Faculty Publications
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Item An Overview of Mechanical Alloying and Conventional Metallurgical Methods(Springer, 2024) Bhajantri, V.F.; Kanaginahal, G.M.; Jambagi, S.Mechanical alloying (MA) is a powder processing technique that involves the cyclic process of cold welding, fracturing, and rewelding of powder particles within a high-energy ball mill. This method has the ability to create several forms of non-equilibrium phases, such as supersaturated solid solutions, nanocrystalline materials, metallic glasses, high-entropy alloys, and more. Materials with shape memory properties have been utilized in various applications. This article enlightens on MA and other conventional metallurgical methods. The article provides a description of the current and future applications of MA. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Phase transformation, structural evolution, and mechanical property of nanostructured feal as a result of mechanical alloying(Springer New York LLC barbara.b.bertram@gsk.com, 2009) Rajath Hegde, M.M.R.; Surendranathan, A.O.The objective of the work is to synthesize nanostructured FeAl alloy powder by mechanical alloying (MEA). The work concentrates on the synthesis, characterization, and structural and mechanical properties of the alloy. Nanostructured FeAl intermetallics are prepared directly by MEA in a high-energy ball mill. Milling is performed under toluene solution to avoid contamination from the milling media and atmosphere. Mixtures of elemental Fe and Al are progressively transformed into a partially disordered solid solution with an average composition of Fe-50 at.% Al. Phase transformation, structural changes, morphology, particle size measurement, and chemical composition during MEA are investigated by X ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDS). Vickers microhardness (VMH) indentation tests are performed on the powders. The XRD and SEM studies reveal the alloying of elemental powders as well as transition to nanostructured alloy; crystallite size of 18 nm is obtained after 28 h of milling. Expansion/contraction in lattice parameter accompanied by reduction in crystallite size occurs during transition to nanostructured alloy. Longer milling introduces ordering in the alloyed powders as proved by the presence of superlattice reflection. Elemental and alloyed phases coexist while hardness increases during MEA. copy2009 Springer Science+Business Media, Inc.Item Synthesis, characterization and annealing of mechanically alloyed nanostructured FeAl powder(2009) Rajath Hegde, M.M.R.; Surendranathan, A.O.Elemental powders of Fe and Al were mechanically alloyed using a high energy rate ball mill. A nanostructure disordered Fe(Al) solid solution was formed at an early stage. After 28 h of milling, it was found that the Fe(Al) solid solution was transformed into an ordered FeAl phase. During the entire ball milling process, the elemental phase co-existed with the alloyed phase. Ball milling was performed under toluene to minimise atmospheric contamination. Ball milled powders were subsequently annealed to induce more ordering. Phase transformation and structural changes during mechanical alloying (MEA) and subsequent annealing were investigated by X-ray diffraction (XRD). Scanning electron microscope (SEM) was employed to examine the morphology of the powders and to measure the powder particle size. Energy dispersive spectroscopy (EDS) was utilised to examine the composition of mechanically alloyed powder particles. XRD and EDS were also employed to examine the atmospheric and milling media contamination. Phase transformation at elevated temperatures was examined by differential scanning calorimeter (DSC). The crystallite size obtained after 28 h of milling time was around 18 nm. Ordering was characterised by small reduction in crystallite size while large reduction was observed during disordering. Micro hardness was influenced by Crystallite size and structural transformation. © Higher Education Press and Springer-Verlag 2009.Item Phase transformation, structural evolution and mechanical property of nanostructured FeAl as a result of mechanical alloying(2009) Rajath Hegde, M.M.R.; Surendranathan, A.O.Objective of the work was to synthesize nanostructured FeAl alloy powder by mechanical alloying (MEA). The work concentrated on synthesis, characterization, structural and mechanical properties of the alloy. Nanostructured FeAl intermetallics were prepared directly by MEA in a high energy rate ball mill. Milling was performed under toluene solution to avoid contamination from the milling media and atmosphere. Mixtures of elemental Fe and Al were progressively transformed into a partially disordered solid solution with an average composition of Fe-50 at % Al. Phase transformation, structural changes, morphology, particle size measurement and chemical composition during MEA were investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDS) respectively. Vickers micro hardness (VMH) indentation tests were performed on the powders. XRD and SEM studies revealed the alloying of elemental powders as well as transition to nanostructured alloy, crystallite size of 18 nm was obtained after 28 hours of milling. Expansion/contraction in lattice parameter accompanied by reduction in crystallite size occurs during transition to nanostructured alloy. Longer milling duration introduces ordering in the alloyed powders as proved by the presence of superlattice reflection. Elemental and alloyed phase coexist while hardness increased during MEA. © 2009 Allerton Press, Inc.Item Enhancement of heat transfer characteristics of transformer oil by addition of aluminium nanoparticles(2011) Rajesh, E.; Prabhu, K.N.A two step approach involving the synthesis of Al nanoparticles by mechanical milling followed by dispersion of the nanoparticles in the base fluid is adopted in the present work to prepare transformer oil based nanofluids. Stainless steel (AISI 304) probes of diameter 15 mm and height 70 mm were used to determine the cooling rate intensities of nanofluids. Heat transfer coefficients were determined using Kobasko's method. A dynamic contact angle analyzer was used to determine the contact angle of the droplet on the substrate. The addition of Al nanoparticles to the base fluid decreases the wettability and improves its heat transfer capability. The vapour phase stage existed for a longer period of time for transformer oil than for Al-transformer oil based nanofluids. The dispersion of nanoparticles in the base fluid is believed to disrupt the vapour blanket stage in the early stage of the cooling process. The peak heat transfer coefficient increases with an increase in the Al nanoparticle content in the oil. The addition of 0.5 vol % nanoparticles enhances the peak heat transfer coefficient by about 70 %. Copyright © 2011 by ASTM International.Item Enhancement of heat transfer characteristics of transformer oil by addition of aluminium nanoparticles(ASTM International, 2012) Rajesh, E.; Prabhu, K.N.A two step approach involving the synthesis of Al nanoparticles by mechanical milling followed by dispersion of the nanoparticles in the base fluid is adopted in the present work to prepare transformer oil based nanofluids. Stainless steel (AISI 304) probes of diameter 15 mm and height 70 mm were used to determine the cooling rate intensities of nanofluids. Heat transfer coefficients were determined using Kobasko's method. A dynamic contact angle analyzer was used to determine the contact angle of the droplet on the substrate. The addition of Al nanoparticles to the base fluid decreases the wettability and improves its heat transfer capability. The vapour phase stage existed for a longer period of time for transformer oil than for Al-transformer oil based nanofluids. The dispersion of nanoparticles in the base fluid is believed to disrupt the vapour blanket stage in the early stage of the cooling process. The peak heat transfer coefficient increases with an increase in the Al nanoparticle content in the oil. The addition of 0.5 vol % nanoparticles enhances the peak heat transfer coefficient by about 70%. Copyright © 2011 by ASTM International, 100 Barr Harbor Drive, PO Box C700,.Item Interparticle interactions and lacunarity of mechano-chemically activated fly ash(Elsevier, 2015) Patil, A.G.; Shanmugharaj, A.M.; Anandhan, S.A class F fly ash was subjected to high-energy ball milling-induced mechano-chemical activation aided by a surfactant. The resultant nanostructured fly ash was characterized by various techniques. X-ray fluorescence results showed that the amount of iron oxide was reduced from 4.39% to 2.75% after pre-treatment of fly ash by magnetic separation. Ethyl acetate as the milling medium, a ball to powder ratio of 12:1 and 2wt% of surfactant reduced the average particle size of fly ash to 329nm and led to a specific surface area of 8.73m2/g. The decrease in crystallite size of mechano-chemically activated fly ash was confirmed from a reduction in peak intensity with a broadened amorphous phase by X-ray diffraction studies. X-ray photoelectron spectroscopic characterization illustrated that peak area of major elements (O, Si and Al) increased after milling. Morphological and FTIR studies revealed that the smooth and inert surface of the fly ash was converted to a rough and more reactive one after mechano-chemical activation. The surface modification of fly ash with the surfactant was determined from FTIR spectroscopy. Also, a fractal approach was used to characterize the lacunarity of the agglomerates in the nanostructured fly ash. © 2014 Elsevier B.V.Item Characterization of composites based on biodegradable poly(vinyl alcohol) and nanostructured fly ash with an emphasis on polymer-filler interaction(SAGE Publications Ltd info@sagepub.co.uk, 2016) Patil, A.G.; SelvaKumar, M.; Anandhan, S.A thermal power station fly ash (FA) was mechanochemically activated by high-energy ball milling that yielded nanostructured FA. This nanostructured FA was incorporated into biodegradable poly(vinyl alcohol) (PVA) matrix by solution mixing and ultrasonication. Transmission electron micrographs revealed that the smooth spherical particles of FA were changed into irregular and rough ones; in addition, the particle size of FA was reduced to a few hundred nanometers, and its specific surface area value increased after the high-energy milling process. All these factors, in turn, led to a thermodynamically favorable interaction between the mechanochemically activated FA and PVA as evidenced by Fourier transform infrared spectroscopy. The incorporation of a very small amount of the nanostructured FA led to an increase in crystallinity of the polymer matrix. The glass transition temperature of the PVA matrix increased by about 18°C when 5 wt% of the nanostructured FA was used as the reinforcement. © The Author(s) 2014.Item Solid state amorphization of Mg-Zn-Ca system via mechanical alloying and characterization(Elsevier B.V., 2017) Manne, B.; Bontha, S.; Ramesh, M.R.; Krishna, M.; Balla, V.K.Magnesium based bulk metallic glasses have attracted significant attention of researchers due to better mechanical and corrosion properties when compared to their crystalline counterparts especially for biomedical applications. Scaling up the part size and production volumes of such materials through liquid metallurgy route is challenging. In this work amorphous Ca5Mg60+xZn35?x (X = 0, 3 and 7) alloys have been successfully synthesized through solid state amorphization using a high energy planetary ball mill. X-ray diffraction was used to identify the crystalline phases of the powder during reaction. Evolution of amorphous phase was analysed using a parameter involving the ratio of integral area of peaks to the integral area of background (IPB) obtained from XRD patterns. Results showed reaction time increases with decreasing Zn content in Ca5Mg60+xZn35?x (X = 0, 3 and 7) alloy to obtain maximum amorphous structure with a small amount of residual crystalline phase. Prolonged milling of these powders, to eliminate residual crystalline phases, resulted in the nucleation of Mg102.08Zn39.6 phase. The composition dependent characteristic temperatures and thermal stabilities were studied using differential scanning calorimetry. © 2016 The Society of Powder Technology JapanItem Microstructure and Adhesion Strength of Ni3Ti Coating Prepared by Mechanical Alloying and HVOF(Pleiades Publishing compmg@maik.ru, 2018) Reddy, N.C.; Ajay Kumar, B.S.; Ramesh, M.R.; Koppad, P.G.In the present work we report the development of Ni3Ti intermetallic compound by high energy ball milling of Ni and Ti powders. The ball milled powders were taken at various intervals (4, 6, 8, 10, and 11 h) to analyze the formation of NixTix intermetallic compounds. The ball milled powders were analyzed using scanning electron microscopy and X-ray diffraction. The layered shaped powder particles of Ni3Ti phase were formed after 11 h of ball milling, which was confirmed by X-ray peaks. Further High-Velocity Oxy-Fuel (HVOF) process was used to coat Ni3Ti and Ni3Ti + (Cr3C2 + 20NiCr) on MDN 420 steel. Both the coated materials displayed excellent cohesion with minimal porosity less than 2%. The tensile adhesion strength test was carried out on these coatings to check the bond strength. Out of the two the Ni3Ti coating showed excellent bond strength of 41.04 MPa compared to that of Ni3Ti + (Cr3C2 + 20NiCr) coating. © 2018, Pleiades Publishing, Ltd.