Faculty Publications
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Item Overview of high-entropy alloys(De Gruyter, 2023) Prakash, O.; Chandrakar, R.; Kumar, A.; Michalska-Domańska, M.New materials and alloys are being developed by using latest technology and manufacturing techniques. Significant progress in alloy system has led to development of special alloys, such as alloys of iron, copper, superalloys, and high-entropy alloys. High-entropy alloys with multiple constituent elements, higher mixing entropy, improved property, and structure make them different from other alloy systems. High-entropy alloy concepts have come into focus after successful development of these alloys, from 2004. Basic concepts, design strategy, phase formation rule, and basic core effects for enhancements of property and structural stability of highentropy alloys are discussed in this chapter. © 2023 Walter de Gruyter GmbH, Berlin/Boston. All rights reserved.Item Melting and casting route(De Gruyter, 2023) Chandrakar, R.; Prakash, O.; Kumar, R.; Tiyyagura, H.R.; Chandraker, S.The melting and casting route is the most common and relatively cheap route of production of high-entropy alloys. In this route, the constituent elements are mixed in liquid state. Multicomponent alloys in the shape of buttons, rods, ribbons, and bars have been created using the melting and casting route, with various cooling rates. Vacuum arc melting is the most common melting and processing process. This chapter reviews melting and casting routes and related synthesis techniques in manufacturing of high-entropy alloys. © 2023 Walter de Gruyter GmbH, Berlin/Boston. All rights reserved.Item Emerging processing routes(De Gruyter, 2023) Prakash, O.; Kumar, R.; Tapas, V.; Kumar, A.; Naveen, B.High-entropy alloys (HEAs) are produced using a number of processing techniques. HEAs have been produced in a variety of materials, including films, dense solid castings, and powder metallurgy components. The three types of processing routes-melting and casting, powder metallurgy, and deposition techniques-can be broadly divided into three classes. In order to create HEAs in the form of rods, bars, and ribbons, melting and casting procedures have been used, along with equilibrium and nonequilibrium cooling rates. The vacuum arc melting, vacuum induction melting, and melt spinning processes are the most widely used melt processing methods. The primary solid-state processing method to create sintered goods has been mechanical alloying (MA), followed by sintering. The surface modification methods utilized to create both thin films and thick layers of HEAs on various substrates include plasma nitriding, cladding, and sputtering. This chapter provides a brief overview of the various synthesis and processing methods used to create HEAs. The processing pathways for equiatomic and nonequiatomic HEAs are comparable. © 2023 Walter de Gruyter GmbH, Berlin/Boston. All rights reserved.Item On the corrosion resistance of some selective laser melted alloys(Elsevier B.V., 2018) Suryawanshi, J.; Baskaran, T.; Prakash, O.; Arya, S.; Ramamurty, U.The electrochemical corrosion resistances of selective laser melted (SLM) 316 L austenitic stainless steel (SS), 18(Ni) 300-grade maraging steel (MS), and Al-12 wt.% Si (AS) alloy in a 0.1 M NaCl solution at room temperature were evaluated. The effects of laser scanning strategy (single melt vs. checker board styles), post-SLM heat treatment, and corroding surface orientation (with respect to the scan and build directions) on the corrosion behavior were examined. In all cases, results were compared with those obtained on samples with the same compositions, but manufactured using conventional means. The experimental results show that, for the particular set of experimental conditions employed in this study, SLM in general improves the corrosion resistances of Al-12 wt.% Si and stainless steel alloys and degrades the corrosion resistance of the maraging steel, in comparison to the respective corrosion resistances of their conventionally manufactured counterparts. These results are discussed in terms of microstructural refinement and porosity that are common to the SLM alloys. © 2018 Acta Materialia Inc.Item High-Resolution Fiber Optic Sensor based on Coated Linearly Chirped Bragg Grating(Elsevier GmbH, 2020) Singh, M.; Raghuwanshi, S.K.; Prakash, O.; Kumar, P.K.a fiber optic strain sensor is proposed and experimentally demonstrated using fiber Bragg grating (FBG) based interrogation scheme. Due to fast response time and better sensitivity of graphene oxide (GO) material, coated linearly chirped fiber Bragg grating (LCFBG) is used in this work. Interrogation scheme is used for the efficient strain sensing by placing LCFBG within the Sagnac loop (wavelength dependent receiver). The GO deposition is confirmed by ultraviolet–visible spectroscopy, atomic force microscopy (AFM), and field emission scanning electron micrograph (FESEM). Our proposed fiber optic strain sensor possesses better resolution, stable operation in the infra-red region. In addition, sensor demonstrates 5.25 ?? static strain and 0.645 ??/?Hz dynamic strain resolutions, respectively. © 2020 Elsevier GmbHItem High sensitivity detection of chemicals based on sinusoidally apodized structured grating assisted liquid filled directional coupler(Springer, 2021) Raghuwanshi, S.K.; Singh, Y.; Singh, M.; Chack, D.; Kumar, R.; Prakash, O.The grating has a significant role in sensing applications. Similarly, the grating-assisted coupler has excellent potential in chemical sensing applications. The power coupling between two closely coupled waveguide couplers can be significantly tuned by incorporating grating between them. The grating has been taken of silica material with sinusoidal shape in variation. The grating layer is assumed to be embedded within the sensing layer while considering a changeable effective refractive index depending on the sensing layer substances. In the present paper, grating assisted directional coupler has been numerically analysed using its own developed MATLAB-based algorithm of finite difference method (FDM) scheme. FDM method has been applied to solve the Eigenvalue equation to obtain allowed Eigenvalues and corresponding Eigen vectors (TE and TM cases). In FDM, the analysis domain has been fine discretized into the mesh of 1-D equal spacing for reasonable accurate computation results. In experimental validation, Fibre Bragg grating (FBG) has been suspended between two high refractive index coupler regions, which act as a power coupling zone. Also, the coupling length has been changed from 5 to 20 ? m for tuning purposes and then optimized for grating parameters viz. length, period, etc. The whole structure is 2-Dimensional (x and y directions) with invariant in the y-direction. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Item Phase Evolution of Novel MoNbSiTiW Refractory High-Entropy Alloy Prepared by Mechanical Alloying(Springer, 2022) Prakash, O.; Chandrakar, R.; Chandraker, S.; Rao, K.R.; Kumar, R.; Kumar, A.; Dubey, V.Refractory high-entropy alloys (RHEAs) are new types of material that have been developed for high-temperature applications. RHEAs should have enhanced high-temperature strength while maintaining a sufficient level of room-temperature toughness. The phase evolution of novel MoNbSiTiW RHEAs was investigated after mechanical alloying (MA) for 35 h. X-ray diffraction (XRD) was used to analyze the phase evolution, and analysis of particle morphologies was done using a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). XRD results indicate that NbMoSiTiW RHEAs with up to 10 h of mechanical alloying have a stable solid solution phase with body centered cubic (BCC) structure. Further milling of NbMoSiTiW RHEAs promotes the evolution of intermetallic compounds until 35 h of mechanical alloying. The Williamson-Hall process was incorporated for crystalline size and lattice strain measurement and the results show that, after 35 h of mechanical alloying, the crystalline size decreased from 298 nm to 25 nm, and an enhancement in lattice strain was observed from 0.1% to 0.65%. © 2022, The Minerals, Metals & Materials Society.Item Laser cladding technology for high entropy alloys: effect and applications(Institute of Physics, 2024) Prakash, O.; Chandrakar, R.; Martin, L.; Verma, J.; Kumar, A.; Jaiswal, A.A multi-component category of an alloy containing very specific properties revolutionized the area of material science and the present engineering era. Laser cladding, a technique for surface coating, enhances surface quality and modifies properties using advanced coating technologies. In current trends, Laser cladding is mainly used in equipment and machine parts for enhancing surface properties, repairing damaged parts and surface coating caused by its advantages such as small heat-affected zone, low substrate damage, low dilution rate and exceptional metallurgical material bonding among coating and used substrate. Laser cladding improves substrates’ mechanical and various functional-specific properties, ensuring a high-quality balance between mechanical and surface attributes. The research society was able to investigate laser-cladding HEAs coatings because of the superior attributes of HEAs compared to ordinary alloys. This paper reviews current developments in laser-cladding HEAs coatings and the application of laser-cladding technology to HEAs materials. The laser cladding high-entropy alloy coatings have potential applications in corrosion, wear, and oxidation resistance, as well as their respective substrates. Cladded coatings composed of HEAs materials are measured to have shown potential applications in recent technology, opening exciting possibilities for the future. The study also discusses current trends and future prospects. © 2024 The Author(s). Published by IOP Publishing Ltd.