Browsing by Author "Lagos, M.A."
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item A comparative study of the feasibility of cellular MAX phase preforms formation by microwave-assisted SHS and SPS techniques(2020-05) Dmitruk, Anna; Lagos, M.A.; Naplocha, Krzysztof; Egizabal, Pedro; EXTREMAT; Tecnalia Research & InnovationTwo methods were evaluated in terms of manufacturing of MAX phase preforms characterized with open porosity: microwaveassisted self-propagating high-temperature synthesis (SHS) and spark plasma sintering (SPS). The main purpose of fabrication of such open-porous preforms is that they can be successfully applied as a reinforcement in metal matrix composite (MMC) materials. In order to simulate the most similar conditions to microwave-assisted SHS, the sintering time of SPS was significantly reduced and the pressure was maintained at a minimum value. The chosen approach allows these two methods to be compared in terms of structure homogeneity, complete reactive charge conversion and energy effectivity. Study was performed in Ti-Al-C system, in which the samples were compacted from elemental powders of Ti, Al, C in molar ratio of 2:1:1. Manufactured materials after syntheses were subjected to SEM, XRD and STEM analyses in order to investigate their microstructures and chemical compositions. As was concluded, only microwave-assisted SHS synthesis allows the creation of MAX phases in the studied system. SPS technique led only to the formation of intermetallic secondary phases. The fabrication of MAX phases’ foams by microwave-assisted SHS presents some interesting advantages compared to conventional manufacturing methods. This work presents the characterization of foams obtained by microwave-assisted SHS comparing the results with materials produced by SPS. The analysis of SPS products for different sintering temperatures provided the better insight into the synthesis of MAX phases, supporting the established mechanism. Dissimilarities in the heating mechanisms that lead to the differing synthesis products were also discussed.Item Development of Beta Titanium Alloys by Spark Plasma Sintering(2017) Lagos, M.A.; Amigo, A.; Vicente, A.; Agote, Iñigo; EXTREMATBeta titanium alloys have attracted considerable attention especially for orthopedic implants applications owing to their unique combination of low elastic modulus, superior bio-corrosion resistance and excellent biocompatibility. However, the PM production of these alloys is difficult due to the significant amount of refractory metals (Ta, Mo, Zr, Nb, etc). This work presents a processing route combining mechanical mixing of elemental powders (pre-alloying) and Spark Plasma Sintering in order to obtain fully dense materials with homogeneous microstructure. Two different compositions (TiMo and TiNb) with high amount of alloying elements were developed. The alloys were sintered at temperatures between 1100 and 1250ºC. The phases were evaluated by X-ray diffraction and diffraction of backscattered electrons, appreciating its mechanical properties by micro-hardness and bending tests. A transformation to Beta Titanium is obtained predominantly with a small grain size, and micro-hardness in the order of forged materials.Item Development of electric resistance sintering process for the fabrication of hard metals: Processing, microstructure and mechanical properties: Processing, microstructure and mechanical properties(2017-08-01) Lagos, M.A.; Agote, Iñigo; Schubert, T.; Weissgaerber, T.; Gallardo, J.M.; Montes, J.M.; Prakash, L.; Andreouli, C.; Oikonomou, V.; Lopez, D.; Calero, J.A.; EXTREMATThis work presents the development of the Electrical Resistance Sintering (ERS) process for the fabrication of hard metals. The compositions of the materials produced were WC with 6 and 10 wt% of Co. In addition to the specific characteristics of the technology, the characterization of the produced parts is presented and compared to materials obtained by conventional processes. The parts produced by ERS present densities comparable to the ones obtained by conventional methods. The microstructural comparison shows a considerable grain size reduction in the ERS materials which consequently brings a hardness increase. ERS materials show similar fracture toughness to conventional ones. The very fast sintering allows performing the process without any protective atmosphere, therefore making this process very attractive for the production of materials that need to be sintered under non-oxidising environments. The total duration of the cycle, including heating, holding time and cooling is few seconds. Finally, some considerations about the scale up and possible industrialization of the technology are explained.Item Effect of Material and Process Atmosphere in the Preparation of Al-Ti-B Grain Refiner by SHS(2015-09) Vicario, Iban; Poulon-Quintin, Angeline; Lagos, M.A.; Silvain, JF; PROMETAL; EXTREMATAl-Ti-B master alloys are widely used in the aluminum industry as grain refiners for the control of the microstructure of the aluminum alloys. The SHS (self-propagating high-temperature synthesis) is an ex situ method that uses exothermic reactions to sustain the chemical reaction in a combustion wave. The advantages of SHS are the low energy requirement, simplicity and product purity. However, the raw material used has to be very pure, with a very small size leading to the necessity of a reactor with a protective gas to produce the reaction. The purpose of this investigation is to fabricate SHS master alloys with commercial standard raw materials, with lower purity and higher grain size without a reactor or protective gas in order to (1) decrease the price and (2) improve the productivity of master alloy manufacturing. The possibility of using cheap borated salts instead of expensive pure boron has been studied. Different compositions of aluminum master alloy have been developed. Bigger TiB2 grain size has been obtained when using bigger commercial raw materials. Larger titanium powder can produce an aluminum master alloy with a maximum of 30% of aluminum without reactor. In comparison, SHS reaction is much more difficult when using finer titanium powder.Item Fabrication of chromium carbide cermets by electric resistance sintering process: Processing, microstructure and mechanical properties: Processing, microstructure and mechanical properties(2021-02) Lagos, M.A.; Agote, I.; Leizaola, I.; Lopez, D.; Calero, J.A.; EXTREMATChromium carbide-based cermets are suitable for use in abrasive and corrosive environments. This work presents the fabrication of chromium carbide-based cermets by a very fast sintering process: Electric Resistance Sintering. The thermal cycle duration was less than 1 s and without protective atmosphere. Two different compositions were studied: Cr3C2-25NiCr (wt%) and WC-20Cr3C2-7Ni (wt%). Microstructure and crystallographic phases of the initial powders and sintered materials are presented. In addition, hardness and toughness were characterized and compared to conventional materials. One important issue of ERS is the size and homogeneity of the pieces. This work presents the also the fabrication of a mining wear piece and some aspects about scaling up.Item Joining of ceramic matrix composites to high temperature ceramics for thermal protection systems(2016-02-01) Jiménez, C.; Mergia, K.; Lagos, M.A.; Yialouris, P.; Agote, Iñigo; Liedtke, V.; Messoloras, S.; Panayiotatos, Y.; Padovano, E.; Badini, C.; Wilhelmi, C.; Bárcena, Jorge; EXTREMATThe current work reports a novel approach for the integration of external protective SIC multilayers with ceramic matrix composite (C-f/SiC) with the view of application in aerospace heat protection systems. The integration method is based on diffusion brazing bonding. As a joining agent the MAX-Phase Ti3SiC2, produced by self-propagating high temperature synthesis, has been employed. The pressure applied during the joining process and its effect on the microstructure of the integrated structure is discussed. Microstructural analysis of the resulting joints is conducted using scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction measurements. Analysis of the joints showed that the bonds are uniform, dense, with few crack vertical to the interface which are not detrimental for the performance of the joints. Ground re-entry tests showed that the joints survive 5 re-entry cycles at 1391 and 1794 degrees C without any detectable damage. (C) 2015 Elsevier Ltd. All rights reserved.Item OBTENCIÓN Y CARACTERIZACIÓN DE ALEACIONES BASADAS EN γ-TiAl MEDIANTE MÉTODOS PULVIMETALÚRGICOS(UPV-EHU, 2014) Lagos, M.A.; Agote, Iñígo; San Juan, José MaríaEn esta tesis doctoral se ha estudiado la obtención y caracterización de aleaciones basadas en γ-TiAl mediante varios métodos pulvimetalúrgicos no convencionales. Las aleaciones basadas en γ-TiAl son muy interesantes para aplicaciones aeroespaciales debido a su bajo peso y a sus buenas propiedades mecánicas hasta 700-800 ºC. Sin embargo, un gran inconveniente es la dificultad en la fabricación de estas aleaciones por métodos convencionales. En los métodos de fusión, suele existir variabilidad en las propiedades, debido generalmente a las segregaciones de composición que se producen en los lingotes. La pulvimetalurgia presenta una importante ventaja en cuanto al control de la composición. En este trabajo se estudian tres rutas tecnológicas, dos basadas en la síntesis por combustión y otra basada en la sinterización por corriente eléctrica. En general, la principal ventaja de estas técnicas es la reducción del tiempo de procesado y la posibilidad de utilizar polvos elementales, cuyo coste es inferior a los pre-aleados. Se ha estudiado el efecto de los parámetros de procesado en los diversos métodos y se han optimizado las rutas tecnológicas para obtener la mayor densidad y homogeneidad microestructural posible. Una vez definidas las condiciones de procesado más interesantes para cada ruta, se ha caracterizado comparativamente la densidad, la microestructura, las fases cristalográficas y las propiedades mecánicas de tracción y fluencia. También se han comparado los valores obtenidos con los de los métodos convencionales. Por último, se han considerado algunos aspectos ligados al escalado de la sinterización por corriente eléctrica, aspecto importante a la hora de una posible aplicación industrial.Item PM Based Titanium Matrix Composites for Aerospace Applications: Processing, Mechanical Properties and Scale Up: Processing, mechanical properties and scale up(2017) Lagos, M.A.; Agote, Iñigo; Atxaga, G.; Pambaguian, L.; EXTREMATThe reinforcement of titanium with a hard phase is an efficient way to increase the stiffness and strength of conventional titanium alloys. The high reactivity of titanium is a critical challenge in the processing of Titanium Matrix Composites (TMCs). For this reason, Powder Metallurgy is considered a very promising route for the manufacturing of TMCs. In this work, a master alloy (Ti-TiC) was developed by combustion synthesis. This alloy was further blended with conventional titanium alloy and the final consolidation was performed by Spark Plasma Sintering. In addition to the processing details, microstructural and thermomechanical characterization is presented. Materials obtained present higher Young Modulus and strength than conventional Ti-6Al-4V, with higher thermal conductivity and maintaining similar thermal expansion coefficient (CTE). The good corrosion resistance of the material makes it a candidate for possible applications in aerospace. This work presents also the scale up of the process to obtain aerospace demonstrators.Item Ti3SiC2-Cf composites by spark plasma sintering:: Processing, microstructure and thermo-mechanical properties(2019-08) Lagos, M.A.; Pellegrini, C.; Agote, I.; Azurmendi, N.; Barcena, J.; Parco, M.; Silvestroni, L.; Zoli, L.; Sciti, D.; EXTREMATMAX phases, and particularly Ti3SiC2, are interesting for high temperature applications. The addition of carbon fibers can be used to reduce the density and to modify the properties of the matrix. This work presents the densification and characterization of Ti3SiC2 based composites with short carbon fibers using a fast and simple fabrication approach: dry mixing and densification by Spark Plasma Sintering. Good densification level was obtained below 1400 °C even with a high amount of fibers. The reaction of the fibers with the matrix is limited thanks to the fast processing time and depends on the amount of fibers in the composite. Bending strength at room temperature, between 437 and 120 MPa, is in the range of conventional CMCs with short fibers and according to the resistance of the matrix and the presence of residual porosity. Thermo-mechanical properties of the composites up to 1500 °C are also presented.