Browsing by Author "Egizabal, Pedro"
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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 an Innovative Low Pressure Die Casting Process for Aluminum Powertrain and Structural Components(Wiley-VCH Verlag, 2018) Merchán, Mikel; Egizabal, Pedro; García de Cortázar, Maider; Irazustabarrena, Ane; Galarraga, HaizeAn 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.Item Effect of high‐density current electropulsing on corrosion cracking of titanium aluminide intermetallic(Wiley-VCH Verlag, 2021-02-05) Babutskyi, Anatolii; Chrysanthou, Andreas; Chyzhyk, Ganna; Cortázar, Maider García; Egizabal, Pedro; Smelina, MarijaThe effect of electropulsing on the corrosion cracking of titanium aluminide produced by self‐propagating high‐temperature synthesis has been investigated. The electropulsing treatment led to improved corrosion resistance in sodium fluoride solution and also eliminated corrosion cracking at the α2/γ interface during corrosion in a solution of nitric and hydrofluoric acids. This behavior was attributed to thermal and athermal effects resulting from electropulsing and leading to the interaction of conduction electrons with the defect structure. The effect of magnetic field accompanying electropusling on depinning of dislocations also has been discussed. Support for this is provided on the basis of X‐ray diffraction analysis and microhardness testing.Item Effect of high‐density current electropulsing on corrosion cracking of titanium aluminide intermetallic(Wiley-VCH Verlag, 2021) Babutskyi, Anatolii; Chrysanthou, Andreas; Chyzhyk, Ganna; Cortázar, Maider García; Egizabal, Pedro; Smelina, MarijaThe effect of electropulsing on the corrosion cracking of titanium aluminide produced by self‐propagating high‐temperature synthesis has been investigated. The electropulsing treatment led to improved corrosion resistance in sodium fluoride solution and also eliminated corrosion cracking at the α2/γ interface during corrosion in a solution of nitric and hydrofluoric acids. This behavior was attributed to thermal and athermal effects resulting from electropulsing and leading to the interaction of conduction electrons with the defect structure. The effect of magnetic field accompanying electropusling on depinning of dislocations also has been discussed. Support for this is provided on the basis of X‐ray diffraction analysis and microhardness testing.Item Mechanical Properties Assessments for Materials of High Porosity and Light Alloys with Predominant Embedded Phases(Springer Science and Business Media Deutschland GmbH, 2021) Parashkevova, Ludmila; Drenchev, Ludmil; Egizabal, Pedro; Georgiev, Ivan; Kostadinov, Hristo; Lilkova, Elena; Tecnalia Research & InnovationIn the present contribution, upgrading the findings of previous works, [11], new models are proposed for evaluation of effective mechanical properties of light alloys regarded as multiphase composites. This study concerns three - phase composites with high volume fraction of non-matrix phases. The elastic properties assessments of such materials are calculated by analytical approach based on the variant of Differential Effective Medium (DEM) method. Here in the methodology from [10, 11] is further developed for two cases: composite type A and composite type B. The composite A consists of matrix and two inclusion phases. The matrix material is much softer than the inclusions material of the first kind and at it is much harder than the inclusions of second kind. The composite B is a closed cell porous material. It is assumed that the high porosity is induced by spherical pores of two sets very different by size: Di≫ di. At high volume fraction of pore space the average diameter of small pores is comparable to the inter-pores distance (cell’s wall). For assessment of the elastic moduli of both composites A an B a two-step homogenization procedures are applied. New yield conditions for the composites A and B are derived to define the initial plastic state of composites. Hill’s strain energy equivalent condition and leading role of matrix are taken into account describing the transition point from elastic to plastic state.Item Modelling of Light Mg and Al Based Alloys as “in situ” Composites(SPRINGER INT PUBLISHING AG, GEWERBESTRASSE 11, CHAM, CH-6330, SWITZERLAND, 2017-10-26) Parashkevova, Ludmila; Egizabal, Pedro; Todorov, Michail; Georgiev, Ivan; Georgiev, Krassimir; Georgiev, Ivan; Tecnalia Research & InnovationThe present paper is aimed to further elucidate the microstructure properties relationship of light alloys containing additional hard particles. The materials studded are magnesium alloys from the system AZ (Mg–Al–Mn–Zn) and mechanically alloyed aluminum reinforced with carbide and oxide particles. Strengthening and hardening phenomena in Metal Matrix Multiphase heterogeneous Materials (MMMM) are considered in this study from the view point of mechanics of nano- and micro-composites. A semi-analytical approach is adopted taking into account the manufacturing processing and microstructure features. Multilevel homogenization procedure is performed, accounting for size effects. In the model applied the metal matrix is considered as an elastic–plastic micropolar media and the hard phases (precipitations Mg17Al12, TiC, Al4C3, Al2O3) are treated as conventional elastic Cauchy materials. Experimentally observed dependence of the characteristic matrix length on the volume fraction of the hardening phases is modeled and numerically simulated in the case of ball-milled Al alloyed with Al4C3 and Al2O3. For AZ alloys the impact of intermetallic phase Mg17Al12 is discussed in the frame of presented composite model and the strengthening effect of the addition of small amount of TiC is estimated.Item Numerical Modeling of the Influence of Nanometric Ceramic Particles on the Nucleation of AlSi10MnMg Alloy(2022-05-17) Jimenez, Ane; Sanchez, Jon Mikel; Girot, Franck; Renderos, Mario; Egizabal, Pedro; CIRMETAL; Tecnalia Research & InnovationIn recent years, many researchers have attempted to model the solidification process of nano-reinforced materials. In the present document, the effect on the heterogeneous solidification regime of the different sizes, shapes, and chemical compositions of nanometric ceramic particles in an AlSi10MnMg alloy is studied. This article develops a mathematical model to predict the solidification behavior of a general nano-reinforced alloy, then validates the results using experimental techniques. The main objective of the model is to minimize the costly and time-consuming experimental process of fabricating nano-reinforced alloys. The proposed model predicts the critical Gibbs energy and the critical radius required for nucleation in the heterogeneous solidification regime. Conversely, the experimental part focuses on understanding the solidification process from the differential thermal analysis (DTA) of the solidification curves. It was concluded that if subcooling is involved, cubic and pyramidal particles work better as nucleating particles in the studied alloy.Item Technical and environmental evaluation of a new high performance material based on magnesium alloy reinforced with submicrometre-sized TiC particles to develop automotive lightweight components and make transport sector more sustainable(2019-05) Ferreira, Victor; Merchán, Mikel; Egizabal, Pedro; García de Cortázar, Maider; Irazustabarrena, Ane; López-Sabirón, Ana M.; Ferreira, German; CIRMETAL; Tecnalia Research & Innovation; SGThis study evaluated the use of submicrometre-sized particles based on titanium carbide from both technical and environmental points of view. The objective was to improve the mechanical properties of the magnesium alloy intended for use in the automotive component industry. To this end, an Al/TiC master compound containing 60 wt.% of TiC was produced through a self-propagating, high-temperature synthesis process and embedded in a magnesium alloy by a mechanical stirring method. The life cycle assessment methodology was then used to evaluate the environmental impact of the manufacturing of the magnesium alloy reinforced with submicrometre-sized particles. X-ray diffraction and scanning electron microscopy techniques revealed the nature and purity of the TiC present in the material and revealed particle sizes below submicrometre range (300–500 nm). The incorporation of TiC particles into the magnesium alloy resulted in improvements in yield stress and ultimate tensile strength of more than 10% and 18%, respectively, and increases in ductility values by 30%. Finally, the results indicated that the submicrometre particle production had a low environmental impact compared with the total impact associated with manufacturing the magnesium alloy reinforced with submicrometre-sized particles; the greatest environmental burden was attributed to the magnesium production stage. However, this impact is offset in the use phase of the vehicle, providing approximately 28,000 km of mileage for a car.