Faculty Publications
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Item Development and characteristics of accumulative roll bonded Mg-Zn/Ce/Al hybrid composite(Elsevier Ltd, 2017) Anne, G.; Ramesh, M.R.; Shivananda Nayaka, H.; Arya, S.B.; Sahu, S.Accumulative roll bonding (ARB) process have been used develop Mg-2%Zn/Ce/Al hybrid composite and microstructure, mechanical and corrosion properties were investigated. The electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) revealed that the grains are significantly reduced and reaches up to 1 ?m in Mg-2%Zn layer and 1.8 ?m in Al layer having high angle misorientation of grain boundaries after subjected to 5-passes of the ARB process. The Al17Mg12, AlMg4Zn11 and Al11Ce3 intermetallic phases were observed through the XRD analysis. Mechanical properties of the hybrid composite improved with increase in the number of ARB passes which is attributed to work hardening, grain refinement and uniform distribution of Ce particles. Presence of Ce in the hybrid composite restricts the phenomenon of dynamic recrystallization and prevents the grain growth during ARB process. The corrosion rate of Mg-Zn/Ce/Al hybrid composite (0.72 mm/y) improved about 3.3 times as compared to that of Mg-2%Zn alloy (2.37 mm/y). © 2017 Elsevier B.V.Item Microstructure Evolution and Mechanical and Corrosion Behavior of Accumulative Roll Bonded Mg-2%Zn/Al-7075 Multilayered Composite(Springer New York LLC barbara.b.bertram@gsk.com, 2017) Anne, G.; Ramesh, M.R.; Shivananda Nayaka, H.; Arya, S.B.; Sahu, S.Multilayered composite of Mg-2%Zn/Al-7075 was developed by accumulative roll bonding (ARB) of wrought Mg-2%Zn and aluminum 7075 alloy. The Mg-2%Zn/Al-7075 multilayered composite exhibited density of 2295 kg/m3 and an average grain size of 1 and 1.3 ?m in Mg-2%Zn and Al-7075 layers, respectively. A thorough microstructural characterization was performed on the composites by scanning electron microscope, electron backscatter diffraction (EBSD), transmission electron microscope and phase analysis by x-ray diffraction. In addition, mechanical properties were evaluated by microhardness and tensile tests. Corrosion behavior of the multilayered composite was examined using electrochemical polarization test. EBSD analysis showed the presence of ultrafine grains with high-angle grain boundaries. The composite exhibited a significant improvement in ultimate tensile strength (~1.82 times) and elongation (~1.5 times) as compared with Mg-2%Zn alloy, after four-pass ARB process. © 2017, ASM International.Item Effects of combined multiaxial forging and rolling process on microstructure, mechanical properties and corrosion behavior of a Cu-Ti alloys(Institute of Physics Publishing helen.craven@iop.org, 2019) Ramesh, S.; Anne, G.; Shivananda Nayaka, H.; Sahu, S.; Arya, S.Combined multiaxial forging (MAF) and rolling was performed on Cu-3% Ti (wt%) alloy at room temperature with emphasis on microstructural evolution, improvement in mechanical properties, and corrosion resistance. Microstructural changes were confirmed from various characterization techniques, and co-related with mechanical properties. TEM analysis revealed high shear band density in the 3 pass MAF + 90% rolled sample appearing due to high strain. EBSD analysis revealed transformation to low angle grain boundaries from high angle grain boundaries. Maximum microhardness and UTS reached to 340 HV and 960 MPa, respectively in the processed samples. Significant grain refinement was observed in MAF processed Cu-3%Ti alloy, and after combined MAF + rolling, higher dislocation density and refinement of shear bands were observed. In addition, potentio-dynamic polarization test was used to study the corrosion behavior of the alloy. Scanning electron microscope (SEM) was used to analyze the corroded surface morphology. © 2019 IOP Publishing Ltd.Item Influence of Multidirectional Forging on Microstructural, Mechanical, and Corrosion Behavior of Mg-Zn Alloy(Springer New York LLC barbara.b.bertram@gsk.com, 2019) Ramesh, S.; Anne, G.; Shivananda Nayaka, H.S.; Sahu, S.; Ramesh, M.R.Multidirectional forging (MDF) was applied to Mg-6%Zn alloy up to 5 passes successfully at 280 °C. MDF-processed materials were characterized using optical microscope, scanning electron microscope, electron backscatter diffraction, transmission electron microscope, and x-ray diffraction. Obtained results showed a significant reduction in grain size (up to 3.8 ?m) having a large fraction of high-angle grain boundaries after 5 passes of MDF process. Maximum tensile strength of 230 MPa was achieved for 5-pass MDF-processed Mg-6%Zn alloy which is about ~ 2.0 times higher in comparison with that of homogenized alloy (117 MPa) and was attributed to higher dislocations density and grain refinement. Corrosion behavior of the alloy was investigated in 0.1 M NaCl solution using potentiodynamic polarization test, electrochemical impedance spectra analysis, and immersion tests. It was found that the corrosion rate of 5-pass MDF sample improved (0.34 mm/year) ~2.5 times in comparison with that of homogenized Mg-6%Zn alloy (0.86 mm/year) due to fine grain structure, which creates more grain boundaries that act as a corrosion barrier. © 2019, ASM International.Item Effect of Equal Channel Angular Pressing on Properties Evaluation of Biodegradable Mg-Zn-Mn Alloy(Springer Science and Business Media Deutschland GmbH, 2021) Ramesh, S.; Kumar, G.; Jagadeesh, C.; Anne, G.; Shivananda Nayaka, H.Equal channel angular pressing (ECAP) was used to process Mg-4Zn-1Mn alloy at 300 °C using route Bc up to 4 pass with a cumulative strain of 3.2. Optical microscope (OM), microstructures results shows homogenized sample grain size was 260 µm, after 4 pass ECAP grain size was decreased to 6 µm. Electron back-scattered diffraction (EBSD) shows the misorientation angle converted from low-angle grain boundaries (LAGB) to high-angle grain boundaries (HAGB). Dislocation density and fine grains were observed from transmission electron microscope (TEM) images. Strength has been increased from 156 to 218 MPa and hardness increased to 68 Hv after 4 pass of ECAP. Fractography analysis revealed that dimple size decreases as ECAP passes increased. XRD analysis shows the peak broadening and intensity variation, because of grain refinement. The corrosion behavior of the homogenized and ECAP-processed samples were investigated by electrochemical tests using simulated body fluids (SBF) at 37 ± 1 °C. The lower corrosion resistance of ECAP-processed Mg-4Zn-1Mn alloy attributed to the strain-induced crystalline defects, subgrain boundaries and high-density dislocations. Enhanced strength and ductility combined with lower corrosion resistance of ECAP-processed Mg-4Zn-1Mn has greater potentials for biomedical implants. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.Item On the microstructure, texture and electrochemical properties of severely deformed and artificially aged lightweight AA2050 Al-Cu-Li alloy(Institute of Physics, 2024) Jagadeesh, C.; Shivananda Nayaka, H.; Sekar, P.; Ramesh, S.; Anne, G.Lightweight 3rd generation Al-Cu-Li alloy AA2050 was severely deformed via Multi Axial Forging (MAF) at 170 °C followed by artificial aging at 150 °C. Effect of MAF and post MAF aging on microstructure and precipitation was investigated using transmission electron microscopy (TEM). Formation of deformation bands and large dislocation cells were evident on MAF processed samples. Post MAF peak aging resulted in the distribution of fine T1 precipitates in grain interiors with reduction in grain boundary precipitation. Bulk texture studies reveal the formation of strong Goss and S texture components upon MAF processing. Further, low temperature artificial aging doesn’t exhibit significant changes in texture characteristics, either in terms of texture intensities or texture components. Polarization studies showed that peak aged samples exhibited better corrosion resistance compared to un-aged samples. Overall, 12 pass MAF processed and peak aged samples showed higher corrosion resistance. Further, corrosion surface morphologies examination revealed the change in corrosion mechanisms with thermomechanical treatments. Improved corrosion resistance after MAF and peak aging widens the requirements in aerospace and aircraft applications for such engineering alloys. © 2024 The Author(s). Published by IOP Publishing Ltd.