Journal Articles

Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884

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Author: search.filters.author.Sekar, P.Subject: search.filters.subject.Crystallographic textures

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    Bio-corrosion impacts on mechanical integrity of ZM21 Mg for orthopaedic implant application processed by equal channel angular pressing
    (Springer, 2021) Sekar, P.; Nyahale, M.B.; Naik, G.M.; Narendranath, N.; Prabhu, A.; Rekha, P.D.
    The mechanical integrity of rolled ZM21 Mg was improved by equal channel angular pressing (ECAP) to function as a potential biodegradable bone screw implant. Electron backscattered diffraction (EBSD) revealed deformed grains of 45 µm observed in rolled ZM21 Mg. They were transformed to equiaxed fine grains of 5.4 µm after 4th pass ECAP. The yield strength of rolled and ECAPed ZM21 Mg alloys were comparable. In contrast, 4th pass ZM21 Mg exhibited relatively higher elongation when compared to rolled sample. The mechanical properties of rolled and ECAPed ZM21 Mg were dependant on both grain refinement and crystallographic texture. The rolled and 4th pass ECAPed tensile samples exhibited nonlinear deterioration of mechanical properties when tested after 7, 14, 21 and 28 days immersion in Hank’s solution. The evaluation signifies that regardless their processing condition, ZM21 Mg alloys are suitable for surgical areas that requires high mechanical strength. In addition, the 4th pass ECAP samples were viable to MG-63 cells proving themselves to be promising candidates for future in vivo studies. [Figure not available: see fulltext.] © 2021, The Author(s).
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    A study on the effect of process parameters and scan strategies on microstructure and mechanical properties of laser directed energy deposited IN718
    (Elsevier Ltd, 2023) Thanumoorthy, R.S.; Sekar, P.; Bontha, S.; Balan, A.S.S.
    The present study focuses on understanding the effect of scan strategy on the microstructure and mechanical properties of LDED fabricated IN718 built at optimized process conditions from single track analysis. Initially, single track studies were conducted by varying laser power, scan speed, and feed rate (3 levels) to optimize process parameters for bulk deposition. Based on the dilution, aspect ratio, track continuity and melt pool shape, best process parameter were chosen for depositing bulk structures. Bulk rectangular specimens were fabricated using the LDED process for different infill rotation (0°, 45°, 67°, and 90°) at optimized process conditions. Infill rotation did not show any significant change in the density of the samples. However, grain size measurement from EBSD and SEM micrographs revealed a substantial difference in grain size between samples without infill rotation (0°) and samples with infill rotation (45°, 67°, and 90°). XRD and EDS mapping revealed higher the formation of secondary laves phases with infill rotation as a result of higher cooling rate. Similarly, melt pool shape and arrangement showed significant variation with different infill angles. Samples with 0° and 90° infill rotation exhibited strong crystallographic texture along the build direction. There was a significant variation in the microhardness and tensile strength of the build with variation in infill rotation. This variation in mechanical properties were attributed to grain size, LAGB's fraction, secondary phases, and crystallographic texture. © 2023 Elsevier B.V.