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UPCommons - E-prints UPC Universitat Politècnica de Catalunya (59.763 recursos)
E-prints UPC cobreix dues finalitats: per una banda, és el dipòsit institucional de la UPC que recull els articles de revista, les comunicacions de congrés i els reports de recerca generats en les activitats de recerca del personal docent i investigador de la universitat; per l'altra, és una eina que permet accelerar la producció científica, allotjant versions de documents prèvies a la publicació en una revista o a les actes d’un congrés.

Articles de revista

Mostrando recursos 1 - 20 de 50

1. Evaluation of essential work of fracture in a dual phase high strength steel sheet - Gutierrez, David; Pérez Caro, Lluís; Lara, Antoni; Casellas Padró, Daniel; Prado Pozuelo, José Manuel
La tenacidad de fractura de aceros de alta resistencia (AHSS), es una propiedad interesante para optimizar el com- portamiento a impacto, pero su caracterización experimental en chapas metálicas es compleja debido a su espesor. En este trabajo se plantea el método del Trabajo Esencial de Fractura (TEF), como alternativa al cálculo de la tenacidad. Este método ya ha sido utilizado con éxito en polímeros y aceros dúctiles, aunque la información sobre su aplicación en AHSS es escasa. Se ha evaluado la tenacidad en un acero de fase dual de 800 MPa de resistencia y se ha comparado con la de un acero de embutición. Los...

2. Dynamic recovery and dynamic recrystallization competition on a Nb- and N-bearing austenitic stainless steel biomaterial: Influence of strain rate and temperature - Souza, R.C.; Silva, E.S.; Jorge, A.M.; Cabrera Marrero, José M.; Balancin, O.
The objective of this study was to investigate the dynamic softening behavior of an austenitic stainless steel with high nitrogen (type ISO 5832-9) through hot torsion tests, in the temperature range of 900–1200 °C and in the strain rate range of 0.01–10 s−1. The shape of flow stress curves indicated that the softening was promoted by dynamic recovery followed by dynamic recrystallization with high level of recovery. The microstructure evolution indicated that even though after large straining as that of the steady state stresses a combination of strained and recrystallized grains was observed. The delay of dynamic recrystallization, which is...

3. Texture analysis in ultrafine grained coppers processed by equal channel angular pressing - Higuera Cobos, Oscar Fabián; Cabrera Marrero, José M.
Electrolytic tough pitch (ETP) and fire refined high conductivity (FRHC) copper samples were severely deformed at room temperature by equal channel angular pressing (ECAP) up to 16 passes ( ε ~ 1 per pass), following route Bc. The effect of the initial texture on the evolution of texture after the ECAP process for both materials was analyzed. The annealed materials present a marked anisotropy, with a texture controlled by the <110> fiber. According to the orientation distribution function (ODF), this initial behavior allows the presence of a strong C ({001} <110>) component after the first two ECAP passes in both coppers. However in the second pass the C component significantly...

4. Mechanical, microstructural and electrical evolution of commercially pure copper processed by equal channel angular extrusion - Higuera Cobos, Oscar Fabián; Cabrera Marrero, José M.
Samples of commercially pure copper (ETP copper) were subjected to equal-channel angular pressing (ECAP) for up to 16 passes at room temperature following route Bc. Microstructural evolution was determined by oriented image microscopy (OIM) and differential scanning calorimetry (DSC) was used to estimate the stored deformation energy and the recrystallization temperature after each ECAP pass. On the other hand, electrical properties were correlated with the associated energy that results from the defects induced by ECAP. Results show that the stored energy rises on increasing ECAP deformation, while the recrystallization temperature decreases significatively. Also, mechanical properties after each pass were evaluated...

5. Microstructures and mechanical properties of pure copper deformed severely by equal-channel angular pressing and high pressure torsion - Lugo, N; Llorca, N; Cabrera Marrero, José M.; Horita, Z
Pure Cu of 99.98 wt.% purity has been processed at room temperature by diverse techniques of severe plastic deformation, namely equalchannel angular pressing (ECAP), high pressure torsion (HPT) and a combination of both in order to find out the evolution on the microstructural homogeneity for each of the processes and their combination. Starting with a grain size of ∼60 m, severe plastic deformation has been introduced to the material while maintaining the sample dimensions unchanged through the processes of ECAP and HPT. A significant decrease in grain size was observed by transmission electronic microscopy (TEM). Microtensile and microhardness tests were carried out...

6. Thermal stability of ultrafine grains size of pure copper obtained by equal-channel angular pressing - Lugo Chacón, Nayar Adolfo; Llorca, N.; Suñol Martinez, Juan Jose; Cabrera Marrero, José M.
Ultrafine grain of pure copper 99.98% was produced by severe plastic deformation using the equalchannel angular pressing (ECAP) method. Copper samples were ECAPed from 1 to 8 passes following route BC; fine grain sizes of 250 nm were developed after eight passes. Important enhancement in the mechanical strength properties was obtained. Subsequent heat treatments (HT) were carried out to evaluate the thermal stability of the grains of the ECAPed samples. Microstructure and mechanical properties were evaluated to determine the recovery and recrystallization temperatures. Differential scanning calorimetry (DSC) tests were conducted to all samples in order to determinate these temperatures. The activation energy...

7. Microstructural, thermical and mechanical characterization of ZK60 alloy processed through ECAP - Dumitru, Florina Diana; Ghiban, Brândusa; Cabrera Marrero, José M.; Higuera, Oscar Fabián; Ghiban, Nicolae; Gurau, Gheorghe H.

8. Hot deformation activation energy (QHW) of austenitic Fe-22Mn-1.5Al-1.5Si-0.4C TWIP steels microalloyed with Nb, V, and Ti - Reyes Calderón, F.; Mejía Granados, Ignacio; Cabrera Marrero, José M.
The activation energy for hot deformation ( Q HW ) of high-Mn microalloyed TWIP steels was determined from experimental uniaxial hot compression curves. The presence of microalloying elements such as Nb, V, and Ti, increases the Q HW value from 366 in the non-microalloyed one to 446 kJ/mol in the V-microalloyed TWIP steel. This change represents an increase from 16% up to 22% of Q HW values.

9. Effect of microalloying elements (Nb, V and Ti) on the hot flow behavior of high-Mn austenitic twinning induced plasticity (TWIP) steel - Reyes Calderón, F.; Mejía Granados, Ignacio; Boulaajaj, A.; Cabrera Marrero, José M.
This research work studies the effect of microalloying elements such as Nb, V and Ti on the hot flow behavior of high-Mn austenitic TWIP steel. For this purpose, isothermal uniaxial hot compression tests were carried out at three temperatures (900, 1000 and 1100 1 C) and four constant strain rates (10 1 , 10 2 ,10 3 and 10 4 s 1 ). Experimental results revealed that hot flow curves of microalloyed TWIP steels show single peak curves for all test conditions. Results are discussed in terms of the peak stress ( s p ) and peak strain ( e p ) and its dependence on the strain rate ( _ e ) and temperature. The addition of microalloying elements such as Nb, V and Ti in...

10. Determination of the critical parameters for the onset of dynamic recrystallization (DRX) in advanced ultrahigh strength steels (A-UHSS) microalloyed with boron - Altamirano Guerrero, Gerardo; Mejía Granados, Ignacio; Cabrera Marrero, José M.
In this research work, the double differentiation mathematical method was used to identify more accurately the criti- cal stress ሺ ߪ ௖ ) and critical strain ሺ ߝ ௖ ) associated with the onset of dynamic recrystallization (DRX), which is based on changes of the strain hardening rate )ߝ߲/ߪ߲ ൌ ߠሺ as a function of the flow stress (Poliak and Jonas method, simplified by Najafizadeh and Jonas). For this purpose, a low carbon advanced ultra-high strength steel (A-UHSS) microalloyed with different amounts of boron (14, 33, 82, 126 and 214 ppm) was deformed by uniaxial hot-compression tests at high tempe- ratures 1100 ݀݊ܽ ሺ950,1000,1050 ° )ܥ and constant true strain rates ሺ 10 ିଷ ,10 ିଶ 10 ݀݊ܽ ିଵ ݏ ିଵ ) . Results indicate that both ߪ ௖ and ߝ ௖ increase with decreasing deformation temperature and in creasing...

11. On the onset of dynamic recrystallization in steels - Varela Castro, Gonzalo; Cabrera Marrero, José M.; Prado Pozuelo, José Manuel
The knowledge of the flow behavior of metallic all oys subjected to hot forming operations is of particular interest for designers and engineers in the practice of industrial forming processes simulations (i.e. rolling mill). Nowadays dynamic recrystallization (DRX) is recognized as one of the most relevant and meaningful mechanis ms available for the control of microstructure. This mechanism occurs during hot forming operations over a wide range of metals and alloys and it is known to be as a powerful tool which can be used to the control of the microstructure and properties of alloys. Therefore is important to kno w, particularly in low stacking fault energy (SFE) materials, the precise time for which...

12. Equal channel angular pressing of Cu-Al bimetallic rods - Llorca Isern, Nuria; Escobar, Ana Maria; Roca, Antoni; Cabrera Marrero, José M.
Coextrusion and corolling are the major processes to produce bimetallic rods, tubes and wires, the objective being to perform clad metals, bimetallic joints or seals. The aim of the present work is to produce bimetallic rods showing an ultra fine grained microstructure with enhanced properties. Bimetallic Cu-Al rods were deformed by equal channel angular pressing (ECAP) in order to study their microstructure. ECAP is an int eresting process for producing bulk materials with refined microstructure and, consequently, chan ges in physical, chemical and mechanical properties can be observed. Higher shear strength a nd dimensional stability are among the advantages of this process. A comparative experimen tal study of pure commercial copper with cylindrical inner aluminium rods...

13. Comportamiento termomecánico de un acero microaleado al Nb-V - Cartaya, E. A.; Varela, G.; Cabrera Marrero, José M.; Prado Pozuelo, José Manuel
Empleando ensayos de compresión simple en ca- liente y relajación de tensiones después de la de - formación en un dilatómetro modelo DIL805T, se obtuvieron las curvas de fluencia y relajación de dos aceros, el primero de ellos al C – Mn y otro HS- LA con idéntica composición química base, micro- aleado con Nb – V. Los ensayos de compresión simple fueron efectua- dos a temperaturas en el rango austenítico, desde 900 – 1.200 ºC y velocidades de deformación de 0.001, 0.01, 0.1, 1 y 10 s - 1 . Se obtuvieron las curvas de fluencia para las diferentes condiciones, permitien- do el estudio del efecto de los elementos microale- antes sobre la recristalización dinámica y...

14. The origin of microstructure inhomogeneity in Mg-3Al-1Zn processed by severe plastic deformation - Fatemi Varzaneh, Mahmood; Zarei-Hanzaki, A.; Vaghar, R.; Cabrera Marrero, José M.
A Mg–3Al–1Zn alloy has been severely deformed by accumulative back extrusion to investigate the effects of processing parameters (temperature and deformation pass) on the microstructure homogeneity. The results indicate that the activation of different grain refinement mechanisms in magnesium may result in an inhomogeneous microstructure, i.e. a bimodal grain size distribution. However, a rapid rate of homogeneity development has been occurred through applying further subsequent passes. This has been justified considering the imposed strain reversal during accumulative back extrusion processing.

15. Effect of V on Hot Deformation Characteristics of TWIP Steels - Reyes, Francisco; Calvo Muñoz, Jessica; Cabrera Marrero, José M.; Mejía, Ignacio
Twinning induced plasticity (TWIP) steels, which rely on high Mn contents to promote twinning as the deformation mechanism, exhibit high ultimate strengths together with outstanding combinations of ultimate strength and ductility. In terms of mechanical properties, one of the most important microstructural features is grain size. The knowledge of the kinetics of recrystallization mechanisms, i.e., dynamic recrystallization (DRX) and static recrystallization (SRX), can be used in order to control the grain size of the final product by a proper rolling schedule design. The focus of this work is the characterization of the DRX kinetics of two TWIP steels. The basic composition of the steels is Fe–21Mn–0.4C–1.5Al–1.5Si, and one...

16. Comportamiento a fractura de aceros metaestables - Mateo García, Antonio Manuel; Gutierrez, D.; Lara, A.; Zapata Dederle, Ana Cristina; Rodríguez Calvillo, Pablo; Fargas Ribas, Gemma; Calvo Muñoz, Jessica; Casellas Padró, Daniel

17. Characterization of precipitation kinetics of Inconel 718 superalloy by the stress relaxation technique - Calvo Muñoz, Jessica; Cabrera Marrero, José M.; Shu, Sheyu
Inconel 718 is a nickel-chromium-iron superalloy which presents excellent mechanical properties at high temperatures, as well as good corrosion resistance and weldability. These characteristics can be optimized with an appropriate control of microstructural features such as grain size and precipitation. Precipitates of different nature can form in these alloys, i.e. γ’’ (a metastable metallic compound Ni3Nb), γ’ (Ni3(Ti, Al), carbides and/or δ phase (intermetallic Ni3Nb). Aging treatments are usually designed to obtain the precipitation required in order to optimize mechanical properties. However, precipitation can also appear induced by deformation and therefore interfere with hot forming operations, such as forging. Under these conditions, precipitation may lead to an increase...

18. Effect of the testing conditions on the hot ductility and fracture mechanisms of a C-Mn steel - Calvo Muñoz, Jessica; Cabrera Marrero, José M.; Rezaeian, A.; Yue, S.

19. EBSD study of a hot deformed austenitic stainless steel - Mirzadeh, H.; Cabrera Marrero, José M.; Najafizadeh, A.; Rodríguez Calvillo, Pablo
The microstructural evolution of a 304 H austenitic stainless steel subjected to hot compression was studied by the electron backscattered diffraction (EBSD) technique. Detailed data about the boundaries, coincidence site lattice (CSL) relationships and grain size were acquired from the orientation imaging microscopy (OIM) maps. It was found that twins play an important role in the nucleation and growth of dynamic recrystallization (DRX) during hot deformation. Moreover, the conventional discontinuous DRX (DDRX) was found to be in charge of grain refinement reached under the testing conditions studied. Furthermore, the recrystallized fraction (X) was determined from the grain average misorientation (GAM)...

20. OptiLam: design of optimised rolling schedules - Peña, B.; Arribas, M.; Carrillo, A.R.; Barbero, J. I.; Calvo Muñoz, Jessica; Song, Yue
Nowadays il is known that the Ihennomcchanical schedules applied during hot rolling of fIal products provide the steel with improvcd mechanical properties. In Ihis work an oplimisation tool, OptiLam (OptiLam v.l), bascd on él predictive software alld capabIe oC generating optimised rolling schedulcs to obtain Ihe dcsired mechanical properties in the fiual product is described. OptiLam includes somc well-knowll Illctallurgical modcls which predict microstmctural evolution duril1g hot rolling and the trnnsConnation austenite/ferrite during the cooling. Furthennore, an oplimisation algorithlll, which is bascd 011 the gradient mclhod, has been added, in order to design thermoI11cchanical sequences whell a spccific final grain size is desired. OptiLam has been...

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