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UPCommons - E-prints UPC Universitat Politècnica de Catalunya (80,168 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 71

1. High temperature scratch testing of hard PVD coatings deposited on surface treated tool steel - Pujante, Jaume; Vilaseca, Montserrat; Casellas, Daniel; Riera Colom, María Dolores
Scratch testing is one of the most usual characterisation techniques for systems with thin hard coatings. Scratch tests are performed at run at room temperature, due to the risk of degradation of the indenter diamond tip at high temperature and added test complexity. However, results obtained at room temperature may differ from the final system performance in high temperature applications, due to factors such as substrate thermal softening. In this work, a simple and a robust test for the mechanical characterisation of hard PVD coatings at high temperature and open atmosphere has been developed, based on a modification of the scratch...

2. EBSD characterization of repetitive grain refinement in AZ31 magnesium alloy - Fatemi Varzaneh, S. M; Zarei Hanzaki, A; Cabrera Marrero, José M.; Rodríguez Calvillo, Pablo
A polycrystalline Mg-3Al-1Zn was subjected to high plastic strains by applying accumulative back extrusion (ABE) process. Electron back scatter diffraction analyses were used to explore the grain refinement mechanisms. A novel grain refinement trend was found at large strains, where new recrystallized grains were repetitively refined through dynamic recrystallization. The grain size was diminishing continuously up to the fourth ABE pass, after which no further grain refinement was noticed upon successive passes. (C) 2014 Elsevier B.V. All rights reserved.

3. Estudio comparativo del conformado en caliente de un acero microaleado usando criterios termodinámicos continuos y criterios fenomenológicos - Alcelay Larrión, José Ignacio; Al Omar Mesnaoui, Anas; Prado Pozuelo, José Manuel
En las últimas décadas, los mapas de procesado han sido ampliamente utilizados para diseñar, controlar y optimizar los procesos de conformado en caliente. En el presente trabajo, se presenta un estudio comparativo entre mapas de procesado elaborados usando criterios termodinámicos continuos y criterios fenomenológicos. Por ello, se llevaron a cabo ensayos de compresión en caliente en el rango de temperaturas 900 - 1150 °C y de velocidades de deformación =10-4 - 10 s-1. El comportamiento en caliente del acero estudiado ha sido estudiado analizando las curvas de fluencia y la interacción entre el comportamiento microestructural y los parámetros de control...

4. Influence of chemical composition and tempering treatment on toughness of bainitic 38MnV7 steel - Rancel, Lucia; Gómez, Manuel; Cabrera Marrero, José M.; Medina, Sebastián F.
This work studies the influence of Mn and the V/N ratio on the toughness of 38MnV7 steel. Four steels with different Mn, N and Ti contents were studied. Lowering the Mn content to approximately 1.5% considerably enhanced toughness by reducing Mn segregation and consequently achieved a more uniform bainitic microstructure. Rais ing the N content to reach a V/N ratio of close to 5 enhanced the intragranular nucleation of bainite and thus also improved toughness. Isothermal transformation prevented the presence of retained austenite and allowed a complete bainitic transformation. O ne of the steels contained Ti to control austenite grain growth by the precipitation of TiN particles. However,...

5. Calorimetric analysis of a Mg-Zn-Zr alloy processed by equal channel angular pressing via route A - Dumitru, Florina Diana; Ghiban, Brândusa; Cabrera Marrero, José M.; Higuera Cobos, Oscar Fabián; Gurau, Gheorghe; Ghiban, Nicolae
Being the lightest structural element, magnesium a nd its alloys has attracted significant interest in the last years, but because of its hexa gonal close packed structure, magnesium presents relatively low strength and ductility. One of the m ethods to improve the mechanical properties of the processed materials is through Severe Plastic D eformation (SPD). ZK60 magnesium alloy samples were subjected to 4 passes of equal-channel angular pressing (ECAP) at a processing temperature of 250°C, following route A. The micros tructure was determined with an Olympus BX51 optical microscope. Differential Scanning Calo rimetry (DSC) was used to estimate the stored energy and the recrystallization temperature after each ECAP pass

6. Strain hardening behavior of ARMCO iron processed by ECAP - Cabrera Marrero, José M.; Muñoz Bolaños, Jairo Alberto; Higuera Cobos, Oscar Fabián
The strain hardening behavior of an ARMCO iron processed by ECAP at room temperature up to sixteen passes following route Bc was investigated through Hollomon and differential Crussard-Jaoul models. Results indicate that the Hollomon analysis shows some deviations from the experimentally determined true stress – true strain curves while the differential Crussard-Jaoul analysis based on the Ludwik equation and the modified Crussard- Jaoul analysis based on the Swift equation fit better when two work hardening exponents are considered. As expected, the strength of the material increased with the number of ECAP passes. Indeed the ultimate tensile stress reached a maximum...

7. Influence of composition, grain size, and oxide particles on the strength of consolidated ball-milled iron - Benito Páramo, José Antonio; Cabrera Marrero, José M.; Casas, C.; Gregoire, V.
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...

8. Microstructural unit controlling cleavage crack propagation in high strength bainitic steels - Medina, Sebastián F.; Rancel, Lucia; Gómez, Manuel; Cabrera Marrero, José M.; Gutierrez, Isabel
The strengthening mechanisms which are operative in bainite are very well known: small bainite packet, small width of the laths, dislocation density and size and number of carbide particles (Fe 3 C), among others. Bainite packet size has been traditionally c onsidered as the value measured by optical microscopy (OM), as electron back scattered diffraction (EBSD) technique is relatively recent. In a V - microalloyed steel with bainitic microstructure of C=0.38% , V=0.12% and N= 0.0214% the average length and width of ferrite laths and of cementite carbides were measured. On the other hand, the bainite packet size was measured by OM and EBSD with a misorientation of 15º . These values of the microstructural units have been taken in account...

9. Alternative methods to attach components in printed circuit boards to improve their recyclability - Canal Marques, André; Cabrera Marrero, José M.; Malfatti, Célia de Fraga; Ortega Vega, Maria Rita
Printed circuit boards (PCB), which form the basis of the elect ronics industry, generate wastes that are difficult to dispose of and recycle due to the diversity of their materials and components and thei r difficult separation. The replacement of Pb-Sn welding for le ad-free alloys to attach components in printed circuit boards is an att empt to minimize the problem of Pb toxicity, but it does not ch ange the problem of separation of the components for later reuse and/or recycling. This article presents a review of the environmental problem of printed circuit boards, the initial development of alternative fixation studies, and reliability tests for comparison with con ventional boards and commercial systems to...

10. Hot ductility behavior of high-Mn austenitic Fe-22Mn-1.5Al-1.5Si-0.45C TWIP steels microalloyed with Ti and V - Salas-Reyes, A. E.; Mejía, Ignacio; Bedolla Jacuinde, Arnoldo; Boulaajaj, Ahmed; Calvo Muñoz, Jessica; Cabrera Marrero, José M.
This research work studies the influence of microalloying elements (Ti and V) and the solidification route on the hot ductility behavior of high-manganese TWIP steels. Uniaxial hot tensile tests in the temperature range of 700–1100 °C under a constant strain rate of 10-3 s-1 were carried out. Hot ductility as a function of reduction of area (RA) showed a significant improvement in the V-microalloyed TWIP steel, when compared to a non-microalloyed TWIP steel with a similar composition, in the intermediate temperature range of 800–900 °C. The highest value of 86% RA is attributed to the onset of dynamic recrystallization (DRX)...

11. Modeling of the hot flow behavior of advanced ultra-high strength steels (A-UHSS) microalloyed with boron - Mejía, Ignacio; Altamirano, G.; Bedolla Jacuinde, Arnoldo; Cabrera Marrero, José M.
In this research work, modeling of the hot flow behavior was carried out in a low carbon advanced ultra-high strength steels (A-UHSS) microalloyed with different amounts of boron (14, 33, 82, 126 and 214 ppm). For this purpose, experimental stress–strain data of uniaxial hot-compression tests over a wide range of temperatures (1223, 1273, 1323 and 1373 K (950, 1000, 1050 and 1100 °C)) and strain rates (10-3, 10-2 and 10-1 s-1) were used. The stress–strain relationships as a function of temperature and strain rate were successfully described on the basis of the approach proposed by Estrin, Mecking, and Bergström, together...

12. Texture and fatigue behavior of ultrafine grained copper produced by ECAP - Higuera Cobos, Oscar Fabián; Berríos-Ortiz, Jonathan Antonio; Cabrera Marrero, José M.
Electrolytic Tough Pitch (ETP) and Fire Refined High Conductivity (FRHC) copper samples were severely deformed by equal channel angular pressing (ECAP) and the effect of plastic deformation on the microstructure, texture and fatigue was investigated. The microstructural behavior was determined by analysis of the final texture through Inverse Pole Figures (IPF) and Orientation Distribution Function (ODF) maps, which revealed a marked decrease in the normal grain size of the ECAPed coppers and also the presence of recrystallization processes. The effect of the initial texture on the evolution of the texture after 8 ECAP passes for the two coppers was also...

13. Effect of Nb and Mo on the hot ductility behavior of a high-manganese austenitic Fe-21Mn-1.3Al-1.5Si-0.5C TWIP steel - Mejía, Ignacio; Salas Reyes, A.E.; Bedolla Jacuinde, Arnoldo; Calvo Muñoz, Jessica; Cabrera Marrero, José M.
This research work studies the influence of single microalloying elements (Nb and Mo) and the solidification route on the hot ductility behavior of a high-manganese austenitic Twinning Induced Plasticity (TWIP) steel. For this purpose uniaxial hot tensile tests in the temperature range of 700-1100 degrees C under a constant true strain rate (10(-3) s(-1)) were carried out to evaluate the hot ductility as a function of reduction in area (%RA). In general, results revealed a beneficial influence of Nb and Mo additions to TWIP steels on the hot ductility behavior, particularly in the intermediate temperature range of 800-900 degrees C,...

14. ZK60 alloy processed by ECAP: Microstructural, physical and mechanical characterization - Dimitru, F.D; Higuera Cobos, Oscar Fabián; Cabrera Marrero, José M.
Lately, magnesium alloys have been extensively investigated through severe plastic deformation (SPD) methods in order to extend their application to structural components. In the present work, as-extruded ZK60 magnesium alloy samples were subjected to 4 passes of equal-channel angular pressing (ECAP) at a processing temperature of 250 degrees C, following route Bc. The microstructural evolution of the deformed grains was analyzed using electron back-scattered diffraction (EBSD). The Orientation Imaging Microscopy (OIM) maps, together with the grain boundary misorientation distribution showed a reduction in the grain size accompanied by a large proportion of high angle grain boundaries. Calorimetric analysis showed a...

15. Classical controlled rolling of low C steels microalloyed with Ti and Mo - Calvo Muñoz, Jessica
Two low-C steels, one microalloyed with Ti and the other with Ti and Mo were subjected to a classical controlled rolling schedule using torsion testing. The specific torsion schedules were a simulation of an industrial schedule adapted to the characteristic transformation temperatures of each steel. It is shown that such steels can develop a pancaked austenite, despite the fact that the alloys do not contain Nb. However, compared to Nb bearing steels, restoration between deformation passes is relatively rapid in the pancaking region. In order to reduce the loss of pancaking, the temperatures of the finishing rolling schedule were shifted...

16. Microstructural and calorimetric analysis of ZK60 alloy processed by ECAP - Dumitru, Florina Diana; Ghiban, Brândusa; Cabrera Marrero, José M.; Higuera Cobos, Oscar Fabián; Gurau, Gheorghe; Ghiban, Nicolae
In the last years many research efforts have been made in order to extend the application of wrought magnesium to structural components. One of the methods to improve the mechanical properties of the processed materials is through severe plastic deformation (SPD). ZK60 magnesium alloy samples were subjected to 6 passes of equal-channel angular pressing (ECAP) decreasing the temperature after the fourth pass, following an alternative route A. The structural characterization was realized by microstructural evolution using Oriented Image Microscopy (OIM) and XRD analysis. Differential Scanning Calorimetry (DSC) was used to estimate the stored energy and the recrystallization temperature after each...

17. Printed circuit boards: a review on the perspective of sustainability - Cabrera Marrero, José M.; Canal Marques, André; Malfatti, Célia de Fraga
Modern life increasingly requires newer equipments and more technology. In addition, the fact that society is highly consumerist makes the amount of discarded equipment as well as the amount of waste from the manufacture of new products increase at an alarming rate. Printed circuit boards, which form the basis of the electronics industry, are technological waste of dif fi cult disposal whose recycling is complex and expensive due to the diversity of materials and components and their dif fi cult separation. Currently, printed circuit boards have a fi xing problem, which is migrating from traditional Pb e Sn alloys to lead-free alloys without de fi nite choice. This replacement is an attempt to minimize the problem of...

18. Estudio macro-micro en un acero de bajo contenido de carbono obtenido con el proceso de colada continua - Acevedo, Jorge; Cabrera Marrero, José M.
En una palanquilla de acero (0.075%C, 0.017%Si, 1.186%Mn, 0.052%P, 0.271%S y 0.075%Cr) fabricada con el proceso de colada continua, se simula con el método de los elementos finitos la transferencia de calor y la microestructura de solidificación. Las temperaturas que enmarcan los límites de la solidificación son obtenidas en función de la composición química del material. Con una formulación macro-micro se relaciona la transferencia de calor con la microestructura de solidificación. Los espaciados dendríticos primarios y secundarios se simulan con modelos analíticos en función de los parámetros termo-físicos M y N, que son ajustados linealmente entre resultados numéricos y experimentales....

19. Microstructure influencing physical and mechanical properties of electrolytic tough pitch copper produced by equal channel angular pressing - Higuera Cobos, Oscar Fabián; Cabrera Marrero, José M.
Samples of electrolytic tough pitch (ETP) copper were subjected to equal-channel angular pressing (ECAP) for up to 16 passes at room temperature following route Bc. The microstructural evolution was followed by Oriented Image Microscopy (OIM) and Differential Scanning Calorimetry (DSC) was used to estimate the activation energy and the recrystallization temperature after each ECAP pass. Also, mechanical properties after each pass were evaluated by tensile tests. Finally, electrical properties were analyzed. Results show that the stored energy increases on increasing ECAP deformation, while the recrystallization temperature decreases signi¿cantly. From a mechanical point of view a stable state is attained after 4...

20. Effect of boron on the hot ductility behavior of a low carbon advanced ultra-high strength steel (A-UHSS) - Mejía, Ignacio; Altamirano, G.; Bedolla Jacuinde, Arnoldo; Cabrera Marrero, José M.
This research work studied the effect of boron additions (14, 33, 82, 126, and 214 ppm) on the hot ductility behavior of a low carbon advanced ultra-high strength steel. For this purpose, specimens were subjected to a hot tensile test at different temperatures [923 K, 973 K, 1023 K, 1073 K, 1173 K, and 1273 K (650 °C, 700 °C, 750 °C, 800 °C, 900 °C, and 1000 °C)] under a constant true strain rate of 10-3 s-1. The reduction of area (RA) of the tested samples until fracture was taken as a measure of the hot ductility. In general,...

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