hexagonal closed packed crystalline structure and a limited number of easily activated independent slip systems at room temperature. This creates some challenges for magnesium and its alloys for various industrial applications. One technique to improve both strength and ductility, without any tangible weight penalty, of magnesium and its alloys is to add nanosize (less than 100 nm) reinforcements (e.g. nanoparticles) to the matrix as creat so-called magnesium nanocomposites. Various nano-reinforcing materials including oxides (Al2O3, TiO2, Y2O3, ZnO, ZrO2), carbides (SiC, B4C, TiC), nitrides (BN, AlN, TiN), borides (TiB2, SiB6, ZrB2), and carbonaceous materials (carbon nanotube and carbon nanoplatelets). The volume fraction of these nano-size reinforcing structures are normally less than 3 vol.% to avoid the clustering (agglomeration) of the nano-reinforcements which can adversely affect strength and ductility. That is, depending on the matrix (magnesium and magnesium alloys) and the nanosize reinforcement, there is an optimum volume fraction beyond which the properties (strength and ductility) would decrease. Though various aspects of the microstructure/mechanical property/manufacturing process of the magnesium nanocomposites have been studied so far, the failure and, in particular, fracture of these materials have not been yet classified properly. Investigating the fracture of magnesium nanocomposites, including the type of fracture, fracture mechanism, the effect of the nano-reinforcements on the fracture of Mg nanocomposites, enables the researchers to assess the role of nanosized reinforcement on the modes of failure and mechanical properties. This paper aims at providing a review of the fractography of compressive and tensile tests of nanocomposites Mg, classifying fractography by all kinds of reinforcement and working conditions of the Mg nanocomposite. Also, the effect of test temperature, cyclic loading, and heat treatment on the fracture of magnesium -matrix nanocomposite is discussed thoroughly. Among various nanoparticles and according to the review of the available literature, Al, Y2O3, and NiTi can significantly improve the tensile strength of the Mg matrix while ZnO and Sm2O3 reinforced nanocomposites show higher compressive yield stress.

Background: Magnesium alloys and nanocomposites have been of great importance to automotive, aerospace and marine industries owing to their superior specific mechanical properties, impact resistance, superior damping capacities, and biocompatibility. Low-cost manufacturing of magnesium- based materials is the key to realize the high impact. We reviewed patents relating to production of magnesium- based materials using low cost techniques. Objective: Recent trends in the field of magnesium technology has driven researchers to develop magnesium materials applicable in both structural and biomedical applications. Incorporation of biocompatible secondary reinforcements into the magnesium matrix is important to meet the current requirements. Methods: In the current study, low cost naturally available eggshell particles are reinforced into magnesium- zinc alloy using powder metallurgy technique assisted microwave sintering technique and tested for a mechanical, thermal and damping response. Results: Addition of eggshell improved the grain size of the Mg2.5Zn alloy by ~60%. The microhardness values of Mg2.5Zn10ES composite is 73 Hv which is a significant 30% improvement when compared to Mg2.5Zn alloy (56 Hv). Enhanced thermal stability was observed with the presence of eggshell as Mg2.5Zn10ES composite did not self-ignite even at a temperature of 750°C. The compressive yield strength of the composite was ~25% greater than the alloy owing to superior grain refinement of ~60%. Conclusion: The presence of eggshell particles assisted in refining the microstructure, thereby significantly enhancing the compression properties of the Mg-2.5Zn alloy and led to a better thermal and dimensional stability of the synthesized composites. Structure-property correlations are drawn to understand the behavior of the composites.

This work deals with the compression energy absorption aspects of an open-cell nickel foam–natural rubber hybrid material. A comprehensive numerical analysis and elaborate experiments were the main tools used in this investigation. Open-cell nickel foam was analyzed as tetrakaidecahedron geometry. Inputs to the geometric dimensions were obtained by subjecting the nickel foam samples to x-ray micro-computed tomography (µCT) technique. A Mooney–Rivlin 2 parameter-based material model was implemented for the rubber part. Analysis was carried out using finite element-based commercial software ANSYS® with explicit dynamics as the chosen analysis scheme. During analysis, symmetry boundary conditions were applied considering each unit cell to be a mirror image of the adjacent cells. Static compression experiments were conducted on fabricated samples for validation of analysis with regard to energy absorption behavior. Scanning electron microscopy examination was carried out on hybrid samples both pre- and post-compression test for better understanding of compression mechanism. The compression energy absorption value of hybrid sample is significantly better than open-cell nickel foam and natural rubber values. The study clearly demonstrates interfacial bonds failure coupled with progressive deformation of foam cell ligaments as the main reasons for enhanced energy absorption during compression loading and presents the results quantitatively as a novel feature. In the end, the paper thoroughly compares the analysis and results in a critical way.

Hardfacing is done to increase the service life of structural components. Hardfacing is widely done in nuclear and petrochemical industries, mining and sugar refineries. Hardfacing is done on farming equipment to extend their service life as they are prone to impact, abrasion and corrosion. Generally, Ni-base, Co-base and Fe-base alloys are used for hardfacings. Among them, Ni-base alloys are preferred to Co-base and Fe-base alloys as these alloys can retain its hardness even at the elevated temperatures. Colmonoy alloys are predominantly used in nuclear reactor as the dose rate of these alloys is 1/265th that of Co-base alloys. Plasma Transferred Arc (PTA), Gas Tungsten Arc (GTA) and Laser are the major hardfacing processes. The hardfacing process governs the four major aspects of the coating, viz. microstructure, substrate dilution, wear and mechanical properties. This paper provides an in-depth understanding of various research works carried out on Ni alloy hardfacings by different processes on different substrates in those four domains. The outcome of this paper would be beneficial to present and future researchers on Ni alloy hardfacings and also to many hardfacing industries.

In general, the traditional alloys are essentially based on the domination of a single principle element, such as the aluminium (Al)-base alloys, magnesium (Mg)-base alloys, iron (Fe)-base alloys, nickel (Ni)-base super alloys, etc. For the traditional lightweight alloys, such as the alloys of aluminum, the concentration of minor alloying elements added to the major element (Al) is typically less than or equal to [ ≤] five atomic percent. In this research paper, the intricacies specific to the development of aluminium-based multicomponent alloys as a viable option to engineer the development of advanced lightweight alloys is presented and adequately discussed. The alloys, Alx(LiMgCuZn)100-x were designed based on the multi-element alloying approach in which the concentration of each alloying element was either greater than or equal to [≥] five atomic percent, except for the element aluminum [70 atomic percent and 75 atomic percent]. The multicomponent alloys, Al70Li10Mg10Cu5Zn5 and Al75Li10Mg5Cu5Zn5, were synthesized using the technique of disintegrated melt deposition [DMD]. The calculated mixing entropy of the Al70Li10Mg10Cu5Zn5 alloy was > 1R [R is gas constant, 8.314 J/K mol], classifying it to be a medium entropy alloy (MEA). For the Al75Li10Mg5Cu5Zn5 alloy, the mixing entropy was less than 1R, classifying it to be a low entropy alloy (LEA). Characterization studies were carefully done on the as-synthesized multicomponent alloys. The microstructure and mechanical properties of the two alloys is presented and briefly discussed. Particular emphasis will be given to both examining and understanding microstructural evolution and the resultant influence of microstructure on mechanical properties of the engineered alloys. A comparison of the properties of the two alloys [Medium Entropy Alloy and Low Entropy Alloy] is highlighted.

The present study investigates Mg-SiO2 nanocomposites as biodegradable implants for orthopedic and maxillofacial applications. The effect of presence and progressive addition of hollow silica nanoparticles (0.5, 1, and 1.5) vol.% on the microstructural, mechanical, degradation, and biocompatibility response of pure Mg were investigated. Results suggest that the increased addition of hollow silica nanoparticles resulted in a progressive increase in yield strength and ultimate compressive strength with Mg-1.5 vol.% SiO2 exhibiting superior enhancement. The response of Mg-SiO2 nanocomposites under the influence of Hanks’ balanced salt solution revealed that the synthesized composites revealed lower corrosion rates, indicating rapid dynamic passivation when compared with pure Mg. Furthermore, cell adhesion and proliferation of osteoblast cells were noticeably higher than pure Mg with the addition of 1 vol.% SiO2 nanoparticle. The biocompatibility and the in vitro biodegradation of the Mg-SiO2 nanocomposites were influenced by the SiO2 content in pure Mg with Mg-0.5 vol.% SiO2 nanocomposite exhibiting the best corrosion resistance and biocompatibility when compared with other nanocomposites. Enhancement in mechanical, corrosion, and biocompatibility characteristics of Mg-SiO2 nanocomposites developed in this study are also compared with properties of other metallic biomaterials used in alloplastic mandibular reconstruction in a computational model.

Lightweight energy-saving magnesium (Mg) nanocomposites could be titled materials of future. Remarkable specific strength along with acceptable ductility is two key features of these materials which have made them a unique class of emerging materials. However, magnesium nanocomposites are at the initial stages of development and therefore systematic research is required to establish microstructure/property relationships at different potential conditions (i.e. temperatures and strain rates). In this paper, a recently introduced magnesium-samarium oxide (Mg–Sm2O3) nanocomposite, with different volume fractions of nanosize Sm2O3 particles as reinforcement, is employed to study ambient temperature rate-dependent plastic response of the material. To study the rate-dependent response of the materials, a depth-sensing nanoindentation measurement technique was used which is considered a non-destructive, robust, and convenient method to assess the controlling mechanisms of creep phenomenon in small scales. Tests were performed on both nanocomposites and pure Mg for the purpose of comparison. Microstructural observations and nanoindentation data indicate that the creep resistance of the materials is directly associated with the volume fraction of the nanoparticles. The results of this study would provide the required reference lines for the forthcoming elevated temperature creep assessment of the materials.

Ni-Cr-B-Si alloy is used for hardfacing of 316 L N Stainless Steel components in Sodium-cooled Fast Reactors (SFRs) to enhance wear resistance and also to prevent self-welding. Since the shear force is acting between the substrate and the deposit due to dissimilar thermal expansion during high temperature operating conditions, it is necessary to focus on the hardfacing process which provides good bonding shear strength between them. Though low substrate dilution is advisable to attain high microhardness of the deposit, the deposit should not get de-bonded due to shear. To seek solution to this problem, three major hardfacing processes, viz., Plasma Transferred Arc, Gas Tungsten Arc and Laser processes were considered. Hardfaed shear specimens were prepared using each process and tested as per the ASTM A264. Faster cooling rate leads to finer grains and higher microhardness. The influence of dilution on the microhardness was studied. Scanning Electron Mircographs and Energy Dispersive Spectroscopic studies at the fractured surfaces were done to ascertain the reason for strength. Finally, the laser hardfacing process which provides a combination of good shear strength, high microhardness as well as low dilution is recommended for hardfacing of the components of the SFRs for their reliable operations.

Graphene and its derivatives, due to their extraordinary mechanical, thermal, and tribological properties, are extensively used to fabricate bulk graphene-based nanocomposites. On the other hand, m...

Magnesium-based materials are the most sought-after metallic materials for weight saving applications. Its low density (∼33% lighter than aluminum) makes it an ideal choice for aerospace, space, sports, automobile and electronic industries. Magnesium based components can be even lighter if these components are manufactured hollow. However, studies on the structural integrity of hollow magnesium-based components are limited and hence, this study documents the structural stability of hollow magnesium-based components. Centralized cylindrical holes (1, 1.5, 2 and 3 mm in diameter) were drilled in 8 mm diameter magnesium samples synthesized by disintegrated melt deposition followed by hot extrusion. The effects of these centralized hole on the physical and compression properties were then investigated. Compression test results demonstrated a significant increase in the compressive yield strength (∼62%) and ultimate compressive strength (∼11%) for the 1.5 mm drilled magnesium sample when compared to undrilled monolithic magnesium. Further, the strength (yield and ultimate) to weight ratio was higher for all the drilled samples compared to pure magnesium. These results present an opportunity to light weight magnesium-based components using a controlled defect while improving or maintaining the overall compressive response of the material. Using Finite Element Analysis, an optimum drill diameter was also calculated which can be used as a foundation for future studies.

This study deals with magnesium-based materials, considered as potential biodegradable implants that degrade within the body after curing the wound and restoring the bone tissue. Magnesium based materials need favorable mechanical and corrosion properties to be implanted inside the human body. Magnesium despite having good mechanical properties if immersed in a corrosive environment would tend to lose its mechanical integrity. The role of cerium oxide (CeO2) nanoparticles and zinc (Zn) an alloying element in improving the mechanical and corrosive properties of the base material will be studied to find its scope in orthopedic applications. The aim of the current work is to synthesize Mg/CeO2 and Mg-Zn/CeO2 nanocomposites by powder metallurgy method. Significant grain refinement and increase in hardness is noticed for both the nanocomposites due to the fair distribution of cerium nanoparticles. The room temperature compressive yield strength and ultimate compressive strength for Mg/CeO2 and Mg-Zn/CeO2 nanocomposites were higher than pure Mg. The addition of 1.0 vol% of CeO2 to pure Mg and Mg-0.5 vol% of Zn system showed controlled degradation rate in Hank’s balanced salt solution (HBSS) for 1, 2, 3, 4 and 7 days respectively.

In the present study, a new magnesium based multicomponent alloy consisting of five alloying elements was synthesized using the technique of Disintegrated Melt Deposition (DMD). Most of the conventional Mg based alloys have one dominant principle element with a small amount of other alloying elements. In this work, the alloy having a chemical composition of Mg70Al18Zn6Ca4Y2 (atomic pct.) was designed by incorporating multiple alloying elements (Al, Zn, Ca and Y) with high amount of alloying element concentration (2 to 18 atomic pct.) into principle element, Mg. Investigations were done on the microstructure and mechanical properties of the developed alloy. The formation and presence of phases and microstructural evolution of the alloy were examined using scanning electron microscopy, energy dispersive x-ray (EDX) analysis and x-ray diffraction (XRD) analysis. The mechanical properties of the developed alloy was determined by way of hardness tests and compression testing. Significantly high macrohardness (59 HRB) and microhardness (150 HV) was realized in Mg70Al18Zn6Ca4Y2 multicomponent alloy. The measured hardness values in this alloy was much higher when compared to those of commercial Mg alloys.

Magnesium based metal-metal composite was synthesized through the disintegrated melt deposition technique with the inclusion of aluminium and titanium powders. To examine the metallurgical features of the metal-metal composite the samples of the produced composite was subjected to x-ray diffraction analysis and scanning electron microscopy analysis. To study the tribology of the metal-metal composite, pins of composites were subjected to dry sliding wear test as per standards and the specific wear and the coefficient of friction was taken as response variables. Two different computational techniques such as pattern search and simulated annealing was used to identify the optimal values of specific wear and coefficient of friction along with the identification of optimal parameter combinations. The optimum values of specific wear and coefficient of friction obtained from the pattern search technique is found to be closer to the calculated values compared to the simulated annealing technique.

Sand casting is a widely used process for making various products used in numerous industries such as medical, electrical, automotive etc. However, the poor mechanical properties and microstructural defects are the challenging concern to the foundry engineers for a last decade. In the present work, the microstructural and mechanical assets of Al 1230 alloy are investigated by slow and rapid cooling in a sand casting process. The effect of cooling strategy is analyzed using a scanning electron microscope (SEM) and ultimate tensile strength. Eventually, it is observed that the rapid cooling is a more suitable technique, which enhances the microstructural and mechanical properties of the cast component by inducing of silicon particles during the process. Hence, the proposed work is very useful to smart industries for achieving desired mechanical property while fabricating sand cast components.

Magnesium (Mg), as the lightest metallic material, is 33% lighter than aluminum which makes it, potentially, a great replacement for aluminum and its alloys. However, Mg in pure and alloyed conditions is brittle at ambient temperature which largely limits their applications. One key solution to enhance the strength and ductility of Mg and its alloys is to embed thermally-stable nano-size reinforcements within the Mg matrix to produce so-called “Mg nanocomposites”. The Mg nanocomposites are considering revolutionizing energy-saving lightweight materials of the future with enhanced strength and ductility properties. Mg nanocomposites are, however, at the initial degrees of improvement and consequently, systematic research is required to set up microstructure/property relationships at distinct potential conditions (i.e. temperatures and strain rates). In the present study, a nanoindentation testing approach is adopted to assess ambient-temperature small scale mechanical properties of a group of Mg nanocomposites reinforced with rare-earth element nanoparticles (NPs), i.e. Sm2O3. This paper tried to assess various nanoindentation-driven properties of the Mg-Sm2O3 nanocomposites and compare them with the pure Mg as the baseline.

The life span of many engineering components depends upon their surface properties. The improved surface properties of the materials are essential for enhancing the mechanical and tribological performance of the material. In many applications, the components required only improved surface properties without changing the entire volume properties of the material. The friction stir process (FSP) is a novel processing technique for the fabrication of such surface composites. In the present investigation, the surface composites were fabricated by incorporating molybdenum disulfide (MoS2) and graphite (Gr) as reinforcement on the surface of aluminum alloy (Al 1120) through the friction stir process (FSP) at tool rotational speed of 1400 rpm and tool feed rate of 40 mm/min process parameters using square profile FSP tool. The tribological behaviors of fabricated surface composites were calculated by using a pin on disk tribometer. It was observed that the wear resistance of surface composites improved as compared to the matrix material.

In tribo-corrosion systems, the failure occurs due to the combined effect of micro-abrasion and corrosion mechanisms. Magnesium and its alloys as biodegradable materials are being used as temporary implants for bio medical application. Objective of this study is to examine the tribo-corrosion behavior of Mg-2 vol% SiO2 hollow nanospheres in artificial saliva solution (ASS) for different applied voltage ranging from − 500 to 500 mV and applied loads ranging from 10 to 50 N. Wear rate and corrosion rate are recorded from the experiments separately using the tribo-corrosion setup. The tribo-corrosion maps were plotted in voltage-load space to study the wastage maps, mechanisms involved and the synergic effect of abrasion and corrosion in ASS under simulated body conditions. The mechanisms of failure during simulated tests are studied using scanning electron microscopy. The study will be useful in understanding the degradation rate of the pure Mg-2 vol% SiO2 nano syntactic biodegradable foam.

To realize light-weight materials with high strength and ductility, an effective route is to incorporate strong and stiff metallic elements in light-weight matrices. Based on this approach, in this work, magnesium–iron (Mg-Fe) composites were designed and characterized for their microstructure and mechanical properties. The Mg-Fe binary system has extremely low solubility of Fe in the Mg-rich region. Pure magnesium was incorporated with 5, 10, and 15 wt.% Fe particles to form Mg-Fe metal–metal composites by the disintegrated melt deposition technique, followed by hot extrusion. Results showed that the iron content influences (i) the distribution of Fe particles in the Mg matrix, (ii) grain refinement, and (iii) change in crystallographic orientation. Mechanical testing showed that amongst the composites, Mg-5Fe had the highest hardness, strength, and ductility due to (a) the uniform distribution of Fe particles in the Mg matrix, (b) grain refinement, (c) texture randomization, (d) Fe particles acting as effective reinforcement, and (e) absence of deleterious interfacial reactions. Under impression creep, the Mg-5Fe composite had a creep rate similar to those of commercial creep-resistant AE42 alloys and Mg ceramic composites at 473 K. Factors influencing the performance of Mg-5Fe and other Mg metal–metal composites having molybdenum, niobium, and titanium (elements with low solubility in Mg) are presented and discussed.

In this study, a pure magnesium material reinforced with 0.5, 1, 1.5, and 2 w% of CaO was prepared through disintegrated melt deposition technique (DMD process). Nanocomposites were investigated for their sliding wear behavior in dry condition at room temperature. The amount of CaO, load, sliding distance, and sliding velocity were selected as input design parameters at their five level in central composite design using minitab 18.1 statistical software. The influence of design parameters on wear loss is reported through the response surface methodology (RSM). Analysis of variance (ANOVA) was used to confirm the soundness of the developed regression equation. The results indicate the contribution of linear, quadratic, and interaction terms of design parameters on response. Three-dimensional response surface and two-dimensional contour plots indicate the interaction effect. The result shows that an increase in the sliding velocity contributes to a decrease in the wear loss of the composites because of the emergence of protective oxidative layer at the surfaces of the pins, which is confirmed through field emission scanning electron microscope and energy dispersive X-ray analysis analyses of the pin surfaces. Wear loss of the material decreased as the amount of CaO increased. The ANOVA analysis concluded that the sliding distance and load contribute significantly to wear loss of the composites, and their percentage of contribution is 64.02% and 3.69%.

Metal matrix composites (MMCs) have been developed in response to the enormous demand for special industrial materials and structures for automotive and aerospace applications, wherein both high-strength and light weight are simultaneously required. The most common, inexpensive route to fabricate MMCs or metal matrix nanocomposites (MMNCs) is based on casting, wherein reinforcements like nanoceramics, -carbides, -nitrides, elements or carbon allotropes are added to molten metal matrices; however, most of the mentioned reinforcements, especially those with nanosized reinforcing particles, have usually poor wettability with serious drawbacks like particle agglomerations and therefore diminished mechanical strength is almost always expected. Many research efforts have been made to enhance the affinity between the mating surfaces. The aim in this paper is to critically review and comprehensively discuss those approaches/routes commonly employed to boost wetting conditions at reinforcement-matrix interfaces. Particular attention is paid to aluminum matrix composites owing to the interest in lightweight materials and the need to enhance the mechanical properties like strength, wear, or creep resistance. It is believed that effective treatment(s) may enormously affect the wetting and interfacial strength.

Magnesium matrix syntactic foams (MgMSFs) are emerging lightweight materials with unique capabilities to exhibit remarkable thermal, acoustic, and mechanical properties. In the current study, lightweight glass micro balloon (GMB)-reinforced Mg syntactic foams were synthesized via the powder metallurgy technique using hybrid microwave sintering. The processing employed in the study yielded MgMSFs with refined grain sizes, no secondary phases, and reasonably uniform distributions of hollow reinforcement particles. The developed MgMSFs exhibited densities 8%, 16%, and 26% lower than that of the pure Mg. The coefficient of thermal expansion reduced (up to 20%) while the ignition resistance improved (up to 20 °C) with the amount of GMB in the magnesium matrix. The MgMSFs also exhibited a progressive increase in hardness with the amount of GMB. Although the MgMSFs showed a decrease in the yield strength with the addition of GMB hollow particles, the ultimate compression strength, fracture strain, and energy absorption capabilities increased noticeably. The best ultimate compression strength at 321 MPa, which was ~26% higher than that of the pure Mg, was displayed by the Mg-5GMB composite, while the Mg-20GMB composite showed the best fracture strain and energy absorption capability, which were higher by ~39 and 65%, respectively, when compared to pure Mg. The specific strength of all composites remained superior to that of monolithic magnesium. Particular efforts were made in the present study to interrelate the processing, microstructural features, and properties of MgMSFs.

This article investigates the effect of preprocessing of powders on improving the properties of pure bulk magnesium synthesized via microwave assisted powder metallurgy method. Preprocessing was done by compacting the powder prior to primary processing (cold compaction & microwave sintering) and secondary processing (hot extrusion). Various characterization studies were conducted to determine the microstructural features, temperature governed properties and mechanical properties. Results revealed that preprocessing (compaction) led to improved properties i.e. higher yield strength, better grain refinement and higher resistance to ignition.

Friction and wear behaviour of magnesium/glass microballoon (GMB) foams synthesized by Disintegrated Melt Deposition (DMD) were investigated under dry sliding conditions. The coefficient of friction (μ) decreases with increasing GMB content. Mg-25wt.% GMB exhibits ∼13% lower μ pure compared to magnesium. Wear resistance of magnesium showed a significant enhancement (∼2.5 times) post GMB addition. Abrasion and oxidation were identified as dominant wear mechanisms post worn-surface analysis. Delamination wear, which has traditionally limited the advantages of composites with discontinuous reinforcements in sliding wear conditions for structural and biomedical applications can be effectively addressed by the development of these proposed syntactic foams.

All types of electronic equipment, especially microwave frequency ranged gears, experience the ill effects of electric and electromagnetic impedance. To electronic frameworks, such signals constitute a serious form of pollution. The impacts may go from simply irritating to catastrophic. To prevent such problem, this article aims at developing magnesium iron micro-composites; Mg/xFe (where x = 0, 5 and 15; denoting percentage of iron by weight) using disintegrated melt deposition (DMD) technique. This work studies the electrical conductivity, magnetic features, mechanical suitability, and electromagnetic interference shielding (EMI) capabilities of the composite. Observations were also made in reference to the impact of porosity on the shielding capability of the composite. The samples were tested in the X-band (8.2–12.4 GHz) to evaluate the properties. The results displayed an increased shielding capability with an increment in the amount of Fe microparticles. The study strives to accomplish that, with the addition of iron particulates of micron size, the electrical conductivity of the composites decreases and its magnetic strength increases. The ferromagnetic nature of the iron inclusions contributes critically towards the shielding mechanism of the composite.

Magnesium (Mg) nanocomposites are created when nano-size particles are embedded into the Mg (or Mg alloy) matrix. The Mg nanocomposites, cited as high-strength energy-saving materials of future, are a group of emerging materials with excellent combination of strength and ductility and superior specific strength property (strength-to-weight ratio). Having said this, Mg nanocomposites are considered as promising replacement for other structural alloys (i.e. aluminum and titanium) wherever low density and high strength are required, i.e. transportation, aerospace, defense, etc. To be able to apply this group of materials for real components, different failure mechanisms at ambient and elevated temperatures under static and dynamic loading condition must be well documented. Compared with other metals and alloys, rate-dependent plastic deformation (creep), at ambient and elevated temperatures, of these novel materials is not yet well studied which seems a tangible lack of knowledge. This is required since the materials in service are often exposed to medium and elevated temperatures and/or static loads for long duration of time and this encourages creep failure on them. To this end, the information and the controlling mechanisms on time/temperature-dependent response of the material need to be developed to be able to predict the response of the Mg nanocomposites where the materials are under creep conditions. This paper aims at providing an overview on (i) creep-resistant Mg alloys (as matrix) and their chemical compositions, and (ii) responses of the Mg nanocomposites at different creep conditions (time and temperature). The controlling mechanisms contributing to the strength and ductility of the Mg nanocomposites due to the presence of the nanoparticles have been reviewed briefly in the present article. In this paper both traditional (uniaxial) and depth-sensing indentation creep of Mg nanocomposites are reviewed. Also, some fundamental questions and possible explanations have been raised on the creep characteristics of Mg nanocomposites and the contribution of microstructural features (i.e. grain boundaries, twins, precipitates, nanoparticles). This overview article provides a comprehensive summary to understand one of the failure modes (creep) at ambient and elevated temperature in the energy saving Mg nanocomposites that would be of interest for those in academia who explore novel nanocomposites. Keywords: Mg nanocomposite, Creep, Strength, Reinforcement, Nanoparticles

Several metallurgical issues arise during melting and solidification-based additive manufacturing (AM) methods which limit their use to only a few alloys. This study shows how capillarity-driven bridging can serve as a new and rapid tool of assembling powder particles into 3D structures providing the least metallurgical complexity. According to the established conceptual framework, in-situ binding agent can be derived autogenously from selective interactions of a liquid solvent with superficial layer of powder particles to form in-situ solid interparticle bridges which enables AM at ambient conditions. Magnesium (Mg) is the most difficult engineering metal to handle in all 3D AM processes in view of its intrinsic properties. Supported by transmission and scanning electron microscopies together with Fourier transform infrared and Raman spectroscopy, the introduced 3D printing concept is readily accomplished for Mg alloys by conversion of MgO film, inevitably existing on the outermost layer of Mg powder, into interparticle bridges. In the absence of pyrolysis-adapted sintering profile, these bridges fully decompose during the following sintering step which result in functional Mg parts with chemical composition same as the starting Mg powder with zero contamination, according to chemical and thermal analysis results. The introduced capillary-mediated binding of particles is simple and generic that could be extended to additively manufacture other metals, ceramics and found applications in other traditional ex-situ binder-based processes.

Magnesium based micro-composites are known to have good mechanical integrity and are broadly investigated for different structural applications, however, their electromagnetic interference (EMI) protecting viability has rarely been studied. Thus, with an increasing interest in developing components made of magnesium alloys/composites for EMI SE (shielding effectiveness) applications, this study focusses on the electromagnetic shielding, electrical and magnetic properties of Mg/xTi (x = 5, 10, 15 wt %) micro-composites in correlation to the microstructure. The results indicated that there was grain refinement with progressive addition of Ti particulates in the Mg matrix. It was also found that the electrical conductivity of the composites decreased with increasing Ti amount. The magnetic characterisation performed on the samples verified that the composites are non-magnetic in nature. An interesting observation was made in this study pertaining to the SE values of the micro-composites. The SE values in the X-band microwave range (8.2–12.4 GHz) showed that with an increase in Ti wt%, the SE value remained equal among all the magnesium titanium composites, but improved in comparison to pure magnesium. This was attributed to decreased reflection (SER) (due to decrease in volume of Mg matrix with increase in amount of Ti reinforcements) and simultaneously increased absorption (SEA) (due to increase in amount of Ti which led to multiple internal reflection) coefficients of the shielding effectiveness.

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.

This study examined the effect of AISI H13 steel-tapered tool on the dissimilar friction stir welding of 7075-T651 and 1200-H19 aluminium alloys. Three mechanical tests which include hardness, tensile strength and impact energy were conducted to study the effect of tilt angle, rotational and welding speeds on the weld integrities, 50 and 175 HV were respectively obtained as hardness values for AA1200- H19 and AA 7075- T651, the hardness values were measured for three selected welding speeds of 30, 60 and 90 mm/min representing low, medium and high at a constant rotational speed of 1500 rpm, a tool tilt angle of 2°.The hardness increases with the welding speed from 81.99 to 98.5 HV as the speed increased from 30 to 60 mm/min and dropped to 77 HV at 90 mm/min.The impact energy increased from 12.9 to 21.4 J with an increase in the welding speed from 30 to 60 mm/min and dropped to 5.4 J at 90 mm/min.The ultimate tensile strength (UTS) increased from 126.04 to 151.54 MPa with an increase in the welding speed from 30–60 mm/min and decreased from 151.54 to 128.37 MPa, the hardness at 1500 rpm and 60 mm/min increased from 70.22 to 98.58 HV with an increase in the tilt angle from 1- $${2^^\circ }$$, a further increase from 2–3 o reduced the hardness from 98.58 to 66 HV, UTS increased from 123.32 to 151.54 MPa as tilt angle increased from 1–2 ° and decreased to 122.2 MPa, the medium tilt angle of $${2^^\circ }$$,rotational and traverse speeds of 1500 rpm and 60 mm/min respectively gave the highest impact energy of 21.4 J.

This article reports the mechanical and biocorrosion behaviour of hollow silica nanosphere (SiO2) reinforced (0.5&ndash, 2 vol.%) magnesium (Mg) syntactic foams. Room temperature tensile properties&rsquo, characterization suggests that the increased addition of hollow silica nanospheres resulted in a progressive increase in tensile yield strength (TYS) and ultimate tensile strength (UTS) with Mg-2 vol.% SiO2 exhibiting a maximum TYS of 167 MPa and a UTS of 217 MPa. The degradation behaviour of the developed Mg-SiO2 syntactic foams in four different simulated body fluids (SBFs): artificial blood plasma solution (ABPS), phosphate-buffered saline solution (PBS), artificial saliva solution (ASS) and Hanks&rsquo, balanced saline solution (HBSS) was investigated by using potentiodynamic polarization studies. Results indicate that corrosion resistance of the Mg-SiO2 syntactic foam decreases with increasing chloride ion concentration of the SBF. Mg-1.0 vol.% SiO2 displayed the best corrosion response and its corrosion susceptibility pertaining to corrosion rate and polarisation curves in different SBF solutions can be ranked in the following order: ABPS &gt, PBS &gt, HBSS &gt, ASS. The surface microstructure demonstrated the presence of a better passivated layer on the syntactic foams compared to pure Mg. The observed increase in corrosion resistance is correlated with intrinsic changes in microstructure due to the presence of hollow silica nanospheres. Further, the effect of corrosive environment on the degradation behaviour of Mg has been elucidated.

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 &plusmn, 2 Hv in comparison to the hardness of Al shell region (68 &plusmn, 4 Hv) and Mg-20GMB core region (174 &plusmn, 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.

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 (&uarr, 71.6%), lower ultimate compressive strength (&darr, 23.25%), and enhanced ductility (&uarr, 186.48%) when compared to as-cast pure magnesium.

The utilization of electronic equipment in a wide range of operating frequency and bandwidth has led to the deterioration of corresponding spectrum’s atmosphere. This phenomenon, termed as electromagnetic interference (EMI), drives a need for the development of EM-compatible (EMC) materials. With polymers having the drawback of poor mechanical strength, processing complexity, material wear, nonrecyclability, and high cost, metal-based materials, including composites, with a wide range of electrical and magnetic properties have been suggested as alternatives for EMI shielding. With an increasing demand for innovative EMI shielding, multifunctional electrically conductive alloys and composites have been developed especially in high-power electronics. Conducting alloys and composites of materials such as aluminum, iron, magnesium, copper, etc., have shown potential for commercial application because of their high conductivity, good environmental stability, and facile synthesis. Thus, EM reflection, absorption, and multiple reflection of these materials, incorporated with dielectric and magnetic materials, have been widely investigated. This chapter sheds light on the EMI shielding behavior of various metal-based alloys and composites along with their applications. Further, the effects of microstructure, magnetic properties, electrical capabilities, geometry, etc., on EMI shielding performance of metallic materials are presented.