Browsing by Keyword "Microstructure"
Now showing 1 - 14 of 14
Results Per Page
Sort Options
Item Characterisation of cement pastes with innovative self-healing system based in epoxy-amine adhesive(2015-07-01) Perez, G.; Gaitero, J. J.; Erkizia, E.; Jimenez, I.; Guerrero, A.; Tecnalia Research & Innovation; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓNTwo innovative additions are considered for the development of self-healing concrete: epoxy-containing silica microcapsules and amine-functionalized nanosilica. The effect of two concentrations of the additions on the microstructure of a cement paste with silica fume is studied. The results indicate a proper dispersion of the additions within the matrix, a pozzolanic reaction induced by nanosilica and the stability of the microcapsules that reliably isolate the epoxy from the paste. As the concentration of additions increases, a preferential orientation of the portlandite phase is observed, together with a decrease of the compressive strength due to the presence of a minor content of macropores and to the low strength of the capsules. The self-healing efficiency is confirmed in concrete specimens for 150 μm wide cracks and a particular concentration of the additions. These results will be essential for the subsequent development of a reliable self-healing concrete based in the epoxy-amine adhesive.Item Characterization of Inconel 718® superalloy fabricated by wire Arc Additive Manufacturing: effect on mechanical properties and machinability: effect on mechanical properties and machinability(2021-09) Alonso, Unai; Veiga, Fernando; Suárez, Alfredo; Gil Del Val, Alain; Tecnalia Research & Innovation; FABRIC_INTELWire and Arc Additive Manufacturing has the potential to become an appropriate technique to produce large complex-shaped metallic parts. However, a post-processing machining operation is necessary to reach the final geometry. In this work, Inconel 718 walls were manufactured in a monitored environment and their microstructure and mechanical properties were characterised. Then, slot milling operations were performed to investigate the influence of cutting speed and machining direction. The conclusions drawn from this article can be used as a guide for a correct definition of strategies and milling parameters. It was observed that at higher cutting speeds a better surface quality and lower torques are obtained. Moreover, the main novelty of this work is that is shows the influence of the anisotropy of WAAM-Inconel 718 on its machinability. Milling along the torch's travel direction offers better dimensional tolerance values with lower cutting torques, being more favourable than machining in the building direction.Item Compound Formation and Microstructure of As-Cast High Entropy Aluminums(2018-03-09) Sanchez, Jon Mikel; Vicario, Iban; Albizuri, Joseba; Guraya, Teresa; Koval, Natalia; Garcia, Jose; CIRMETAL; PROMETALThe aim of this work is to study the microstructure of four high entropy alloys (HEAs) produced by large scale vacuum die casting. Al40Cu15Mn5Ni5Si20Zn15, Al45Cu15Mn5Fe5Si5Ti5Zn20, Al35Cu5Fe5Mn5Si30V10Zr10, and Al50Ca5Cu5Ni10Si20Ti10 alloys formed a mixture of different structures, containing intermetallic compound (IC) and solid solution (SS) phases. The phases observed in the casting alloys were compared with the equilibrium phases predicted by Thermo-Calc. The measured densities varied from 3.33 g/cm−3 to 5.07 g/cm−3 and microhardness from 437 Hv to 887 Hv. Thus, the microhardness and estimated strength/density ratios are significantly higher than other lightweight high entropy alloys (LWHEAs).Item Design, Microstructure and Mechanical Properties of Cast Medium Entropy Aluminium Alloys(2019-12-01) Sanchez, Jon Mikel; Vicario, Iban; Albizuri, Joseba; Guraya, Teresa; Acuña, Eva Maria; CIRMETAL; PROMETALIn this work, the design, microstructures and mechanical properties of five novel non-equiatomic lightweight medium entropy alloys were studied. The manufactured alloys were based on the Al65Cu5Mg5Si15Zn5X5 and Al70Cu5Mg5Si10Zn5X5 systems. The formation and presence of phases and microstructures were studied by introducing Fe, Ni, Cr, Mn and Zr. The feasibility of CALPHAD method for the design of new alloys was studied, demonstrating to be a good approach in the design of medium entropy alloys, due to accurate prediction of the phases, which were validated via X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. In addition, the alloys were manufactured using an industrial-scale die-casting process to make the alloys viable as engineering materials. In terms of mechanical properties, the alloys exhibited moderate plastic deformation and very high compressive strength up to 644 MPa. Finally, the reported microhardness value was in the range of 200 HV0.1 to 264 HV0.1, which was two to three times higher than those of commercial Al alloys.Item Determination of Solidification of Rigidity Point Temperature Using a New Method(2020-04-03) Villanueva, Ester; Vicario, Iban; Sánchez, Jon Mikel; Crespo, Ignacio; PROMETAL; CIRMETALThis work aims to calculate the rigidity point temperature of aluminum alloys by three new methods and compare them with currently employed methods. The influence of major and minor alloying elements over the rigidity point temperature is also discussed. Until now it has been difficult to determine the exact temperature of the rigidity point, since small variations in the data obtained give variable results, making it difficult to automate the process with high accuracy. In this work we suggested three new mathematic methods based on the calculation of higher order derivatives of (dT/dt) with respect to time or temperature compared to those currently employed. A design of experiments based on the Taguchi method was employed to compare the effect of the major and minor alloying elements for the AlSi10Mg alloy, and to evaluate the accuracy of each developed method. Therefore, these systems will allow better automation of rigidity point temperature (RPT) determination, which is one of the most important solidification parameters for solidification simulators. The importance of the correct determination of this parameter lies in its relation to quality problems related to solidification, such as hot tearing. If the RPT presents very low-temperature values, the aluminum casting will be more sensitive to hot tearing, promoting the presence of cracks during the solidification process. This is why it is so important to correctly determine the temperature of the RPT. An adequate design of chemical composition by applying the methodology and the novel methods proposed in this work, and also the optimization of process parameters of the whole casting process with the help of the integrated computational modeling, will certainly help to decrease any internal defective by predicting one of the most important defects present in the aluminum industry.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 Effect of Heat Treatment on the Microstructure and Hardness of Ni-Based Alloy 718 in a Variable Thickness Geometry Deposited by Powder Fed Directed Energy Deposition(2022-05-31) Ramiro, Pedro; Galarraga, Haize; Pérez-Checa, Anabel; Ortiz, Mikel; Alberdi, Amaia; Bhujangrao, Trunal; Morales, Elena; Ukar, Eneko; Tecnalia Research & Innovation; FABRIC_INTEL; CIRMETAL; Caracterización y Validación. Materiales; Caracterización y Validación. MecánicosFeature addition to existing parts is a trending application for Directed Energy Deposition (DED) and can be used to add complex geometry features to basic forged geometries with the aim to reduce and simplify the number of processing steps as machining and assembling. However, the mechanical properties of as-deposited Inconel 718 fabricated by Powder-fed Directed Energy Deposition (Powder-fed DED) are far lower than the relevant specifications, making it necessary to apply different heat treatment with the purpose of improving deposited material performance. In addition, the effects of heat treatments in both variable thickness deposited geometry and forge substrate have not been studied. In this study, the effect of heat treatment within the Aerospace Materials Specifications (AMS) for cast and wrought Inconel 718 on the microstructure and hardness of both the Ni-Based Alloy 718 deposited geometry and substrate are analyzed in different parts of the geometry. The microstructure of all samples (as-deposited and heat-treated) is analyzed by Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS), confirming the formation of aluminum oxides and titanium nitrides and carbonitrides in the deposited structure.Item Influence of Heat Input on the Formation of Laves Phases and Hot Cracking in Plasma Arc Welding (PAW) Additive Manufacturing of Inconel 718(2020-06) Artaza, Teresa; Bhujangrao, Trunal; Suárez, Alfredo; Veiga, Fernando; Lamikiz, Aitzol; FABRIC_INTEL; Tecnalia Research & InnovationNickel-based alloys have had extensive immersion in the manufacturing world in recent decades, especially in high added value sectors such as the aeronautical sector. Inconel 718 is the most widespread in terms of implantation. Therefore, the interest in adapting the manufacture of this material to additive manufacturing technologies is a significant objective within the scientific community. Among these technologies for the manufacture of parts by material deposition, plasma arc welding (PAW) has advantages derived from its simplicity for automation and integration on the work floor with high deposition ratios. These characteristics make it very economically appetizing. However, given the tendency of this material to form precipitates in its microstructure, its manufacturing by additive methods is very challenging. In this article, three deposition conditions are analyzed in which the energy and deposition ratio used are varied, and two cooling strategies are studied. The interpass cooling strategy (ICS) in which a fixed time is expected between passes and controlled overlay strategy (COS) in which the temperature at which the next welding pass starts is controlled. This COS strategy turns out to be advantageous from the point of view of the manufacturing time, but the deposition conditions must be correctly defined to avoid the formation of Laves phases and hot cracking in the final workpiece.Item MECHANICAL IMPROVEMENT OF HARDENING AND TEMPERING STEEL WITH THE ADDITION OF SiC AND TiCN NANOPARTICLES IN THE STEEL MELT(2022-07) Callejo, Lorena M.; Pérez, Iñaki; Callejo-Piedra, Lorena M.; Pérez-Bilbao, Iñaki; CIRMETAL; Tecnalia Research & InnovationNovel processing technologies have allowed the reinforcement of several steel grades and alloys through the fine dispersion of different types of particles. However, the addition of ceramic particles in the steel melt causes agglomeration and coarsening phenomena. For this reason, little research has been carried out to add ceramic particles in steel in the traditional steelmaking process. Here we report a hardened and tempered steel grade that is reinforced for the first time through the addition of ceramic nanoparticles, such as TiCN and SiC, into the steel melt at laboratory scale. The results obtained from the tensile tests and hardness measurements reveal the mechanical behaviour of the steel grade is enhanced after the addition of the nanoparticles.Item Microstructural Evolution as a Function of Increasing Aluminum Content in Novel Lightweight Cast Irons(2021-10-18) Obregon, Alejandro; Sanchez, Jon Mikel; Eguizabal, David; Garcia, Jose Carlos; Arruebarrena, Gurutze; Hurtado, Iñaki; Quintana, Ion; Rodriguez, Patxi; PROMETAL; CIRMETALIn the context of the development of new lightweight materials, Al-alloyed cast irons have a great potential for reducing the weight of the different part of the vehicles in the transport industry. The correlation of the amount of Al and its effect in the microstructure of cast irons is not completely well established as it is affected by many factors such as chemical composition, cooling rate, etc. In this work, four novel lightweight cast irons were developed with different amounts of Al (from 0 wt. % to 15 wt. %). The alloys were manufactured by an easily scalable and affordable gravity casting process in an induction furnace, and casted in a resin-bonded sand mold. The microstructural evolution as a function of increasing Al content by different microstructural characterization techniques was studied. The hardness of the cast irons was measured by the Vickers indentation test and correlated with the previously characterized microstructures. In general, the microstructural evolution shows that the perlite content decrease with the increment of wt. % of Al. The opposite occurs with the ferrite content. In the case of graphite, a slight increment occurs with 2 wt. % of Al, but a great decrease occurs until 15 wt. % of Al. The addition of Al promotes the stabilization of ferrite in the studied alloys. The hardness obtained varied from 235 HV and 363 HV in function of the Al content. The addition of Al increases the hardness of the studied cast irons, but not gradually. The alloy with the highest hardness is the alloy containing 7 wt. % Al, which is correlated with the formation of kappa-carbides and finer perlite.Item Microstructure Evolution in a Fast and Ultrafast Sintered Non-Equiatomic Al/Cu HEA(2021-05-21) Reverte, Eduardo; Cornide, Juan; Lagos, Miguel A.; Campos, Mónica; Alvaredo, Paula; EXTREMATOne of the attractive characteristics of high entropy alloys (HEAs) is the ability to tailor their composition to obtain specific microstructures and properties by adjusting the stoichiometry to obtain a body-centered cubic (BCC) or face-centered cubic (FCC) structure. Thus, in this work, the target composition of an alloy of the FeCrCoNi family has been modified by adjusting the Al/Cu ratio in order to obtain a BCC crystalline structure. However, processing conditions always play a key role in the final microstructure and, therefore, in this work, the microstructure evolution of FeCrCoNiAl1.8Cu0.5 HEA sintered by different powder metallurgy (PM) techniques has been investigated. The techniques used range from the conventional PM sintering route, that uses high heating rates and sintering times, going through a fast sintering technique such as spark plasma sintering (SPS) to the novel and promising ultrafast sintering technique electrical resistance sintering (ERS). Results show that the increase in the processing time favours the separation of phases and the segregation of elements, which is reflected in a substantial change in the hardness of the alloy. In conclusion, the ERS technique is presented as a very promising consolidation technique for HEA.Item Phase prediction, microstructure and high hardness of novel light-weight high entropy alloys(2019-01) Sanchez, Jon Mikel; Vicario, Iban; Albizuri, Joseba; Guraya, Teresa; Garcia, Jose Carlos; CIRMETAL; PROMETALGuided by CALPHAD modeling, low-density and multiphase three novel High Entropy Alloys (HEAs), Al40Cu15Cr15Fe15Si15, Al65Cu5Cr5Si15Mn5Ti5 and Al60Cu10Fe10Cr5Mn5Ni5Mg5 were produced by large scale vacuum die casting. A mixture of simple and complex phases was observed in the as-cast microstructures, which demonstrates good agreement with CALPHAD results. The measured densities varied from 3.7 g/cm3 to 4.6 g/cm3 and microhardness from 743 Hv to 916 Hv. Finally, the hardness of all the light-weight HEAs (LWHEAs) with densities below 4.6 g/cm3 manufactured to date were reviewed. The hardness of Al40Cu15Cr15Fe15Si15 and hardness to density ratio of Al65Cu5Cr5Si15Mn5Ti5 are the highest of all LWHEAs reported up to date.Item Synthesis and characterization of epoxy encapsulating silica microcapsules and amine functionalized silica nanoparticles for development of an innovative self-healing concrete(2015-09-01) Perez, G.; Erkizia, E.; Gaitero, J. J.; Kaltzakorta, I.; Jiménez, I.; Guerrero, A.; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓN; Tecnalia Research & Innovation; CIRMETALSilica microcapsules encapsulating an epoxy compound (CAP) and silica nanoparticles functionalized by an amine group (NS) are synthesized to be used as self-healing system for smart cementitious composites. The innovative character of this system comes from the use of silica shell microcapsules to improve the durability and compatibility with the cement and from the use of functionalized nanosilica to obtain an amine functionalized cementitious matrix. Characterization of the particles indicates that they are amorphous and possess a proper morphology and size to be considered as additions to cement. The stability of the epoxy compound inside the microcapsules and the presence of amine groups bonded to silica nanoparticles are also confirmed. Moreover, NS shows a pozzolanic activity superior to that of the silica fume used as reference, while CAP is to a high degree stable upon reaction with lime. The results confirm that the synthesized particles are a suitable starting point to address the development of a smart self-healing concrete.Item Tailored synthesis of TiC/a-C nanocomposite tribological coatings(2005-10-25) Martínez-Martínez, D.; López-Cartes, C.; Justo, A.; Fernández, A.; Sánchez-López, J.C.; García-Luis, A.; Brizuela, Marta; Onate, J.I.; TECNOLOGÍAS DE HIDRÓGENO; INGENIERÍA DE SUPERFICIES; Tecnalia Research & InnovationComposite coatings made of nanocrystalline TiC (nc-TiC) particles and amorphous carbon (a-C) have been prepared in a double magnetron sputtering system using graphite and titanium targets under Ar bombardment. Chemical composition and microstructure of coatings were studied by transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and x-ray diffraction (XRD) for a set of samples prepared varying the ratio and intensity of power applied to each magnetron. Changes in coatings microstructure, from a quasipolycrystalline TiC to a nanocomposite formed by nanocrystals of TiC embedded in an amorphous matrix of carbon (nc-TiC/a-C), are observed depending on the synthesis conditions. Tribological and mechanical properties of coatings were tested using a pin-on-disk tribometer and an ultramicrohardness indenter, respectively. Coatings with moderate hardness (7-27 GPa), low friction (0.1-0.2), and low wear rates (k similar to 10(-7) mm(3)/N m) were obtained. A percentage between 15% and 30% of TiC is found as an optimum value to get a good compromise between good mechanical and tribological properties. Finally, a mapping of the mechanical and tribological properties of the nc-TiC/a-C system is presented for the synthesis conditions employed