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  • Influencia de la distribución bimodal de grano, contenido en oxígeno y vías de consolidación sobre la resistencia y la ductilidad para hierro UF obtenido por molienda mecánica

     Casas Quesada, Casimir
    Department of Materials Science and Metallurgy, Universitat Politècnica de Catalunya
    Theses

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    En la presente tesis se analizarán las microestructuras y las propiedades mecánicas de compactos fabricados a partir de un polvo de hierro con microestructura nanocristalina. Este polvo se obtiene a partir de un proceso de severa deformación plástica mediante molienda mecánica en un molino planetario de bolas. Las piezas másicas obtenidas a partir de este material por consolidación estática en tibio poseen una alta dureza pero presentan una gran fragilidad y una ductilidad nula. Se aplican tratamientos térmicos a temperaturas entre 625ºC y 675ºC a tiempos de 30 minutos, por el método convencional, con el objetivo de mejorar la ductilidad mediante la formación de una distribución bimodal de grano. Este tipo de microestructura se genera por un proceso de crecimiento heterogéneo de grano, en el cual se forman granos de tamaño micrométrico rodeados de una matriz de grano ultrafino. Esta microestructura permite al material desarrollar una mayor ductilidad, manteniendo una alta resistencia. Las microestructuras se caracterizaran a mediante microscopía electrónica de barrido, microscopía electrónica de transmisión y EBSD. En cuanto a las propiedades mecánicas, estas se medirán mediante microindentaciones y ensayos de microtracción.Además de la formación de estructuras bimodales, se pretende mejorar el proceso de unión metalúrgica entre las partículas de hierro y eliminar en la medida de lo posible los defectos de origen pulvimetalúrgico presentes en el material, con el objetivo de aumentar su resistencia además de la ductilidad. En el presente trabajo se estudiaran procedimientos alternativos para el tratamiento térmico de los compactos y se compararan con la vía convencional. Los nuevos sistemas propuestos en esta tesis son en primer lugar el Ultra-Fast Annealing, que consiste en tratamientos a temperatura mayor a la convencional, por encima de 680ºC, aplicando velocidades de calentamiento de 100ºC/segundo. Estas condiciones permiten realizar el tratamiento térmico en tiempos muy cortos, entre 20 y 35 segundos. En segundo lugar el Hot Isostatic Pressing, donde se aplican alta temperatura y presión simultáneamente. Por otro lado, se estudiará la influencia del contenido en oxígeno sobre las muestras consolidadas y tratadas convencionalmente. Durante el proceso de molienda mecánica, inevitablemente se produce una cierta contaminación por oxígeno del polvo de hierro. El oxígeno se introduce en el hierro durante la molienda mecánica y posterior consolidación, formando partículas de óxido. La ubicación, fracción en volumen y tamaño de estas partículas afectará la evolución microestructural del material durante los tratamientos térmicos, y afectará las propiedades mecánicas de las probetas durante los ensayos de microtracción.

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    Influence of composition, grain size and iron oxide particles on the strength of consolidated ball-milled iron  Open access

     Benito Paramo, Jose Antonio; Casas Quesada, Casimir; Cabrera Marrero, Jose Maria
    The 6th international conference on nanomaterials by severe plastic deformation
    DOI: doi:10.1088/1757-899X/63/1/012024
    Presentation's date: 2014-07-03
    Presentation of work at congresses

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    In this paper iron powders with two oxygen content (0.2 and 0.6% wt.) have been mechanically milled and consolidated by hot static pressing at different temperatures to obtain different grain sizes. At lower temperatures the grain size was in the nanostructured and ultrafine range and with increasing temperature abnormal grain growth was observed for both compositions. This led to the development of bimodal grain size distributions. In the samples with lower oxygen content the grain size and the percentage of coarse grain areas were larger than in the case of high oxygen content. The strength and ductility have been determined by tensile tests. For low oxygen content, the presence of large coarse grains allowed plastic strain in some cases, and for the samples consolidated at higher temperatures, yield strength of 865 MPa with a 8% total strain were obtained. For the samples with high oxygen content plastic deformation was no possible in any case. The observed stress for both compositions was analysed by two approaches, one based exclusively in grain boundary strengthening and the other one based in two effects acting at the same time: grain boundary and particle strengthening. Whereas grain boundary strengthening seems to fit with the strength of the samples in the nanostructured range, when coarse ferrite grains appear the addition of particle strengthening help to get better results. This indicates that the presence of oxides dissolved inside the large grains reinforce the structure of ball-milled iron.

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    Influence of composition, grain size, and oxide particles on the strength of consolidated ball-milled iron  Open access

     Benito Paramo, Jose Antonio; Cabrera Marrero, Jose Maria; Casas, C.; Gregoire, V.
    IOP Conference Series: Materials Science and Engineering (Online)
    Vol. 63, p. 1-7
    DOI: 10.1088/1757-899X/63/1/012024
    Date of publication: 2014-07
    Journal article

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    In this paper iron powders with two oxygen content (0.2 and 0.6% wt.) have been mechanically milled and consolidated by hot static pressing at different temperatures to obtain different grain sizes. At lower temperatures the grain size was in the nanostructured and ultrafine range and with increasing temperature abnormal grain growth was observed for both compositions. This led to the development of bimodal grain size distributions. In the samples with lower oxygen content the grain size and the percentage of coarse grain areas were larger than in the case of high oxygen content. The strength and ductility have been determined by tensile tests. For low oxygen content, the presence of large coarse grains allowed plastic strain in some cases, and for the samples consolidated at higher temperatures, yield strength of 865 MPa with a 8% total strain were obtained. For the samples with high oxygen content plastic deformation was no possible in any case. The observed stress for both compositions was analysed by two approaches, one based exclusively in grain boundary strengthening and the other one based in two effects acting at the same time: grain boundary and particle strengthening. Whereas grain boundary strengthening seems to fit with the strength of the samples in the nanostructured range, when coarse ferrite grains appear the addition of particle strengthening help to get better results. This indicates that the presence of oxides dissolved inside the large grains reinforce the structure of ball-milled iron.

  • Influence of composition, grain size, and oxide particles on the strength of consolidated ball-milled iron

     Benito Paramo, Jose Antonio; Gregoire, V.; Casas Solé, Concepció; Cabrera Marrero, Jose Maria
    The 6th international conference on nanomaterials by severe plastic deformation
    p. 012024-1-012024-7
    DOI: 10.1088/1757-899X/63/1/012024
    Presentation's date: 2014-06
    Presentation of work at congresses

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    In this paper iron powders with two oxygen content (0.2 and 0.6% wt.) have been mechanically milled and consolidated by hot static pressing at different temperatures to obtain different grain sizes. At lower temperatures the grain size was in the nanostructured and ultrafine range and with increasing temperature abnormal grain growth was observed for both compositions. This led to the development of bimodal grain size distributions. In the samples with lower oxygen content the grain size and the percentage of coarse grain areas were larger than in the case of high oxygen content. The strength and ductility have been determined by tensile tests. For low oxygen content, the presence of large coarse grains allowed plastic strain in some cases, and for the samples consolidated at higher temperatures, yield strength of 865 MPa with a 8% total strain were obtained. For the samples with high oxygen content plastic deformation was no possible in any case. The observed stress for both compositions was analysed by two approaches, one based exclusively in grain boundary strengthening and the other one based in two effects acting at the same time: grain boundary and particle strengthening. Whereas grain boundary strengthening seems to fit with the strength of the samples in the nanostructured range, when coarse ferrite grains appear the addition of particle strengthening help to get better results. This indicates that the presence of oxides dissolved inside the large grains reinforce the structure of ball-milled iron.

  • Influence of composition, grain size, and oxide particles on the strength of consolidated ball-milled iron

     Benito Paramo, Jose Antonio; Cabrera Marrero, Jose Maria; Casas Quesada, Casimir
    International Symposium on Metastable, Amorphous and Nanostructured Materials
    Presentation's date: 2014-06
    Presentation of work at congresses

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  • Can Young's modulus of metallic alloys change with plastic deformation?

     Roca Vallmajor, Antoni; Villuendas, Aránzazu; Mejía, Ignacio; Benito Paramo, Jose Antonio; Llorca Isern, Nuria; Llumà Fuentes, Jordi; Jorba Peiró, Jordi
    Materials Science Forum
    Vol. 783-786, p. 2382-2387
    DOI: 10.4028/www.scientific.net/MSF.783-786.2382
    Date of publication: 2014-05-23
    Journal article

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    The information in the basic references about the relation between elastic constants and particularly Young’s modulus (E) behavior and plastic deformation indicates that this parameter is constant or almost constant. At the beginning of the XX century several authors indicated that E of some metals decreased when cold deformation increased and detected reductions up to 15% in steels, aluminum, copper, brass... In the last years this behavior is taking into account during the finite-element analysis of sheet metal stamping or other plastic deformation processes. This work includes an extensive review of papers of our research team and of other authors related with the behavior of Young’s modulus during plastic deformation of some metallic alloys. This parameter can diminish up to 10% by plastic deformation (tension test) in iron, aluminum, and stainless steel (UNS S 30403) but remains practically unaltered in aluminum alloys deformed before or after aging. Results of Young’s modulus in nanostructured copper and copper alloys determined by ultrasonic technique are also presented. Additional results of Young’s modulus of UNS G10180 and UNS G10430 steels measured during loading and unloading steps in tension test are also included. High differences in the E values were detected between both steps.

  • Can Young's modulus of metallic alloys change with plastic deformation?

     Roca Vallmajor, Antoni; Villuendas, Aránzazu; Mejía, Ignacio; Benito Paramo, Jose Antonio; Llorca Isern, Nuria; Llumà Fuentes, Jordi; Jorba Peiró, Jordi
    International Conference on Processing and Manufacturing of Advanced Materials
    p. 2382-2387
    DOI: 10.4028/www.scientific.net/MSF.783-786.2382
    Presentation's date: 2013-12-03
    Presentation of work at congresses

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    The information in the basic references about the relation between elastic constants and particularly Young’s modulus (E) behavior and plastic deformation indicates that this parameter is constant or almost constant. At the beginning of the XX century several authors indicated that E of some metals decreased when cold deformation increased and detected reductions up to 15% in steels, aluminum, copper, brass... In the last years this behavior is taking into account during the finite-element analysis of sheet metal stamping or other plastic deformation processes. This work includes an extensive review of papers of our research team and of other authors related with the behavior of Young’s modulus during plastic deformation of some metallic alloys. This parameter can diminish up to 10% by plastic deformation (tension test) in iron, aluminum, and stainless steel (UNS S 30403) but remains practically unaltered in aluminum alloys deformed before or after aging. Results of Young’s modulus in nanostructured copper and copper alloys determined by ultrasonic technique are also presented. Additional results of Young’s modulus of UNS G10180 and UNS G10430 steels measured during loading and unloading steps in tension test are also included. High differences in the E values were detected between both steps.

  • Influence of oxygen content on the strength and ductility of pure iron obtained by mechanical milling

     Casas Quesada, Casimir; Benito Paramo, Jose Antonio; Cabrera Marrero, Jose Maria
    European Congress and Exhibition on Advanced Materials and Processes
    Presentation's date: 2013-09
    Presentation of work at congresses

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    Efecto de la distribución bimodal de grano en la ductilidad de hierro nanoestructurado obtenido por proceso de molienda mecánica  Open access

     Casas Quesada, Casimir; Benito Paramo, Jose Antonio; Cabrera Marrero, Jose Maria
    Congreso Nacional de Pulvimetalurgia
    p. 187-196
    Presentation's date: 2012-06-21
    Presentation of work at congresses

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    El presente trabajo versa sobre la fabricación de piezas consolidadas de hierro a partir de polvo de hierro puro con estructura nanocristalina obtenido mediante el proceso de molienda mecánica (MM) en un molino de bolas planetario. Las piezas son sometidas a tratamientos térmicos posteriores a la consolidación para obtener una distribución bimodal de grano. Dichos compactos son caracterizados mecánicamente (ensayos de microtracción y microindentación) y microestructuralmente (EBSD, MEB). La microestructura bimodal compuesta de una matriz de granos inferiores a los 100 nanómetros rodeando granos de tamaño superior a 1 micrómetro, refleja altas propiedades mecánicas como límite elástico y dureza gracias a los granos finos, y, como se muestra en el trabajo, se produce una mejora de la ductilidad gracias a los granos micrométricos. En el trabajo actual se ha analizado en profundidad los fenómenos de deformación plástica para este tipo de material y microestructura.

  • Mejora de la tenacidad en aceros bainiticos-microaleados de alta resistencia para componentes de automoción

     Riera Colom, Maria Dolores; Calvo Muñoz, Jessica; Benito Paramo, Jose Antonio; Prado Pozuelo, Jose Manuel; Cabrera Marrero, Jose Maria
    Competitive project

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  • Endurecimiento de chapa de acero TWIP durante ensayos cíclicos tracción-compresión

     Calvo Muñoz, Jessica; Benito Paramo, Jose Antonio; Cabrera Marrero, Jose Maria
    Congreso Nacional de Propiedades Mecánicas de Sólidos
    p. 121-126
    Presentation of work at congresses

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    Studying the Hall-Petch effect regarding sub-micrometer steel (0.6% C)  Open access

     Rodríguez Baracaldo, R.; Cabrera Marrero, Jose Maria; Benito Paramo, Jose Antonio
    Ingeniería e investigación
    Vol. 31, num. 3, p. 112-120
    Date of publication: 2011-12
    Journal article

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    Este trabajo describe la obtención y caracterización mecánica de una aleación de acero 0,6% C con estructura de tamaño de grano inferior a 1 μm. El proceso para la obtención de piezas masivas se inicia sometiendo el polvo a severa deformación plástica en un molino planetario de bolas y a continuación se realiza la consolidación a alta presión y temperaturas entre 350 y 500 °C. El estudio de la evolución del tamaño de grano muestra que los consolidados sin tratamiento térmico posterior conservan su estructura en el rango nanométrico. En muestras con tratamiento térmico se observa un crecimiento controlado debido a los numerosos puntos de nucleación y la presencia de precipitados de cementita. Los resultados de dureza y tamaño de grano obtenidos cumplen la relación de Hall -Petch. Finalmente se analiza la influencia de las técnicas de obtención y de caracterización mecánica empleadas en este trabajo frente a diferentes fuentes bibliográficas.

  • Caracterització de la deformació en calent i conformabilitat d'acers TWIP per definir rutes de processament que permetin optimitzar

     Cabrera Marrero, Jose Maria; Benito Paramo, Jose Antonio; Calvo Muñoz, Jessica
    Competitive project

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  • Process planning and metallurgical issues for laser asisted spin froming of dual phase automotive steel

     Romero, Pablo; Otero, N.; Otero, J.; Benito Paramo, Jose Antonio; Rodríguez Calvillo, Pablo
    International Deep Drawing Research Group Conference
    p. 1-12
    Presentation's date: 2011-06-07
    Presentation of work at congresses

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  • Young's modulus variation during unloading for a wide range of AHSS steel sheets

     Cobo Molina, Raul; Hernandez Rossi, Ricardo; Benito Paramo, Jose Antonio; Riera Colom, Maria Dolores
    International Deep Drawing Research Group
    p. 1-10
    Presentation's date: 2011-06-07
    Presentation of work at congresses

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  • Predicción del springback en el conformado asistido por láser de chapas de acero DP800 mediante simulación con Abaqus

     Cobo Molina, Raul; Brígido Belmonte, Albert; Benito Paramo, Jose Antonio; Romero, Pablo; Otero, Nerea; Riera Colom, Maria Dolores
    Congreso Nacional de Tratamientos Térmicos y de Superficie
    p. 85-96
    Presentation's date: 2010-10
    Presentation of work at congresses

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  • Tensile and compressive test in nanocrystalline and ultrafine carbon steel

     Rodríguez Baracaldo, R.; Benito Paramo, Jose Antonio; Cabrera Marrero, Jose Maria
    Journal of materials science
    Vol. 45, num. 17, p. 4796-4804
    DOI: 10.1007/s10853-010-4600-7
    Date of publication: 2010-09
    Journal article

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    Plastic deformation behavior was investigated in near fully dense nanostructured and ultrafine-grained bulk samples of carbon steel (0.55 wt% C) under compression and tension tests. The specimens were obtained by hot pressure from mechanically milled powder at 400 and 500 0C. Subsequent heat treatments at temperatures going from 600 to 900 0C produced samples with ferrite grain sizes from 30 nm to 17 lm. Nanocrystalline grained steel samples presented very high strength with low ductility. Once, in the ultrafine range, as the ferritic grain size was increased, the strength was decreased and the ductility was improved. The porosity and carbon atoms within the structure were analyzed in order to explain the results of strength and strain obtained.

  • Cobre nanocristalino y ultrafino obtenido por molienda mecánica

     Rodríguez Baracaldo, R.; Benito Paramo, Jose Antonio; Cabrera Marrero, Jose Maria
    Ingeniería e investigación
    Vol. 30, num. 1, p. 141-145
    Date of publication: 2010
    Journal article

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  • The influence of deformation on microstructure evolution of low alloy TRIP steel

     Suarez Fernandez, Lucia; Benito Paramo, Jose Antonio; Rodríguez Calvillo, Pablo; Houbaert, Yvan; Casellas Padro, Daniel; Petrov, Roumen H.; Prado Pozuelo, Jose Manuel
    Materials science forum
    Vol. 638-642, p. 3531-3536
    DOI: 10.4028/www.scientific.net/MSF.638-642.3531
    Date of publication: 2010
    Journal article

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  • Ductility of Bulk Nanocrystalline and Ultrafine Grain Iron and Steel

     Benito Paramo, Jose Antonio; Tejedor Busquets, Robert; Rodríguez Baracaldo, R.; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    Materials science forum
    Vol. 633 - 634, num. 197, p. 197-203
    DOI: 10.4028/www.scientific.net/MSF.633-634.197
    Date of publication: 2009-11
    Journal article

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  • PROCESAMIENTO, PROPIEDADES Y CARACTERÍSTICAS DE ACEROS DESTINADOS AL SECTOR ELECTRICO

     Benito Paramo, Jose Antonio; Prado Pozuelo, Jose Manuel; Calvo Muñoz, Jessica; Riera Colom, Maria Dolores; Suarez Fernandez, Lucia; Rodríguez Calvillo, Pablo; Cabrera Marrero, Jose Maria
    Competitive project

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    Analysis of the decrease of the apparent young's modulus of advanced high strength steels and its effect in bending simulations  Open access

     Cobo Molina, Raul; Pla, M.; Hernandez Rossi, Ricardo; Benito Paramo, Jose Antonio
    International Deep Drawing Research Group Conference
    p. 109-117
    Presentation's date: 2009-06-01
    Presentation of work at congresses

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    In this paper the evolution of the Young’s Modulus (E) during unloading with plastic deformation has been studied for different Dual-Phase AHSS from DP780 to DP1400. During unloading, all the DP steels studied showed the presence of microplasticity so an Apparent Young’s Modulus (EA) has been defined. Although that in all cases EA decreased with a non-linear behavior as the plastic strain was increased, it has been observed that the final percentage of decrease seems to be related to the microstructure of DP steels. As the ferrite content increased as in the lower strength DP steels, the reduction of EA is larger, reaching a 21%. The introduction of the variation of the elastic response during unloading in the simulation of a bending operation has allowed obtaining an improvement of the accuracy in springback prediction in all the DP steels studied. For the low strength DP steels the final shape obtained by simulation is in fact the same than the real one. As the strength of steel is increased, the accuracy is less, especially in the DP 1400 steel, in which differences in bending angle higher than a 15% are still found.

  • AUMENTO DE LA DUCTIBILIDAD EN FRIO DE MATERIALES METÁLICOS CON TAMAÑO DE GRANO NANOCRISTALINO Y ULTRAFINO

     Prado Pozuelo, Jose Manuel; Benito Paramo, Jose Antonio; Riera Colom, Maria Dolores; Llumà Fuentes, Jordi; Jorba Peiró, Jordi; Cabrera Marrero, Jose Maria
    Competitive project

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  • Microstructural evolution and mechanical response of nanocrystalline and ultrafine-grained steel obtained by mechanical milling

     Rodríguez-Baracaldo, R R Tejedor; Benito Paramo, Jose Antonio; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    Materials science and engineering A. Structural materials properties microstructure and processing
    Vol. 493, p. 215-220
    Date of publication: 2008-09
    Journal article

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  • Influence of the carbon content on the strain rate sensitivity of nanocrystalline steels

     Tejedor Busquets, Robert; Rodriguez-Baracaldo, R; Benito Paramo, Jose Antonio; Caro, J; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    Scripta materialia
    Vol. 59, num. 6, p. 631-634
    DOI: doi:10.1016/j.scriptamat.2008.05.024
    Date of publication: 2008-09
    Journal article

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  • Obtención caracterización de aceros con grano nanométrico y ultrafino fabricados mediante molienda mecánica

     RODRÍGUEZ BARACALDO, RODOLFO
    Department of Materials Science and Metallurgy, Universitat Politècnica de Catalunya
    Theses

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  • Study of the plastic deformation in nanocrystalline and ultrafine iron and carbon steels

     Benito Paramo, Jose Antonio; Tejedor, R; Rodríguez-Baracaldo, R; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    Materials science forum
    Vol. 584-586, p. 617-622
    Date of publication: 2008-07
    Journal article

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  • Study of the influence of the decrease of the apparent young's modulus during unloading in the springback prediction

     Cobo Molina, Raul; Hernandez Rossi, Ricardo; Benito Paramo, Jose Antonio; Casellas Padro, Daniel; Riera Colom, Maria Dolores
    International Deep Drawing Research Group
    p. 785-791
    Presentation's date: 2008-06-16
    Presentation of work at congresses

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  • Strain rate sensitivity of nanocrystalline and ultrafine-grained steel obtained by mechanical attrition

     Rodriguez-Baracaldo, R; Benito Paramo, Jose Antonio; Caro, J; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    Materials science and engineering A. Structural materials properties microstructure and processing
    Vol. 485, num. 1-2, p. 325-333
    Date of publication: 2008-06
    Journal article

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  • Plastic deformation of a nanostructured and ultra-fine grained Fe-1%Cr with a bimodal grain size distribution

     Tejedor Busquets, Robert; Rodríguez Baracaldo, R.; Benito Paramo, Jose Antonio; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    International journal of material forming
    Vol. 1, num. 1, p. 487-490
    DOI: 10.1007/s12289-008-0109-x
    Date of publication: 2008-04-01
    Journal article

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  • Análisis de la fractura de un acero de bajo contenido en carbono con grano nanométrico y ultrafino obtenido por molienda mecánica

     Tejedor, R; Rodríguez, R Baracaldo; Benito Paramo, Jose Antonio; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    Anales de mecánica de la fractura
    Vol. 25, num. 1, p. 157-162
    Date of publication: 2008-03
    Journal article

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  • MIRAS-SMOS Antenna Relative Phase Calibration

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Benito Paramo, Jose Antonio; Martín Neira, Manuel
    IEEE International Symposium on Antennas and Propagation
    p. 1-5
    Presentation of work at congresses

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  • Procesos de severa deformación plástica para obtener materiales de grano nanométricos y ultrafinos

     Rodríguez-Baracaldo, R; Benito Paramo, Jose Antonio; Cabrera Marrero, Jose Maria
    Ingeniería e investigación
    Vol. 27, num. 1, p. 101-105
    Date of publication: 2007-04
    Journal article

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  • Mechanical response of nanocrystalline steel obtained by mechanical attrition

     Rodriguez-Baracaldo, R; Benito Paramo, Jose Antonio; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    Journal of materials science
    Vol. 42, num. 5, p. 1757-1764
    Date of publication: 2007-03
    Journal article

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  • High temperature wear resistance of (TiAI)N PVD coating on untreated and gas nitrided AISI H13 steel with different heat treatments

     Rodriguez-Baracada, R; Benito Paramo, Jose Antonio; Puchi-Cabrera, E S; Staia, M H
    Wear
    Vol. 262, num. 3-4, p. 380-389
    Date of publication: 2007-02
    Journal article

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  • Determination of the work hardening exponent by the Hollomon and differential Crussard-Jaoul analyses of cold ferrite-pearlite steels

     Mejía, I; Maldonado, C; Benito Paramo, Jose Antonio; Jorba Peiró, Jordi; Roca Rosell, Antoni-maria Claret
    Materials science forum
    Vol. 509, p. 37-42
    Date of publication: 2006-03
    Journal article

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  • Resistencia mecánica a compresión de hierro nanocristalino consolidado en tibio

     Rodríguez, R; Benito Paramo, Jose Antonio; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    Congreso Nacional de Materiales
    p. 95-98
    Presentation of work at congresses

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    Study of the nanometric grain size distribution in iron compacts obtained by mechanical milling  Open access

     Llumà Fuentes, Jordi; Benito Paramo, Jose Antonio; Roca Rosell, Antoni-maria Claret; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    Materials science forum
    Vol. 503-504, p. 1007-1012
    Date of publication: 2006-01
    Journal article

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    A study has been carried out on the grain size distribution of cylindrical compacts obtained by consolidation of iron powder severely deformed by mechanical milling. Consolidation has been performed in two consecutive steps: cold and hot conditions. The hot one was done at two temperatures, namely 425 and 475ºC. After milling, the iron powder has a grain size of 8 nm (± 4 nm) with an average hardness of 800 HV. After hot compaction the grain size increases up to 50 nm, especially at 475ºC where a small fraction of grains reach larger values than the average. The grain size was evaluated by two different techniques, X-Ray Diffraction and Transmission Electron Microscopy. Results showed some differences between both methods. The advantage of using TEM is that grain size distribution, and not only the average size, can be obtained. Small discs were also obtained from the compacted specimen in order to fracture them on a “ball on three balls” equipment. The fracture behaviour of the samples was then studied by SEM.

  • Change of Young's modulus of cold-deformed pure iron in a tensile test

     Manero Planella, Jose M.; Benito Paramo, Jose Antonio; Jorba Peiró, Jordi; Roca Vallmajor, Antoni
    Metallurgical and materials transactions A-Physical metallurgy and material
    Vol. 36A, num. 12, p. 3317-3324
    DOI: 10.1007/s11661-005-0006-6
    Date of publication: 2005-12
    Journal article

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    Changes in Young's modulus E (determined according to ASTM E-111) of polycrystalline pure iron deformed by a tensile test at room temperature are determined. From its original mean value. 210 GPa, E decreased with deformation to a mean value of 196 GPa at epsilon = 0.060. Thereafter, slight recovery occur-red and E stabilized to 198 GPa until the appearance of neck (epsilon = 0.100). With the aim to examine the causes of this behavior, residual stresses and textures were measured and the dislocation structure was observed by transmission electron microscopy (TEM). Longitudinal residual stresses,, increased from the first step of deformation (epsilon = 0.015) and remained constant until the samples fractured. There was no significant difference in texture throughout the deformation process, during which the increment of alpha fiber was smooth. Thus, the decrease of E cannot be attributed to residual stresses or textures. A relationship between dislocation arrangement and decrease of E is proposed. Following the model established by Mott, dislocations can bow out in their glide planes, giving extra elastic strain and thus a decrease of E. The increase of the dislocation density during the first steps of deformation lowers the E values, since the extra elastic strain increases. At higher strains, when the cellular dislocation structure has formed (between epsilon = 0.060 and 0.080), the dislocations in cell interiors are capable of giving an extra elastic strain, whereas the dislocations trapped in the cell walls are not. However, the dislocation density in cell interiors is lower than the dislocation density in the early stages of deformation in which the cell structure has not been developed. This produces the slight recovery of E measured at these strains. From epsilon = 0.080, the values of E stabilized since no changes in dislocation density in cell interiors are observed.

  • Study of the inelastic response of TRIP steels after plastic deformation

     Pérez Brunet, Roberto; Benito Paramo, Jose Antonio; Prado Pozuelo, Jose Manuel
    ISIJ international
    Vol. 45, num. 12, p. 1925-1933
    DOI: 10.2355/isijinternational.45.1925
    Date of publication: 2005-12
    Journal article

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  • OPTIMIZACIÓN DE RUTAS DE PROCESAMIENTO DE MATERIALES METÁLICOS PARA LA OBTENCIÓN DE GRANO ULTRAFINO

     Benito Paramo, Jose Antonio; Cabrera Marrero, Jose Maria; Llumà Fuentes, Jordi; Jorba Peiró, Jordi
    Competitive project

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  • MECHANICAL RESPONSE OF NANOMETRIC IRON

     Benito Paramo, Jose Antonio
    Micromechanics and Microstructure Evolution: Modeling, Simulation and Experiments
    Presentation's date: 2005-09-12
    Presentation of work at congresses

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  • Empirical model for time evolution thermal-depending properties of aluminium alloys

     Llumà Fuentes, Jordi; Benito Paramo, Jose Antonio
    International Conference on Computational Plasticity
    p. 974-977
    Presentation's date: 2005-09-06
    Presentation of work at congresses

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  • Estudio de la fractura de compactos de hierro con grano nanométrico obtenidos por molienda mecánica

     Villunedas, A; Llumà Fuentes, Jordi; Benito Paramo, Jose Antonio; Roca Rosell, Antoni-maria Claret; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    Encuentro del Grupo Español de Fractura
    p. 514-518
    Presentation's date: 2005-03-09
    Presentation of work at congresses

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  • Estudio de la fractura de compactos de hierro con grano nanométrico obtenidos por molienda mecánica

     Villuendas, Aránzazu; Llumà Fuentes, Jordi; Benito Paramo, Jose Antonio; Roca Rosell, Antoni-maria Claret; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    Anales de mecánica de la fractura
    num. 22, p. 514-518
    Date of publication: 2005-03
    Journal article

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  • Study of the nanometric grain size distribution in iron compacts obtained by mechanical milling

     Llumà Fuentes, Jordi; Benito Paramo, Jose Antonio; Roca Rosell, Antoni-maria Claret; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    International Conference on Nanomaterials by Severe Plastic Deformation
    p. 1007-1012
    Presentation of work at congresses

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  • DETERMINATION OF THE WORK HARDENING EXPONENT BY HOLLOMON AND DIFFERENTIAL CRUSSADR-JAOUL ANALYSIS OF COLD DRAWN FERRITE-PEARLITE STEELS

     Benito Paramo, Jose Antonio
    XIII INTERNATIONAL MATERIALS RESEARCH CONGRESS
    Presentation's date: 2004-08-22
    Presentation of work at congresses

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  • ENSAYOS DE DOBLE COMPRESIÓN PARA ESTUDIO DE LA RECRISTALIZACIÓN ESTÁTICA DE ACEROS INOXIDABLES

     Benito Paramo, Jose Antonio
    Congreso Nacional de Propiedades Mecánicas de Sólidos
    Presentation's date: 2004-06-22
    Presentation of work at congresses

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  • Obtención de polvo de hierro con grano ultrafino mediante severa deformación plástica en molino de bolas

     López, A; Arias, E; Benito Paramo, Jose Antonio; Roca Rosell, Antoni-maria Claret; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    Congreso Nacional de Materiales
    p. 359-364
    Presentation's date: 2004-06-15
    Presentation of work at congresses

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  • Obtención de polvo de hierro en grano ultrafino mediante severa deformación plástica en molino de bolas

     López, A.; Arias, E.; Benito Paramo, Jose Antonio; Roca, A.; Cabrera Marrero, Jose Maria; Prado Pozuelo, Jose Manuel
    Congreso Nacional de Materiales
    p. 359-364
    Presentation of work at congresses

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