Papers by Fernando Audebert
Philosophical Magazine Letters - PHIL MAG LETT, 2008
Nanoquasicrystalline Al-based alloys, containing icosahedral particles in an α-Al matrix, exhibit... more Nanoquasicrystalline Al-based alloys, containing icosahedral particles in an α-Al matrix, exhibit high strength at elevated temperature. The metastability of the quasicrystals can limit the use of these alloys. In the present work, the microstructural evolution of Al93(Fe3Cr2)7 and Al93Fe3Cr2Nb2 (at%) alloys was studied using heat treatments and structural characterization by XRD, TEM and STEM-EDX analysis. It was observed that the Nb is dissolved in the Al–Fe–Cr icosahedral phase. This provides higher thermal stability, retaining the fine nanoquasicrystalline microstructure for longer times at high temperature.
Materials Science and Engineering: A
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When rapid quenching occurs, avoiding crystallization, the undercooled liquid becomes an amorphou... more When rapid quenching occurs, avoiding crystallization, the undercooled liquid becomes an amorphous solid whose structure is metastable not only with respect to crystalline state, but also with respect to a theoretical deal glass. It is possible, then, that this structure can evolve towards a more amorphous stable state. This evolution is called structural relaxation and it causes important changes in physical, chemical and mechanical properties. The study of structural relaxation is a very important matter because, in many cases, the optimum properties of amorphous materials are obtained after an adequate heat treatment. This paper reports that, up to now different properties have been used for structural relaxation studies: dilatation, Young's modulus, enthalphy, lifetime of positron annihilation, microhardness, electrical resistivity, and Curie temperature. The Young's modulus is a very suitable parameter to analyze the relaxation in metallic glasses because the changes ca...
Materials Science Forum, 2008
Fe-Si alloys have excellent soft magnetic properties, specially around 12 at% Si. However, its in... more Fe-Si alloys have excellent soft magnetic properties, specially around 12 at% Si. However, its industrial application is limited because of the lack of ductility, which causes cracking during rolling operations for the fabrication of thin sheets. The reason of the brittleness of the high silicon alloys is a disorder/order reaction at low temperatures. The aim of this work is to analyze the effect of the addition of Aluminum on the crystalline structure of Fe-Si alloys. Samples with a chemical composition of Fe88Si12 and Fe87Si12Al1 (at%) were prepared by Spray Forming. The structure was studied by means of X-ray diffraction and Mössbauer Spectroscopy. The presence of the DO3 and α- Fe phases were observed
Applied Physics A: Materials Science & Processing, 1999
Applied Physics A: Materials Science & Processing, 1999
Materials Science & Engineering A, 2019
We demonstrate the outstanding dynamic strength of nano-quasicrystalline Al93Fe3Cr2Ti2 at.% alloy... more We demonstrate the outstanding dynamic strength of nano-quasicrystalline Al93Fe3Cr2Ti2 at.% alloy and composites.
Unlike most crystalline Al alloys, this alloy exhibits substantial strain rate sensitivity and retains ductility at high strain rates. This opens new pathways for use in safety-critical materials requiring impact resistance.
Journal of Alloys & Compounds, 2019
Al-Sn based alloys are widely used as plain bearings in several engineering applications, particu... more Al-Sn based alloys are widely used as plain bearings in several engineering applications, particularly in internal combustion engines. The microstructures of these alloys are composed by two main phases, alpha-Al and betha-Sn. The latter provides the low friction coefficient required for bearing applications. The new combustion engines and hybrid systems impose harder working conditions to plain bearings, thus the bearing materials need to be stronger with improved friction properties. The conventional Al20Sn1Cu (wt.%) alloy produced at different cooling rates by means of different casting processes such as Belt Casting, Twin Roller and Single Roller Melt Spinning techniques was studied. The effects of the cooling rate and of the Mn addition on the microstructure and properties were studied. The samples produced by
the melt-spinning technique with cooling rates higher than ~5 x 10E5 K/s conducts the alloy to a solidification pathway in a metastable condition through a miscibility gap. A microstructure characterized by an homogeneous small rounded b-Sn particles distributed in a refined alpha-Al grain size matrix is obtained.
Samples produced with cooling rate higher than ~1.4 x 10E6 K/s show an anisotropic microstructure of a <100> alpha-Al crystallographic texture in a columnar microstructure. The melt-spun samples with an
isotropic microstructure reach a Vickers hardness 86% higher and an improved wetting property than the alloy produced by the traditional Belt-Casting technique. However the melt-spun samples with crystallographic texture showed a downfall in the properties. The addition of Mn leads to a more homogeneous and refined microstructure independently of the casting technique used.
International Journal of Engineering Research and Application, 2019
The exposure of pistons to extreme mechanical and thermal loads in modern combustion engines has ... more The exposure of pistons to extreme mechanical and thermal loads in modern combustion engines has necessitated the use of efficient and detailed analysis methods to facilitate their design. The finite element analysis has become a standard design optimisation tool for this purpose. In literature two different approaches have been suggested for reducing the geometry of the cylinder and crank slider mechanism,toidealise piston finite element analysisload models,whilst trying to maintain realistic boundaries to obtain accurate results. The most widely used geometry is the combination of piston and gudgeon pin while the second geometry includes some portion of the connecting rod's small end and cylinder in addition to the piston and gudgeon pin.No clear analyses have been made in literature about the relative effectiveness of the two approaches in terms ofmodel accuracy. In this work both approaches have been carried out and analysed with respect to a racing piston. The results suggest that the latter approach is more representative of the load conditions that the piston is subjected to in reality.
Rapidly solidified Mg based alloys are of interest for industrial applications as a structural ma... more Rapidly solidified Mg based alloys are of interest for industrial applications as a structural material and for hydrogen storage. Mg-Cu-Rare Earth alloys have shown high glass forming ability; full amorphous structure with thickness of mm size can be obtained within these systems. However, their brittle behavior limits their industrial applications. In the present work, the Al effect in substitution of Cu in the Mg 65 Cu 25 MM 10 (at%, MM: mischmetal) was studied. Samples up to 15at% Al were prepared by splat cooling and their microstructure, stability and mechanical properties were characterised. The crystallization temperature increases with the Al addition; the amorphous phase with different Al content has a Young's modulus of ~55GPa; the microhardness increases with the Al content in the amorphous and crystallized samples and the fracture of the alloy containing 10at% Al showed ductile vein patterns characteristics of ductile metallic glasses. The partial Cu substitution by Al can improve the stability and mechanical properties of the amorphous Mg 65 Cu 25 MM 10 alloy.
In this paper we report the effect of alloying elements on hydrogen storage properties of melt-sp... more In this paper we report the effect of alloying elements on hydrogen storage properties of melt-spun Mg-based alloys. The base alloys Mg 90 Si 10 , Mg 90 Cu 10 , Mg 65 Cu 35 (at%) were studied. We also investigated the effect of rare earths (using MM: mischmetal) and Al in Mg 65 Cu 25 Al 10 , Mg 65 Cu 25 MM 10 and Mg 65 Cu 10 Al 15 MM 10 alloys. All the melt-spun alloys without MM show a crystalline structure, and the Mg 65 Cu 25 MM 10 and Mg 65 Cu 10 Al 15 MM 10 alloys showed an amorphous and partially amorphous structure respectively. At 350˚C all the alloys had a crystalline structure during the hydrogen absorption-desorption tests. It was observed that Si and Cu in the binaries alloys hindered completely the activation of the hydrogen absorption. The partial substitution of Cu by MM or Al allowed activation. The combined substitution of Cu by MM and Al showed the best results with the fastest absorption and desorption kinetics, which suggests that this combination can be used for new Mg-alloys to improve hydrogen storage properties.
Rapidly solidified Mg based alloys are of interest for industrial applications as a structural ma... more Rapidly solidified Mg based alloys are of interest for industrial applications as a structural material and for hydrogen storage. Mg-Cu-Rare Earth alloys have shown high glass forming ability; full amorphous structure with thickness of mm size can be obtained within these systems. However, their brittle behavior limits their industrial applications. In the present work, the Al effect in substitution of Cu in the Mg 65 Cu 25 MM 10 (at%, MM: mischmetal) was studied. Samples up to 15at% Al were prepared by splat cooling and their microstructure, stability and mechanical properties were characterised. The crystallization temperature increases with the Al addition; the amorphous phase with different Al content has a Young's modulus of ~55GPa; the microhardness increases with the Al content in the amorphous and crystallized samples and the fracture of the alloy containing 10at% Al showed ductile vein patterns characteristics of ductile metallic glasses. The partial Cu substitution by Al can improve the stability and mechanical properties of the amorphous Mg 65 Cu 25 MM 10 alloy.
We report a study of the structure-processing-property relationships in a high strength Al 93 Fe ... more We report a study of the structure-processing-property relationships in a high strength Al 93 Fe 3 Cr 2 Ti 2 nano-quasicrystalline alloy and composites containing 10 and 20 vol% ductilising pure Al fibres. The superimposed contributions of several different strengthening mechanisms have been modelled analytically using data obtained from systematic characterisation of the monolithic alloy bar. An observed yield strength of 544 MPa has been substantiated from a combination of solid solution strengthening, work hardening, precipitation hardening and Hall-Petch grain size dependent effects. These materials have been shown by other authors in previous published work to be highly sensitive to the size distribution of particles in the powder from which they are made, and the subsequent thermomechanical processing conditions. The processing condition employed in this study provided micron-sized grains with a strong [111] preferential orientation along the extrusion direction and a bimodal size distribution of the icosahedral nano-quasicrystalline precipitates. Both were deemed to be a significant contributor to the high yield strength observed. The addition of pure Al fibres was found to decrease the yield strength linearly with increasing Al content, and to augment the ductility of the composites.
NATO Science Series, 2005
Al-based systems allow obtaining microstructures composed of different combination of several cla... more Al-based systems allow obtaining microstructures composed of different combination of several classes of phases: crystalline solid solutions, amorphous solid solutions, crystalline intermetallic compounds and quasicrystals. Many Al-Fe based systems are icosahedral phase former, but non icosahedral phase was reported in Al-Ni based systems. The strong hetero-atomic interaction in the liquid of Al-based alloys appears to have a big effect on
When rapid quenching occurs, avoiding crystallization, the undercooled liquid becomes an amorphou... more When rapid quenching occurs, avoiding crystallization, the undercooled liquid becomes an amorphous solid whose structure is metastable not only with respect to crystalline state, but also with respect to a theoretical deal glass. It is possible, then, that this structure can evolve towards a more amorphous stable state. This evolution is called structural relaxation and it causes important changes in physical, chemical and mechanical properties. The study of structural relaxation is a very important matter because, in many cases, the optimum properties of amorphous materials are obtained after an adequate heat treatment. This paper reports that, up to now different properties have been used for structural relaxation studies: dilatation, Young's modulus, enthalphy, lifetime of positron annihilation, microhardness, electrical resistivity, and Curie temperature. The Young's modulus is a very suitable parameter to analyze the relaxation in metallic glasses because the changes ca...
Latin American applied research Pesquisa aplicada latino americana = Investigación aplicada latinoamericana
At present, the development of nations is closely tied to the strength of its science and technol... more At present, the development of nations is closely tied to the strength of its science and technology system and the use of knowledge to generate innovations that respond to the demands and expectations of the social and productive framework.This paper summarizes the basis for policies and actions taken by the Ministry of Science, Technology and Productive Innovation of Argentina. They are based on the understanding of innovation as a cornerstone of development, which must be continually sustained by strengthening their basic structures in science, technology, productive sectors, society and the intermediate structures that contribute to the synergy of the innovations’ generating system.
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Papers by Fernando Audebert
Unlike most crystalline Al alloys, this alloy exhibits substantial strain rate sensitivity and retains ductility at high strain rates. This opens new pathways for use in safety-critical materials requiring impact resistance.
the melt-spinning technique with cooling rates higher than ~5 x 10E5 K/s conducts the alloy to a solidification pathway in a metastable condition through a miscibility gap. A microstructure characterized by an homogeneous small rounded b-Sn particles distributed in a refined alpha-Al grain size matrix is obtained.
Samples produced with cooling rate higher than ~1.4 x 10E6 K/s show an anisotropic microstructure of a <100> alpha-Al crystallographic texture in a columnar microstructure. The melt-spun samples with an
isotropic microstructure reach a Vickers hardness 86% higher and an improved wetting property than the alloy produced by the traditional Belt-Casting technique. However the melt-spun samples with crystallographic texture showed a downfall in the properties. The addition of Mn leads to a more homogeneous and refined microstructure independently of the casting technique used.
Unlike most crystalline Al alloys, this alloy exhibits substantial strain rate sensitivity and retains ductility at high strain rates. This opens new pathways for use in safety-critical materials requiring impact resistance.
the melt-spinning technique with cooling rates higher than ~5 x 10E5 K/s conducts the alloy to a solidification pathway in a metastable condition through a miscibility gap. A microstructure characterized by an homogeneous small rounded b-Sn particles distributed in a refined alpha-Al grain size matrix is obtained.
Samples produced with cooling rate higher than ~1.4 x 10E6 K/s show an anisotropic microstructure of a <100> alpha-Al crystallographic texture in a columnar microstructure. The melt-spun samples with an
isotropic microstructure reach a Vickers hardness 86% higher and an improved wetting property than the alloy produced by the traditional Belt-Casting technique. However the melt-spun samples with crystallographic texture showed a downfall in the properties. The addition of Mn leads to a more homogeneous and refined microstructure independently of the casting technique used.