Critical Assessment of Two-Dimensional Methods for the Microstructural Characterization of Cemented Carbides

Cemented carbides, or hard metals, are ceramic–metal composites usually consisting of tungsten carbide particles bound by a cobalt-based alloy. They are the backbone materials for the tooling industry, as a direct consequence of the outstanding range of property combinations, depending on their effective microstructural assemblage, i.e., the physical dimensions and relative content of their constitutive phases. Hence, reliable microstructural characterization becomes key for hard metal grade selection and quality control. This work aimed to assess the practical twodimensional characterization methods for the most important one- and two-phase properties of cemented carbides, i.e., the carbide grain size, phase fraction, carbide contiguity, and binder mean free path. Three different methods—point, line, and area analysis—were implemented to characterize four microstructurally distinct grades. The images were acquired by optical and scanning electron microscopy, with the latter through both secondary and backscattered electrons. Results were critically discussed by comparing the obtained values of properties and the different characterization methodology. Inspection technique combinations were finally ranked based on accuracy, accessibility, and operability considerations. The line method was used to analyze all the properties, the area method, for the one-phase properties, and the point method, for only the phase fraction. It was found that the combination of optical microscopy and the line analysis method was suitable for a direct inspection and rapid estimation for carbides above fine grain size. The most precise results were achieved using line analysis of the images obtained by the backscattered electrons of the scanning electron microscope

Surface patterning of cemented carbides by means of nanosecond laser

A nanosecond laser combined with a two-axis reflection control unit is used to shape polygonal pyramids with defined geometry on a specific cemented carbide grade. In total, 12 different surface patterns have been fabricated, including four pyramid shapes, i.e., triangle, square, hexagon and octagon, and three lateral side angles, i.e., 30°, 45° and 60°. Characterization of the geometrical features shows satisfactory agreement between produced patterns and aimed ones. The precision is improved when the number of polygon sides and/or both side and slope angles increase. Side effects, such as re-deposition, cracks and pores, were discerned through scanning electron microscopy inspection. They become less obvious when the polygon side length or side angle increases, as the material melting becomes less important. Based on the observations, a borderline curve can be plotted for describing the production capability of such surface patterns on cemented carbides using the laser technologyPostprint (author's final draft

Critical assessment of two-dimensional methods for the microstructural characterization of cemented carbides

Cemented carbides, or hard metals, are ceramic–metal composites usually consisting of tungsten carbide particles bound by a cobalt-based alloy. They are the backbone materials for the tooling industry, as a direct consequence of the outstanding range of property combinations, depending on their effective microstructural assemblage, i.e., the physical dimensions and relative content of their constitutive phases. Hence, reliable microstructural characterization becomes key for hard metal grade selection and quality control. This work aimed to assess the practical twodimensional characterization methods for the most important one- and two-phase properties of cemented carbides, i.e., the carbide grain size, phase fraction, carbide contiguity, and binder mean free path. Three different methods—point, line, and area analysis—were implemented to characterize four microstructurally distinct grades. The images were acquired by optical and scanning electron microscopy, with the latter through both secondary and backscattered electrons. Results were critically discussed by comparing the obtained values of properties and the different characterization methodology. Inspection technique combinations were finally ranked based on accuracy, accessibility, and operability considerations. The line method was used to analyze all the properties, the area method, for the one-phase properties, and the point method, for only the phase fraction. It was found that the combination of optical microscopy and the line analysis method was suitable for a direct inspection and rapid estimation for carbides above fine grain size. The most precise results were achieved using line analysis of the images obtained by the backscattered electrons of the scanning electron microscopeThe work leading to this publication was supported by the Feodor Lynen Research Fellowship of the Alexander von Humboldt Foundation, by the individual research grant from the Deutsche Forschungsgemeinschaft (DFG-425923019), by the Spanish Ministerio de Ciencia e Innovación MICINN-FEDER (Spain) through grant PID2019-106631GB-C41 (AEI/10.13039/501100011033), and by the “Open Access Publication Funding” program of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) and Saarland University. The work also obtained funding for the FIB/SEM instrument used for SEM imaging and EBSD by the Deutsche Forschungsgemeinschaft (INST 256/510-1 FUGG)Postprint (published version

La educación híbrida en centros de secundaria catalanes: La competencia digital como variable clave

The COVID-19 pandemic had an impact on compulsory formal education and various responses were given to the lack of face-to-face attendance: from the most improvised (emergency remote teaching model) to more informed practices of digital education, such as the hybrid educational model. This non experimental, descriptive-inferential study aims to investigate whether the self-perceived digital teaching skills (SDTS) by teachers (n=346) and the self-perceived digital skills (SDS) by students (n=1322) and families (n=531) from 15 secondary education schools in Catalonia are related to variables of virtual/online education in the model of hybrid education: teaching and learning activities; assessment proposals; aids provided and received to promote learning. A specific online questionnaire was prepared for each group of participants. The results indicate that a high level of SDTC by teachers is related to more innovative methodological and assessment proposals (projects, formative assessment), and in the case of students, with a better predisposition to learn online, while in families we found no relationship between the SDS and the help received and provided to their children. The conclusions point to the need to promote a higher level of digital teaching skills in teachers, to guarantee more suitable hybrid educatio The COVID-19 pandemic had an impact on compulsory formal education and various responses were given to the lack of face-to-face attendance: from the most improvised (emergency remote teaching model) to more informed practices of digital education, such as the hybrid educational model. This non-experimental, descriptive-inferential study aims to investigate whether the self-perceived digital teaching skills (SDTS) by teachers (n=346) and the self-perceived digital skills (SDS) by students (n=1322) and families (n=531) from 15 secondary education schools in Catalonia are related to variables of virtual/online education in the model of hybrid education: teaching and learning activities; assessment proposals; aid provided and received to promote learning. A specific online questionnaire was prepared for each group of participants. The results indicate that a high level of SDTC by teachers is related to more innovative methodological and assessment proposals, and, in the case of students, their SDS are related with a better predisposition to learn online, while in families we found no relationship between the SDS and the help received and provided to their children. The conclusions point to the need to promote a higher level of digital teaching skills in teachers to guarantee more suitable hybrid education practices and to foster digital competences in students. n practices and to foster digital competences in students.La pandemia de COVID-19 impactó en la educación formal obligatoria y se dieron diversas respuestas a la privación de presencialidad, desde improvisadas (modelo de enseñanza remota de emergencia) hasta prácticas más informadas de educación digital, como el modelo de educación híbrida. Este estudio no experimental, descriptivo-inferencial pretende indagar si la Competencia Digital Docente Autopercibida (CDDA) del profesorado (n=346) y la Competencia Digital Autopercibida (CDA) del alumnado (n=1322) y de las familias (n=531) de 15 centros de educación secundaria de Cataluña está relacionada con aspectos relevantes de la educación online en el modelo de educación híbrida: actividades de enseñanza y aprendizaje; propuestas de evaluación, y ayudas al aprendizaje. Se elaboró un cuestionario online para cada colectivo. Los resultados indican que una alta CDDA está relacionada con propuestas metodológicas y evaluativas innovadoras y, en el caso del alumnado, su CDA se relaciona con una mejor predisposición a aprender online, mientras que no encontramos relación entre la CDA de las familias y las ayudas recibidas y proporcionadas a sus hijos e hijas. Las conclusiones señalan la necesidad de fomentar la competencia digital entre el profesorado para contribuir a la propuesta de prácticas educativas híbridas más adecuadas que, a su vez, fomenten las competencias digitales del alumnado

Resistencia mecánica de carburos cementados: influencia de la temperatura y la microestructura

En esta investigación se ha evaluado el efecto de la temperatura en la resistencia mecánica de carburos cementados (WC-Co) con diferente camino libre medio de la fase ligante. La misma se determinó a 600°C con discos ensayados en flexión biaxial (3B3). Se determina la resistencia y el módulo de Weibull y se comparan con los valores obtenidos a temperatura ambiente. Se ha realizado un análisis fractográfico detallado para intentar discernir la naturaleza y el tamaño de los defectos que originan la rotura, así como los mecanismos responsables de ésta. Los resultados se discuten y racionalizan en el marco de la mecánica de la fractura elástica lineal, prestando atención al efecto de la temperatura y la microestructura en la fiabilidad mecánica. Adicionalmente, el número de fragmentos de las probetas rotas y la superficie de fractura macroscópica también se han relacionado con la resistencia mecánica y la tenacidad de fractura de los WC-Co investigados.Postprint (published version

Innovación docente: el análisis de casos en orientación

Podeu consultar el document complet a: http://diposit.ub.edu/dspace/handle/2445/65797Este proyecto (2012PID-UB/136) se ha centrado en el estudio, profundización e implementación de la metodología del caso en las diferentes asignaturas del área de orientación de los estudios de grado y de máster de la Facultad de Pedagogía de la Universidad de Barcelona. El dominio de esta metodología, por parte de los estudiantes, fomenta y facilita el desarrollo de competencias transversales que constituyen una herramienta significativa en el proceso de aprendizaje y evaluación. El desarrollo del proyecto ha favorecido la reflexión de los docentes implicados en el proyecto, la selección de las estrategias más adecuadas para la puesta en práctica de la metodología del caso en orientación y, la elaboración, adecuación y evaluación de materiales docentes ya usados. Además, ha dado lugar a la construcción conjunta de un nuevo material docente que lleva por título: “Metodología del caso en orientación”, y que será publicado próximamente

High levels of standardized ileal digestible amino acids improve feed efficiency in slow- growing pigs at late grower- finisher stage

Publication history: Accepted - 4 July 2021; Published online - 6 March 2022.Slow-growing pigs negatively affect production efficiency in conventional pig farms by increasing the occupation time of the facilities and being a limiting factor for the All-In/All-Out swine production systems. This subset of pigs is usually managed with the rest of the pigs, and their nutrient requirements may not be fulfilled. The purpose of the present study was to compare the productive performance of slow- and fast-growing pigs to different standardized ileal digestible (SID) amino acids (AA) dietary levels at late grower–finisher stage. A total of 84 pigs were weighed, tagged, and classified as slow-growing (SG; n = 48; 24.1 ± 1.38 kg) or fast-growing pigs (FG; n = 36; 42.7 ± 1.63 kg) at 11 weeks of age. Pigs were housed in mixed sex pens (n = 8 SG+6 FG/pen) equipped with feeding stations to record daily feed intake per individual pig. Pigs were assigned to three dietary treatments resulting in a 2 × 3 factorial arrangement at 15 weeks of age. Isoenergetic diets were formulated by increasing the ideal protein profile based on the following SID lysine (Lys) levels: 0.92%, 1.18% and 1.45%. Pigs were weighed bi-weekly until 21 weeks of age. Fast-growing pigs were 33.7 kg heavier, gained 255 g/day and consumed 625.5 g/day more than SG pigs (p 0.05). However, feed conversion ratio was 0.3 lower for SG pigs fed 1.45% SID Lys/AA compared to SG pigs fed 0.92% SID Lys/AA (p = 0.002). Feed conversion ratio was not different within the FG pigs’ dietary treatments (p > 0.05). The efficiency of SG pigs may be improved when dietary SID AA levels are increased from 0.92 up to 1.45% SID Lys/AA. Thus, nutrient requirements may vary depending on growth rate at the same age, and SG pigs may require higher dietary SID AA levels than FG pigs to achieve similar productive performance.Teagasc Walsh Scholarship. Grant Number: 0415, Open access funding provided by IReL WOA Institution: Irish Agriculture and Food Development Authority Blended DEAL: IRe