Effect of alloying elements on the Sr modification of Al-Si cast alloys

Strontium-based modifier alloys are commonly adopted to modify the eutectic silicon in aluminum-silicon casting alloys by changing the silicon shape from an acicular to a spherical form. Usually, the modifier alloy necessary to properly change the silicon shape depends on the silicon content, but the alloying elements’ content may have an influence. The AlSr10 master alloy’s modifying effect was studied on four Al-Si alloys through the characterization of microstructural and mechanical properties (micro-hardness and impact tests). The experimental results obtained on gravity cast samples highlighted the interdependence in the modification of silicon between the Si content and the alloying elements. After modification, a higher microstructural homogeneity characterized by a reduction of up to 22.8% in the size of intermetallics was observed, with a generalized reduction in secondary dendritic arm spacing. The presence of iron-based polygonal-shaped intermetallics negatively affects Sr modification; coarser silicon particles tend to grow close to α-Fe. The presence of casting defects such as bifilm reduces Sr modification’s beneficial effects, and little increase in absorbed impact energy is observed in this work

Residual stress analysis applied to HPDC aluminium components: a case study

High-Pressure Die Casting (HPDC) is a casting process largely diffused in the aluminium foundries. By HPDC is possible to obtain aluminium castings with thin walls and high specific mechanical properties in short cycle times. Aluminium HPDC castings are commonly intended for the automotive sector: engine, covers, engine blocks and more in general the powertrain. In recent years, one of the most important focus in the automotive sector is decreasing the powertrain weight, acting on stock allowances in certain parts of the casting. This reduction can affect the dimensional features and in turn the residual stress inside the casting. Despite that, it is possible to obtain beneficial compression states into the castings by mean of post-process operations, such as shot-blasting, to reduce or remove residual stresses by mean of heat treatments. Residual stresses can be assessed by an X-Ray residual stress measurement device, a nondestructive technique that allows observing the process parameters effect into the casting. In this work, after a detailed analysis of the residual stress measurement available for aluminium castings, a powertrain component realized in aluminium alloy EN AC 46000 was analysed. These analyses involved both dimensional response and related residual stresses in the as-cast state and the shot-blasted-state on a valve cover, to understand and prevent the residual stress states into the aluminium castings

Crop residues and agro-industrial by-products from the province of La Rioja (Argentina) suitable for oyster mushroom culture

In La Rioja province (Argentina) large amounts of lignocellulosic residual biomass are generated annually. A survey was conducted to identify crop residues and agro-industrial by-products in the province, which could be suitable for oyster mushroom culture. Their morphological composition was characterized and a proxy for the mass that is generated annually by each of them was estimated. The availability of the biomass was also evaluated by assessing the processing, distribution, seasonality, cost and other common uses that may compete with its application as substrate. Eight residual crops and eight agro-industrial by-products were identified, being olive and grape pomace the most abundant, followed by grape pruning, and olive and jojoba litter. The use as substrate of these last two together with Prosopis bran and olive pits, has not been registered in the production of oyster mushrooms. In production assays with commercial strains of Pleurotus species, biological efficiency (BE) ranged from 28 % to 72 %, depending on the substrate and fungal species. In a context of high-quality food production deficit and nutritional problems related to it, this province has an interesting potential to introduce the production and consumption of oyster mushrooms as a feasible solution for food regional supply.Fil: Fracchia, S.. Universidad Nacional de La Rioja; ArgentinaFil: Miranda, V.. Universidad Nacional de La Rioja; ArgentinaFil: Sede, Silvana Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Barbero, I.. Universidad Nacional de San Luis; ArgentinaFil: Barros, J.. Universidad Nacional de La Rioja; ArgentinaFil: Delgado, Nicolás. Universidad Nacional de La Rioja; Argentin

Dual-readout Calorimetry

The RD52 Project at CERN is a pure instrumentation experiment whose goal is to understand the fundamental limitations to hadronic energy resolution, and other aspects of energy measurement, in high energy calorimeters. We have found that dual-readout calorimetry provides heretofore unprecedented information event-by-event for energy resolution, linearity of response, ease and robustness of calibration, fidelity of data, and particle identification, including energy lost to binding energy in nuclear break-up. We believe that hadronic energy resolutions of {\sigma}/E $\approx$ 1 - 2% are within reach for dual-readout calorimeters, enabling for the first time comparable measurement preci- sions on electrons, photons, muons, and quarks (jets). We briefly describe our current progress and near-term future plans. Complete information on all aspects of our work is available at the RD52 website http://highenergy.phys.ttu.edu/dream/.Comment: 10 pages, 10 figures, Snowmass White pape

Electrodeposited cu thin layers as low cost and effective underlayers for Cu2O photocathodes in photoelectrochemical water electrolysis

Cu2O is one of the most studied semiconductors for photocathodes in photoelectrochemical water splitting (PEC-WS). Its low stability is counterbalanced by good activity, provided that a suitable underlayer/support is used. While Cu2O is mostly studied on Au underlayers, this paper proposes Cu(0) as a low-cost, easy to prepare and highly efficient alternative. Cu and Cu2O can be electrodeposited from the same bath, thus allowing in principle to tune the final material\u2019s physico-chemical properties with high precision with a scalable method. Electrodes and photoelectrodes are studied by means of electrochemical methods (cyclic voltammetry, Pb underpotential deposition) and by ex-situ X-ray absorption spectroscopy (XAS). While the potential applied for the deposition of Cu has no influence on the bulk structure and on the photocurrent displayed by the semiconductor, it plays a role on the dark currents, making this strategy promising for improving the material\u2019s stability. Au/Cu2O and Cu/Cu2O show similar performances, the latter having clear advantages in view of future use in practical applications. The influence of Cu underlayer thickness was also evaluated in terms of obtained photocurrent

The Missing Piece: The Structure of the Ti3C2TxMXene and Its Behavior as Negative Electrode in Sodium Ion Batteries

The most common MXene composition Ti3C2Tx (T = F, O) shows outstanding stability as anode for sodium ion batteries (100% of capacity retention after 530 cycles with charge efficiency >99.7%). However, the reversibility of the intercalation/deintercalation process is strongly affected by the synthesis parameters determining, in turn, significant differences in the material structure. This study proposes a new approach to identify the crystal features influencing the performances, using a structural model built with a multitechnique approach that allows exploring the short-range order of the lamella. The model is then used to determine the long-range order by inserting defective elements into the structure. With this strategy it is possible to fit the MXene diffraction patterns, obtain the structural parameters including the stoichiometric composition of the terminations (neutron data), and quantify the structural disorder which can be used to discriminate the phases with the best electrochemical properties

Colata per gravità di un FGM in lega di alluminio: ottimizzazione del trattamento termico e proprietà finali

Le leghe di alluminio sono largamente utilizzate nel settore dell’autoveicolo per produrre ad esempio blocchi motore, coperchi punterie, pistoni, grazie all’ottima correlazione tra resistenza meccanica e leggerezza che le contraddistingue. In particolare, i pistoni sono soggetti a fratture per fatica vista la loro duale richiesta di resistenza alla fatica termica e di duttilità lungo l’intero volume del pezzo. I FGM (Functionally Graded Materials) sono materiali compositi avanzati ideati per garantire una graduale variazione di proprietà e composizione lungo il volume del materiale stesso. In questo lavoro, la lega per pistoni EN AC 48000 è impiegata insieme alla lega EN AC 42100 per la realizzazione di un FGM, con l’obiettivo di ottenere una variazione di proprietà lungo il volume del pezzo che garantisca le caratteristiche meccaniche ottimali per un pistone. Le proprietà finali richieste vengono ottenute per mezzo di trattamento termico T6 con solubilizzazione a 530°C ed invecchiamento artificiale a 175°C fornendo caratteristiche meccaniche apprezzabili

Diversificación de la producción de alimentos: cultivo de hongos comestibles utilizando residuos locales (Valle Fértil, San Juan)

Desde hace más de 15 años el programa PROHUERTA, a través de la Estación Experimental Agropecuaria San Juan del INTA, viene promoviendo la autoproducción de alimentos y su diversificación en familias con Necesidades Básicas Insatisfechas (NBI) del departamento Valle Fértil. Tomando la experiencia que tiene el Laboratorio de Micología Aplicada del CRILAR – CONICET en la provinciade La Rioja, se propone continuar con la diversificación de la producción agrícola a escala familiar, acercando la tecnología desarrollada por este laboratorio para la producción de hongos comestibles tipo gírgolas (Pleurotus sp). Estos hongos son cultivados por su agradable y característico sabor y apreciados debido a sus propiedades nutricionales y medicinales. Pueden crecer y degradar gran diversidad de residuos lignocelulósicos, tienen tiempos cortos de desarrollo y fructificación, se cultivan de manera sencilla y económica y además tienen como ventaja la posibilidad de poder producirse sin suelo.EEA San JuanFil: Vitale Guardia, Pablo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Juan; ArgentinaFil: Fracchia, S. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja (CRILAR); ArgentinaFil: Rothen, C. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja (CRILAR); Argentin

Gestione delle conchiglie nella colata in gravità e possibili vie per migliorarne prestazioni e durata

La colata in gravità è una tecnologia di largo impiego nelle fonderie di alluminio: seppur ben nota è ancora attuale. Nonostante molte ricerche negli ultimi anni si siano focalizzate sullo studio di processi ad elevata produttività come la pressocolata, vi è ancora una larga serie di prodotti che viene ottenuta tramite colata in gravità, grazie a cui è possibile ottenere getti con difettosità ridotta e proprietà meccaniche superiori. Nonostante la colata in gravità sia una tecnologia che non è possibile definire innovativa, l’evoluzione subita dai componenti in termini di geometria, dimensioni e volumi, ha imposto un aumento della produttività a fronte di una riduzione delle tolleranze accettabili. Questi cambiamenti hanno inficiato sulla vita delle conchiglie in acciaio, utensili che si usurano sempre più facilmente. Per ottimizzare il processo produttivo è necessario introdurre su questa tecnologia già conosciuta degli elementi innovativi. In questo studio è presentato lo stato dell’arte dei metodi per aumentare la vita delle conchiglie nella colata in gravità con particolare attenzione all’effetto della rugosità superficiale della conchiglia e del metodo di verniciatura sulla resistenza ad usura ed alla metallizzazione dell’acciaio. L’alluminio fuso infatti, durante il processo di colata, interagisce con l’acciaio di cui è costituita la conchiglia, producendo usura da erosione e metallizzazione delle superfici con cui entra in contatto. Per limitare il danneggiamento della conchiglia si utilizzano comunemente delle vernici, al fine di creare una barriera tra i due materiali. Tuttavia il processo di verniciatura spesso viene effettuato basandosi su principi qualitativi e troppo spesso semi-quantitativi. Questo studio vuole investigare in modo più approfondito le fasi da seguire per l’ottenimento di una verniciatura ottimale, andando a utilizzare differenti vernici commerciali e valutandone la loro resistenza sia dal punto di vista sia della finitura superficiale della conchiglia che della resistenza alle alte temperature, simulando le condizioni d’uso reali della conchiglia, attraverso prove di usura e prove di immersione in alluminio fuso