21 research outputs found
Microestructura y comportamiento mecánico de la aleación Ti-6AI-4V procesada mediante fabricación aditiva de lecho de polvo Electron Beam Melting
No full text171 p.En este trabajo se han estudiado la relación de algunas variables de fabricación para la aleación de titanio Ti-6Al-4V fabricado por el proceso de fabricación aditiva electron beam melting (EBM) y las características y propiedades intrínsecas del material resultante. La microestructura propia, obtenida por el proceso EBM, ha sido modificada mediante tratamientos térmicos basados en tres enfoques estudiando el efecto de varias velocidades de enfriamiento después de un tratamiento de recocido ß, el efecto de la temperaturas y tiempos de recocido en los espesores de las láminas ¿, y de parámetros de envejecimiento, tiempo y temperatura, tras un proceso de solubilización y temple al agua. Se han establecido una serie de correlaciones que relacionan el espesor de la lámina ¿ y las propiedades mecánicas del material. Se ha desarrollado una comprensión fundamental de los mecanismos de crecimiento de grietas por fatiga en relación con la microestructura direccional del EBM Ti-6Al-4V. Para ello se ha estudiado la propagación de grietas en dirección paralela y perpendicular a la dirección de fabricación del proceso EBM, para diferentes relaciones de tensión y etapas del proceso de crecimiento de grietas. Se ha investigado la interacción entre la microestructura direccional EBM y se ha comparado con la interacción de la microestructura recocida ß equiaxial obtenida tras un recocido por encima de la temperatura ß transus. Finalmente, también se ha realizado una comparación de microestructura, propiedades mecánicas y propiedades de fatiga entre el proceso EBM y el proceso LMD para el material Ti-6Al-4V.Tecnali
Microestructura y comportamiento mecánico de la aleación Ti-6AI-4V procesada mediante fabricación aditiva de lecho de polvo Electron Beam Melting
No full text171 p.En este trabajo se han estudiado la relación de algunas variables de fabricación para la aleación de titanio Ti-6Al-4V fabricado por el proceso de fabricación aditiva electron beam melting (EBM) y las características y propiedades intrínsecas del material resultante. La microestructura propia, obtenida por el proceso EBM, ha sido modificada mediante tratamientos térmicos basados en tres enfoques estudiando el efecto de varias velocidades de enfriamiento después de un tratamiento de recocido ß, el efecto de la temperaturas y tiempos de recocido en los espesores de las láminas ¿, y de parámetros de envejecimiento, tiempo y temperatura, tras un proceso de solubilización y temple al agua. Se han establecido una serie de correlaciones que relacionan el espesor de la lámina ¿ y las propiedades mecánicas del material. Se ha desarrollado una comprensión fundamental de los mecanismos de crecimiento de grietas por fatiga en relación con la microestructura direccional del EBM Ti-6Al-4V. Para ello se ha estudiado la propagación de grietas en dirección paralela y perpendicular a la dirección de fabricación del proceso EBM, para diferentes relaciones de tensión y etapas del proceso de crecimiento de grietas. Se ha investigado la interacción entre la microestructura direccional EBM y se ha comparado con la interacción de la microestructura recocida ß equiaxial obtenida tras un recocido por encima de la temperatura ß transus. Finalmente, también se ha realizado una comparación de microestructura, propiedades mecánicas y propiedades de fatiga entre el proceso EBM y el proceso LMD para el material Ti-6Al-4V.Tecnali
Microstructure Evolution, Tensile Properties, and Fatigue Damage Mechanisms in Ti-6Al-4V Alloys Fabricated by Two Additive Manufacturing Techniques
No full textAbstractAdditive Manufacturing (AM) technology is capable of building 3D near-net-shaped functional parts directly from computer models, using unit materials, such as powder or wire. AM offers superior geometrical flexibility with significantly reduced manufacturing lead time, energy, and material waste. These benefits make AM desirable for critical transportation applications, providing that structural integrity and performance requirements are met or exceeded. In this study, structural materials fabricated by two AM techniques were investigated: Laser Engineered Net Shaping (LENS) and Electron Beam Melting (EBM). Ti-6Al-4V alloys were produced using both methods and various processing conditions, which resulted in different microstructures and mechanical properties given their unique thermal histories. Characteristic microstructures were determined for all cases. Room temperature tensile and fatigue crack growth (FCG) properties were also evaluated and compared in different orientations with respect to the deposition direction. The effects of post-deposition heat treatment on tensile and FCG properties were determined. The results are systematically presented and discussed from both the material/process optimization, as well as structural design and fatigue life prediction perspectives
Microstructure, static properties, and fatigue crack growth mechanisms in Ti-6Al-4V fabricated by additive manufacturing: LENS and EBM
No full textPublisher Copyright: © 2016 Elsevier Inc.Additive manufacturing (AM) technology is capable of building 3D near-net-shaped functional parts directly from computer models using unit materials, such as powder or wire. Additive manufacturing's computer-aided design offers superior geometrical flexibility. The near-net-shaping capability also significantly reduces materials waste. These benefits make AM desirable for critical applications, such as aerospace, ground transportation, and medical. Confident utilization of the technology requires thorough understanding of the AM materials, ensuring that structural integrity and performance requirements are met or exceeded. In this study, Ti-6Al-4V fabricated by two AM techniques: Laser Engineered Net Shaping (LENS) and Electron Beam Melting (EBM) were investigated and critically compared. Samples were built using various processing parameters and heat treated under different conditions, which resulted in different microstructures and mechanical properties. Characteristic microstructures were determined for all cases. Room temperature tensile and fatigue crack growth properties were also evaluated and compared in different orientations with respect to the building direction. The effects of post-AM heat treatments on microstructure and properties were also studied. The results are systematically presented and discussed from the material/process optimization, structural design, and fatigue life prediction perspectives.Peer reviewe
Intervención social y drogodependencias
No full textSe plantea de modo cronológico cómo surgió la formación de los Servicios Sociales de Base en la Comunidad Autónoma Vasca desde 1982 hasta hoy en día. A partir de este nivel más amplio se pasa arealizar una reflexión sobre cuál es el lugar que los Servicios Sociales Generales ocupan en el ámbito de las drogodependencias, así como la necesaria coordinación entre los Servicios Sociales generales y los específicos. Por último, se exponen las características generales del programa de tratamiento para drogodependientes "Comunidad Terapéutica Haize-Gain" y el enfoque que desde este servicio se le da a la intervención social.Lan honek planteatzen du, kronologiaren arabera, nola hasi ziren eratzen Oinarrizko Gizarte Zerbitzuak Euskal Erkidego Autonomoan, 1982tik gaurko egunera bitarte. Maila zabalago horretatik, Gizarte Zerbitzu Orokorrek drogomenpekotasunen alorrean duten lekuaz gogoetatzera pasatzen da, eta Gizarte Zerbitzu Orokorren eta Berezien arteko ezinbesteko koordinazioa azpimarratzen da. Azkenik, "Haize-Gain Komunitate Terapeutikoa" drogazaleen tratamendurako programaren ezaugarri nagusiak azaltzen dira, bai eta partehartze sozialari zerbitzu horretatik ematen zaion ikuspegia.On présente, chronologiquement, l'apparition des Services Sociaux de Base dans la Communauté Autonome Basque depuis 1982 jusqu'à nos jours. A partir de cette situation plus important on réaliseune étude sur la place qu'occupent les Services Sociaux Généraux dans le milieu des toxicomanies ainsi que sur la coordination nécessaire entre les Services Sociaux généraux et spécifiques. Pour terminer, on expose les caractéristiques générales du programme de traitement pour toxicomanes "Comunidad Terapéutica Haize-Gain" ("Communauté Thérapeutique Haize-Gain") et l'approche que l'on donne à l'intervention sociale depuis ce service.A chronological outline is made of the formation of the Social Base Services in the Basque Autonomous Community from 1982 to the current day. The author then reflects on which is the role of the General Social Services in the filed of drug addiction, as well as on the necessary coordination between the general and the specific social services. Finally, the author reveals the general characteristics of the "Haize-Gain Therapeutic Community" treatment program for drug addicts and how social intervention is approached by this service
Investigation of phase stability, mechanical properties, and tribological behavior of Al-based entropy alloys
No full textPublisher Copyright: © 2024 The AuthorsThis study investigates three novel Al-based entropy alloys in the Al90-xCu5Zn5(Mg,Sn,Ti)X system. The empirical thermo-physical parameters and CALPHAD calculations were studied to comprehend phase stability. Although empirical parameters suggested potential for solid solution formation, CALPHAD calculations predicted multiphase microstructures, which were confirmed through experimental analyses. Microstructural characterization and cooling curve analyses revealed the formation of various phases at specific temperatures during solidification. The addition of Mg increased hardness through Mg2Sn phase formation, while Ti further enhanced hardness by stabilizing primary Al3Ti phase. Mechanical testing demonstrated a strength-ductility trade-off, with Ti-containing alloy exhibiting the highest compressive strength but lowest ductility. Wear resistance of the experimental alloys was higher than AlSi10MnMg, and Mg and Ti additions improved wear performance compared to AlSi9Cu3(Fe). This comprehensive study highlights the potential of Al–Cu–Zn based multi principal component alloys with Mg, Sn, and Ti additions for developing lightweight materials with tailored mechanical and tribological properties.Peer reviewe
Research on Coatings and Infiltration to Strengthen Ceramic Lost Cores Used in High-Pressure Die Casting Processes
No full textPublisher Copyright: © 2019, The Author(s).Lost cores used to manufacture complex aluminium components through high-pressure die casting (HPDC) processes need to withstand very high injection velocities and pressures. The conventional sand cores used in other casting processes, such as sand casting or low-pressure die casting, do not support the aggressive process parameters of the HPDC, so advanced ceramic cores must be used. These cores must be strong enough not to get broken during the casting process, but, at the same time, they must have a minimum porosity to be easily removed from the casting to obtain the finished part. Due to this porosity, the aluminium penetrates the core surface during the casting process. So, the criterion here is to find the necessary compromise between strength and porosity and to protect the core surface from the aluminium penetration. In this work, two research lines have been followed to address these challenges. On the one hand, different refractory coatings have been applied to the ceramic core surface with the aim of sealing it. Amongst the coatings analysed, boron nitride-based one has been found to be the most suitable and cost-effective solution to avoid aluminium penetration. On the other hand, silica has been proved to be a suitable infiltration agent to increase the strength of the core.Peer reviewe
Development of an Innovative Low Pressure Die Casting Process for Aluminum Powertrain and Structural Components
No full textPublisher Copyright: © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimAn innovative Low Pressure Die Casting (LPDC) process has been developed for aluminum cast components based on the application of an extra pressure during the solidification process. The new process, named “Low Pressure Squeeze Casting” (LPSC) has been proved to be able to increase the solidification rate, refining the microstructure of the casting, and reducing its shrinkage porosity. Furthermore, the cycle time is also reduced, increasing the productivity of the process. Two demonstrators from the automotive and wind power industries have been produced to validate the process in a relevant industrial environment.Peer reviewe
Fatigue crack growth mechanisms at the microstructure scale in as-fabricated and heat treated Ti-6Al-4V ELI manufactured by electron beam melting (EBM)
No full textPublisher Copyright: © 2017Electron beam melting (EBM) is a metal powder bed fusion additive manufacturing (AM) technology that fabricates parts by selectively scanning consecutive powder layers with an electron beam. Additive manufacturing technologies are increasing in importance for aerospace and medical applications, where the demand for a fundamental understanding and predictability of static and dynamic material properties are high. Ti-6Al-4V is the most widely used and studied alloy for this technology, and is the focus of this work in its Extra Low Interstitial (ELI) variation. The layered manufacturing of metallic components by EBM creates a unique directional microstructure, and consequently, anisotropic properties. Microstructure evolution, and its influence on mechanical properties of the alloy in the as-fabricated condition, has been documented by various researchers. However, fatigue crack propagation and the effects of the directional structure have not been sufficiently studied, imposing a barrier for this technology's potential extension to high-integrity applications. In this study, fatigue crack growth (FCG) both parallel and perpendicular to the build directions was studied for different stress ratios and crack growth stages. The interaction between the directional as-fabricated EBM microstructure and FCG was investigated and compared to that of the equiaxed β annealed microstructure obtained by annealing above the β transus temperature. The FCG threshold, ΔKth, was analytically modeled for the two relative crack propagation directions at different stress ratios, and FCG microstructural mechanisms were established for all three regions of crack propagation.This research was performed under the Additive Manufacturing program of the Integrative Material Design Center (iMdc) at Worcester Polytechnic Institute, in collaboration with the Additive Manufacturing Demonstration Facility of Oak Ridge National Laboratory, and sponsored by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office, under contract DE-AC05-00OR22725 with UT-Battelle, LLC. Ph.D. candidates Yuwei Zhai and Anthony Spangenberger of the iMdc also collaborated actively in the material characterization performed during this study.Peer reviewe
Improved ultrasonic degassing of AlSi10Mg alloy and its performance evaluation with the reduced pressure test (RPT) method
No full textPublisher Copyright: © 73rd World Foundry Congress "Creative Foundry", WFC 2018 - Proceedings.All Rights Reserved.Porosity is detrimental to the mechanical properties of aluminium alloy castings, thus, in most of the cases, especially in structural parts, reduction of porosity is desired and pursued. Porosity can be caused by gas formation, solidification shrinkage, or non-metallic compound formation. In this work, the reduction of gas porosity formed by the hydrogen dissolved in the molten AlSi10Mg aluminium alloy has been studied employing an ultrasonic degasser in combination with purging gas blowing. Qualitative study of the hydrogen content of different samples has been performed employing the widespread reduced pressure test (RPT). Different factors affecting to RPT test have also been studied.This work has been done within the A-L STRUC project funded by the ELKARTEK program of the asquB e overnG ment with grant number KK-20170/ 0020. This work has been done within the AL-STRUC project funded by the ELKARTEK program of the Basque Government with grant number KK-2017/00020.Peer reviewe
