La universidad y la promoción del cambio social

Aunque pensar en la universidad no es cosa nueva, y mucho menos pensar en el cambio social, sí resulta actual y necesaria la revisión de los esfuerzos universitarios modernos, traducidos en hechos concretos, porque forman parte de la dinámica de transformación social que se desarrolla en su entorno; cuestión que, en ocasiones, se desenvuelve frente a nosotros aún sin que podamos simplemente reconocerla. Para superar este estado de puro reconocimiento, múltiples universidades en el país han desarrollado modalidades diversas de participación en los grandes y pequeños procesos de cambio social intencionado. Ello ha cuestionado, en cierta medida, el ser y el quehacer de la propia universidad.ITESO, A.C.Fundación Friedrich NaumannPraxi

Sustentabilidad y tecnología. Herramientas para la gestión segura y eficiente del hábitat

Por décadas permeó una visión de la tecnología como una de las principales fuentes del ataque al medio ambiente y de su degradación. Hoy se le considera como un aliado para combatir los efectos negativos de la perenne negligencia ecológica humana. El uso de la tecnología para la implementación de estrategias innovadoras y eficaces en favor del medio ambiente, un hábitat seguro y sustentable, se abordó en el Congreso Internacional sobre Sustentabilidad en los Hábitats, realizado en 2016. De este encuentro entre estudiantes, especialistas, autoridades y organizaciones civiles de América Latina, Asia y Europa emana este libro, que incluye dos ejes de relevancia global: los retos en el manejo sustentable de los recursos naturales y el uso de tecnologías para la edificación sustentable. En el primero se atienden desde los riesgos asociados al crecimiento demográfico desproporcionado hasta acciones de carácter remedial para la contaminación; mientras que en el segundo se aborda el desarrollo de tecnología e infraestructura para mejorar el hábitat urbano, así como procesos donde alumnos y profesores confeccionan soluciones para la sustentabilidad energética. En su conjunto, es una obra de consulta que busca ser un detonador para generar nuevas líneas de trabajo, repensar las soluciones y dialogar con lectores interesados en la construcción de un mundo mejor.Consejo Estatal de Ciencia y Tecnología de Jalisc

The Effect of Interrupted Homogenization on β-Al₅FeSi → α-Alx (Fe and Mn) Si Transformation in the A6063 Aluminum Alloy

The aluminum alloys corresponding to the 6000 series are mainly manufactured by mechanical forming processes. Their properties are enhanced by the homogeneous distribution of intermetallic phases such as β-Al5FeSi or α-Alx (Fe, Mn) Si. By thermal homogenization treatment, the intermetallic compound β-Al5FeSi changes its morphology from a needle type with a monoclinic structure to an acicular form known as α-Al12(Fe, Mn)3Si with an fcc structure. In the present study, samples of the 6063 alloy were subjected to different temperatures of homogenization (798, 823, and 848 K) and treatment times from 0 to 660 min (in intervals of 30 min) to evaluate their effects on the microstructures and morphologies of the intermetallic phases. For the kinetic study, the microstructures of the β and α intermetallic phases were quantified using the Image-Pro software. The results indicate that as the temperature and homogenization time increase, the percentage of phase α also increments. The results of the kinetic analysis revealed that the β → α transformation is controlled by two stages; the first corresponds to the diffusion of Mn atoms from the matrix to the interface of reaction for the formation of the intermetallic phases, while the second corresponds to the nucleation and growth of the iron- and manganese-rich intermetallic phases

The Effect of Interrupted Homogenization on β-Al5FeSi → α-Alx (Fe and Mn) Si Transformation in the A6063 Aluminum Alloy

The aluminum alloys corresponding to the 6000 series are mainly manufactured by mechanical forming processes. Their properties are enhanced by the homogeneous distribution of intermetallic phases such as β-Al5FeSi or α-Alx (Fe, Mn) Si. By thermal homogenization treatment, the intermetallic compound β-Al5FeSi changes its morphology from a needle type with a monoclinic structure to an acicular form known as α-Al12(Fe, Mn)3Si with an fcc structure. In the present study, samples of the 6063 alloy were subjected to different temperatures of homogenization (798, 823, and 848 K) and treatment times from 0 to 660 min (in intervals of 30 min) to evaluate their effects on the microstructures and morphologies of the intermetallic phases. For the kinetic study, the microstructures of the β and α intermetallic phases were quantified using the Image-Pro software. The results indicate that as the temperature and homogenization time increase, the percentage of phase α also increments. The results of the kinetic analysis revealed that the β → α transformation is controlled by two stages; the first corresponds to the diffusion of Mn atoms from the matrix to the interface of reaction for the formation of the intermetallic phases, while the second corresponds to the nucleation and growth of the iron- and manganese-rich intermetallic phases

Wearing Behavior of the α-Al9FeMnSi Intermetallic Compound Formed by Reactive Sintering onto AISI 304L Stainless Steel

In this study, using mixtures of pure Al, Si, Mn, and Fe powders, the α-Al9FeMnSi intermetallic compound was formed onto AISI 304L stainless steel samples by reactive sintering. The processing parameters were temperature (800, 850, and 900 °C) and applied pressure (15 and 20 MPa), using a constant holding time of 7200 s. In this paper, the influence of pressure and temperature on the microstructure, microhardness, and wear resistance of the formed layers was studied. Using X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness testing, and wearing measurements (pin on disc tests), the cross-section and top side of the coatings were observed and analyzed. We were able to determine the phase composition of cladded layers and interfaces as well as their morphology. The results indicated that several layers were formed during reactive sintering, i.e., an Al-diffusion layer on the top of the substrate, an interface, and the α-Al9FeMnSi coating itself. The microhardness values of the different layers formed were determined, ranging from 400 to 500 HV for the intermetallic coating, to 120 HV for the substrate. In this way, it was found that the formed intermetallic coating is suitable to increase the corrosion resistance of stainless steel. Additionally, all the coating showed high adherence to the substrate, exhibiting high microhardness and wear resistance. Pin on disc wearing tests showed the wearing mechanisms are predominantly delamination and ablation of the cladded layers and substrate

The Effect of Heat Treating and Deformation by Rolling and Forging on the Mechanical Properties of the 4032-Type Alloy Prepared from Recycled Materials

In the present work, the relationship between deformation, microstructure and mechanical properties of the Sr-modified 4032-type eutectic aluminum alloy was studied. The alloy was prepared from recycled materials, mainly from maritime and automotive 356 alloy scrap samples. Solubilizing heat treatment was carried out at a temperature of 450 °C with a holding time of 8 h. Finally, different samples were subjected to rolling and forging processes at a temperature of 450 °C, thus achieving a reduction of 25% of the original thickness. As expected, the microstructure and properties changed significantly due to the deformation processes, where an important factor was the change in the morphology of eutectic silicon, not only produced by the application of deformation, but also on the effect of adding strontium as a modifying agent. The samples were characterized by optical microscopy and scanning electron microscopy, where it was possible to observe not only the effect of strontium on the morphology of eutectic silicon but also the effect of the heat treatment performed. The tensile tests showed that there was indeed a notable increase in the ultimate tensile stress, yield strength, and resistance to fracture, while initial hardness also considerably increased. Finally, the fracture analysis showed that, after thermal treatment and deformation, all the samples analyzed presented a fracture within the ductile regime. It was shown that the combination of deformation and the addition of strontium led to improved globulization of the eutectic silicon

A-242 Aluminium Alloy Foams Manufacture from the Recycling of Beverage Cans

This paper presents and discusses a methodology implemented to study the process of the preparation of aluminium alloy foams using the alloy A-242, beginning from the recycling of secondary aluminium obtained from beverage cans. The foams are prepared by a melting process by adding 0.50 wt.% calcium to the A-242 aluminium alloy with the aim to change its viscosity in the molten state. To obtain the foam, titanium hydride is added in different concentrations (0.50 wt.%, 0.75 wt.%, and 1.00 wt.%) and at different temperatures (923, 948 K, and 973 K) while the foaming time is kept constant at 30 s. For a set of experimental parameter values, aluminium alloy foams with the average relative density of 0.12 were obtained and had an 88.22% average porosity. In this way, it is possible to state that the preparation of aluminium alloy foams A-242 processed from the recycling of cans is possible, with characteristics and properties similar to those obtained using commercial-purity metals

A Kinetic Study on the Preparation of Al-Mn Alloys by Aluminothermic Reduction of Mn₃O₄ and MnO Powders

The study of aluminothermic reduction in manganese compounds is a complex challenge in preparing Al-Mn alloys. The primary objective of this study was to ascertain the activation energy values for the aluminothermic reduction of MnO and Mn3O4 oxides derived from alkaline batteries. The study melted aluminum found in beverage cans and utilized the technique of powder addition with mechanical agitation. The kinetics of the reaction were studied under the effects of temperature (750, 800, and 850 °C), degree of agitation (200, 250, and 300 rpm), and the initial concentration of magnesium in molten aluminum (1, 2, 3, and 4% by weight). Kinetic measurements for Mn3O4 particles suggest a reaction mechanism that occurs in stages, where manganese undergoes oxidation states [Mn+3] to [Mn+2] until it reaches the oxidation state Mn0, which allows it to dissolve in the molten aluminum, forming alloys with up to 1.5 wt.% of Mn. Therefore, the kinetic of the aluminothermic reduction of MnO is described by the geometric contraction model, while the mechanism of Mn3O4 reduction occurs in two stages: geometric contraction, followed by an additional stage involving the diffusion of chemical species to the boundary layer. In addition, this stage can be considered a competition between the formation of MnO and the chemical reaction itself

Mathematical modelling for furnace design refining molten aluminum

The design of an aluminium melting furnace has faced two challenges: mathematical modelling and simulative optimization. This paper first uses fluid dynamics to model the aluminium process mathematically. Then, the model is utilized to simulate a round shaped reverberatory furnace for melting aluminium alloys. In order to achieve the highest thermal efficiency of the furnace, modelling and simulation are performed to predict complex flow patterns, geometries, temperature profiles of the mixture-gas air through the main chamber, as well as the melting tower attached to the furnace. The results led to the establishment of optimal position and angle of the burner, which are validated through physical experiments, ensuring recirculation of the combustion gases through the melting chamber and the melting tower. Furthermore, a proper arrangement of refractory materials is derived to avoid heat losses through the outer surface of the furnace. Temperature profiles are also determined for the optimization to arrive at the final design of the furnace. Compared with manual designs previously practiced, the simulation-based optimal design of furnaces offers excellent guidance, an increase in the aluminium processing and magnesium removal for more refined alloys, and an increased processing rate of aluminium chip accession