In this work, Fe-2Cu-0.8C-CaF 2 self-lubricating composites with calcium fluoride solid lubricant (3 □ 12 wt.%) were examined for their friction and wear at 5 and 10 m/s, at 500 °C. Addition of CaF 2 decreased density and hardness of composites. During sliding, materials gained weight due to oxidation. Compared to the base matrix (Fe-2Cu-0.8C), composites showed lower weight gain and lower coefficient of friction. Increase in porosity with CaF 2 content increased oxidation resulting in higher weight gain and increased friction due to wear debris abrasion. Increase in speed reduced weight gain due to higher material loss. Adhesion was the dominant wear mechanism in base matrix; delamination and wear debris abrasion in composites. Temperature rise at sliding surfaces was theoretically estimated. Increase in speed increased temperature, which reduced friction due to softening and shearing of solid lubricant. Composite with 3 wt.% CaF 2 showed least surface damage and 6 wt.% showed lowest coefficient of friction, i.e., lower by 16% and 10% at 5, 10 m/s than base matrix. Tribological response of the composites to a broad range of applied parameters, viz. speed, load and temperature taken from earlier works and present work is briefly summarized. The study suggests the dominant role of CaF 2 content and the wear debris in altering the tribological response. Further, the stability of the developed composites at high temperature and high load conditions was also established. The study suggests that the developed composites could serve high-load and high-temperature applications for heavy machinery such as bearings, shafts and gears.

Integrating Ga2O3 power electronics on a silicon substrate can reduce the system cost and improve heat dissipation, but high on-resistance in vertical power devices is its major drawback. We solve this challenge with an electrically conductive epitaxial TiN (100) buffer layer that can be deposited on Si (100) without SiOx formation. While our thin MgO interlayer strategy prevents GaTiOx at the TiN-Ga2O3, it also results in a large vertical resistance. By tailoring the Ga2O3:Si "seed layer" deposition process, we achieve a state-of-the-art on-resistance of 3.3 m Omega cm(2) in epitaxial Ga2O3 (100) diodes on Si (100), setting an upper bound for Ga2O3/TiN interface resistance. Temperature-dependent leakage analysis suggests its primary source is Poole-Frenkel emission of electrons from defect levels 0.57 eV below the conduction band.

The strain hardening behavior of friction stir welded AA7039 (Al-4.2Zn-3.1 Mg) alloy was explored in terms of dislocation density, crystallite size, hardening capacity, hardening exponent, and strain hardening rate. Strain hardening behavior was analyzed for base metal and friction stir welded specimens. Four different models were used to calculate the dislocation density viz., Scherrer model, uniform strain model (USM), uniform stress distribution model (USDM), and uniform strain energy distribution model (USDEM). Maximum dislocation density was obtained in base metal for all models (maximum for USM, 3.9 x1015m-2) with a minimum crystallite size of 15.81 nm. The low dislocation density in FSW samples is due to the higher heat input in the FSW process. Strain hardening stages were shown by Kocks-Mecking type plots. Lower strain hardening capacity was obtained for BM, i.e. 0.427 as compared to FSW samples, due to the higher dislocation density of BM. It was determined that there is an inverse relationship between the strain hardening capacity and the strain hardening exponent. Strain hardening rate was higher for BM than FSW specimens, and similar results were obtained from mathematical relations that indicate the adequacy of the results. The ultimate tensile strength was 2.5% higher than the BM at a rotational speed of 1325 rpm, 35 mm/min of welding speed and 1.65 degrees tilt angle. The maximum strength friction stir-welded specimen showed a more ductile fracture surface than the BM because the grain boundary phase disappeared or broke up in the thermomechanical affected zone.

Vanadium oxide (VO2), which exhibits a metal-to-insulator (MIT) transition at 68∘C, has been of immense technological interest for many applications such as sensor, electro-optic, and memory devices. In this work, we demonstrate the epitaxial integration of VO2 onto Si(100) via a TiN buffer layer, which is compatible with complementary metal–oxide–semiconductor (CMOS) technology. Our study revealed that the growth of epitaxial VO2 on TiN was mediated by a thin layer of epitaxial TiO2. The orientation relationship between various layers was established to be (011)V O2M ∥ (110)TiO2 ∥ (100)TiN ∥ (100)Si and [100]V O2M ∥ [001]TiO2 ∥ [011]TiN ∥ [011]Si. Through pole figures, reciprocal space maps (RSM), and transmission electron microscopy (TEM), we confirmed the presence of tilted rotational domains. We quantified the degree of misorientation in various VO2 films by introducing a relevant parameter, η, determined by analyzing the (011) pole figures. We found a correlation indicating that the thermal hysteresis of the phase transition, determined from in-situ temperature-dependent XRD, decreases with the degree of misorientation. This decrease in misorientation suggests the presence of more geometrically compatible grain boundaries, leading to a decrease in thermal hysteresis.

FCC phase High-entropy alloys (HEAs) has excellent plasticity and toughness but low tensile property. To strengthen the HEA without plasticity reducing, Cu28.36 Ni22.32 Fe19.12Co15.17Cr12.26Mo2.77 HEA with dual FCC phase were successfully prepared by plasma arc additive manufacturing using a combined cable wire with multi-element composition. The results show that the prepared alloys were composed of Cu-poor FCC1 and Cu-rich FCC2, along with a small amount of Mo-rich precipitation phases. The ultimate tensile strength, yield strength is 531 MPa, 332 MPa, it is increased by 14.48 % and 32.75 % compared with arc melting technology with excellent elongation of 32.26 %. Compared with the vacuum induction melting technology, the strength is increased by 276.5 %. Dual phase obviously increased the mechanical properties. The Co and Cr element in the alloy is relatively low, which can reduce the production cost.

In laser shock processing (LSP) of aero-engine blades, overlap marks due to spot overlapping cause irregular surface morphology that becomes a source of cracks under fatigue behaviors. This reduces the beneficial effect of compressive residual stress induced by LSP and undermines fatigue performance of blades. In this paper, laser shock imprinting (LSI) is proposed to improve fatigue performance of aero-engine blades. In this process, a layer of contact film with micro-grooves is placed between the absorption layer and the workpiece (blade) of the LSP. By using the double action of laser shock wave and micro-grooves in contact film, blade surface morphology is transformed towards the direction conducive to improve its fatigue performance. Using ABAQUS software, Johnson-Cook model and Fabbro model were considered to study the plastic rheological behavior of blade surface material induced by LSI. Effect of process parameters namely, peak pressure, impact number and spot overlapping ratio on residual stress and micro-plastic deformation of blade surface were studied. Simulation results showed that under the action of laser shock wave, blade surface material flowed into micro-grooves in contact film via extrusion plastic deformation. This resulted in micro-bulge morphology having geometrically specific arrangement on blade surface, which achieved accurate control of micro-plastic deformation on blade surface. Increase in peak pressure and impact number increase the surface micro-bulges height. However, increase in peak pressure lowers the stress difference between bulging edge and non-bulge zones. It was found that 33% spot overlapping impact resulted in more uniform surface micro-bulge morphology on blade surface.

In conventional Mg-metal matrix composites (Mg-MMCs), the incorporation of micron-sized ceramic reinforcements results in significant improvements in strength properties, but with drastic reduction in ductility that limits its use in real-time applications. To overcome this major limitation, Mg-composites with nano-scale reinforcements have been developed (magnesium metal matrix nano-composites, Mg-MMNCs). Based on numerous research works, it has been established that Mg-MMNCs possess superior properties, wherein both strength and ductility improvements can be achieved, along with excellent wear resistance. In this article, the mechanical and tribological properties of Mg-MMCs and Mg-MMNCs are discussed taking specific examples from existing literature, and a comparative understanding on their salient features is presented.

In this work, a plasma arc additive manufacturing technique with a double-wire feedback mechanism was used to manufacture Inconel 625 Ni–Cu functionally graded materials. The microstructure, mechanical properties and corrosion properties of the deposited alloy were evaluated. Microstructure observation and tensile testing of parts with different element contents indicated that functionally graded materials were obtained through the manufacturing process. The results have shown that due to the very high growth restriction factor Q of Cu, its addition can increase the constitutional supercooling zone, resulting in a decrease in columnar and dendrites and an increase in equiaxed crystals in the Inconel 625 Ni–Cu functionally graded material, as well as changing the Schmid factor (SF) distribution. The tensile strength and ductility of the Inconel 625 Ni–Cu functionally graded materials increased with increasing Cu content, while the corrosion resistance of the alloy decreased with increasing Cu content during electrochemical corrosion tests.

Stainless steel 304 (SS304) experiences corrosion when it is exposed to a saline atmosphere, which attains severity due to its high surface wettability. Topographical modification of metallic surfaces is an effective route to reduce wettability and thereby mitigate liquid-mediated corrosion. In this work, topographical modification of stainless steel 304 flat surface in the form of micropillars was done (pillar width: 100 μm, inter-pillar distance: 100 μm and height: 80 μm). Micropillars were fabricated by a chemical etching process. Wetting and corrosion of the micropillars was studied over long-time duration in comparison with flat surface, before and after intermittent and continuous exposures to saline water for 168 h. Wetting was characterized by measuring the static water contact angle on the test surfaces and their corrosion by electrochemical polarization tests (electrolyte: 3.5 wt.% sodium chloride solution). The relationship between the nature of wetting of the test surfaces and their corrosion was examined. Micropillars showed predominantly composite wetting over a long time, which imparted an effective resistance against corrosion over a long time to the SS304 surface. When compared to the flat surface, the corrosion rates of the micropillars were lower by two orders of magnitude, prior to and also upon long-time contact with the NaCl solution. Micropillars lowered corrosion due to composite wetting, i.e., solid-liquid-air interface that reduced the area that was in contact with the NaCl solution. The efficiency of corrosion inhibition (η) of micropillars was 88% before long-time contact, 84% after intermittent contact, and 77% after continuous contact with NaCl solution. Topographical modification in the form of micropillars that can impart composite wetting is an effective route to induce long-term anticorrosion ability to the SS304 surface.

Growing concerns like depleting mineral resources, increased materials wastage, and structural light-weighting requirements due to emission control regulations drive the development of sustainable metal matrix composites. Al and Mg based alloys with relatively lower melting temperatures qualify for recycling applications and hence are considered as the matrix material for developing sustainable composites. The recent trend also explores various industrial by-products and agricultural wastes as green reinforcements, and this article presents insights on the properties of Al and Mg based sustainable metal matrix composites with special emphasis on green reinforcements and processing methods.

Natural fiber- reinforced composites are currently being researched for their selection and use in the industries spanning aerospace, automotive, ground transportation, and several other high- performance-critical end products. Two of the key reasons in favor for the selection and use of natural fibers are, their biodegradability coupled with an overall ease of availability that makes the production of engineered composites not only cost effective but also economically viable. However, the selection and use of natural fibers/matrix is curtailed primarily because of three competing drawbacks, namely (i) high moisture absorption, (ii) inferior mechanical properties, and (iii) poor interfacial bonding strength between fiber and matrix, when compared one-on-one with the synthetic fibers/matrix. Due to these reasons, natural fibers are often used in combination with synthetic fibers for engineering composites, so as to achieve a material that offers the possibility of improved performance at the desired level. In this research study, composite laminates with novolac resin and sisal/coir/E-glass fiber reinforcement (60:40) were fabricated using the hand lay-up method. The fabricated composite laminates were characterized for macromechanical properties, namely, tensile strength and water absorption test was conducted to explore the moisture absorption characteristics of composite laminates. Test results revealed the composite laminates with natural fibers/resins to possess many attributes in favor of their selection and use in structural components.

Thermomechanical processing (TMP) is a significant route to tune the microstructure and mechanical properties of high‐entropy alloy (HEA), which employs plastic deformation and heat treatment. Herein, bulk CoCrFeNiAl0.4 high‐entropy alloy has been fabricated by powder plasma arc additive manufacturing (PPA‐AM), which was subjected to TMP including different extents of plastic deformations and followed by annealing. The evolution of microstructure and mechanical properties of the HEAs during TMP is studied, and the contribution of strengthening mechanisms to the improvement of mechanical properties is quantified. By increasing the plastic deformation of TMP, the hardness and yield strength of the alloys increase by 94% and 105%, respectively, and are accompanied by a strain of 29.1%. Based on analysis and calculations, it is found that grain boundary strengthening significantly contributes to the improved performance of bulk CoCrFeNiAl0.4 HEA fabricated by PPA‐AM + TMP. PPA‐AM + TMP synthesis is an innovative way to prepare bulk HEAs with a refined microstructure and better mechanical properties.

Corrosion and tribology are surface phenomena. Modifying surfaces of materials without resorting to altering their bulk properties is an effective route to alleviate corrosion, friction and wear, encountered in engineering applications. With the advancements in the field of nanotechnology, surface protective coatings with nanomaterials can be readily developed to explore their functionality in mitigating chemical/physical damage of surfaces. Surface protection enhances performance and operating lifetimes of industrial machinery components. This review presents insights on various types of recently developed nanostructured coatings, their synthesis routes, corrosion behaviour and tribological performance. It provides the state-of-the-art information on the development of nanostructured coatings, namely, ceramic coatings, metallic coatings and nanocomposite coatings with metal and polymer matrices. Biomimetic approaches in making nanostructured coatings and challenges encountered in the development of nanostructured coatings are highlighted.

Magnesium (Mg) is the lightest structural metal available in abundance on earth crust. It is an excellent candidate for weight critical applications. For example, the replacement of currently used aluminium alloys in transportation sector by magnesium materials would promote fuel energy savings and emission control. In recent years, there is a growing interest on the utilization of Mg materials for biomedical applications. This is primarily due to the bioresorbable and nontoxic nature of Mg which makes it an ideal choice for body implants. This paper therefore deliberates on the properties of Mg-based materials for potential use in various engineering and biomedical applications. The development of Mg-alloys and composites are discussed in detail, highlighting the influence of various alloying elements and reinforcements. The processing methods applicable for Mg materials are briefly introduced, followed by a summary on the current trends and the actual use of Mg-based materials in automobile, aerospace, consumer electronics, and biomedical applications.

In this work, the microstructure of CoCrFeNiTa0.4 based high entropy alloy was studied. HEAs with the same structure were prepared successfully by replacing Ta with relatively less expensive Nb (Ta0.2Nb0.1, Ta0.2Nb0.3, Ta0.2Nb0.5 replacing Ta-0.4) using powder plasma arc additive manufacturing (PPA-AM), an emerging AM technology. The microstructural phases, phase hardness and mechanical properties of CoCrFeNiTa0.4 and CoCrFeNiTa0.2Nb0.1-0.5 have been analyzed. From this investigation, it is evident that the CoCrFeNiTa0.2Nb0.3 alloy can replace CoCrFeNiTa0.4 alloy with improved structure and mechanical properties along with a cost saving of 29%. This is also the first report to demonstrate the microstructure - mechanical properties relationship in CoCrFeNiTaNb high entropy alloy. (C) 2021 Elsevier B.V. All rights reserved.

Aluminum and its composites have been a subject of research for their good strength-to-weight ratio and with the advent of nanotechnology, aluminum nanocomposites have evolved as a new class of material with properties superior to conventional microcomposites. This article presents an overview of aluminum nanocomposites, their types, fabrication routes and industrial applications. A special focus has been given to carbonic nanocomposites, in particular with graphene and carbon nanotubes as reinforcement. The article summarizes mechanical and tribological properties of these composites and the mechanisms involved therein. A section is dedicated on the development of aluminum nanocomposites by disruptive Additive Manufacturing (AM) technology and the advantages offered by AM in comparison to conventional technologies. Potential applications of these nanocomposites, challenges encountered in their fabrication and the scope for future research have also been presented.

By using cold metal transfer technique, Cu-Al alloy with addition of silicon (Si) and magnesium (Mg), viz (1) Cu-6.5% Al and (2) Cu-6.5% Al-1.2% Si-0.5% Mg were manufactured additively. Four samples were deposited: Cu-6.5% Al alloy as samples 1 and 2, and Cu-6.5% Al-1.2% Si-0.5% Mg alloy as samples 3 and 4. The alloys were homogenized by heat treatments: (1) 800°C (2 h) for sample 2 and (2) sample 4, to improve their mechanical properties. Detailed microstructural investigation conducted using scanning and transmission electron microscopies showed formation of various intermetallic phases. Results revealed that (1) the addition of Si and Mg increases the strength properties and ductility and (2) heat treatments improved strength properties but reduce the ductility of the alloys. The article discusses the correlation of the identified microstructure and the evaluated mechanical properties of the additively manufactured alloys.

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, Cu—4.9% Al alloy with little Si (the weight percentage is 1.3%) and little Mn (the weight percentage is 0.8%) was deposited by wire arc additive manufacturing. Microstructure and properties of the deposited alloy was investigated. Microstructural characterization was done using optical microscopy, scanning electron microscopy and transmission electron microscopy. Microstructural investigation revealed that aluminum was enriched at the interlayer (i.e. inside the deposited layers), whereas silicon and manganese were found enriched at the border layers (i.e. at the border of the deposited layers). Evaluation of the mechanical properties showed that the deposited sample had good strength and ductility. The addition of silicon effectively improved the hardness and tensile strength properties of the deposited alloy.