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Antuco (37.4°S, 71.4°W; Chile) is a dominantly basaltic stratovolcano whose original ~ 3300 m altitude main cone experienced a catastrophic sector collapse at ~ 7.1 cal ka BP, producing a volcanic debris avalanche deposit (VDAD) with hummocky surface and ~ 6.4 km3 of volume. We carried out geological studies of its debris avalanche deposit, which was distributed to the W and displays a longitudinal facies transformation from edifice’s megablocks and block to mixed facies in distal areas (up to 25 km from the scar). Our observations support the behavior of the avalanche beginning as a translational slide, and then as plug flow when confined within the Laja River valley. Clay abundance and high content of hydrothermally altered material may suggest active participation of water; flow velocities are estimated to ~100 m s−1. We primarily identify the steep-sided flanks of the cone, and hydrothermal alteration promoted the edifice instability, while basement seismogenic structures may have ultimately triggered the landslide. Subsequent landslide-led events include the transformation of the volcanic activity with explosive eruptions producing a sequence of dilute pyroclastic density currents (PDCs) ending ~3.4 ky BP, and extensive lava effusion rapidly reconstructing the collapsed edifice. Moreover, the Antuco VDAD also blocked the natural output of the Laja Lake, increasing its level by ~200 m and then triggering cataclysmic outburst floods by dam rupture, preserved as high-energy alluvial beds with ages between 2.8 and 1.7 ky BP. The Antuco constitutes an excellent example of a critical chain of events initiated by a stratovolcano lateral collapse and warns for detailed hazard investigations to better comprehend its related impacts.

Several commercial alloys use silicon (Si) to improve titanium (Ti) resistance to creep and oxidation at high temperatures and to improve Ti corrosion resistance in acid media. According to the Ti-Si phase diagram, reported stable solid phases in the Ti-rich region are β-Ti, α-Ti, Ti3Si, and Ti5Si3. Nevertheless, very few works in the literature discuss Ti3Si intermetallic production. As such, this work studied the possibility of obtaining an α-Ti-Ti3Si alloy by hot pressing α-Ti supersaturated solid solution powders obtained by mechanical alloying. The consolidation of milled powders was performed using uniaxial hot press equipment. Structural and morphological evolutions during the sintering process were investigated by X-ray diffraction and scanning electron microscopy. Electrochemical behaviors of sintered samples were evaluated by open circuit potential and linear sweep voltammetry. Results show a fine and uniform Ti3Si alloy distribution in the α-Ti matrix produced by the proposed powder metallurgy route. The sintered samples demonstrated high micro-hardness and resistance to sulfuric acid corrosion. Additionally, Ti3Si was shown to have a significant hardening effect on the α-Ti matrix. Electrochemical behavior further demonstrates that a fine and homogeneous Ti3Si distribution in the α-Ti matrix contributes to a more stable superficial oxide layer against sulfuric acid corrosion.

This study investigated the synthesis of Ag-SnO2-ZnO by powder metallurgy methods and their subsequent electrical contact behavior. The pieces of Ag-SnO2-ZnO were prepared by ball milling and hot pressing. The arc erosion behavior of the material was evaluated using homemade equipment. The microstructure and phase evolution of the materials were investigated through X-ray diffraction, energy-dispersive spectroscopy and scanning electron microscopy. The results showed that, although the mass loss of the Ag-SnO2-ZnO composite (9.08 mg) during the electrical contact test was higher than that of the commercial Ag-CdO (1.42 mg), its electrical conductivity remained constant (26.9 ± 1.5% IACS). This fact would be related to the reaction of Zn2SnO4’s formation on the material’s surface via electric arc. This reaction would play an important role in controlling the surface segregation and subsequent loss of electrical conductivity of this type of composite, thus enabling the development of a new electrical contact material to replace the non-environmentally friendly Ag-CdO composite.

The increase in longevity worldwide has intensified the use of different types of prostheses for the human body, such as those used in dental work as well as in hip and knee replacements. Currently, Ti-6Al-4V is widely used as a joint implant due to its good mechanical properties and durability. However, studies have revealed that this alloy can release metal ions or particles harmful to human health. The mechanisms are not well understood yet and may involve wear and/or corrosion. Therefore, in this work, commercial pure titanium and a Ti-6Al-4V alloy were investigated before and after being exposed to a simulated biological fluid through tribological tests, surface analysis, and ionic dissolution characterization by ICP-AES. Before exposure, X-ray diffraction and optical microscopy revealed equiaxed α-Ti in both materials and β-Ti in Ti-6Al-4V. Scratch tests exhibited a lower coefficient of friction for Ti-6Al-4V alloy than commercially pure titanium. After exposure, X-ray photoelectron spectroscopy and surface-enhanced Raman spectroscopy results showed an oxide film formed by TiO2, both in commercially pure titanium and in Ti-6Al-4V, and by TiO and Al2O3 associated with the presence of the alloys. Furthermore, inductively coupled plasma atomic emission spectroscopy revealed that aluminum was the main ion released for Ti-6Al-4V, giving negligible values for the other metal ions.

Ti-based alloys are being widely used as bio-implant materials because of their excellent properties. This work reports the synthesis of Ti–30Nb–13Ta–2Mn (wt. %) foams with and without bimodal microstructure using NaCl (0, 20 and 30 vol %) as space-holder particles (SHP). Samples with bimodal microstructure were obtained by mixing milled and un-milled powders in a proportion of 1:4. Samples without bimodal microstructure were synthesized using only un-milled powders. Hot pressing was used to consolidate the green samples using argon gas as protective atmosphere under 30 MPa at 780 °C for 30 min. The consolidated metallic foams were characterized by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) to study their microstructure and phase analyses. The Young's modulus values were between 39 and 19 GPa, and the yield strength values were obtained between 180 and 400 MPa. From the mechanical properties point of view, samples with bimodal microstructure and with 20 and 30 vol % of NaCl have a great potential to be explored for biomedical applications due to their mechanical properties of Young's modulus smaller than 30 GPa and yield strength higher than 180 MPa. Further, the foams were modelled using finite element analysis (FEA) with random distribution of the pores in order to estimate the compressive behavior, and the Young's modulus measured using FEA was in an excellent agreement with the experimental data.

El progresivo debilitamiento del poder estatal en Latinoamérica nos ha dirigidoa tiempos de crisis en los cuales la constante presión de los poderesen el nivel global ha obligado a los gobiernos a plantearse situaciones talescomo la apertura de los mercados y con esto el quebrantamiento de aquellasinstituciones encargadas de velar por el bien social. Inmersos en un sistemacapitalista avanzado que opaca y transforma la realidad de forma constante,vemos cómo el campo educativo no escapa a dichas circunstancias, lo queafecta no solo su estructura, sino también su razón de ser y su direccionamiento.En razón de esto, podríamos pensar en una educación que en vez deimpulsar la integración del sujeto a un sistema busque la emancipación delser humano, pero no en términos de industria y capital, sino que apunte a laemancipación del ser humano en el desarrollo de sus gustos y capacidades ylo lleve de la mano a nuevas alternativas.

En el presente trabajo se estudia el efecto de la densidad de corriente sobre la morfologia del cobre depositado por electrolisis desde una solucion acida de sulfato de cobre en presencia y ausencia de iones cloruros como impurezas. Para ello, tecnicas de cronopotenciometria y microscopia electronica de barrido son utilizadas. El estudio revela que, para ambas situaciones en presencia y ausencia de iones cloruros, los perfiles temporales del potencial catodico son desplazados en direccion catodica con el incremento de la densidad de corriente, los cuales estan asociados a la ocurrencia simultanea de reacciones catodicas durante la electrolisis de cobre. Los resultados morfologicos demuestran una influencia directa de la densidad de corriente representada por transiciones en los mecanismos de electrocristalizacion asociadas a etapas de nucleacion y crecimiento de las particulas depositadas. Los cambios en los patrones morfologicos son corroborados por un deposito de cobre tipo dendritico y granular en la solucion de electrolitos sin iones cloruros, a diferencia del deposito de cobre observado en la solucion de electrolitos con presencia de iones cloruros los cuales se observa una morfologia dendritica y laminada. Estos resultados claramente demuestran aspectos mecanisticos sobre la electrolisis de cobre. Palabras clave: Densidad de corriente, Iones cloruros, Morfologia, Potencial catodico.

Ag–CdO composites are still one of the most commonly used electrical contact materials in low-voltage applications owing to their excellent electrical and mechanical properties. Nevertheless, considering the restriction on using Cd due to its toxicity, it is necessary to find alternative materials that can replace these composites. In this study, the synthesis of Ag−ZnO alloys from Ag−Zn solid solutions was investigated by hot mechanochemical processing. The hot mechanochemical processing was conducted in a modified attritor mill at 138 °C under flowing O2 at 1200 cm3/min for 3.0 h. The microstructure and phase evolution were investigated using X-ray diffractometry, field emission gun scanning electron microscopy and transmission electron microscopy. The results suggest that it is possible to complete the oxidation of Ag−Zn solid solution by hot mechanochemical processing at a low temperature and short time. This novel synthesis route can produce Ag−ZnO composites with a homogeneous distribution of nanoscale ZnO precipitates, which is impossible to achieve using the conventional material processing methods. Considering the fact that the fundamental approach to improving electric contact material performance resides in obtaining uniform dispersion of the second-phase in the Ag matrix, this new processing route could open the possibility for Ag−ZnO composites to replace non-environmentally friendly Ag−CdO.

This work presents the effects of high energy milling with different Ni and Zr ratios on the amorphization of ternary Cu-Ni-Zr alloys (initially, Cu-43Ni-7Zr, Cu-12Ni-31Zr, Cu-33Ni-7Zr, and Cu-12Ni-23Zr; and later, Cu-23Ni-15Zr and Cu-11Ni-7Zr). Microstructure was determined using X-Ray diffraction and electron microscopy. Results were compared to thermodynamic models. In the ternary alloys under study, the lattice parameter of the Cu-Ni solid solution was generally correlated to the amounts of nickel incorporated into the Cu lattice. However, longer milling times reduced that lattice parameter and facilitated Zr insertion into the solid solution. For example, after 5 h of milling time, microstructural analysis showed the formation of a solid solution with cubic structure in Cu-43Ni-7Zr. This pattern is consistent with the presence of a lattice parameter between that of Cu and Ni (α−phase); in contrast, the Cu-33Ni-7Zr alloy showed an α-phase and another similar to Zr. Results suggest that, as the amount of nickel increases, the ability to form an amorphous phase decreases. Additionally, experimental and thermodynamic data showed a solid-solution formation stage, followed by an amorphous phase formation stage that occurred as milling time and Zr content increased. Fil: Martínez, Carola. Pontificia Universidad Católica de Valparaíso; Chile Fil: Aguilar, Claudio. Universidad Tecnica Federico Santa Maria; Chile Fil: Briones, Francisco. Pontificia Universidad Católica de Valparaíso; Chile Fil: Guzmán, Danny. Universidad de Atacama; Chile Fil: Zelaya, Maria Eugenia. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Troncoso, Loreto. Universidad Austral de Chile; Chile Fil: Rojas, Paula. Universidad Adolfo Ibañez; Chile

Elemental powders of Cu and Ni, binary alloys (Cu-Ni and Cu-Zr) and ternary alloy (Cu-Ni-Zr) obtained by mechanical alloying and uniaxial compaction hot microstructure and mechanical properties were investigated. The alloys studied were: pure Cu, pure Ni, binary alloys (Cu-Ni; Cu-Zr) and ternary alloys (Cu-Ni-Zr) under the same mechanical milling and hot pressing conditions. The samples were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM); the mechanical properties were studied by compression tests and hardness in Vickers scale (HV0.5) on polished surfaces at room temperature. According to XRD results, hot pressing process crystallite size increase and microstrain decreases in the compact samples due to the release of crystalline defects. The compacted samples have porosity of approximately 20%. The milling powder samples have a higher hardness than the unmilled samples, this because during milling crystal defects are incorporated together with the microstructural refinement. Ternary alloy is the one with the highest hardness of all systems studied, reaching 689 HV0.5. In compression tests determined a strain 5 %, Zr-containing samples become more fragile presenting the lowest values of compressive strength. In contrast, samples of Ni and Cu-Ni binary alloy are more resistant to compression.

The effect of NaCl on the leaching of white metal from a Teniente Converter was investigated in NaCl-H2SO4 media under environmental conditions. The copper dissolution from white metal was studied using ferric ions in the range of 1&ndash, 10 g/L, NaCl in the range of 30&ndash, 210 g/L, and sulfuric acid in the range of 10&ndash, 50 g/L. The test without NaCl produced a dissolution of 55%, through the addition of NaCl, the dissolution increased to nearly 90%. The effect of sulfuric acid on the copper dissolution was not significant in the studied range, as the excess sulfuric acid simply increased the iron precipitation. The positive effect of NaCl seems to be related to the action of chloro-complex oxidizing agents in relation to the Cu+2/Cu+ couple. A simplified two-stage mechanism is proposed for the leaching of white metal. In the first stage, the white metal produces covellite and Cu2+, and in the second stage it produces elemental sulfur and Cu2+. The first stage is very rapidly compared to the second stage.

This work discusses the formation of Ti–30Nb–13Ta–xMn (x: 2, 4 and 6 wt%) solid solution by mechanical alloying using a shaker mill. A solid solution was formed after 15 h of milling and an amorphous phase was formed after 30 h of milling, according to X-ray diffraction results. Disappearance of strongest X-ray diffraction peaks of Nb, Ta and Mn indicated the formation of solid solution, while, X-ray diffraction patterns of powders milled for 30 h showed an amorphous hump with crystalline peaks in the angular range of 35–45° in 2θ. TEM image analysis showed the presence of nanocrystalline intermetallic compounds embedded in an amorphous matrix. Mn2Ti, MnTi and NbTi4 intermetallic compounds were detected and revealed crystallites with size ranging from 3 to 20 nm. The Gibbs free energy for the formation of solid solution and amorphous phase of three ternary systems (Ti–Nb–Ta, Ti–Nb–Mn and Ti–Ta–Mn) was calculated using extended Miedema's model. Experimental and thermodynamic data confirmed that solid solution was first formed in the alloy with 6wt% Mn followed by the formation of an amorphous phase as milling time increases. The presence of Mn promoted the formation of amorphous phase because the atomic radius difference between Mn with Ti, Nb and Ta.

Pure Ti and Ti-based alloys exhibit two equilibrium phases: at lower temperatures they have a hexagonal close packed (α-Ti) crystalline structure while at higher temperatures they possess a body-centered cubic (β-Ti) structure. However, in special conditions, they could exhibit a metastable face-centered cubic (γ-Ti) crystalline structure. This paper aims to investigate the influence of Sn amount and milling time on the formation of γ-Ti phase on the Ti-Ta based alloy. Four alloys with compositions Ti-13Ta-xSn (x: 3, 6, 9 and 12 at. %) were obtained by high energy milling. The alloys were analyzed by X-ray diffaction patterns, transmission and scanning electron microscopy. For the Ti-13Ta-3Sn alloy, the β-Ti phase is formed in greater quantity, ∼70% at 100 h. For the Ti-13Ta-6Sn and Ti-13Ta-9Sn alloys, the phase that is in greater quantity is γ-Ti, around 100% at 100h. The Ti-13Ta-6Sn alloy shows a greater tendency to form the γ-Ti phase, since the quantity is close to 100% at 50 h milling time. Thermodynamic calculations are comparable with experimental data. The calculations were made using the MAAT software based on Miedema’s model. The MAAT is a free software that can be download from www.rpm.usm.cl .

The Planchon Peteroa Volcanic Complex (PPVC) is located on the border of Chile and Argentina, and is one of the most active volcanic systems in the Andes. Holocene activity has included magma-water interaction with an evolving series of crater lakes, mainly sourced from Peteroa volcano. This study examines data from the 2018/19 eruption, together with the volcanic history of the PPVC, to elucidate the complex interplay between magmatic activity and summit water and ice. From February 2016 to mid-2019, three seismic swarms occurred in the PPVC, preceding the explosive eruption from September 2018 to April 2019. The activity originated from a small vent nested within the easternmost crater, the most active portion of the complex (Peteroa). The explosions interacted with a crater lake, producing ash plumes up to 2 km above the crater and building a small tephra cone. To investigate the eruption mechanisms, we performed remote sensing analysis of plume dispersal, thermal anomalies and ground deformation, and characterized the volcanic products, including grain size, componentry, morphology, internal textures, composition and mineralogy. Our results suggest that the precursory seismicity beginning in 2016 was related to the intrusion of a new magma batch that reached the surface during the 2018/19 eruption. The eruption was also preceded by thermal anomalies, geomorphic changes and increased hydrothermal activity at the surface, though without any ground deformation recognized through radar interferometry (InSAR). The eruption initially produced predominantly recycled ash (phreatic activity), then evolved to increasing proportions of juvenile magma (phreatomagmatic) by April 2019. The juvenile clasts had a trachyandesite composition (~59 wt% SiO2), with vesicular and dense scoria containing plagioclase and pyroxene. The ash surfaces show external quenching cracks and step fractures consistent with phreatomagmatic fragmentation within the active crater lake. Textural characteristics also point to a slowly ascending batch of magma that was relatively viscous by the time it interacted with water in the crater lake. Notably, these juvenile particles are distinctive from the pre-2018 products. Ash erupted from 2010/11 did not contain recognizable juvenile material, and is inferred to have been a mainly phreatic eruption. Our findings suggest that the interplay between phreatic and phreatomagmatic eruptions fed by small magma batches intruding at shallow levels characterize much of the eruptive behavior of the PPVC during the last three decades. Multi-parametric assessment is a powerful tool to discriminate between phreatic and phreatomagmatic eruptions.

The aim of this work was to study the synthesis and electrochemical properties of Ti 2 wt %-Si alloys prepared by mechanical alloying (MA) and heat treatment. The MA process was performed under Ar atmosphere. The structural, morphological, and compositional evolutions during the milling and subsequent heat treatment were investigated by X-ray diffraction, energy-dispersive spectroscopy, and scanning electron microscopy. The electrochemical behavior was evaluated by open circuit potential and linear sweep voltammetry measurements. The results showed that the MA process promotes the formation of a supersaturated &alpha, Ti-Si solid solution. During heat treatment, the Si remaining in the mechanically alloyed powders and the Si from the &alpha, Ti-Si supersaturated solid solution reacted with Ti to form Ti-Si intermetallic compounds. These compounds have a fine and homogeneous distribution in the &alpha, Ti matrix, which cannot be achieved by conventional casting methods. Additionally, the electrochemical evaluations revealed that the mechanically alloyed and heat-treated Ti 2 wt %-Si powders have better corrosion resistance in 1.63 M H2SO4 than the pure Ti and MA Ti-Si samples. This is likely due to the particular microstructure produced during the milling and subsequent heat treatment.

En este estudio se fabricaron diferentes materiales (base cobre) bajo las mismas condiciones de molienda: molino empleado fue un SPEX 8000D, atmósfera de argón, acido esteárico, RBP=10:1, con tiempos varia-bles desde 1 hasta 120 horas, con el objetivo de comparar los cambios microestructurales durante el proceso de: Cobre puro, Aleaciones Cu-Ni, Aleaciones Cu-Zr y aleaciones Cu-Ni-Zr. Las muestras, tras la molienda, fueron analizadas mediante difracción de rayos X, microscopía electrónica de transmisión y calorimetría dife-rencial de barrido. De acuerdo a los resultados, el cobre al ser sometido al proceso alcanza un tamaño de cris-talita que se hace asintótico a partir de las 5 horas, mientras que en el sistema Cu-Ni, en vez de apreciarse un refinamiento microestructural a ese mismo periodo, se advierte una total solubilización del níquel en cobre (40-60 y 50-50) y de cobre en níquel (60-40). Por su parte, en el sistema binario Cu-Zr, se encontró, tam-bién para 5 horas, que el sistema estaba prácticamente amorfizado (60-40 y 50-50) al igual que en el caso de las aleaciones ternarias Cu-Ni-Zr (60-10-30 y 50-10-40). In this study, different, copper-based materials were fabricated under equal milling conditions (SPEX 8000D, argon atmosphere, stearic acid, BPR=10:1) and variable amounts of time, from 1 to 120 hours, in order to compare the microstructural changes during the process. The materials were: Pure copper; Cu-Ni alloys; CuZr alloys; and Cu-Ni-Zr alloys. Subsequent to milling, the samples were measured with X-Ray Diffraction, Electron Transmission Microscopy, and Differential Scanning Calorimetry. According to the results, copper, upon being subjected to the process, reaches a crystallite size that tends towards an asymptote starting at 5 hours. In the Cu-Ni system, instead of observing a microstructural refinement during this same period, there was rather a total solubilization of the nickel into the copper (40-60 and50-50), and of the copper into the nickel (60-40). As for the Cu-Zr binary system, it was found that, for five hours as well, the system was practically amorphous (60-40 and 50-50), a condition also present in the Cu-Ni-Zr ternary alloys (60-10-30 and 50-10-40). Fil: Rojas, Paula. Pontificia Universidad Catolica de Valparaiso; Chile. Universidad Adolfo Ibañez; Chile Fil: Martínez, Carola. Pontificia Universidad Catolica de Valparaiso; Chile. Pontificia Universidad Catolica de Valparaiso; Chile Fil: Viancos, Francisco. Pontificia Universidad Catolica de Valparaiso; Chile Fil: Aguilar, Claudio. Universidad Técnica Federico Santa María. Departamento de Ingeniería Metalúrgica y Materiales; Chile Fil: Guzmán, Danny . Universidad de Atacama. Departamento de Ingeniería Metalúrgica y Materiales; Chile Fil: Zelaya, Maria Eugenia. Comision Nacional de Energia Atomica. Gerencia del Area de Investigaciones y Aplicaciones no Nucleares. Gerencia de Fisica (CAB); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Development of titanium foams with low Young’s modulus as a potential implant material has attracted significant attention. In this work, the effect of manganese on the mechanical properties in compression of Ti–13Ta–30Nb–xMn foams (x = 2–6 wt-%) has been studied. Titanium based alloys produced by mechanical alloying were processed to obtain foams using ammonium hydrogen carbonate with a mean particle size of 35 μm (50% v/v) as a space-holder. Powders and space-holder were mixed and uniaxially pressed to form compacts. The space holder was removed by heating the green compacts to 180°C for 1.5 h before sintering at 1300°C for 4 h in Ar. The Young’s modulus of the foam was lower than that of pure Ti, and the yield strength increased with the Mn addition. The Gibson–Ashby, Meyer and Nielsen models were applied to predict the mechanical properties of the titanium foams.

Magnesium and its alloys are widely recommended for automotive, electronics and biomedical industries due to their strength to weight ratio. The mechanically alloyed magnesium with Ni, Cu and Ca alloys exhibits superior properties. In this work, the ternary Mg70Ni10Ca20 and Mg85Cu10Ca5 alloys were synthesized by mechanical alloying for 10 h in SPEX mill with 10:1 ball to powder ratio under argon (Ar) atmosphere. Their structural and phase transformation with respect to milling time and composition were studied by X-ray diffraction (XRD), scanning electron microscopy and energy dispersive X-ray spectroscopy. The XRD pattern showed the formation of amorphous with nano crystalline peaks. The Mg2Cu and CaCu intermetallic phases were identified in Mg85Cu10Ca5 alloy and Mg2Ni and MgNi2 intermetallic compounds were identified in Mg70Ni10Ca20 alloy. A crystallite size of 44.45 nm was measured from the α-Mg XRD peak in Mg-Cu-Ca alloy, and 45.59 nm was measured for the Mg2Ni phase in Mg-Ni-Ca alloy.

This work discusses the extension of solid solubility of Cr and Mo in Cu processed by mechanical alloying. Three alloys processed, Cu–5Cr–5Mo, Cu–10Cr–10Mo and Cu–15Cr–15Mo (weight%) using a SPEX mill. Gibbs free energy of mixing values 10, 15 and 20 kJ mol −1 were calculated for these three alloys respectively by using the Miedema's model. The crystallite size decreases and dislocation density increases when the milling time increases, so Gibbs free energy storage in powders increases by the presence of crystalline defects. The energy produced by crystallite boundaries and strain dislocations were estimated and compared with Gibbs free energy of mixing values. The energy storage values by the presence of crystalline defects were higher than Gibbs free energy of mixing at 120 h for Cu–5Cr–5Mo, 130 h for Cu–10Cr–10Mo and 150 h for Cu–15Cr–15Mo. During milling, crystalline defects are produced that increases the Gibbs free energy storage and thus the Gibbs free energy curves are moved upwards and hence the solubility limit changes. Therefore, the three alloys form solid solutions after these milling time, which are supported with the XRD results.

Nowadays, Ag–CdO alloys are widely used in electrical contact applications, because of their good electrical and thermal conductivity is as well as high resistance to arc erosion and contact welding. Considering the restricted use of Cd due to its toxicity, it is necessary to find a material that can replace those alloys. The objective of this work was to study the possibility of obtaining an Ag–ZnO alloy from an Ag–Zn solid solution powders by means of a mechanochemical method. The mechanochemical process was carried out in a SPEX 8000D mill, under air and with ethanol as a reaction agent. Based on the results obtained, it can be concluded that an Ag–ZnO alloy with a fine and uniform ZnO distribution in the Ag matrix can be obtained by applying the mechanochemical process for 25 h.

Phase evolution during mechanical alloying (MA) of elemental Mg and Cu powders and their subsequent heat treatment is studied. Elemental Mg and Cu powders in a 2:1 atomic ratio were mechanically alloyed in a SPEX 8000D mill using a 10:1 ball-to-powder ratio. X-ray diffraction (XRD) shows that the formation of the intermetallic Mg2Cu takes place between 3 and 4 h of milling, although traces of elemental Cu are still present after 10 h of milling. The thermal behavior of different powder mixtures was evaluated by differential scanning calorimetry (DSC). The combination of DSC, heat treatment and XRD has shown a sequence of phase transformations that results in the intermetallic Mg2Cu from an amorphous precursor. This amorphous phase is converted into Mg2Cu by heating at low temperature (407 K). Short MA times and the formation of the amorphous precursor, together with its subsequent transformation into Mg2Cu at low temperatures; represent an advantageous alternative route for its preparation.

The objective of this work was to study the influence of copper and nickel on the kinetics of strain-induced martensite in austempered ductile cast iron. The austempered ductile cast irons were obtained from two ductile cast irons with different copper and nickel contents by means of austempering treatment. The deformation was carried out using a rolling mill. The quantification of the phases was obtained by means of X ray diffraction, while the microstructural characterization was carried out using optical and scanning electron microscopy. It was proved that the kinetics of strain-induced martensite in austempered ductile cast iron can be modeled using the equations proposed by Olson- Cohen and Chang et al. Based on the results obtained from these analyses, it is possible to conclude that the nickel and copper complicate the martensite transformation because these elements increase the staking fault energy of the austenite and its thermodynamic stability.El objetivo de este trabajo fue estudiar el efecto del cobre y níquel en la cinética de la transformación martensítica inducida por deformación en fundiciones nodulares austemperadas. Las fundiciones utilizadas se fabricaron mediante austemperado, a partir de dos fundiciones nodulares, con diferentes contenidos de cobre y níquel. La deformación se realizó en un laminador de rodillo. La cuantificación de las fases se realizó mediante difracción de rayos X, mientras que la caracterización microestructural se efectuó utilizando microscopía óptica y electrónica de barrido. Se comprobó que la cinética de transformación martensítica inducida por deformación en fundiciones nodulares austemperadas puede ser modelada mediante los modelos de Olson-Cohen y Chang et al. Basándose en los resultados obtenidos de estos ajustes, se concluye que tanto el níquel como el cobre dificultan la transformación martensítica debido a que estos elementos aumentan la energía de falla de apilamiento de la austenita, además de aumentar su estabilidad termodinámica.

The manufacture of alloys in solid state has many differences with the conventional melting (casting) process. In the case of high energy milling or mechanical alloying, phase transformations of the raw materials are promoted by a large amount of energy that is introduced by impact with the grinding medium; there is no melting, but the microstructural changes go from microstructural refinement to amorphization in solid state. This work studies the behavior of pure metals (Cu and Ni), and different binary alloys (Cu-Ni and Cu-Zr), under the same milling/mechanical alloying conditions. After high-energy milling, X ray diffraction (XRD) patterns were analyzed to determine changes in the lattice parameter and find both microstrain and crystallite sizes, which were first calculated using the Williamson-Hall (W-H) method and then compared with the transmission electron microscope (TEM) images. Calculations showed a relatively appropriate approach to observations with TEM; however, in general, TEM observations detect heterogeneities, which are not considered for the W-H method. As for results, in the set of pure metals, we show that pure nickel undergoes more microstrain deformations, and is more abrasive than copper (and copper alloys). In binary systems, there was a complete solid solution in the Cu-Ni system and a glass-forming ability for the Cu-Zr, as a function of the Zr content. Mathematical methods cannot be applied when the systems have amorphization because there are no equations representing this process during milling. A general conclusion suggests that, under the same milling conditions, results are very different due to the significant impact of the composition: nickel easily forms a solid solution, while with a higher zirconium content there is a higher degree of glassforming ability. La fabricación de aleaciones en estado sólido tiene muchas diferencias con el proceso de fusión (colada) convencional. En el caso de la molienda de alta energía o aleado mecánico, las trasformaciones de fases de las materias primas son promovidas por una gran cantidad de energía que se introduce mediante impacto con medios de molienda; no hay fusión, pero sí cambios microestructurales que van desde refinamiento microestructural hasta amorfización en estado sólido. En este trabajo se estudia el comportamiento de metales puros (Cu y Ni) y diferentes aleaciones binarias (Cu-Ni y Cu-Zr) sometidas a las mismas condiciones de molienda con el objetivo de analizar el efecto del proceso en metales similares (Cu y Ni) y con solubilidades muy diferentes (Cu-Ni y Cu-Zr). Después de la molienda de alta energía, se analizaron los patrones de difracción de rayos X para determinar cambios en parámetros de red, y calcular las micro-deformaciones y el tamaño de las cristalitas, los cuales fueron calculados por el método de Williamson Hall (W-H), para luego ser comparados con los datos de las imágenes obtenidas por microscopía electrónica de transmisión (MET). Los cálculos muestran una apropiada similitud con las observaciones en MET; sin embargo, en general, las observaciones muestran heterogeneidades que no son consideradas en el método de W-H. De acuerdo a los resultados, en los metales puros se observó mayor cantidad de micro-deformaciones en níquel y fue más abrasivo que el cobre. En las aleaciones binarias, el sistema Cu-Ni formó soluciones sólidas con solubilidad total y las del sistema Cu-Zr mostraron amorfización, en función del contenido de Zr. Los métodos matemáticos no pueden ser aplicados en los casos donde se detecta amorfización debido a que aún no han sido creadas ecuaciones que representen este fenómeno cuando ocurre durante la molienda. Como conclusión se observó que bajo las mismas condiciones de molienda los resultados pueden ser muy diferentes debido al impacto significativo de la composición: el níquel formó fácilmente solución sólida mientras que el circonio incremento la habilidad de formación de vidrios.

In this work the effect of mechanical activation on the barite carbothermic reduction has been investigated. The mechanical activation of barite and coke was carried out in a SPEX 8000 D mill. The microstructural and morphological characterization of the powders was obtained by X-ray diffraction and scanning electron microscopy. The kinetics of barite carbothermic reduction was studied using differential scanning calorimetry and thermogravimetry. The experimental results revealed that the mechanical activation process improves the kinetics of barite carbothermic reduction. It was found that 3.6 ks of milling decreases the activation energy of barite reduction from 519 to 276 kJ/mol. This behavior can be explained considering the increase of reactants enthalpy due to the energy stored by the powders and the intimate contact between fine barite and coke particles promoted by the milling process.

They were carried out experiments of biosorption batch and in continuous to remove copper from aqueous solutions using as adsorbent green algae and olive residues under virgins conditions and chemically activated. The results of batch biosorption indicate that the algae present mayor elimination capacities than the waste of olives, with uptakes of copper of the order of 96 % using activated algae with dissolution of Na2SO4 under the optimum conditions. The results of the columns tests show that the virgin algae permits the removal of more copper ions than the activate algae, with removal efficiency of 98 % during the firth 20 min, a breakthrough time of 240 min and a saturation at time of 600 min. In the second cycle the regenerated biomass showed a best performance indicating that they can be used for another biosorption cycle.Se realizaron experimentos de biosorción batch y en continuo para remover cobre desde soluciones acuosas usando como adsorbentes algas verdes y residuos de aceituna en condiciones vírgenes y activadas químicamente. Los resultados de la biosorción a escala batch indican que las algas presentan mayor capacidad de eliminación que los orujos, alcanzándose captaciones de cobre del orden de 96 % con algas activadas con disoluciones de Na2SO4 bajo condiciones óptimas de las variables estudiadas. Los resultados de los ensayos en columna muestran que las algas vírgenes captan más iones cobre que las activadas con Na2SO4, con eficacias de eliminación del 98 % durante los primeros 20 min, con un tiempo de ruptura de 240 min y una saturación a los 600 min. Al ser sometidas a un segundo ciclo de biosorción, las algas regeneradas muestran un mejor rendimiento lo que indica que pueden ser usadas en otro ciclo de eliminación.

Amorphous Mg 50 Ni 50 alloy was produced by mechanical alloying (MA) of the elemental powders Mg and Ni using a SPEX 8000D mill. The alloyed powders were microstructurally characterized by X-ray diffraction (XRD). The thermal transformation of amorphous Mg 50 Ni 50 into stable intermetallics (Mg 50 Ni 50 → remaining amorphous + Mg 2 Ni → Mg 2 Ni + MgNi 2 ) was analyzed using the Kissinger and isoconversional methods based on the non-isothermal differential scanning calorimetry (DSC) experiments. The apparent activation energies ( E a ) and the transformation diagrams, temperature–time–transformation ( T – T – T ) and temperature–heating rate–transformation (T–HR–T), were obtained for both processes. A good agreement was observed between the calculated transformation curves and the experimental data, which verifies the reliability of the method utilized.

In order to study the relationship between the milling time used in the production of Mg50Ni50 amorphous alloy and its thermal stability, seven amorphous alloys were produced by milling for 20, 25, 30, 35, 40, 50 and 60 h each sample. The obtained powders were morphological and structurally characterized by scanning electron microscopy (SEM), Xray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The thermal stability of amorphous alloys was study by differential scanning calorimetry (DSC). Based on the obtained results, it can be concluded that the increase in the added energy when milling for longer time causes the homogenization of the microstructure with an increase in amorphous phase, which dissolves a larger amount of nickel in its structure. Therefore, the simultaneous crystallization of the Mg2Ni and MgNi2 intermetallic compounds at 345 °C can be explained.Para estudiar la relación entre el tiempo de molienda aplicado en la obtención de una aleación amorfa Mg50Ni50 producida por aleado mecánico (AM) y su estabilidad térmica, se fabricaron siete aleaciones amorfas con tiempos de molienda de 20, 25, 30, 35, 40, 50 y 60 h. Los polvos se caracterizaron morfológica y microestructuralmente mediante microscopía electrónica de barrido (MEB) y pruebas conjuntas de difracción de rayos-X (DRX) y microscopía electrónica de transmisión (MET), respectivamente. La estabilidad térmica de las aleaciones fue estudiada por calorimetría diferencial de barrido (CDB). Con base en los resultados obtenidos se determinó que el aumento en la cantidad de energía adicionada a los polvos mediante tiempos prolongados de AM, homogeneiza la microestructura de éstos, produciendo un aumento de la cantidad de fase amorfa, la cual posee una mayor cantidad de níquel en su estructura, lo que facilita la cristalización simultanea del Mg2Ni y MgNi2 a temperaturas cercanas a los 345 °C.

La investigación realizada por este grupo de trabajo tiene como objetivo principal el estudio y fabricación de vidrios metálicos base cobre (Cu-Ni-Zr) mediante aleado mecánico. Se planteó la caracterización de los ele-mentos puros (Cu y Ni), aleaciones binarias Cu-Ni y Cu-Zr y aleaciones ternarias Cu-Ni-Zr en las mismas condiciones de molienda de alta energía. En este trabajo se presenta el cambio microestructural del Níquel al ser sometido a molienda de alta energía. Para este fin se utilizó un molino SPEX 8000D con las siguientes condiciones de molienda: atmósfera de argón, acido esteárico, RBP=10:1, con tiempos desde 1 hasta 60 horas, 1 h de molienda efectiva y seguida de 0,5 h de descanso. Las muestras posteriores a la molienda fueron anali-zadas mediante difracción de rayos X, microscopía electrónica de transmisión y espectroscopia de absorción atómica, obteniendo el tamaño de cristalita, parámetro de red y contaminación de Fe. Los resultados obteni-dos muestran que el níquel al ser sometido a molienda mecánica alcanza un tamaño de cristalita de aproxi-madamente 10 nm que se hace asintótico a partir de las 5 horas; el parámetro de red incrementa al aumentar el tiempo de molienda, posiblemente debido al incremento del componente interfacial conjuntamente a la incorporación de Fe dentro de la red, producto del alto porcentaje de contaminación a las 60 h. Research by this working group's takes as a principal aim the study and manufacture of bulk metal glass based copper (Cu-Ni-Zr) by mechanical alloying. First, the characterization of the milled pure copper, Cu-Ni and Cu-Zr binary alloys and Cu-Ni-Zr ternary alloys in the same conditions of high energy millings. In this work, the microstructural change of Nickel to be subjected to high energy milling is presented. For this purpose a SPEX 8000D mill with the following conditions of milling: argon, stearic acid, BPR = 10:1, with milling time from 1 to 60 hours, 1 h of effective milling followed by a rest period of 0,5 h. Subsequent to the milling samples were analyzed by ray-X diffraction, transmission electron microscopy and atomic absorption spectroscopy, obtaining the crystallite size, lattice parameters and Fe contamination. The results show that nickel when subjected to mechanical milling reaches a crystallite size of about 10 nm which is asymptotic from 5 h; the lattice parameter increases with increasing milling time, possibly due to increased interfacial component together with the incorporation of Fe, due to the high percentage contamination at 60 h. Fil: Martínez, Carola. Pontificia Universidad Catolica de Valparaiso; Chile. Universidad Adolfo Ibañez; Chile Fil: Rojas, Paula. Pontificia Universidad Catolica de Valparaiso; Chile Fil: Aguilar, Claudio . Universidad Técnica Federico Santa María. Departamento de Ingeniería Metalúrgica y Materiales; Chile Fil: Guzmán, Danny . Universidad de Atacama. Departamento de Ingeniería Metalúrgica y de Materiales; Chile Fil: Zelaya, Maria Eugenia. Comision Nacional de Energia Atomica. Gerencia del Area de Investigaciones y Aplicaciones no Nucleares. Gerencia de Fisica (CAB); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

The unprecedented increase in human life expectancy have produced profound changes in the prevailing patterns of disease, like the observed increased in degenerative disc diseases, which cause degradation of the bones. Ti-Nb-Ta alloys are promising materials to replace the damaged bone due to their excellent mechanical and corrosion resistance properties. In general metallic foams are widely used for medical application due to their lower elastic moduli compare to bulk materials. In this work we studied the synthesis of 34Nb-29Ta-xMn (x: 2, 4 and 6 wt.% Mn) alloy foams (50% v/v) using ammonium hydrogen carbonate as a space holder. Alloys were produced through mechanical alloying in a planetary mill for 50h. Green compacts were obtained by applying 430 MPa pressure. To remove the space holder from the matrix the green compacts were heated to 180 °C for 1.5h and after sintered at 1300 °C for 3h. Foams were characterized by x-ray diffraction, scanning, transmission electron microscopy and optical microscopy. The elastic modulus of the foam was measured as ~30 GPa, and the values are almost equal to the values predicted using various theoretical models.

Este trabajo tuvo como objetivo estudiar la relación existente entre la composición química y el volumen atómico en el sistema Ag - x % at Zn (x ≤ 20). Para este fin, se fabricaron 10 soluciones sólidas mediante fundición y aleado mecánico. La caracterización microestructural se llevó a cabo utilizando difracción de rayos-X. El parámetro reticular fue calculado mediante el método de Rietveld, mientras que la composición química se determinó utilizando espectroscopia de energía dispersiva de rayos-X. En base a los resultados obtenidos se puede concluir que existe una relación lineal inversa entre el volumen atómico de la solución sólida y su contenido Zn, presentando una desviación negativa de la ley de Vegard (-2,96%). Adicionalmente, se propuso una ecuación que vincula el contenido de Zn con el volumen atómico de la solución sólida, la cual presentó un error promedio de predicción menor al 12%. In this work the relationship between the chemical composition and atomic volume in the Ag - x % Zn (x ≤ 20) system was studied. For this purpose, 10 solid solutions were obtained by means of casting and mechanical alloying. The microstructural characterization was carried out by means of X ray diffraction. The lattice parameter was obtained using the Rietveld's method, while the chemical composition was determined by dispersive energy X-ray spectroscopy. Based on the results obtained, it can be concluded that there is an inverse lineal relationship between the atomic volume of the solid solution and its Zn concentration, which shows a negative deviation from Vegard`s law (-2.96%). Additionally, it was proposed an equation which relates the Zn concentration with the atomic volume of the solid solution, which showed a prediction error less than 12%.

Microstructural evolution during mechanical alloying of Ag and Zn, and subsequent heat treatments were investigated. The mechanical alloying was carried out in a SPEX 8000D miller. The microstructural characterization was obtained by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The thermal behavior was studied using differential scanning calorimetry (DSC). Based on the results obtained, it can be concluded that at the early stages of milling was possible to detect the ɛ, β, β′, α solid solutions and remaining Zn. Later, the ɛ, β, β′ and Zn phases disappeared while the Zn concentration of the α solid solution was strongly increased. After 7.2 ks of milling, the mechanical alloying process reached a steady state. During this period, both the composition and crystallite size of the α solid solution remained practically unchanged. On the other hand, subsequent heat treatments of milled powders showed that the α solid solution could also be obtained by the combination of mechanical alloying and heat treatment. Finally, the evolution of the microstructure during milling and annealing was combined to propose an optimal processing route in order to obtain a α solid solution.

This work studied the structural evolution of Cu– x Mo ( x = 5 and 8 wt.%) alloys processed by mechanical alloying using x-ray diffraction profiles, scanning electron microscopy, differential scanning calorimetric and microhardness. X-ray diffraction analysis was done using the modified Williamson–Hall and Warren–Averbach methods. These were used to determine structural properties, such as crystallite size, stacking fault probability and energy, dislocation density of metallic powder as a function of the amount of Mo and milling time. The main results obtained for both alloys were higher dislocation density and Vickers microhardness values were measured and crystallites sizes of around 10 nm were measured for both systems at 50 h of milling. Lattice defects increase the free energy and the free energy curves shift upwards, therefore the solubility limits change and Cu–Mo solid solution is formed.

The objective of this work is proposing a simple thermodynamic model to explain the increase in the solubility limit of the powders of the Cu–Mo systems or other binary systems processed by mechanical alloying. In the regular solution model, the effects of crystalline defects, such as; dislocations and grain boundary produced during milling were introduced. The model gives results that are consistent with the solubility limit extension reported in other works for the Cu–Cr, Cu–Nb and Cu–Fe systems processed by mechanical alloying.

This work studies the structural evolution of Cu– x Cr ( x = 3, 5 and 8 wt.%) alloys processed by mechanical alloying using X-ray diffraction profiles, scanning microscopy and microhardness analysis. X-ray diffraction analysis using the modified Williamson–Hall and Warren–Averbach methods were used to determine structural properties, such as crystallite size, stacking fault probability and energy, dislocation density, lattice parameters and crystallite size distribution of metallic powder as a function of Cr amount and milling time. Lattice defects increase the Gibbs free energy and the Gibbs free energy curves shift upward, therefore the solubility limit change.

El presente trabajo estudia la evolución de la estructura de una mezcla de polvos Cu-8% peso de Cr, aleada mecánicamente, por medio del análisis de perfiles de difracción de rayos X. Se encontró que al aumentar el tiempo de molienda, el tamaño de cristalitas y la energía de falla de apilamiento disminuyeron, y los valores de microdeformación y probabilidad de falla de apilamiento aumentaron. La distribución de cristalitas se desplazo hacia valores menores de tamaño de cristalitas al incrementar el tiempo de molienda. Después de 50 horas de molienda, los datos indicaron que se ha producido una solución sólida de cromo en cobre. This work studies the evolution of the microstrucutre of a mechanically alloyed Cu-8 wt. % Cr powder mixture by X-Ray profiles analysis. The process was carried out using a SPEX8000D upon mix with stainless steels containers and balls, keeping a constant powder to balls weight ratio of 10. Increasing the milling time, crystallite size and stacking fault energy decreased and microstrain and stacking fault probability increased. The crystallite size distribution shifts to lower crystallite size values by increasing the milling time. After a milling time of 50 hours, the data showed that a solid solution of chromium in copper was produced.

An oversaturated solid solution of H in a nanocomposite material formed mainly by nanocrystalline Mg2Ni, some residual nanocrystalline Ni and an Mg rich amorphous phase has been found for the first time. The nanocomposite was produced by mechanical alloying starting from Mg and Ni elemental powders, using a SPEX 8000D mill. The hydriding characterization of the nanocomposite was carried out by solid‐gas reaction method in a Sievert’s type apparatus. The maximum hydrogen content reached in a period of 21 Ks without prior activation was 2.00 wt.% H under hydrogen pressure of 2 MPa at 363 K. The X-ray diffraction analysis showed the presence of an oversaturated solid solution between nanocrystalline Mg2Ni and H without any sign of Mg2NiH4 hydride formation. The dehydriding behaviour was studied by differential scanning calorimetry and thermogravimetry. The results showed the existence of two desorption peaks, the first one associated with the transformation of the oversaturated solid solution into Mg2NiH4, and the second one with the Mg2NiH4 desorption.