UPCommons - E-prints UPC Universitat Politècnica de Catalunya
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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.
2.
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.
3.
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...
4.
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...
5.
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...
6.
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...
7.
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...
8.
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.
9.
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...
10.
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
11.
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...
13.
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)...
14.
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...
15.
Modeling and prediction of hot deformation flow curves - Mirzadeh, H.; Cabrera Marrero, José M.; Najafizadeh, A.
The modeling of hot flow stress and prediction of flow curves for unseen deformation conditions
are important in metal-forming processes because any feasible mathematical simulation needs
accurate flow description. In the current work, in an attempt to summarize, generalize, and
introduce efficient methods, the dynamic recrystallization (DRX) flow curves of a 17-4 PH
martensitic precipitation hardening stainless steel, a medium carbon microalloyed steel, and a
304 H austenitic stainless steel were modeled and predicted using (1) a hyperbolic sine equation
with strain dependent constants, (2) a developed constitutive equation in a simple normalized
stress-normalized strain form and its modified version, and (3) a feed-forward artificial neural
network (ANN)....
16.
Shear banding phenomenon during severe plastic deformation of an AZ31 magnesium alloy - Cabrera Marrero, José M.; Fatemi-Varzaneh, S.M.; Zarei-Hanzaki, A.
Severe plastic deformation was applied on a wrought AZ31 magnesium alloy by a new method called accumulative back extrusion (ABE). Instabilities of plastic flow in the form of localized shear bands were experimentally observed during ABE processing of the AZ31 alloy. The obtained microstructures show the appearance of shear bands in ABE processed specimens, the extent of which was observed to be decreased by increasing the temperature. The restricted flow (due to the deformation geometry) was discussed as the main cause of the latter behavior. A noticeable grain refinement was observed inside the shear bands which was attributed to the...
17.
Constitutive relationships for hot deformation of austenite - Mirzadeh, H.; Cabrera Marrero, José M.; Najafizadeh, A.
Constitutive equations were used to derive the flow stress of a 17–4 PH stainless steel during hot compression testing. Two general
methods were used: (i) a conventional method of finding apparent materials constants; and (ii) a physically based approach which
accounts for the dependence of the Young’s modulus and the self-diffusion coefficient of austenite on temperature. Both methods were
critically discussed and some modifications and easy-to-apply methods were also introduced. The second approach was also performed
for peak and critical stresses to find out the effect of dynamic recrystallization on the ideal theoretical values. The discussion of results
proved that when the deformation mechanism is...
18.
Hot ductility behavior of a low carbon advanced high strength steel (AHSS) microalloyed with boron - Mejía, Ignacio; Bedolla Jacuinde, Arnoldo; Maldonado, Cuauhtémoc; Cabrera Marrero, José M.
The current study analyses the influence of boron addition on the hot ductility of a low carbon advanced high strength NiCrVCu steel. For this purpose hot tensile tests were carried out at different temperatures
(650, 750, 800, 900 and 1000 ◦C) at a constant true strain rate of 0.001 s−1. Experimental results showed a substantial improvement in hot ductility for the low carbon advanced high strength steel when microalloyed with boron compared with that without boron addition. Nevertheless, both steels showed poor ductility when tested at the lowest temperatures (650, 750 and 800 ◦C), and such behavior is associated to the...
19.
Determination of the critical conditions for the initiation of dynamic recrystallization in boron microalloyed steels - Mejía, Ignacio; Bedolla Jacuinde, Arnoldo; Maldonado, Cuauhtémoc; Cabrera Marrero, José M.
From the present research, the critical conditions associated with the onset of dynamic recrystallization (DRX) of hot deformed boron microalloyed steels were precisely determined based on changes in the
strain hardening rate ( ) as a function of the flow stress. For this purpose, a low carbon steel microalloyed with four different amounts of boron (29, 49, 62 and 105 ppm) was deformed by uniaxial hot-compression tests at high temperature (950, 1000, 1050 and 1100 ◦C) and constant true strain rate (10−3, 10−2 and 10−1 s−1). Results indicate that the critical conditions for the initiation of dynamic recrystallization depend on the...
20.
Analysis of copper effect on microstructures and mechanical properties in microalloyed steels - Elwazri, A. M.; Fatehi, A.; Calvo Muñoz, Jessica; Bai, D.; Yue, S.
The microstructure and mechanical properties under cool deformation conditions was investigated for three steels of approximately 0.03% carbon with different alloying additions of niobium and copper. Compression testing of the three steels was employed to study the influence of processing conditions (cool deformation)
and chemical composition (niobium and copper) on the microstructure and mechanical properties.
Overall, for the steel compositions examined, the addition of copper increased the strength. This can be explained by solid solution hardening effect of copper. The results show that there is very fine equiaxed
ferrite that has formed, either by recrystallization or transformation induced by cool deformation
1.
