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search.filters.applied.f.access: openAccess × Author: Gebert, Annett × Author: Hariharan, Avinash × Start date: 2020 × DDC: 670 × Type: Article × WGL Institute: IFWD ×

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Now showing 1 - 3 of 3
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    Fabrication of four-level hierarchical topographies through the combination of LIPSS and direct laser interference pattering on near-beta titanium alloy
    (New York, NY [u.a.] : Elsevier, 2022) Schell, Frederic; Alamri, Sabri; Hariharan, Avinash; Gebert, Annett; Lasagni, Andrés Fabián; Kunze, Tim
    Complex repetitive periodic surface patterns were produced on a near-beta Ti-13Nb-13Zr alloy, using two-beam Direct Laser Interference Patterning (DLIP) employing a picosecond-pulsed laser source with wavelengths of 355 nm, 532 nm and 1064 nm. Different types of Laser-induced periodic surface structures (LIPSS) are produced, including low and high spatial frequency LIPSS, which are observed frequently on top of the line-like DLIP microstructures, as well as quasi-periodic microstructures with periods greater than the laser wavelength. The feature size of the fabricated LIPSS features could be tuned as function of the utilized laser process parameters.
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    Novel low modulus beta-type Ti–Nb alloys by gallium and copper minor additions for antibacterial implant applications
    (Rio de Janeiro : Elsevier, 2022) Alberta, Ludovico Andrea; Vishnu, Jithin; Hariharan, Avinash; Pilz, Stefan; Gebert, Annett; Calin, Mariana
    This study aims to develop novel low-modulus, corrosion-resistant Ti-based alloys with enhanced antimicrobial properties for bone-related implant applications. Novel β-type (Ti–45Nb)-based alloys with minor additions of the antibacterial elements Ga and/or Cu (up to 4 wt.%) were produced by a two-step casting process followed by homogenization treatment. Three nominal compositions (Ti–45Nb)96-4 Ga, (Ti–45Nb)96–4Cu and (Ti–45Nb)96-2 Ga–2Cu (wt.%) were prepared based on alloy design approach using [Mo]eq and electron per atom (e/a) ratio. The influence of Ga and/or Cu addition on the phase constitution, mechanical response and corrosion characteristics in simulated body fluids (PBS, 37.5 Â°C) has been investigated. X-ray diffraction studies displayed a single β phase structure for all alloys, with an observed lattice contraction evidenced by the reduction of lattice parameters during Rietveld analysis. Homogenous equiaxed microstructures with grain sizes ranging from 55 Î¼m up to 323 Î¼m were observed for (Ti–45Nb)96-4 Ga, (Ti–45Nb)96-2 Ga–2Cu and (Ti–45Nb)96–4Cu alloys. The alloys displayed excellent plasticity with no cracking, or fracturing during compression tests. Their tensile strength, Young's modulus, maximum tensile strain and elastic energy were measured in the ranges of 544–681 MPa, 73–78 GPa, 17–28% and 2.5–3.7 MJ/m3, in the order (Ti–45Nb)96-4 Ga > (Ti–45Nb)96-2 Ga–2Cu > (Ti–45Nb)96–4Cu. In addition, it has been observed that micro-alloying Ti–Nb alloy with Ga and/or Cu posed no deleterious effect on the corrosion resistance in simulated body fluid conditions. The improvement in strength of the developed alloys has been discussed based on grain boundary and solid-solution strengthening, whereas the improved plasticity is attributed to work hardening.
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    Anelastic-like nature of the rejuvenation of metallic glasses by cryogenic thermal cycling
    (Amsterdam [u.a.] : Elsevier Science, 2022) Costa, Miguel B.; Londoño, Juan J.; Blatter, Andreas; Hariharan, Avinash; Gebert, Annett; Carpenter, Michael A.; Greer, A. Lindsay
    Cryogenic thermal cycling (CTC) is an effective treatment for improving the room-temperature plasticity and toughness in metallic glasses. Despite considerable attention to characterizing the effects of CTC, they remain poorly understood. A prominent example is that, contrary to expectation, the stored energy in a metallic glass first rises, and then decreases, as CTC progresses. In this work, CTC is applied to bulk metallic glasses based on Pd, Pt, Ti, or Zr. The effects on calorimetric and mechanical properties are evaluated. Critically, CTC-induced effects, at whatever stage, are found to decay over about one week at room temperature after CTC, returning the properties to those of the as-cast glass. A model is proposed for CTC-induced effects, treating them as analogous to the accumulation of anelastic strain. The implications for analysis of existing data, and for future research on CTC effects, are highlighted.