Measurements of the production cross-section for a Z boson in association with b- or c-jets in proton–proton collisions at √s = 13 TeV with the ATLAS detector

This paper presents a measurement of the production cross-section of a Z boson in association with bor c-jets, in proton–proton collisions at √s = 13 TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 140 fb−1. Inclusive and differential cross-sections are measured for events containing a Z boson decaying into electrons or muons and produced in association with at least one b-jet, at least one c-jet, or at least two b-jets with transverse momentum pT > 20 GeV and rapidity |y| < 2.5. Predictions from several Monte Carlo generators based on next-to-leading-order matrix elements interfaced with a parton-shower simulation, with different choices of flavour schemes for initial-state partons, are compared with the measured cross-sections. The results are also compared with novel predictions, based on infrared and collinear safe jet flavour dressing algorithms. Selected Z+ ≥ 1 c-jet observables, optimized for sensitivity to intrinsic-charm, are compared with benchmark models with different intrinsic-charm fractions

Martensite decomposition kinetics in additively manufactured Ti-6Al-4 V alloy: in-situ characterisation and phase-field modelling

Additive manufacturing of Ti-6Al-4V alloy via laser powder-bed fusion leads to non-equilibrium ′ martensitic microstructures, with high strength but poor ductility and toughness. These properties may be modified by heat treatments, whereby the ′ phase decomposes into equilibrium + structures, while possibly conserving microstructural features and length scales of the ′ lath structure. Here, we combine experimental and computational methods to explore the kinetics of martensite decomposition. Experiments rely on in-situ characterisation (electron microscopy and diffraction) during multi-step heat treatment from 400 ◦C up to the alloy -transus temperature (995 ◦C). Computational simulations rely on an experimentally-informed computationally-efficient phase-field model. Experiments confirmed that as-built microstructures were fully composed of martensitic ′ laths. During martensite decomposition, nucleation of the phase occurs primarily along ′ lath boundaries, with traces of nucleation along crystalline defects. Phase-field results, using electron backscatter diffraction maps of as-built microstructures as initial conditions, are compared directly with in-situ characterisation data. Experiments and simulations confirmed that, while full decomposition into stable + phases may be complete at 650 ◦C provided sufficient annealing time, visible morphological evolution of the microstructure was only observed for ≥ 700 ◦C, without modification of the prior- grain structure

Sensitivity of austempering heat treatment of ductile irons to changes in process parameters

Austempered ductile iron (ADI) is frequently obtained by means of a three-step austempering heat treatment. The parameters of this process play a crucial role on the microstructure of the final product. This paper considers the influence of some process parameters (i.e., the initial microstructure of ductile iron and the thermal cycle) on key features of the heat treatment (such as minimum required time for austenitization and austempering and microstructure of the final product). A computational simulation of the austempering heat treatment is reported in this work, which accounts for a coupled thermo-metallurgical behavior in terms of the evolution of temperature at the scale of the part being investigated (the macroscale) and the evolution of phases at the scale of microconstituents (the microscale). The paper focuses on the sensitivity of the process by looking at a sensitivity index and scatter plots. The sensitivity indices are determined by using a technique based on the variance of the output. The results of this study indicate that both the initial microstructure and the thermal cycle parameters play a key role in the production of ADI. This work also provides a guideline to help selecting values of the appropriate process parameters to obtain parts with a required microstructural characteristic.Fil: Boccardo, Adrian Dante. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Departamento de Ingeniería Mecanica; ArgentinaFil: Dardati, Patricia Mónica. Universidad Tecnológica Nacional; ArgentinaFil: Godoy, Luis Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados en Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Estudios Avanzados en Ingeniería y Tecnología; ArgentinaFil: Celentano, Diego(EXT). Pontificia Universidad Católica de Chile; Chil

A Microscale Model for Ausferritic Transformation of Austempered Ductile Irons

This paper presents a new metallurgical model for the ausferritic transformation of ductile cast iron. The model allows predicting the evolution of phases in terms of the chemical composition, austenitization and austempering temperatures, graphite nodule count, and distribution of graphite nodule size. The ferrite evolution is predicted according to the displacive growth mechanism. A representative volume element is employed at the microscale to consider the phase distributions, the inhomogeneous austenite carbon content, and the nucleation of ferrite subunits at the graphite nodule surface and at the tips of existing ferrite subunits. The performance of the model is evaluated by comparison with experimental results. The results indicate that the increment of the ausferritic transformation rate, which is caused by increments of austempering temperature and graphite nodule count, is adequately represented by this model.Fil: Boccardo, Adrian Dante. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Departamento de Ingeniería Mecanica; ArgentinaFil: Dardati, Patricia Mónica. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Departamento de Ingeniería Mecanica; ArgentinaFil: Celentano, Diego J.. Universidad Católica de Chile; ChileFil: Godoy, Luis Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados En Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias exactas Físicas y Naturales. Instituto de Estudios Avanzados En Ingeniería y Tecnología; Argentin