Browsing by Author "Achar, B."

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    Microstructural, electrochemical and immersion based corrosion analysis in milling induced magnesium alloy AZ91
    (Russian Association of Corrosion Engineers, 2024) Marakini, V.; Pai, S.; Achar, B.; Sahoo, B.; Bhat K, U.; Devadiga, R.; Rao, S.; Swamy, M.; Mesta, R.
    Present work discusses the effect of face milling operations on the corrosion characteristics of AZ91 alloy. A full factorial L27 design of experiment is prepared and face milling is performed to identify the optimal conditions with lowest roughness. The optimal surface of the alloy obtained from face milling has been compared with the slightly polished surface of as-cast alloy using weight loss and electrochemical polarization testing methods using 3.5% NaCl solution. In weight loss method, the alloy surfaces are solution treated for various time intervals ranging from 0.5 to 72 hours, to study the effect of surface finish obtained from face milling in comparison to polishing (as-cast). Whereas, in polarization method, the tests are conducted for only 0.5 hour on both specimens and compared. The corrosion rates are found to be in direct relation to the surface roughness, as the low roughness surface from face milling showed comparatively low corrosion rate. The polarization curves justified the better corrosion resistance of milled surface when compared to polished surface. Further, FESEM micrograph comparison between the before and after polarization test surfaces showed the severity of corrosion attack in both tested surfaces. Furthermore, the elemental analysis using EDAX test on the before and after polarization test surfaces showed the presence of less oxygen in the milled surface compared to polished surface, which established the better corrosion resistance of milled surfaces which has low surface roughness. © 2024, Russian Association of Corrosion Engineers. All rights reserved.
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    Surface integrity investigation and VIKOR optimisation during the milling of aluminium–lithium alloy using uncoated and PVD-coated carbide tools
    (Taylor and Francis Ltd., 2024) Marakini, V.; Pai, S.P.; Bhat K, U.K.; Thakur, D.; Achar, B.
    In this study, the effect of face milling on the surface integrity of an aluminium–lithium alloy is investigated through an L27 Taguchi design of experiments. Uncoated and PVD-coated carbide inserts are used to investigate the material surface characteristics such as roughness, microhardness, microstructure and residual stresses. Both inserts showed their ability in achieving a better surface finish (Ra ∼ 0.04 µm) than the raw material (Ra ∼ 0.52 µm). Hardness improvement of up to 216.7 HV (uncoated) and 229.3 HV (PVD-coated) from the raw material (180.7 HV) surface is observed. Both inserts showed their ability to generate compressive residual stresses with uncoated inserts producing stresses on the surface. Microstructural changes from milling using both inserts are observed to be minimal. ANOVA showed the effect of process parameters on the surface roughness and microhardness. Furthermore, VIKOR statistical analysis technique is used to identify the optimal conditions for good roughness and microhardness of the alloy. © 2023 Canadian Institute of Mining, Metallurgy and Petroleum.