Effect of Modifiers on the Microstructure of Rapidly Solidified AlSi10Mg Alloy

In this work, melt-spun ribbons of AlSi10Mg added with modifiers (Er, Sr, or nano-TiB2) were produced to investigate the combined effect of modification and rapid solidification on eutectic Si. The resulting eutectic microstructures are more isotropic in comparison to that of the base alloy affecting the mechanical properties of the alloys. The modification of Si morphology and supersaturation caused by the modifiers were investigated by microscopy, X-ray diffraction, and differential scanning calorimetry. Compared to melt-spun AlSi10Mg, the eutectic Si network is finer and less continuous when Er or Sr is added, and disrupted with rounded crystals dispersed in the matrix when adding nano-TiB2. The level of supersaturation decreases in the order Er–nano-TiB2–Sr. A transition from columnar Al grains at the wheel side to finer equiaxed grains at the air side was found in the unmodified ribbon and in the one containing nano-TiB2 by means of electron backscattered diffraction. The Er- and Sr-modified ribbons display equiaxed Al grains of constant size throughout their thickness. The average hardness obtained by nano-indentation tests was lower than that of AlSi10Mg. The less continuous Si network causes the hardness drop but provides more isotropic mechanical properties

Para-fluorination of anilides using electrochemically generated hypervalent iodoarenes

The para-selective fluorination reaction of anilides using electrochemically generated hypervalent ArIF2 is reported, with Et3N ⋅ 5HF serving as fluoride source and as supporting electrolyte. This electrochemical reaction is characterized by a simple set-up, easy scalability and affords a broad variety of fluorinated anilides from easily accessible anilides in good yields up to 86 %

Analysis of shot noise suppression in mesoscopic cavities in a magnetic field

We present a numerical investigation of shot noise suppression in mesoscopic cavities and an intuitive semiclassical explanation of the behavior observed in the presence of an orthogonal magnetic field. In particular, we conclude that the decrease of shot noise for increasing magnetic field is the result of the interplay between the diameter of classical cyclotron orbits and the width of the apertures defining the cavity. Good agreement with published experimental results is obtained, without the need of introducing fitting parameters.Comment: 5 pages, 3 figures, contents changed (final version

Effect of combined additions of Sc, Zr and Ti on hot-cracking resistance and precipitation behaviour in Al-Mg alloy by L-PBF

The request for high-performance aluminum components prompts research into innovative alloys compatible with laser-based additive manufacturing processes, leveraging grain refiners in their composition to mitigate hot- cracking and enhance strength. While the addition of Sc and Zr in Al-Mg alloys has been widely investigated, the high cost and supply risks associated with Sc necessitate reducing its amount and replacing, at least partially, with other inoculants. In this preliminary study, the amount of Sc replaceable with different concentrations of Zr or Ti is evaluated investigating the laser powder bed fusion processability of three powder feedstocks: a pre- alloyed Al-Mg-Zr-Sc powder, a blend of the previous alloy with addition of Zr particles, and a further blend of an alloy depleted of Zr with added Ti particles. The experimental analyses on the laser-processed alloys showed that the standard and the Zr-enriched alloys featured a bimodal microstructure free from cracks with fine equiaxed grains at the edge of the molten pools and coarser grains at their centers. In the alloy variant depleted in Zr with addition of Ti particles a columnar structure was observed and hot-cracks appeared. Thermodynamic simulations of phase formation allowed defining the precipitation kinetics during solidification and direct aging, showing increased precipitation in alloys with higher Zr content, while the presence of Ti resulted in sluggish precipitation. Experimental aging tests demonstrated significant increases in microhardness, with peak values of the modified alloys achieved after 12 h at 375 ◦ C

Elective and emergency laparoscopic cholecystectomy in the elderly: our experience

BACKGROUND: We aimed to analyze outcomes of early and delayed laparoscopic cholecystectomy in the elderly in our General Surgery Division. METHODS: We analyzed 114 LC performed from the 1st of January 2008 to the 31st of December 2012 in our General Surgery division: 67 LC were performed for gallbladder stones and 47 for acute cholecystitis. RESULTS AND DISCUSSION: Comparison between Ordinary and Emergency groups showed that drain placement and post-operative hospital stay were significatively different. There were no significative differences between Early Laparoscopic Emergency Cholecystectomy (E-ELC) and Delayed Laparoscopic Emergency Cholecystectomy (D-ELC). There weren't any differences about Team's evaluation. CONCLUSION: We consider LC a safe and effective treatment for cholelitiasis and acute cholecystitis in Ordinary and Emergency setting, also in the elderly. We also demonstrate that, in our experience, LC for AC is feasible as well

Powder sheets additive manufacturing: Principles and capabilities for multi-material printing

In this work, a novel Metal Additive Manufacturing using Powder sheets (MAPS) method for printing multimaterial composites in one process is proposed. MAPS employs powder sheets (i.e. metal powder-polymer matrix flexible films) as the feedstock material. Its key advantages include a relatively rapid change from one material to another and a minimum wastage of materials due to the elimination of the powder bed. The powder sheets were fabricated using a 'solvent casting' method. They were then employed in a commercialised metal printer for printing metal multi-material composites. To prove the disruptive concept of MAPS, a 60-layer trimetallic multi-material composite (304 L stainless steel, In718 and CoCrFeMnNi high entropy alloy) was additively manufactured using three different types of powder sheet material in the same manufacturing system for the first time. Experimental results indicate a high density (99.80 %) multi-material composites was printed by MAPS. EDX and SEM observations of the multi-material composites revealed variations of chemical composition and microstructure along the build direction. The newly proposed MAPS manufacturing method and results of this study provide insights into a new avenue for multi-material metallic parts