Carlos Garcia-Mateo
@cenim.csic.es
Senior Researcher. Physical Metallurgy Department
National Center for Metallurgical Research
RESEARCH, TEACHING, or OTHER INTERESTS
Materials Science, Metals and Alloys, Pediatrics, Perinatology and Child Health
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Adriana Eres-Castellanos, Vicente Perez-Aroca, Pedro Carrero-Santos, Francisca G. Caballero, and Carlos Garcia-Mateo
Iron and Steel Institute of Japan
Matthias Kuntz, Garry Wicks, Thomas Sourmail, and Carlos Garcia‐Mateo
Wiley
Nanostructured bainitic steel obtained through austempering or bainitic transformation of high Si steels consists of bainitic ferrite and carbon‐enriched retained austenite. Secondary tempering of those microstructures tailors their mechanical properties through its unique nanostructure and austenite stability. Herein, fatigue and tensile properties of a nanobainitic steel in different secondary tempering conditions are presented and the results are discussed based on the deformation mechanisms taking place due to the microstructure evolution during secondary tempering. Influence of secondary tempering and elevated testing temperature on tensile and fatigue properties at room temperature and 250 °C is presented. Based on the present deformation, mechanism results are discussed supported by microstructure evolution results obtained through dilatometry, X‐ray diffraction, and microscopy. Depending on secondary tempering temperature, main influencing mechanisms are martensite formation after secondary tempering during cooling, transformation‐induced plasticity effect, and precipitation hardening obtained by secondary tempering.
Radhakanta Rana, Erick Cordova-Tapia, Jose A. Jimenez, Lucia Morales-Rivas, and Carlos Garcia-Mateo
Informa UK Limited
Adam Skowronek, Adam Grajcar, Carlos Garcia-Mateo, José A. Jiménez, and Roumen H. Petrov
Springer Science and Business Media LLC
AbstractThe development of superior mechanical properties in medium-Mn requires the optimization of microstructural parameters such as retained austenite (RA) stability, volume fraction, and morphology. The present work explores the possibility of using a continuous annealing approach instead of conventional batch annealing to perform an intercritical annealing (IA) treatment in a hot-rolled strip of an Al-alloyed 5Mn steel. Dilatometric studies were performed at a temperature of 680 ºC with soaking times ranging from 1 to 300 min to follow the microstructural changes as a function of time. The microstructures thus obtained were thoroughly characterized by means of X-ray diffraction, SEM and TEM, TEM-EDS microanalysis and EBSD phase and orientation maps. It was observed that with increasing soaking times, the volume fraction of retained austenite gradually increases, albeit at the cost of its stability. The comparison of martensite start temperatures (Ms) based on the chemical composition of austenite at 680 ºC with that experimentally obtained at higher process temperature revealed the effect of the grain size on the reduction of RA stability for longer process times. Accordingly, mechanical tests results showed that the yield stress, tensile strength and hardness decrease with an increase in the IA soaking time.
M. Morawiec, A. Skowronek, A. Kozłowska, C. Garcia-Mateo, and A. Grajcar
Springer Science and Business Media LLC
AbstractThe work presents results on the effect of prior martensite formation on bainite transformation kinetics in a 3% medium-Mn multiphase steel. The material was subjected to two isothermal holding temperatures: 400 °C (without martensite) and 350 °C (with prior martensite). According to obtained dilatometric results, the formation of prior martensite leads to the acceleration of bainite transformation kinetics. The bainite formation starts and finishes much faster, when the prior martensite was present before the isothermal holding. The microstructural investigation of the steel after heat treatment was carried out using light and scanning electron microscopy. The microstructures were composed of fine bainitic laths with retained austenite and small amount of martensitic-austenitic islands at 400 °C. At 350 °C the presence of large tempered martensite laths was detected. The bainite is composed of a mixture of fine and coarse laths. The increase of the bainitic lath thickness is attributed to the coalescence process occurring at the lower holding temperature. The differences in the steel hardness after the two heat treatments were relatively small (~ 13 HV10).
M. Morawiec, J. Opara, C. Garcia-Mateo, J. A. Jimenez, and A. Grajcar
Springer Science and Business Media LLC
AbstractThis work presents insights into the manganese influence on the driving force and bainite transformation kinetics. Three different medium-Mn steels were subjected to theoretical calculations and dilatometric study in order to determine the Mn impact on bainite formation. The theoretical approach shows that the increase of manganese leads to a lower bainite fraction formed during the isothermal stage. This implicates the carbon enrichment of the austenite during thermal treatment. The less bainite is formed, the higher is the fraction of residual austenite which enrichment of carbon is globally low. Meanwhile, the manganese influences the incubation and transformation time. As the manganese content increases, the incubation period and formation time of bainite are longer because the chemical driving force essential to start and complete austenite into bainite transformation decreases. This was proved by theoretical calculations and dilatometric analysis, which show that even a small increase in manganese content leads to a longer time necessary to occur the bainitic transformation. For the steel containing 5% manganese, the driving force was too small that the transformation could occur even after 3 h. Additionally, the XRD analysis was conducted to determine the retained austenite fraction and its carbon enrichment. These results were compared with the theoretical values to determine the accuracy of the applied model.
M. Morawiec, V. Ruiz-Jimenez, C. Garcia-Mateo, J. A. Jimenez, and A. Grajcar
Springer Science and Business Media LLC
AbstractIsothermal bainitic transformation of a lean medium-Mn steel containing (in mass%) 0.18C–3.6Mn–1.7Al–0.23Si–0.2Mo–0.04–Nb after full austenitization at 1100 ºC was studied by means of high resolution dilatometry. The effects of isothermal holding temperatures ranging from 450 to 350 °C on the bainitic transformation kinetics was studied experimentally characterizing the microstructure present after a holding time ranging from 15 min to 2 h. The obtained results showed that the bainitic transformation is uncompleted at temperatures above 425 °C. The carbon enrichment of the austenite during isothermal treatment at 450 °C and 425 °C is not enough to avoid martensitic transformation of the austenite during cooling to room temperature. Thus, it is obtained a mixed structure including bainitic ferrite and martensite. Decreasing the austempering temperature resulted in a more pronounced bainite formation. The kinetics of the transformation during austempering at 350ºC is quite similar to that observed at 400 °C, so that 60 min are needed in both cases to complete the reaction. However, local variations in chemical composition associated to segregation of Mn and Al during casting solidification results in differences in the transformation rate of bainitic reaction between different areas in the material. A balance difference between the dendritic and interdendritic areas is responsible for the differences observed among test samples in the kinetics of the isothermal bainitic transformation and the final microstructure.
Adam Skowronek, Erick Cordova-Tapia, Pilar Tobajas-Balsera, Carlos Garcia-Mateo, José A. Jiménez, Roumen Petrov, and Adam Grajcar
Elsevier BV
Adriana Eres-Castellanos, Muftah Zorgani, Davood Shahriari, Radu Romanica, Jose Antonio Jimenez, Carlos Garcia-Mateo, and Mohammad Jahazi
Elsevier BV
Harold D. Machado, Isaac Toda-Caraballo, Carlos Garcia-Mateo, and Ricardo Aristizábal-Sierra
Elsevier BV
M. Zorgani, C. Garcia-Mateo, and M. Jahazi
Elsevier BV
Francisca G. Caballero and Carlos Garcia-Mateo
Elsevier
Adriana Eres-Castellanos, Lucia Morales-Rivas, Jose Antonio Jimenez, Francisca G. Caballero, and Carlos Garcia-Mateo
Springer Science and Business Media LLC
Abstract The reason why variant selection phenomena occur in ausforming treatments is still not known. For that reason, in this work, the effect of compressive deformation on the macro and micro-texture of a bainitic microstructure was analyzed in a medium-carbon high-silicon steel subjected to ausforming treatments, where deformation was applied at 520 °C, 400 °C and 300 °C. The as-received material presented a very weak $$\\left\\langle {3\\, 3\\, 1} \\right\\rangle$$ 3 3 1 fiber texture along the rod axis, due to prior thermomechanical processing. For the samples isothermally heat-treated, it was detected that the bainitic ferrite inherited a $$\\left\\langle {1\\, 0\\, 0} \\right\\rangle$$ 1 0 0 fiber texture from the $$\\left\\langle {1\\, 1\\, 0} \\right\\rangle$$ 1 1 0 fiber texture present in the prior austenite. The intensity of this transformation texture was more pronounced as the deformation temperature decreased. Also, variant selection was examined at different scales by combining Electron-Backscattered Diffraction and X-ray Diffraction. The quantification of the fraction of crystallographic variants under certain conventions for every condition revealed variant selection in samples subjected to ausforming treatments, where these phenomena were stronger as the deformation temperature was lower. Finally, some of the theories proposed so far to explain these variant selection phenomena were tested, showing that variants were not selected based on their Bain group and that their selection can be better described in terms of their belonging to packets, if these are defined according to a global reference frame. This suggests that the phenomena might have to do with the effect of deformation mechanisms on the prior austenite.
Victor Ruiz-Jimenez, Jose A. Jimenez, Francisca G. Caballero, and Carlos Garcia-Mateo
MDPI AG
Bainitic ferrite plate thickness evolution during isothermal transformation was followed at the same holding temperatures in two nanostructured steels containing (in wt.%) 1C-2Si and 0.4C-3Si. A dynamic picture of how the bainitic transformation evolves was obtained from the characterization of the microstructure present at room temperature after full and partial transformation at 300 and 350 °C. The continuous change during transformation of relevant parameters influencing the final scale of the microstructure, YS of austenite, driving force of the transformation and evolution of the transformation rate has been tracked, and these variations have been correlated to the evolution of the bainitic ferrite plate. Instead of the expected refinement of the plate predicted by existing theory and models, this study revealed a thickening of the bainitic ferrite plate thickness as the transformation progresses, which is partially explained by changes in the transformation rate through the whole decomposition of austenite into bainitic ferrite.
Adriana Eres-Castellanos, Javier Hidalgo, Lucia Morales-Rivas, Francisca G. Caballero, and Carlos Garcia-Mateo
Elsevier BV
Oscar Ríos-Diez, Ricardo Aristizábal-Sierra, Claudia Serna-Giraldo, Adriana Eres-Castellanos, and Carlos García-Mateo
Springer Science and Business Media LLC
M. Zorgani, C. Garcia-Mateo, and M. Jahazi
Elsevier BV
Adriana Eres-Castellanos, Lucia Morales-Rivas, Francisca G. Caballero, and Carlos Garcia-Mateo
Elsevier BV
Hadi Torkamani, Shahram Raygan, Carlos Garcia Mateo, Yahya Palizdar, Jafar Rassizadehghani, Javier Vivas, and David San-Martin
Springer Science and Business Media LLC
AbstractIn this study, dual-phase (DP, ferrite + martensite) microstructures were obtained by performing intercritical heat treatments (IHT) at 750 and 800 °C followed by quenching. Decreasing the IHT temperature from 800 to 750 °C leads to: (i) a decrease in the volume fraction of austenite (martensite after quenching) from 0.68 to 0.36; (ii) ~ 100 °C decrease in martensite start temperature (Ms), mainly due to the higher carbon content of austenite and its smaller grains at 750 °C; (iii) a reduction in the block size of martensite from 1.9 to 1.2 μm as measured by EBSD. Having a higher carbon content and a finer block size, the localized microhardness of martensite islands increases from 380 HV (800 °C) to 504 HV (750 °C). Moreover, despite the different volume fractions of martensite obtained in DP microstructures, the hardness of the steels remained unchanged by changing the IHT temperature (~ 234 to 238 HV). Applying lower IHT temperature (lower fraction of martensite), the impact energy even decreased from 12 to 9 J due to the brittleness of the martensite phase. The results of the tensile tests indicate that by increasing the IHT temperature, the yield and ultimate tensile strengths of the DP steel increase from 493 to 770 MPa, and from 908 to 1080 MPa, respectively, while the total elongation decreases from 9.8 to 4.5%. In contrast to the normalized sample, formation of martensite in the DP steels could eliminate the yield point phenomenon in the tensile curves, as it generates free dislocations in adjacent ferrite.
Oscar Ríos-Diez, Ricardo Aristizábal-Sierra, Claudia Serna-Giraldo, Adriana Eres-Castellanos, and Carlos García-Mateo
Elsevier BV
David San-Martin, Matthias Kuntz, Francisca G. Caballero, and Carlos Garcia-Mateo
MDPI AG
This investigation explores the influence of the austenitisation heat treatment and thus, of the prior austenite grain size (PAGS), on the kinetics of the bainitic transformation, using as A case study two high-carbon, high-silicon, bainitic steels isothermally transformed (TIso = 250, 300, 350 °C), after being austenised at different temperatures (γTγ = 925–1125 °C). A methodology, based on the three defining dilatometric parameters extracted from the derivative of the relative change in length, was proposed to analyse the transformation kinetics. These parameters are related to the time to start bainitic transformation, the time lapse for most of the transformation to take place and the transformation rate at the end of the transformation. The results show that increasing the PAGS up to 70 µm leads to an increase in the bainite nucleation rate, this effect being more pronounced for the lowest TIso. However, the overall transformation kinetics seems to be weakly affected by the applied heat treatment (γTγ and TIso). In one of the steels, PAGS > 70 µm (γTγ > 1050 °C), which weakly affects the progress of the transformation, except for TIso = 250 °C, for which the enhancement of the autocatalytic effect could be the reason behind an acceleration of the overall transformation.
Adriana Eres-Castellanos, Carlos Garcia-Mateo, and Francisca G. Caballero
MDPI AG
Displacive stress and strain induced transformations are those transformations that occur when the formation of martensite or bainitic ferrite is promoted by the application of stress or strain. These transformations have been shown to be one of the mechanisms by which the mechanical properties of a microstructure can be improved, as they lead to a better ductility and strength by the transformation induced plasticity effect. This review aims to summarize the fundamental knowledge about them, both in fully austenitic or in multiphase structures, pointing out the issues that—according to the authors’ opinion—need further research. Knowing the mechanisms that govern the stress and strain induced transformation could enable to optimize the thermomechanical treatments and improve the final microstructure properties.
Adriana Eres-Castellanos, David De-Castro, Carlos Capdevila, Carlos Garcia-Mateo, and Francisca G. Caballero
Informa UK Limited
ABSTRACT The latest progress in machine learning (ML) algorithms enabled to predict some steel physical properties previously modelled by linear regression (LR), such as the Ms temperature. Authors claimed that the performance given by ML models could improve the one of previous LR models, although they did not include fair comparisons. In this work, a large database was used to train different ML algorithms, whose Ms temperature predictions were compared to the ones of previous literature empirical models. ML methods were proved to require longer computational times and wider knowledge, while leading to similar results. Therefore, we recommend that ML methods are not always considered as the first option when trying to solve easy problems that can be modelled by LR techniques.
Matthias Kuntz, , Simon Lille, Garry Wicks, Thomas Sourmail, Victor Jimenez, Carlos Garcia-Mateo, , , ,et al.
Association for Iron & Steel Technology