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Application of a new reagent for analysis of oxygen presence in a lowcarbon steel wire rod

journal of Iron and Steel Research International 2021年第6期28卷 729-738页

作者： M.I.Dávila-Pérez h.j.vergara-hernández O.Vázquez-Gómez F.Reyes-Calderón E.López-Martínez j.M.Salgado-López National Technology of Mexico/T.I.of Morelia Morelia 58120MichoacanMexico National Council for Science and Technology CONACYT Mexico City 03940Mexico Isthmus University Santo Domingo TehuantepecOaxaca 70760Mexico Engineering and Industrial Development Center CIDESI Santiago de Queretaro 76125QueretaroMexico

A microstructural analysis was performed to determine the presence of oxygen in a wire rod section of AISI 1008 steel with a surface mechanical failure produced during wire *** failure zone was analyzed by comparison using three different attack reagents:alkaline sodium chromate(ASC),ASC with hydrogen peroxide and amyl alcohol,and a solution of nitric acid in ethyl *** reagents were applied in samples in the failure zone,showing different types of zones in regions with internal and superficial defects such as carbides,pores,cracks,deformation,and detachment zones,indicating the possible presence of *** areas identified were observed by means of an optical microscope and were correlated with the content of elements that were present in the region using a scanning electron microscope and a scattered X-ray energy spectrometer,which determined that the areas identified by chromate sodium correspond to regions with a high concentration of oxygen and slag-forming elements such as silicon,aluminum,and iron;this is associated with the presence of oxygen in the oxide *** was also observed that the ASC and the modified ASC solution with hydrogen peroxide and amyl alcohol could identify areas with a high presence of oxides,while the nitric acid solution only identified the steel *** modified ASC solution is an alternative to identify the presence of chemical variants of oxygen because the conventional formulation is unstable and has a too short shelf life,and therefore,its application must be carried out at the time of preparation.

关键词： Etching Alkaline sodium chromate Oxide presence Internal defect

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Design and characterization of Ti6Al4V/20CoCrMo−highly porous Ti6Al4V biomedical bilayer processed by powder metallurgy

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Transactions of Nonferrous Metals Society of China 2021年第1期31卷 178-192页

作者： E.MIhALCEA h.j.vergara-hernández O.jIMENEZ L.OLMOS j.ChÁVEZ D.ARTEAGA División de Estudios de Posgrado e Investigación Tecnológico Nacional de México/ITMoreliaAv.Tecnológico#1500Colonia Lomas de SantiaguitoMoreliaC.P.58120México Universidad de Guadalajara DIPJoséGuadalupe Zuno#48Los BelenesZapopanC.P.45100México INICIT Universidad Michoacana de San Nicolás de HidalgoFco.J.Mujica S/NMoreliaC.P.58060México Departamento de Ingeniería Mecánica Eléctrica CUCEIUniversidad de GuadalajaraBlvd.Marcelino García Barragán 1421OlímpicaC.P.44430 GuadalajaraJaliscoMéxico Centro de Geociencias Universidad Nacional Autónoma de MéxicoBlvd.Juriquilla No.3001Querétaro 76230México

The aim of this work was to develop a Ti6Al4V/20CoCrMo−highly porous Ti6Al4V bilayer for biomedical *** powder metallurgy technique,with semi-solid state sintering as consolidation step,was employed to fabricate samples with a compact top layer and a porous bottom layer to better mimic natural *** densification behavior of the bilayer specimen was studied by dilatometry and the resulting microstructure was observed by scan electron microscopy(SEM)and computed microtomography(CMT),while the mechanical properties and corrosion resistance were evaluated by compression and potentiodynamic tests,*** results indicate that bilayer samples without cracks were obtained at the interface which has no negative impact on the *** values of the highly porous layer were in the lower range of those of human *** compression behavior is dictated by the highly porous Ti6Al4V ***,the corrosion resistance of Ti6Al4V/20CoCrMo is better than that of Ti6Al4V,which improves the performance of the bilayer *** work provides an insight into the important aspects of a bilayer fabrication by powder metallurgy and properties of Ti6Al4V/20CoCrMo−highly porous Ti6Al4V structure,which can potentially benefit the production of customized implants with improved wear performance and increased in vivo lifetime.

关键词： bilayer structure composites porosity sintering permeability compression behavior corrosion

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Constrained sintering and wear properties of Cu-WC composite coatings

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Transactions of Nonferrous Metals Society of China 2017年第10期27卷 2214-2224页

作者： j.L.CABEZAS-VILLA L.OLMOS h.j.vergara-hernández O.jIMéNEZ P.GARNICA D.BOUVARD M.FLORES División de Estudios de Posgrado e Investigación TecNM/Instituto Tecnológico de MoreliaAv. Tecnológico #1500 Colonia Lomas de Santiaguito Morelia Michoacán C. P. 58120 México INICIT Universidad Michoacana de San Nicolás de HidalgoFco. J. Mujica S/N Morelia Michoacán C. P. 58060 México Universidad de Guadalajara Departamento de Ingeniería de ProyectosJosé Guadalupe Zuno # 48 Los Belenes Zapopan Jalisco C. P. 45100 México Univ. Grenoble Alpes CNRS SIMaP 38000 Grenoble France

Coatings of metal matrix composites(Cu?WC)were fabricated by solid-state *** reinforcing particles indifferent quantities from5%up to30%(volume fraction)were mixed with Cu *** mixing,the powders were poured ontothe surface of copper *** was carried out at1000°C under a reducing atmosphere in a vertical *** was affected by both rigid substrates and WC particles which retarded the radial and axial densification of ***,the coatings were strongly attached to the substrate,and WC particles were randomly distributed within the *** addition ofthe reinforcing particles enhanced the microhardness and reduced the volume loss in wear tests to1/17compared to the *** predominant wear mechanism was identified as abrasion at a load of5N.20%WC(volume fraction)reinforcingparticles led to the maximum values of properties for the composite coating.

关键词： constrained sintering dilatometry dry sliding wear microhardness metal matrix composites coating

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Kinetic study of austenite formation during continuous heating of unalloyed ductile iron

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International journal of Minerals,Metallurgy and Materials 2015年第1期22卷 27-31页

作者： Octvio Vazquez-Gómez jos Antonio Barrera-Godínez hctor javier vergara-hernndez Faculty of Chemistry Metallurgical Engineering DepartmentAutonomous National University of Mexico Metallurgy Science Postgraduate Programme Morelia Institute of Technology

The austenite formation kinetics in unalloyed cast ductile iron was studied on the basis of dilatometry measurements, and Avrami＇s equation was used to estimate the material＇s kinetic parameters. A continuous heating transformation diagram was constructed us-ing heating rates in the range of 0.06 to 0.83℃·s^-1. As the heating rate was augmented, the critical temperatures, c1A and Aα, as well as the intercritical range, which was evaluated as the difference between the critical temperatures, α c1Δ T =A_a- A_c1 , increased. At a low heating rate, the kinetics of austenite formation was slow as a consequence of the iron＇s silicon content. The effect of heating rate on k and n, the kinetic parameters of Avrami＇s equation, was also determined. Parameter n, which is associated with nucleation sites and growth geometry, de-creased with an increase in heating rate. In addition, parameter k increased with the increase of heating rate, suggesting that the nucleation and growth rates are carbon-and silicon-diffusion controlled during austenite formation under continuous heating.

关键词： ductile iron austenite continuous heating heating rate kinetics dilatometry

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Effect of initial microstructure on austenite formation kinetics in high-strength experimental microalloyed steels

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International journal of Minerals,Metallurgy and Materials 2015年第12期22卷 1304-1312页

作者： Edgar López-Martínez Octavio Vázquez-Gómez héctor javier vergara-hernández Bernardo Campillo Faculty of Chemistry Metallurgical Engineering Department Autonomous National University of Mexico National Council for Science and Technology Metallurgy Science Postgraduate Programme Morelia Institute of Technology Institute of Physical Sciences Autonomous National University of Mexico

Austenite formation kinetics in two high-strength experimental microalloyed steels with different initial microstructures comprising bainite-martensite and ferrite-martensite/austenite microconstituents was studied during continuous heating by dilatometric analysis. Austenite formation occurred in two steps：（1） carbide dissolution and precipitation and （2） transformation of residual ferrite to austenite. Dilatometric analysis was used to determine the critical temperatures of austenite formation and continuous heating transformation diagrams for heating rates ranging from 0.03°C.s^-1 to 0.67°C.s^-1. The austenite volume fraction was fitted using the johnson-Mehl-Avrami-Kolmogorov equation to determine the kinetic parameters k and n as functions of the heating rate. Both n and k parameters increased with increasing heat- ing rate, which suggests an increase in the nucleation and growth rates of austenite. The activation energy of austenite formation was determined by the Kissinger method. Two activation energies were associated with each of the two austenite formation steps. In the first step, the austenite growth rate was controlled by carbon diffusion from carbide dissolution and precipitation; in the second step, it was controlled by the dissolution of residual ferrite to austenite.

关键词： non-isothermal kinetics microalloyed steel austenite heating dilatometry

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Sintering study of Ti6Al4V powders with different particle sizes and their mechanical properties

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International journal of Minerals,Metallurgy and Materials 2018年第12期25卷 1389-1401页

作者： joséLuis Cabezas-Villa joséLemus-Ruiz Didier Bouvard Omar jiménez héctor javier vergara-hernández Luis Olmos University Michoacana of San Nicolás of hidalgo IIMMMorelia 58060México University Grenoble Alpes CNRSSIMaPGrenoble 38000France University of Guadalajara Departamento de Ingeniería de ProyectosZapopan 45100México National Technological Institute of Mexico I.T.MoreliaMorelia 58120México University Michoacana of San Nicolás of hidalgo INICITMorelia 58060México

Ti6Al4V powders with three different particle size distributions(0–20, 20–45, and 45–75 μm) were used to evaluate the effect of the particle size distribution on the solid-state sintering and their mechanical properties. The sintering kinetics was determined by dilatometry at temperatures from 900 to 1260°C. The mechanical properties of the sintered samples were evaluated by microhardness and compression tests. The sintering kinetics indicated that the predominant mechanism depends on the relative density irrespective of the particle size used. The mechanical properties of the sintered samples are adversely affected by increasing pore volume fraction. The elastic Young's modulus and yield stress follow a power law function of the relative density. The fracture behavior after compression is linked to the neck size developed during sintering, exhibiting two different mechanisms of failure: interparticle neck breaking and intergranular cracking in samples with relative densities below and above of 90%, respectively. The main conclusion is that relative density is responsible for the kinetics, mechanical properties, and failure behavior of Ti6 Al4 V powders.

关键词： Ti6Al4V powders dilatometry microhardness sintering kinetics compression failure behavior

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Glial cells in the center of future ischemic stroke treatments

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Neural Regeneration Research 2022年第12期17卷 2659-2660页

作者： Ivóh.hernández Maria joséPérez-Álvarez Genomic Instability Group Spanish National Cancer Research Centre(CNIO)MadridSpain Departamento de Biología(Fisiología Animal)Facultad de Ciencias Universidad Autónoma de Madridand Instituto de Biología Molecular-CBMSOUAM/CSICMadridSpain

In the last century,increasing knowledge about glial cells has revealed their importance in brain physiology and disease and an exciting potential target for new therapeutic interventions(hernández et al.,2021).Ischemic stroke is the most common of all types of *** the second leading cause of disability and mortality,ischemic stroke is a serious socio-economic burden *** it has been strongly associated with aging,during 2020 COVID-19 emerged as a new risk factor for ischemic stroke in younger patients(Cagnazzo et al.,2021).The only therapy or intervention currently available for humans is early reperfusion after the onset of the first ***,due to the high risk of brain hemorrhage,these treatments are suitable for only a small percentage of ***,reperfusion does not prevent post-injury neurodegeneration,hence the importance of finding new therapeutic alternatives to ameliorate ischemic damage and improve post-stroke quality of life.

关键词： mortality treatment younger

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The ecological scale mediates whether trees experience drought legacies in radial growth

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Forest Ecosystems 2023年第3期10卷 298-306页

作者： héctor hernández-Alonso jaime Madrigal-González Fernando Silla Area of Ecology Faculty of BiologyUniversidad de SalamancaE-37007SalamancaSpain iuFOR-EiFAB Campus de SoriaUniversidad de ValladolidE-42004SoriaSpain

The impact of lag effects produced by disturbances on primary production has been a major concern among ecologists during the last *** and extreme climatic events are imposing drastic reductions in radial growth of trees as evidenced in tree-rings series Dendrochronological samples are obtained at tree level but analyzed at an aggregated scale(i.e.,mean chronologies),although aggregating tree-ring chronology on a regional scale may reduce the possibility of studying the variability of individual tree response to drought,by amplifying the average population ***,we conducted experimental research in which 370 trees of 5 species were analyzed to assess the potential statistical and scaling issues that may occur when using regressionbased methods to analyze ecosystem responses to *** legacy effects were quantified using individual and aggregated ***,lag effects were validated using confidence and prediction intervals to identify values falling outside the certainty of the climate-growth model Individual scale legacy effects contrasted with confidence intervals were commonly distributed across species but were scarce when compared with prediction *** analysis of aggregated scale legacies detected significant growth reductions when validated using prediction intervals;however,individual scale legacy lag effects were not *** finding directly contrasts the results obtained when using an aggregated *** results provide empirical evidence on how aggregating ecological data to infer processes that emerge from an individual scale can lead to distorted *** therefore encourage the use of individual based statistical and ecological procedures to analyze tree rings as a means of further understanding the ecosystem responses to disturbances.

关键词： Legacy effects Drought disturbances Tree growth Tree-ring width Dendrochronology Individual scale Mountainous forests

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Effect of retained austenite and nonmetallic inclusions on the thermal/electrical properties and resistance spot welding nuggets of Si-containing TRIP steels

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International journal of Minerals,Metallurgy and Materials 2019年第1期26卷 52-63页

作者： V.h.Vargas I.Mejía V.h.Baltazar-hernández C.Maldonado Metallurgy and Materials Research Institute Universidad Michoacana de San Nicolás de Hidalgo Edificio "U" Ciudad Universitaria Materials Science and Engineering Program Autonomous University of Zacatecas

Five advanced high-strength transformation-induced plasticity(TRIP) steels with different chemical compositions were studied to correlate the retained austenite and nonmetallic inclusion content with their physical properties and the characteristics of the resistance spot welding nuggets. Electrical and thermal properties and equilibrium phases of TRIP steels were predicted using the jMatPro? software. Retained austenite and nonmetallic inclusions were quantified by X-ray diffraction and saturation magnetization techniques. The nonmetallic inclusions were characterized by scanning electron microscopy. The results show that the contents of Si, C, Al, and Mn in TRIP steels increase both the retained austenite and the nonmetallic inclusion contents. We found that nonmetallic inclusions affect the thermal and electrical properties of the TRIP steels and that the differences between these properties tend to result in different cooling rates during the welding process. The results are discussed in terms of the electrical and thermal properties determined from the chemical composition and their impact on the resistance spot welding nuggets.

关键词： transformation-induced plasticity steel retained austenite non-metallic inclusions magnetic saturation electrical properties thermal properties resistance spot welding nugget

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Sintering kinetics of Ni_2FeSb powder alloys produced by mechanical milling

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Transactions of Nonferrous Metals Society of China 2016年第8期26卷 2126-2135页

作者： F.ALVARADO-hernández O.jIMéNEZ G.GONZALEZ-CASTANEDA V.BALTAZAR-hernández j.CABEZAS-VILLA M.ALBITER h.vergara-hernández L.OLMOS Unidad Académica de Ingeniería I Universidad Autónoma de ZacatecasJardín Juárez 147 Centro Histórico Zacatecas Zacatecas C. P. 98000 México Departamento de Ingeniería de Proyectos CUCEI Universidad de GuadalajaraBlvd. Marcelino García Barragán 1421 Olímpica Guadalajara Jalisco C. P. 44430 Mexico INICIT Universidad Michoacana de San Nicolás de HidalgoFco. J. Mujica S/N C.U. Morelia Michoacán C. P. 58060 México División de Estudios de Posgrado e Investigación TecNM/Instituto Tecnológico de MoreliaAv. Tecnológico # 1500 Colonia Lomas de Santiaguito Morelia Michoacán C. P. 58120 México

A ternary Ni2FeSb shape memory alloy was fabricated by powder metallurgy route. Sintering kinetics was estimated from dilatometry tests; whereas the microstructure and morphology of the powder and consolidated bulk samples were evaluated by XRD and SEM, respectively. Microhardness tests were performed on the surface of sintered samples. The results indicated that milling time has an effect on the shape and particle size as well as the homogeneity of the crystalline structures of the powders. Samples with longer milling time presented higher relative densities, better distribution of the elements on the alloy as well as the L21 and martensite phases, which will give the shape memory effect. The estimated activation energy values ranged from 109 to 282 kj/mol at temperatures between 750 and 1273 K, indicating that sintering is controlled mainly by volume diffusion. Microhardness was improved by increasing the milling time and the heating rate.

关键词： Ni-based shape memory alloy mechanical milling solid state sintering microhardness

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