Vicente Salinas Barrera ● Profesor Asistente

The primary objective of this research is to evaluate the feasibility of using ultrasonic acoustic imaging as a non-intrusive, in situ technique to assess the plastic behavior of commercial metals and alloys. Specifically, it aims to explore the potential of ultrasonic acoustic imaging to identify and monitor various plastic deformation mechanisms in stainless steel and aluminum. The selection of materials is based on their distinct plastic deformation behaviors: aluminum releases internal energy through dislocation mechanisms, while stainless steel releases energy through deformation, first by dislocation and then by twinning. To achieve this goal, the study will continuously measure changes in sound velocity and the nonlinear acoustic parameter β while subjecting the materials to uniaxial tensile tests at different levels of applied stress. Previous studies conducted by our research group have demonstrated that changes in sound velocity, in relation to strain, offer a reliable means of quantifying dislocation density in local measurements on aluminum, copper, and stainless steel specimens. Furthermore, these studies have observed that alterations in the nonlinear acoustic parameter, specifically second harmonic generation, exhibit more pronounced changes compared to variations in linear acoustics (speed of sound). Building upon these findings, the proposed research involves the generation of both linear and nonlinear acoustic images over wider spatial regions to advance our understanding of the plastic behavior of materials undergoing different microstructural changes. The challenge of applying the results of this research to in situ measurements in the industry is not trivial, as the highly controlled laboratory conditions are not maintained in service components. In this regard, the incorporation of machine learning tools in the proposal aims to identify the parameters most sensitive to the various deformation mechanisms through clustering techniques. It is expected that the correlation of different acoustic parameters with the various plastic deformation mechanisms of both materials under study will generate an optimal database that reflects the variety of scenarios present in service components, thus paving the way for the industrial use of the proposed characterization system. The adoption of diagnostic techniques and the utilization of metallic material state analysis in service significantly enhance our ability to comprehend and control plastic deformation mechanisms, contributing to improved material reliability and robustness, and facilitating informed decision-making and maintenance strategies. Additionally, ex-situ standard microstructural tests, including XRD (X-ray diffraction), EBSD (electron backscatter diffraction), and TEM (transmission electron microscopy), will be performed to characterize the material’s state after deformation. These complementary tests will provide valuable microstructural information, enabling the correlation of deformation states with the acquired acoustic images. All the acoustic and microstructural information described above, in conjunction with previous research group data, will be stored in a robust and comprehensive database. This database will serve as the input for a Machine Learning algorithm, which will facilitate the identification of patterns of correspondence between acoustic and microstructural parameters. This approach aims to enable the future prediction, with a high level of probability, of the specific type of plastic deformation mechanism that a material is undergoing based on the acoustic parameter measurements. The successful development of this research proposal would yield several significant outcomes. Firstly, it would enable the early detection of microstructural changes in materials long before fractures occur. Moreover, it would establish a non-intrusive tool for characterizing materials by identifying the underlying mechanisms driving plastic deformation and monitoring the evolution of materials in service over time. Ultimately, this research has the potential to advance our understanding of the plastic behavior of stainless steel and aluminum, opening avenues for improved analysis, design, and performance evaluation of materials in various industrial applications.

Medium manganese steels (MMnS) are currently a subject of active scientific research due to a number of reasons. First, their unique combination of strength and ductility makes them promising candidates for lightweight structural applications in automotive and aerospace industries, where reducing weight without sacrificing mechanical properties is critical. Second, their ability to retain austenite at room temperatures offers advantages in terms of formability and resistance to hydrogen embrittlement, which are significant challenges in steel manufacturing. Third, medium Mn steels have shown potential in enhancing wear and impact resistance, making them suitable for applications in mining, construction, and machinery sectors. Additionally, their corrosion resistance and potential for cost-effective alloying with other elements further expand their utility across various engineering fields. Scientific research on medium Mn steels aims to optimize their microstructure, processing parameters, and alloy compositions to unlock their full potential, thereby contributing to the development of advanced materials that meet the performance requirements of modern industries while promoting sustainability and efficiency in manufacturing processes. The proposed research aims to investigate the stability of austenite in medium manganese steels within ternary Fe-C-Mn and Fe-C-Mn-X systems (X: Al, Si, Cr), focusing on its correlation with processing parameters. The primary objective is to assess the stability of austenite via (i) experimentally determining the martensite start temperature (thermal stability) using dilatometry and thermal analysis techniques, and (ii) to evaluate the fraction of austenite as a function of strain (mechanical stability) under tensile test. These measurements will provide crucial data to understand how variations in processing conditions influence austenite stability. Else, the study will correlate austenite stability with mechanical properties through mechanical tests and in-depth microstructural characterization, aiming to establish predictive models. Additionally, thermodynamic and kinetic calculations will aid in assessing the phase transformation behavior under different thermal histories. The research will extend its scope to evaluate impact and wear properties in relation to austenite stability, crucial for applications in industries requiring high strength and toughness, such as mining and construction. By systematically exploring these relationships, the project seeks to advance the fundamental understanding of medium Mn steels, potentially leading to the development of lightweight, durable materials with enhanced performance characteristics. Ultimately, the findings aim to contribute to the optimization of steel manufacturing processes and the realization of more efficient and reliable engineering solutions in demanding operational environments

This project aims to investigate how structural modifications of a dicationic derivative of azobenzene can affect the drug release and load capacity of its photoactive molecular aggregate. To evaluate this, three types of structural modifications are proposed. First, the introduction of functional groups on the photoactive nucleus of dicationic azobenzene is expected to shift the absorption band of the molecular photoswitch. Second, the replacement of the fluorescent organic cations over the structure of the molecular photoswitch, which confer luminescent and amphipathic properties to the system. And third, the modification of the length of the chains over the molecular photoswitch could change the aggregate size. To determine whether these potential modifications can modulate the light-induced release activity of the photoswitchable aggregate, an enzyme inhibitor will be loaded and released by illumination in the presence of the enzyme. Under this scenario, any modification of the enzymatic activity will be correlated with the drug's photorelease.

It is proposed to assess the feasibility of using ultrasound as a nonintrusive, in-situ, probe of plastic behavior in high-entropy alloys (HEAs). More specifically, whether it is possible to use ultrasound to reliably characterize the plasticity deformation mechanism---slip, TWIP, TRIP---of Fe80-xCo10Cr10Mnx. To this end, the speed of sound will be measured, continuously, as a function of applied stress in uniaxial tensile tests. In previous work, proposers have shown that the speed of sound as a function of stress provides a reliable tool to measure dislocation density in aluminum, copper, and stainless steel. In the latter case, it has also been shown to reliably discriminate between slip and twinning as a deformation mechanism. It is now proposed to study the possibility of extending this capability not only to new materials, HEAs, but also to a new mechanism, phase transformation. We will start with the materials whose plastic deformation is slip-dominated, since we have robust experience in this case. We shall then move to the TWIP material, where our more recent experience will be brought to bear, to end up with the unexplored, from the point of view of ultrasound, TRIP material. Samples for tensile loading will be prepared. They will be tested using a universal testing machine and ultrasound measurements of longitudinal wave velocity will be carried out in-situ. A decrease in the wave velocity as a function of applied stress will indicate a proliferation of dislocations; the dislocation density will be determined as a function of stress as will the parameters of Taylor's rule. An increase in wave velocity as a function of stress will indicate a decrease in average grain size. Modeling will be applied to determine whether this is due to twinning or phase transformation. These results will also be validated with post-mortem XRD, TEM, and metallography measurements, as well as ex-situ acoustic measurements. The success of the proposed research would have short-term and long-term benefits: In the short term it would provide a non-intrusive tool---ultrasound---to assist in the search for HEAs with pre-determined properties, as needed for specific applications. In the long-term, it would pave the way for the development of a practical, non-intrusive, tool for the evaluation of HEA pieces in service.

Society is facing an unprecedented challenge in terms of combining sustainability, economic growth and technological development. The industry has tackled these demands by developing novel products and innovative service strategies, taking the maximum advantage of the installed capabilities and cutting edge technologies. Steel industry has taken the lead by supporting internal research and scientific collaborations worldwide, enabling an ever increasing number of scientific developments. Steel plays a major role as the backbone material of civilization for a number of reasons, namely (i) abundance, (ii) relatively cheap, (iii) wide range of properties and applications, (iv) 100% recyclable, (v) potential to improve in-service performance. In the framework of (v), the current proposal aims to provide new grades of steel by means of chemical patterning of austenite. The concept of austenite patterning consists in producing layers in the microstructure with a chemical composition different from the bulk composition, via specific alloying elements and thermal cycles. These layers, after fully austenitization, deliver transformation products on cooling different than expected from the average austenite, allowing a new degree of freedom for tailoring of microstructures. So far there is only one scientific paper on the subject, which has reported outstanding mechanical strength (ultimate) of ca. 2 GPa, with uniform elongations of 7% in a lamellar martensite-austenite microstructure in a single 0.51C-4.35Mn steel. The present proposal sets a detailed working plan to investigate the impact of the initial microstructure and thermal path upon the chemical patterning of austenite in a number of different steel chemistries. The aim is two-folded: to analize the evolution of the phase transformations at different stages of the process as a function of the initial microstructure and heat-treatment parameters, and to gain fundamental insights on the mechanical behavior of the new steel grades. It is hypothesized that the correct interplay of the parameters mentioned above can yield optimized final microstructures with enhanced in-service performance.The methodology incorporates up-to-date assessment tools of thermodynamic equilibria and kinetics (ThermoCalc & Dictra) in selected steel chemistries, accurate tracking of phase transformations via Dilatometry experiments, in-depth characterization of the microstructure and mechanical properties and insitu/ex-situ ultrasound probing of tensile test specimens to better understand the hardening mechanisms. The experimental results will be compared with modeling strategies for both phase transformations and mechanical behavior. The expected results of the proposal will be of interest to the scientific community due to the novelty of the experimental concept and the potential contribution to the understanding of structure-property relations. Else, the findings will be of significance for the design of structural parts, such as high strength and impact toughness for car body crash worthiness. In the case of Chilean mining industry, wear and impact wear resistance are potential applications of the new steel grades to be tested. The proposal is lay out within a novel cooperation framework between a group of specialists on specific aspects of materials science (phase transformations in steel, constitutive modeling, ultrasound probing), oriented to contribute to the fundamental understanding of the microstructure-property relations resulting from chemical patterning of austenite. Additionally, three universities and one industrial partner (University of Twente, The Nederland, Gent University, Belgium; University of Alberta, Canada; and ME Elecmetal, Chile-US, respectively) are supporting the proposal with resources such as workshops, sample preparation, specific characterization techniques, software for post-processing, among others.

The importance of water for life is indisputable. Nevertheless, water quality and availability are affected by increases in consumption and climate change. Indeed, several areas of Chile are suffering acute water scarcity. Consequently, there is a critical need to develop efficient technologies for wastewater recovery. However, considerations must be given to the fact that some wastewaters have toxic recalcitrant pollutants requiring complex treatments, such as landfill leachate (LL). The general goal of the project is to evaluate the viability of experimentally improving LL quality by conjointly using the solar photo-Fenton process and ultrasound (US), thereby enhancing photocatalysis, ultimately reducing wastewater toxicity. The specific goals are to (i) measure the H2O2 and UV irradiation produced by US in LL (laboratory scale); (ii) evaluate the hydroxyl radicals generated during treatment processes (laboratory scale); (iii) maximize organic-pollutant removal in LL by defining the optimal operating conditions for the photo-Fenton/US process (laboratory scale); (iv) maximize organic-pollutant removal in LL by defining optimal US power/frequency in the sonolytic process (pilot-plant scale); and (v) evaluate toxicity elimination and energy consumption in LL treatments with solar-photocatalytic and US processes (laboratory and pilot-plant scales). The proposed investigation will use a scientific methodology, developing reproducible methods to observe the effects of diverse parameters, all with a focus on maximizing contaminants removal. To characterize LL, several parameters will be evaluated, including chemical oxygen demand, biological oxygen demand, total organic carbon, total dissolved nitrogen, pH, metals, ammonia, colour, biodegradability, toxicity, total suspended solids, conductivity and humic acid. To determine the amount of H2O2 generated by US in a simulated LL, a set of experiments will be run to produce the sonochemical process, applying different US frequencies (100 kHz, 200 kHz and 300 kHz) and powers (100 W, 170 W and 250 W), thus obtaining the kinetic reaction to H2O2 production. The amount of UV irradiation formed due to sonoluminescence will be quantified in the same beaker in the simulated LL. Sonoluminescence intensity during the runs will be measured using a spectro-radiometer. To evaluate the hydroxyl radicals (·OH) generated in the simulated LL during treatment processes, a method based on the oxidation of 2-proponol will be used. To determine the optimal operating conditions for the photo-Fenton/US process to maximize the removal of organic pollutants present in the simulated LL, a set of experiments will be carried out in the same photoreactor (1 L), applying different reagent concentrations, treatment times, and pH levels. To establish optimal US power and frequency in the sonolytic process to maximize the removal of organic pollutants present in a real LL (after its pretreatment), a set of runs will be carried out at pilot-plant scale in a solar photoreactor compound parabolic concentrator (CPC; 12 L useful volume). To evaluate toxicity elimination from the real LL an Aliivibrio fischeri test, respirometer assay, and phytotoxicity assay will be used, followed by determining median effective concentrations (EC50) according to the Probit model. Since a main disadvantage of the proposed treatments is high-energy consumption, specific energy consumption (SEC) and electrical energy per order (EEO) will be determined for all processes. All experiments will be done in triplicate, and filtration and coagulation/flocculation processes as a pretreatment will be used prior to all runs. The expected results of the proposed project are to (i) obtain new knowledge related to joint photo- Fenton and ultrasound wastewater treatments, (ii) demonstrate treatment synergies, and (iii) validate the use of advanced oxidation processes for improving LL. Project results will be reported in papers, through thesis work, and at scientific congresses, strengthening national and international research networks.

Dislocations are the main source of plastic behavior of metals, however, it is very difficult to quantitatively study their influence. In order to improve this situation, it is proposed to use its interaction with elastic waves as a non-invasive probe in Aluminum and Steel 304L at different strain-rates. The long-term objective of the research presented in this proposal is to obtain a standardized methodology for the characterization of materials by means of ultrasonic tests. The proposed technique is based on in-situ measurements of wave pulse propagation in rectangular samples (with ASTM Standard) under standard tensile tests, with maximum deformations of the order of 3% to 7%, which includes both the elastic regime and the plastic, additionally considers traction speeds between 0.001 mm / s and 0.5 mm / s. The results are contrasted with measurements of ultrasonic resonance spectroscopy (RUS) and density measurements of dislocations by XRD of pieces of the material obtained from the test pieces under traction study, which will be carried out in collaboration with Prof. Claudio Aguilar of the University Santa Maria. We will also explore a correlation of the results with the microstructural characterization using TEM images On the other hand, it is proposed to implement non-linear measures in-situ during tensile tests, which have been shown to be much more sensitive to the presence of dislocations of a material. The non-linear measurements are based on the application of a continuous ultrasonic wave and the analysis is performed on the amplitude of the first harmonic A2ω as a function of the amplitude of incident mode Aω, those that are related of the form A2ω = βAω, with β a non-linear parameter. For this analysis it is proposed to develop the theory, until now non-existent, between the non-linear parameter and the density of dislocations in collaboration with Prof. Fernando Lund of the Physics Department of the FCFM of the University of Chile. Emphasis will then be placed on in situ measurements, where a quantitative and continuous relationship between the density of dislocations and the stress applied during a tensile test has recently been found, as well as an indication of universality and independence of the initial condition once that the system enters the plastic deformation regime.

Dislocations are at the source of plastic behavior of metals and alloys, yet it is very difficult to quantitatively study their behavior. In order to improve this situation, it is proposed to use their interaction with elastic waves as a nonintrusive probe. The long-term aim of the research presented in this proposal is to enable the development of ultrasound technology as a practical non-intrusive tool for the characterization of plastic behavior of materials. In recent years, proposers have shown, using Resonant Ultrasound Spectroscopy (RUS), that an increase of dislocation density in aluminum by a factor of 6 leads to a change for the speed of shear waves on the order of 1%, a quantity that can be measured with an accuracy on the order of 0.1%. They have also shown that local measurements of the speed of shear waves in aluminum under standard testing conditions in tension provide a quantitative, accurate, nonintrusive and continuous relation between dislocation density and externally applied stress, and that an increase in dislocation density by a factor of ten in copper and aluminum leads to an increase in the value of the (nonlinear) parameter that characterizes second harmonic generation by 20 to 60%. This proposal seeks to go one more step towards a practical implementation of the proposed ultrasonic testing tool for pieces in service. Materials of wide use in industry, 304L steel and TWIP steel, will be used. And in addition to bulk ultrasonic and shear waves, surface Rayleigh waves will be tested, in order to develop techniques that are useful when pieces in service have a geometry that does not lend itself to bulk wave measurement. Both linear (wave propagation velocity and attenuation) and nonlinear (second harmonic generation) acoustics measurements will be performed, using bulk and surface waves, ex situ after mechanical treatment, and in situ under standard testing conditions. In addition, dislocation density will be measured using X-ray diffraction (XRD) , using both the modified Warren-Averbach and Rietveld methods. Additional characterization will be performed using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The expected result of the proposed research is a set of measurements that relate acoustics parameters to dislocation density in 304L and TWIP steels. The specific goal is that these measurements will provide a framework for the development of devices to nondestructively measure the dislocation density of pieces in service.

Las dislocaciones son la principal fuente de comportamiento plástico de metales, sin embargo, es muy difícil de estudiar cuantitativamente su comportamiento. Con el fin de mejorar esta situación, se ha propuesto utilizar su interacción con las ondas elásticas como una sonda no invasiva. Recientemente, se han demostrado, utilizando espectroscopia de resonancia Ultrasonido (RUS), que un aumento de densidad de dislocaciones en aluminio por un factor de 6 conduce a un cambio de la velocidad de las ondas de cizalle del orden de 1, una cantidad que puede medirse con una precisión del orden de 0,1%. Se propone entonces estudiar la contribución de las dislocaciones a las propiedades mecánicas en dos sistemas de interés: En primer lugar, metales poli-cristalinos, en particular muestras de cobre y de aluminio. En segundo lugar, se propone estudiar muestras con estructura de capas múltiples, en particular sistemas de capas intercaladas de cobre y de niobio. El objetivo de largo plazo de esta investigación es permitir el desarrollo de la tecnología de ultrasonido como una herramienta no invasiva para la caracterización de materiales. Se investigará en primera instancia la contribución de las dislocaciones a las constantes elásticas de metales poli-cristalinos, continuando un estudio anterior. Se realizarán nuevas medidas con muestras más puras de aluminio y de cobre, utilizando RUS en primera instancia. Como primer objetivo se plantea obtener un número mayor de muestras, con condiciones más extremas que las ya analizadas aumentando el rango de dislocaciones estudiado. Además de las medidas en el régimen lineal usando RUS, se realizarán medidas de parámetros no-lineales que pueden ser caracterizados a mayores amplitudes de excitación. Estas medidas pueden ser realizadas con el mismo montaje experimental de RUS. Además, se propone hacer un análisis ultrasónico tanto lineal como no lineal en un montaje de deformación estándar donde las medidas se realizarán in situ. En segundo lugar, se propone caracterizar muestras de cobre-niobio, con estructura de capas múltiples. La motivación de este tema radica en el hecho que las interfaces del estado sólido juegan un papel importante en la determinación de las propiedades de los materiales compuestos, especialmente de los materiales estructurales destinados para el servicio en aplicaciones de energía. En la actualidad, las muestras multi-capas de cobre-niobio pueden ser preparadas en tamaños útiles para RUS (desde milímetros hasta centímetros). Pueden ser fabricas con pocas capas (del orden de 10 capas) y espesores de décimas de mm cada una, o con muchas capas (del orden de 3.10⁴) y espesores de 10 nm cada una. La motivación es obtener mediciones precisas de las constantes elásticas efectivas de las muestras mediante hipótesis del tipo homogeneización, y correlacionar sus valores con la cantidad de interfaces presentes. A primer orden, si dos muestras tienen la misma cantidad de niobio y cobre pero con diferentes números de capas y espesores, el proceso de homogenización más simple indica que las propiedades mecánicas deben ser iguales. En la práctica, se espera una contribución de las interfaces, lo cual no será despreciable cuando existan una cantidad considerable de ellas. La relación con las dislocaciones radica en el hecho que estas interfases tienen dislocaciones de tipo misfit, y dependiendo de la orientación de su vector de Burgers y de su densidad, su contribución a la elasticidad de la interface será distinta.