Sta Cast : Linee guida per la progettazione di getti in lega di alluminio

StaCast (New Quality and Design Standards for Aluminium Alloys Cast Products) è un progetto europeo dedicato allefonderie dell’alluminio con l’obiettivo di sviluppare una nuova classificazione dei difetti strutturali nei getti e di definiredei limiti di accettabilità di questi difetti a seconda della destinazione finale prevista. Il raggiungimento di questo obiettivoaiuterà significativamente le fonderie a ridurre il costo della non-qualità, migliorando nel contempo il loro margine dicompetitività grazie al conseguimento di importanti vantaggi, per esempio nei costi dell’energia. StaCast ha condotto unavasta indagine tra le fonderie europee per conoscere le caratteristiche principali della loro produzione, in quale misuraesse utilizzano gli Standard CEN, il bisogno di nuovi strumenti normativi riferiti ai difetti, alle proprietà meccaniche e allaprogettazione meccanica di getti in lega d’alluminio. Questo articolo presenta i principali risultati di tale indagine, che hacoinvolto circa 80 aziende, e l’impostazione dei documenti normativi che sono stati elaborati sulla Classificazione deiDifetti e sul Potenziale Meccanico di getti in lega d’alluminio

Effects of microstructure and casting defects on the fatigue behavior of the high-pressure die-cast AlSi9Cu3(Fe) alloy

Abstract High-pressure die-cast (HPDC) components are being increasingly used due to good flexibility and high productivity. These aspects make HPDC suitable to produce several mass components, especially for the automotive sector. Due to the rapid filling of the die and high cooling rate, the process generally leads to the formation of a wide variety of defects, such as porosity and oxide films. Such defects might act as starting points for fatigue cracks and thus deteriorating the fatigue behavior of the casting. To this respect, the fatigue behavior of die cast aluminum alloys is an important aspect to consider when assessing the performance of complex castings for automotive applications. In the light of these aspects, the goal of this work is to describe how the microstructure affects the fatigue crack initiation and propagation. Die cast AlSi9Cu3(Fe) specimens were produced by means of a specifically designed die and the microstructure was preliminary characterized. Uniaxial fatigue tests were performed at load control with a stress ratio of R = 0.1 and at a single level of stress amplitude. After the fatigue tests, the samples were investigated to assess the propagation of the fatigue cracks; the starting points of cracks were specifically identified and the obtained data suggested how defects strongly influence the damage mechanism of the material

Microstructure and bending properties of die-casting alloys at various chromium contents

A study of the effects of chromium addition on AlSi9Cu3(Fe) alloy was carried out. Die cast EN AC-46000 alloyplates for microstructural investigation and bend testing were produced using a multispecimen die in a highpressure, cold chamber machine. The Cr ranged within the tolerance limits of the EN AC-46000 type alloys,according to the EN 1706 standard. The investigations allowed evaluation of modifications to microstructuraland bending properties produced by Cr additions. In particular, the microstructural analysis revealed that themorphology of primary sludge compounds was mainly cubic-type, such as polyhedral, star-like and blocky,while proeutectic ?-Alx(Fe,Mn,Cr)ySiz intermetallics showed blocky or polyhedral morphology at any Cr level.Increasing the Cr content, the whole area fraction of these particles increased and the primary intermetalliccompounds segregated in the central region of the cross section of the castings. This was associated to amechanism similar to that suggested for the ESCs entrapment. The increase of brittle Fe-rich particles affectedthe fracture load and the displacement to fracture of the alloy at the highest Cr level

Sauver Byzance de la barbarie du monde

Il volume ripercorre la trattazione del mitema di Bisanzio nella letteratura francese e francofona dalle origini ai giorni nostr

Nerve growth factor improves visual loss in childhood optic gliomas: a randomized, double-blind, phase II clinical trial.

Paediatric optic pathway gliomas are low-grade brain tumours characterized by slow progression and invalidating visual loss. Presently there is no strategy to prevent visual loss in this kind of tumour. This study evaluated the effects of nerve growth factor administration in protecting visual function in patients with optic pathway glioma-related visual impairment. A prospective randomized double-blind phase II clinical trial was conducted in 18 optic pathway glioma patients, aged from 2 to 23 years, with stable disease and severe visual loss. Ten patients were randomly assigned to receive a single 10-day course of 0.5 mg murine nerve growth factor as eye drops, while eight patients received placebo. All patients were evaluated before and after treatment, testing visual acuity, visual field, visual-evoked potentials, optic coherence tomography, electroretinographic photopic negative response, and magnetic resonance imaging. Post-treatment evaluations were repeated at 15, 30, 90, and 180 days Brain magnetic resonance imaging was performed at baseline and at 180 days. Treatment with nerve growth factor led to statistically significant improvements in objective electrophysiological parameters (electroretinographic photopic negative response amplitude at 180 days and visual-evoked potentials at 30 days), which were not observed in placebo-treated patients. Furthermore, in patients in whom visual fields could still be measured, visual field worsening was only observed in placebo-treated cases, while three of four nerve growth factor-treated subjects showed significant visual field enlargement. This corresponded to improved visually guided behaviour, as reported by the patients and/or the caregivers. There was no evidence of side effects related to nerve growth factor treatment. Nerve growth factor eye drop administration appears a safe, easy and effective strategy for the treatment of visual loss associated with optic pathway gliomas

Nerve growth factor improves visual loss in childhood optic gliomas: a randomized, double-blind, phase II clinical trial.

Paediatric optic pathway gliomas are low-grade brain tumours characterized by slow progression and invalidating visual loss. Presently there is no strategy to prevent visual loss in this kind of tumour. This study evaluated the effects of nerve growth factor administration in protecting visual function in patients with optic pathway glioma-related visual impairment. A prospective randomized double-blind phase II clinical trial was conducted in 18 optic pathway glioma patients, aged from 2 to 23 years, with stable disease and severe visual loss. Ten patients were randomly assigned to receive a single 10-day course of 0.5 mg murine nerve growth factor as eye drops, while eight patients received placebo. All patients were evaluated before and after treatment, testing visual acuity, visual field, visual-evoked potentials, optic coherence tomography, electroretinographic photopic negative response, and magnetic resonance imaging. Post-treatment evaluations were repeated at 15, 30, 90, and 180 days Brain magnetic resonance imaging was performed at baseline and at 180 days. Treatment with nerve growth factor led to statistically significant improvements in objective electrophysiological parameters (electroretinographic photopic negative response amplitude at 180 days and visual-evoked potentials at 30 days), which were not observed in placebo-treated patients. Furthermore, in patients in whom visual fields could still be measured, visual field worsening was only observed in placebo-treated cases, while three of four nerve growth factor-treated subjects showed significant visual field enlargement. This corresponded to improved visually guided behaviour, as reported by the patients and/or the caregivers. There was no evidence of side effects related to nerve growth factor treatment. Nerve growth factor eye drop administration appears a safe, easy and effective strategy for the treatment of visual loss associated with optic pathway gliomas

Optimizing a Step Casting Geometry to Evaluate the Mechanical Properties of AM60B Magnesium Alloys

The purpose of the research was the optimization of an existing permanent mould in order to achieve sound and reliable Mg alloy castings. To understand how the existing runner system affected the filling behaviour, specific process parameters were investigated. In particular both the material and the die temperatures, and the filling parameters, were analysed using MAGMASOFT\uae software. Firstly, the computational approach allowed to understand that the whole casting process had to be within 4\uf75 seconds in order to not produce freezing phenomena, but anyway turbulence was still present. It was clearly evident that the main problem was in the die geometry, so the decision to design a new one. The ingates were redesigned, as well as the \u201cnon-returning\u201d trap. A better control of the molten metal ingate speed was also obtained by adding a filter. By this configuration an adequate flow rate was achieved to not produce freezing phenomena and a significant reduction of turbulences. The present work shows a comparison of the simulation results to evidence how an optimized design of the runner system can significantly reduce the presence of casting defects, allowing to identify the real mechanical properties of AM60B Mg alloys

Optimization of a step casting die geometry to evaluate the potential mechanical performance of AM60B magnesium alloys

Non-destructive testing has been carried out on AM60B magnesium alloy castings obtained by using two different permanent moulds. The results highlighted a very different defects content. In this paper, the benefits of adopting an optimised die to better evaluate the final castings\u2019 properties are analysed. Numerical simulations have been performed to study the filling and the solidification behaviour of the alloy by changing the die cavity geometry, in order to minimise the presence of defects. The redesigned runner system prevented inclusions to enter the die cavity and allowed a laminar flow of the metal through the gate. Further, defects formation has been investigated using criteria functions provided by the simulation software, and the results confirmed the reliability of the die design. Comparing the simulation and experimental results, it's possible to verify a good correspondence, so allowing to establish semi-empirical rules to forecast the final properties of Mg alloys castings

Optimization of a step casting die geometry to evaluate the potential mechanical performance of AM60B magnesium alloys

Non-destructive testing has been carried out on AM60B magnesium alloy castings obtained by using two different permanent moulds. The results highlighted a very different defects content. In this paper, the benefits of adopting an optimised die to better evaluate the final castings\u2019 properties are analysed. Numerical simulations have been performed to study the filling and the solidification behaviour of the alloy by changing the die cavity geometry, in order to minimise the presence of defects. The redesigned runner system prevented inclusions to enter the die cavity and allowed a laminar flow of the metal through the gate. Further, defects formation has been investigated using criteria functions provided by the simulation software, and the results confirmed the reliability of the die design. Comparing the simulation and experimental results, it's possible to verify a good correspondence, so allowing to establish semi-empirical rules to forecast the final properties of Mg alloys castings