104 research outputs found

    Dataset concerning the analytical approximation of the Ae3 temperature.

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    In this paper we present a new polynomial function for calculating the local phase transformation temperature (Ae3 ) between the austenite+ferrite and the fully austenitic phase fields during heating and cooling of steel:[Formula: see text] The dataset includes the terms of the function and the values for the polynomial coefficients for major alloying elements in steel. A short description of the approximation method used to derive and validate the coefficients has also been included. For discussion and application of this model, please refer to the full length article entitled "The role of aluminium in chemical and phase segregation in a TRIP-assisted dual phase steel" 10.1016/j.actamat.2016.05.046 (Ennis et al., 2016) [1]

    Position-dependent shear-induced austenite-martensite transformation in double-notched TRIP and dual-phase steel samples

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    While earlier studies on transformation-induced-plasticity (TRIP) steels focused on the determination of the austenite-to-martensite decomposition in uniform deformation or thermal fields, the current research focuses on the determination of the local retained austenite-to-martensite transformation behaviour in an inhomogeneous yet carefully controlled shear-loaded region of double-notched TRIP and dual-phase (DP) steel samples. A detailed powder analysis has been performed to simultaneously monitor the evolution of the phase fraction and the changes in average carbon concentration of metastable austenite together with the local strain components in the constituent phases as a function of the macroscopic stress and location with respect to the shear band. The metastable retained austenite shows a mechanically induced martensitic transformation in the localized shear zone, which is accompanied by an increase in average carbon concentration of the remaining austenite due to a preferred transformation of the austenite grains with the lowest carbon concentration. At the later deformation stages the geometry of the shear test samples results in the development of an additional tensile component. The experimental strain field within the probed sample area is in good agreement with finite element calculations. The strain development observed in the low-alloyed TRIP steel with metastable austenite is compared with that of steels with the same chemical composition containing either no austenite (a DP grade) or stable retained austenite (a TRIP grade produced at a long bainitic holding time). The transformation of metastable austenite under shear is a complex interplay between the local microstructure and the evolving strain fields

    Magnetocrystalline effects on the subsurface hydrogen diffusion in Îł-Fe(001)

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    The effect of magnetism on hydrogen adsorption and subsurface diffusion through face-centred cubic (fcc) Îł-Fe(001) was investigated using spin-polarised density functional theory (s-DFT). The non-magnetic (NM), ferromagnetic (FM), and antiferromagnetic single (AFM1) and double layer (AFMD) structures were considered. For each magnetic state, the hydrogen preferentially adsorbs at the fourfold site, with adsorption energies of 4.07, 4.12, 4.03 and 4.05 eV/H atom for the NM, FM, AFM1 and AFMD structures. A total barrier of 1.34, 0.90, 1.32 and 1.25 eV and a bulk-like diffusion barrier of 0.6, 0.2, 0.4 and 0.3 eV were calculated for the NM, FM, AFM1 and AFMD magnetic states. The Fe atoms nearest to the H atom exhibited a reduced magnetic moment, whereas the next-nearest neighbour Fe atoms exhibited a non-negligible local perturbation in the magnetic moment. The presence of magnetically ordered structures has a minimal influence on the minimum energy path for H diffusion through the lattice and on the adsorption of H atoms on the Fe(001) surface, but we computed a significant reduction of the bulk-like diffusion barriers with respect to the non-magnetic state of fcc Îł-Fe

    Atomically resolved chemical ordering at the nm-thick TiO precipitate/matrix interface in V-4Ti-4Cr alloy

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    We have used advanced analytical electron microscopy to characterise the local structure and chemistry at the interface between nm-thick TiO precipitates and the V-based matrix in a V-4Ti-4Cr alloy. Our results reveal the presence of an intergrowth between the fcc TiO and bcc vanadium structures, with a repeat lattice distance that equals 2.5 times the vanadium lattice parameter along the c-axis. Our atomic resolution analysis of the interface will impact the mechanistic understanding of its interaction with interstitials and radiation-induced lattice defects, and consequently trigger the development of improved alloy structures with interfaces engineered for enhanced radiation tolerance

    Metastable austenite driven work-hardening behaviour in a TRIP-assisted dual phase steel

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    The mechanically-induced transformation behaviour of the metastable austenite phase in a high-strength industrial TRIP-assisted Dual Phase steel was monitored in situ using high-energy synchrotron diffraction under uniaxial loading. This allowed direct quantification of the impact of the transformation of the metastable austenite phase (16 vol %), embedded in a ferrite-bainite-martensite matrix, on the work hardening behaviour of this steel. Our results show that the mechanically induced transformation of austenite does not begin until the onset of matrix yielding. We provide experimental evidence which demonstrates for the first time that the austenite transformation increases the work-hardening contribution, σw thereby supporting a driving force approach to transformation induced plasticity. The transformation work required leads to an increase in the macroscopic work-hardening rate after matrix yielding and continues to offset the decrease in the work-hardening rate in the ferrite and martensite phases up to the UTS. Further we show conclusively that martensite yielding does not occur until the completion of the mechanically induced transformation of austenite. Plastic deformation of martensite is immediately followed by local plastic instability leading to necking and ultimate failure of this material

    Martensitic transformation of individual grains in low-alloyed TRIP steels

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    We have performed in situ synchrotron X-ray diffraction experiments on low-alloyed multiphase TRIP steels during cooling, to monitor the martensitic transformation of individual austenite grains within the bulk material. Direct experimental evidence is presented that the stability of the austenite grains is controlled not only by the local carbon level but also by the grain size. This new quantitative information on the martensitic transformation in complex microstructures is of great importance for the design of martensite-based metallic materials.</p

    Characterization of individual retained austenite grains and their stability in low-alloyed TRIP steels

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    In situ three-dimensional (3-D) X-ray diffraction experiments have been performed at a synchrotron source on low-alloyed multiphase TRIP steels containing 0.25 wt.% Si and 0.44 wt.% Al and produced with different bainitic holding times, in order to assess the influence of the bainitic transformation on the thermal stability of individual austenite grains with respect to their martensitic transformation. A detailed characterization of the austenite grain volume distribution at room temperature was performed as a function of the prior bainitic holding time. In addition, the martensitic transformation behaviour of individual metastable grains was studied in situ during cooling to a temperature of 100 K. Both the carbon content and the grain volume play a key role in the stability of the austenite grains below 15 ÎŒm3, while the carbon content exerts the dominant effect in the stability of the bigger grains. Measurements also suggest that the tetragonality of the thermally formed martensite is suppressed.</p

    Eleven-month longitudinal study of antibodies in SARS-CoV-2 exposed and naĂŻve primary health care workers upon COVID-19 vaccination

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    We evaluated the kinetics of antibody responses to Two years into the COVID-19 pandemic and 1 year after the start of vaccination rollout, the world faced a peak of cases associated with the highly contagious Omicron variant of concern (VoC) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) and nucleocapsid (N) antigens over five cross-sectional visits (January-November 2021), and the determinants of pre-booster immunoglobulin levels, in a prospective cohort of vaccinated primary health care workers in Catalonia, Spain. Antibodies against S antigens after a full primary vaccination course, mostly with BNT162b2, decreased steadily over time and were higher in pre-exposed (n = 247) than naive (n = 200) individuals, but seropositivity was maintained at 100% (100% IgG, 95.5% IgA, 30.6% IgM) up to 319 days after the first dose. Antibody binding to variants of concern was highly maintained for IgG compared to wild type but significantly reduced for IgA and IgM, particularly for Beta and Gamma. Factors significantly associated with longer-term antibodies included age, sex, occupation, smoking, adverse reaction to vaccination, levels of pre-vaccination SARS-CoV-2 antibodies, interval between disease onset and vaccination, hospitalization, oxygen supply, post COVID and symptomatology. Earlier morning vaccination hours were associated with higher IgG responses in pre-exposed participants. Symptomatic breakthroughs occurred in 9/447 (2.01%) individuals, all among naive (9/200, 4.5%) and generally boosted antibody responses. Additionally, an increase in IgA and/or IgM seropositivity to variants, and N seroconversion at later time points (6.54%), indicated asymptomatic breakthrough infections, even among pre-exposed. Seropositivity remained highly stable over almost a year after vaccination. However, gradually waning of anti-S IgGs that correlate with neutralizing activity, coupled to evidence of an increase in breakthrough infections during the Delta and Omicron predominance, provides a rationale for booster immunization

    Thermal Evolution of the Proton Irradiated Structure in Tungsten–5 wt% Tantalum

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    We have monitored the thermal evolution of the proton irradiated structure of W–5 wt% Ta alloy by in-situ annealing in a transmission electron microscope at fusion reactor temperatures of 500–1300 °C. The interstitial-type a/2 dislocation loops emit self-interstitial atoms and glide to the free sample surface during the early stages of annealing. The resultant vacancy excess in the matrix originates vacancy-type a/2 dislocation loops that grow by loop and vacancy absorption in the temperature range of 600–900 °C. Voids form at 1000 °C, by either vacancy absorption or loop collapse, and grow progressively up to 1300 °C. Tantalum delays void formation by a vacancy-solute trapping mechanism

    The interplay between functioning problems and symptoms in first episode of psychosis: an approach from network analysis

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    The relationship between psychotic symptoms and global measures of functioning has been widely studied. No previous study has assessed so far the interplay between specific clinical symptoms and particular areas of functioning in first-episode psychosis (FEP) using network analysis methods. A total of 191 patients with FEP (age 24.45 ± 6.28 years, 64.9% male) participating in an observational and longitudinal study (AGES-CM) comprised the study sample. Functioning problems were assessed with the WHO Disability Assessment Schedule (WHODAS), whereas the Positive and Negative Syndrome Scale (PANSS) was used to assess symptom severity. Network analysis were conducted with the aim of analysing the patterns of relationships between the different dimensions of functioning and PANSS symptoms and factors at baseline. According to our results, the most important nodes were “conceptual disorganization”, “emotional withdrawal”, “lack of spontaneity and flow of conversation”, “delusions”, “unusual thought content”, “dealing with strangers” and “poor rapport”. Our findings suggest that these symptoms and functioning dimensions should be prioritized in the clinical assessment and management of patients with FEP. These areas may also become targets of future early intervention strategies, so as to improve quality of life in this populationThis work was supported by the Madrid Regional Government (R&D activities in Biomedicine (grant number S2017/BMD-3740 - AGES-CM 2-CM)) and Structural Funds of the European Union. Ana Izquierdo’s work is supported by the PFIS predoctoral program (FI17/00138) from the Instituto de Salud Carlos III (Spain) and co-funded by the European Union (ERDF/ESF, "A way to make Europe”/ “Investing in your future”) and The Biomedical Research Foundation of La Princesa University Hospital. Angela IbÂŽa˜nez thanks the support of CIBERSAM and of the Spanish Ministry of Science, Innovation and Universities. Instituto de Salud Carlos III (PI16/00834 and PI19/01295) co-financed by ERDF Funds from the European Commission. Covadonga M. DĂ­az-Caneja holds a Juan RodÂŽes Grant from Instituto de Salud Carlos III (JR19/00024). Celso Arango was supported by the Spanish Ministry of Science and Innovation. Instituto de Salud Carlos III (SAM16PE07CP1, PI16/02012, PI19/ 024), co-financed by ERDF Funds from the European Commission, “A way of making Europe”, CIBERSAM. Madrid Regional Government (B2017/BMD-3740 AGES-CM-2), European Union Structural Funds. European Union Seventh Framework Program under grant agreements FP7-4-HEALTH-2009-2.2.1-2-241909 (Project EU-GEI), FP7- HEALTH- 2013-2.2.1-2-603196 (Project PSYSCAN) and FP7- HEALTH-2013- 2.2.1-2-602478 (Project METSY); and European Union H2020 Program under the Innovative Medicines Initiative 2 Joint Undertaking (grant agreement No 115916, Project PRISM, and grant agreement No 777394, Project AIMS-2-TRIALS), FundaciÂŽon Familia Alonso, FundaciÂŽon Alicia Koplowitz and FundaciÂŽon Mutua Madrile˜n
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