Faculty Publications
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Item Grinding wear behaviour of stepped austempered ductile Iron as media material during comminution of Iron ore in ball mills(2010) Raghavendra, H.; Bhat, K.L.; Udupa, K.R.; Rajath Hegde, M.M.R.An attempt has been made to evaluate the suitability of austempered ductile iron (ADI) as media material for grinding iron ore in a ball mill. Spheroidal graphite (S.G) iron balls are austenitised at 900°C for 60 minutes and given stepped austempering treatment at 280°C for 30 minutes and 60 minutes followed by 380°C for 60 minutes in each case. These materials are characterised by measuring hardness, analysing X-ray diffraction (X-RD), studying microstructure using optical and scanning electron microscope (SEM). Grinding wear behaviour of these materials was assessed for wear loss in wet condition at different pH value of the mineral slurry and found that the wear rate of grinding media material decreases with increase in pH of the slurry. The wear resistance of ADI balls were compared with forged En31 steel balls and found that the stepped austempered ductile iron is superior to forged En31 steel balls. © 2010 American Institute of Physics.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 Investigation of microstructure and mechanical properties of microwave consolidated TiMgSr alloy prepared by high energy ball milling(Elsevier B.V., 2022) Pradeep, N.B.; Rajath Hegde, M.M.R.; Rajendrachari, S.; Surendranathan, A.O.The nanostructured TiMgSr (at.% 70:10:20) was synthesized by ball milling process followed by cold compaction and microwave sintering. XRD results after 30 h milling showed crystallite size of ⁓41 nm with a lattice strain of 2.5% and evolution of solid solutions like Mg5.2Sr, MgTiO3. The phases formed from 30 h mechanically alloyed powder are in good agreement with TEM SADP results. Consolidation using microwave sintering resulted in the retention of nanostructure with crystallite size of 78 nm and lattice strain of 1.2%. Densification study results in porosity of 19.8% with almost 20% density reduction compared to CP-Ti. The obtained porosity has promoted density reduction along with low elastic modulus that could be biocompatible with human bone tissue. Nanoindentation test results showed a low modulus of 36 ± 7 GPa with a hardness of 1.8 ± 0.8 GPa. These results are comparable with those Ti alloys produced by various techniques and found to be relatively superior for biomedical applications. © 2022Item Investigation of Structural and Mechanical Properties of Nanostructured TiMgSr Alloy for Biomedical applications(AMG Transcend Association, 2023) Pradeep, P.N.; Rajendrachari, S.; Surendranathan, A.O.; Rajath Hegde, M.M.R.In this study, Nanostructured TiMgSr alloy is produced by cold Isostatic Pressing (CIP) followed by microwave sintering. The fabricated alloy results in the formation of solid binary solutions along with the elemental phases. The CIP compacted alloy was characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) to investigate the phases and the morphology. The presence of intermetallic phases SrTiO3 and Mg17 Sr2 along with elemental Ti, Mg, and Sr crystallites with a narrow peak during the sintering process is prevalent; however, the crystallite size was retained in the nanoscale regime around 58 nm. The developed titanium alloy exhibits a low Young's modulus and good strength. The young's modulus of Ti–Mg–Sr alloys was around 48.11 GPa, significantly closer to human cortical bone (10–30 GPa). Among so far developed Ti-based alloys, the CIP consolidated Ti-Mg-Sr alloy results in low young modulus and hardness. In the future, it may be used practically for biomedical applications. © 2022 by the authors.