Faculty Publications
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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 Optimization of ball-burnishing process parameters on surface roughness, micro hardness of Mg-Zn-Ca alloy and investigation of corrosion behavior(Institute of Physics Publishing helen.craven@iop.org, 2019) Ramesh, S.; Aditya Kudva, S.; Anne, G.; Manne, B.; Arya, S.In this work, optimization of ball burnishing parameters (depth of press, feed, burnishing force, number of passes) and their effect on surface roughness, microhardness and corrosion behavior of Mg-4%Zn-1%Ca alloy is investigated. The Taguchi optimization technique was used to determine the number of experiments and by considering S/N ratios, right combination of ball burnishing parameters were selected. Results obtained from the experiments were investigated and it is understood that depth of press, feed and number of passes have a significant effect on surface roughness, microhardness and consequently improves corrosion resistance of Mg-4%Zn-1%Ca alloy. From ball burnishing experiments it is deduced that there is large increase in microhardness of 107 Hv and surface roughness of 129 nm, achieved for the depth of press 0.45 mm, burnishing force 250 N, feed 450 mm min-1 and number of passes: 2. Corrosion behavior of the alloys were analyzed using potentiodynamic polarization and electrochemical impedance spectroscopy techniques in Hank's balanced salt solution. The lowest corrosion rate was observed in DFN 442 sample (1.43 mm y-1) which is 4.7 times better than the homogenized alloy (6.73 mm y-1). It has been found that the ball burnishing plays an important role on surface roughness, microhardness and corrosion behavior of Mg-4%Zn-1%Ca alloy. © 2019 IOP Publishing Ltd.Item Enhancing surface characteristics of Mg-Zn-Sr alloy through cryo-ball burnishing; modeling and experimentation(Korean Society of Mechanical Engineers, 2024) Kudva, S.A.; Anne, G.; Ramesh, S.; Sharma, P.; Jagadeesh, C.; Ritti, L.; Naik, G.M.; Divya Deepak, G.D.In this investigation, the impact of the cryo-ball burnishing process on both the mechanical and corrosion properties of the Mg-4Zn-1Sr alloy was systematically explored. To better understand the plastic deformation occurring in Mg-4Zn-1Sr during cryo-burnishing, a finite element analysis (FEA) model was developed. The microstructure of cryo-ball burnished samples underwent characterization through scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and surface properties were assessed using atomic force microscopy (AFM). Additionally, electrochemical impedance spectroscopy and potentiodynamic polarization tests were conducted in a simulated body fluid using an electrochemical workstation. Experimental findings revealed significant grain refinement and the presence of residual dislocations during the cryo-burnishing process, as evident in TEM analysis. XRD analysis indicated the presence of Mg, Mg17Sr2 and SrZn2 phases, with observable peak broadening in the cryo-burnished samples, attributed to structural refinement and lattice strain incorporation. Microhardness values increased with greater depth of press, with the DFN 1071 sample displaying a hardness of 80 ± 4 Hv (Ra = 1.853 µm), marking a 54 % improvement compared to the homogenized sample. The enhanced corrosion resistance of the Mg-4Zn-1Sr alloy due to cryo-burnishing is attributed to the combined effects of grain refinement, residual dislocations, and intermetallic phases. © The Korean Society of Mechanical Engineers and Springer-Verlag GmbH Germany, part of Springer Nature 2024.Item Enhancing the functionality of biodegradable Mg–Zn–Mn alloys using poly(lactic) acid (PLA) coating for temporary implants(Springer, 2024) Kumar, P.; Anne, G.; Ramesh, M.R.; Doddamani, M.; Prabhu, A.Polylactic acid (PLA) was coated on biodegradable Mg–Zn–Mn alloys using a sol–gel coating technique for temporary implant applications. The presence of smooth, dense, crack-free PLA coating was evidenced using Fourier transform infrared spectroscopy (FTIR) and a scanning electronic microscope (SEM) equipped with an energy-dispersive X-ray spectroscopy (EDX) module. The strength of the bond between PLA and the Mg–Zn–Mn alloys was investigated as per ASTM D3359 and found to be 4B. The degradation behavior was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy in a simulated body fluid (SBF) solution. The corrosion rate of the PLA–Mg–Zn–Mn sample was found to be 0.00363 mm/y, which is 73% better than the bare Mg–Zn–Mn sample (0.00493 mm/y). In addition, the results of the cytotoxicity assay indicated the cytocompatibility of the implant material on MG-63 osteoblast-like cells, confirming its safety on the bone cells. The efficacy of the use of PLA coating on the biodegradable Mg–Zn–Mn is due to the synergistic effect of both physical and chemical interactions between the PLA layer and the substrate. © American Coatings Association 2024.Item Combined effect of multidirectional forging and heat treatment on erosion and corrosion behaviour of the Mg-Zn-Mn alloys(Korean Society of Mechanical Engineers, 2024) Anne, G.; Hegde, A.; Kudva, S.A.; Sharma, P.; Kumar, P.; Matapati, M.; Ramesh, S.; Sharma, S.S.Multidirectional forging (MDF) was successfully applied to the Mg-4Zn-1Mn alloy for five passes at 300 °C. The grain size of 5 pass MDF processed samples reached 18 ± 3 µm from 256 ± 6 µm, and ?-Mg, MgZn2 and MnZn13 peaks were observed. Further MDF processed samples were solution treated (ST) at 300 °C for 2 h and quenched in SAE 20W40 oil and followed by artificial ageing (A) at 170 °C for four different timings including 1.5 h, 2 h, 2.5 h and 3.5 h respectively. The peak hardness of 219 Hv (5 pass MDF + H sample) was found in 2h artificial ageing which is 3.1 times higher compared to counterpart homogenised samples. Improvement of mechanical properties was attributed to smaller grain size and precipitation strengthening as well as distribution of the secondary phases. The combined effect of MDF and heat treatment was analysed using solid particle erosion tests at 30° and 90° impact angles using alumina. It was observed that higher impact angle (90°) had more erosion rate in all conditions and 5 pass MDF + H samples exhibited better erosion (0.0001 mg/g) due to higher hardness. On the other hand, polarisation and electrochemical impedance spectroscopy measurements were used to assess the alloys’ corrosion behaviour. The 3 pass MDF + H sample was found to have a corrosion rate of 0.0235 mm/y, which is two times lower than the counterpart 3 pass MDF processed samples and sixteen times lower than the homogenised sample (0.3838 mm/y). This was primarily due to the secondary phases’ better distribution and smaller grain size. © The Korean Society of Mechanical Engineers and Springer-Verlag GmbH Germany, part of Springer Nature 2024.Item Synthesis and characteristics of Fe/Ni/Cr oxide nanoparticles/PLA hybrid composite coatings on Mg–Zn–Ca alloy(Elsevier Editora Ltda, 2025) Kumar, P.; Kudva S, A.; T, A.; S, R.; Ramesh, M.R.; Prabhu, A.; Anne, G.Biodegradable materials research is dominated by magnesium and alloys thereof due to their excellent compatibility with biological barriers and biomechanical strength. Despite this, the rapid degradation of these materials in the physiological environment is the primary obstacle hindering their utilization in biomedical applications. This issue must be resolved before considering their use in clinical applications. To improve resistance towards corrosion and enhance biological efficacy and compatibility, the surfaces were coated with polylactic acid (PLA) using dip-coating. In this study, iron (Fe), nickel (Ni), and chromium (Cr) oxide nanoparticles from the Coleus amboinicus extract are synthesized and mixed with PLA to develop hybrid composite coatings, which are then applied onto the Mg–4Zn–1Ca alloy. Coleus amboinicus is known for its various medicinal properties, including immunoregulatory effects, antimicrobial activity, anti-inflammatory properties, and potential use in treating sepsis and other ailments. The extracted FeNiCr was used the develop composite coatings on Mg–4Zn–1Ca alloy. The coating improves biocompatibility, antibacterial properties, and overall performance of biomedical implants. These composite coatings were evaluated for their morphological and optical characteristics using a scanning electron microscope (SEM), 3-D non-contact profilometer, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The corrosion characteristics of developed samples were measured by electrochemical corrosion in standard simulation body fluid (SBF) at 37 °C. Furthermore, cytocompatibility of the PLA hybrid composites on osteoblast cells and apoptosis detection using acridine orange-ethidium bromide. Our developed coating showed ratings of 5B and 4B were obtained for FeNiCr/PLA NC- ball burnished (BB) Mg and FeNiCr/PLA nano composite (NC)–Mg samples, respectively, demonstrating the exceptional coating strength and the substrate. The corrosion rate of the FeNiCr/PLA NC-BB-Mg sample (0.02890 mm/y) is two-fold times increased against comparison with the H Mg sample (0.00012 mm/y). Cytocompatibility indicates their cytocompatibility for bone implant applications. © 2025 The Authors