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Author: search.filters.author.Bontha, S.Subject: search.filters.subject.Anisotropy

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    Effect of Build Orientation on Anisotropy in Tensile Behavior of Laser Powder Bed Fusion Fabricated SS316L
    (Springer, 2024) Thanumoorthy, R.S.; Chaurasia, J.K.; Anil Kumar, V.A.; Pradeep, P.I.; Balan, A.A.S.; Rajasekaran, B.; Sahu, A.; Bontha, S.
    In the present study, Stainless steel 316L (SS316L) cylindrical specimens were fabricated at two different build orientations and two different laser powers using Laser powder bed fusion process (LPBF). Microstructural characterization such as XRD, SEM, EBSD analysis and tensile testing were carried out on fabricated specimens in stress relieved condition to understand the anisotropic behavior of LPBF printed specimens. Horizontally oriented specimens showed higher tensile strength when compared to vertically oriented specimens for both laser powers. XRD and EBSD phase maps did not reveal the presence of any secondary phases. However, build orientation and laser power affected the crystallite size of the samples. Bimodal grain structure comprising coarse columnar grains and fine equiaxed grains were observed from the micrographs. With variation in build orientation, there was a significant change in the average grain size of the specimens. High dislocation density was observed in horizontally oriented samples built at low laser power because of dislocation annihilation that can occur at high temperatures. However, EBSD analysis revealed random weak crystallographic texture which does not vary significantly with laser power or build orientation. Variation in grain size, grain morphology, sub-grain features and dislocation density are the reasons for the anisotropic tensile behavior observed in LPBF printed SS316L coupons in stress relieved condition. © ASM International 2023.
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    Influence of bulk post processing techniques on anisotropy of microstructural and tribological properties of L-DED produced Ti64 alloy
    (Elsevier Ltd, 2025) Suresh, S.; Joshy, J.; Kuriachen, B.; Gurugubelli, R.C.; Kumar, V.; Bontha, S.
    Laser-Direct Energy Deposited (L-DED) Ti64 alloy is known to have high anisotropy, and low wear resistance which reduce the longevity of artificial bone joints. Thus, the primary objective of this study is to compare and contrast the effect of bulk treatments to mitigate these inherent limitations. Keeping printing parameters constant, the printed samples were put through different post-treatments, namely, super-? annealing (1050 °C, 1 h) and deep cryogenic dipping (?196 °C, 48 h). Electron back scatter diffraction (EBSD) and x-ray diffraction (XRD) analysis revealed differences in grain morphology and phase distributions in the treated samples. A linear reciprocating wear test is conducted with Al2O3 as the counter body to mimic the artificial hip socket. The super-? annealing process reduced the anisotropy in wear rate from 76 % to 60 % but did not show an overall betterment. On the other hand, the cryo-treatment showed an 83 % reduction in wear and a slight reduction in anisotropy compared to the as-build sample. The coefficient of friction (COF) plots also displayed an increase for annealed samples (15.4%–31.5 % higher) while showing a major reduction in cryo-treated samples (42.8%–54.7 % reduction). © 2025 Elsevier B.V.