Abstract:This work provides an overview of the aluminum (Al) recycling process, from the scrap upgrading to the melting process. Innovations and new trends regarding the Al recycling technologies are highlighted. Aluminum recycling offers advantages in terms of environmental and economic benefits. The presence of deleterious impurities in recycled Al alloys is increasing and this is the main drawback if compared to primary alloys. The continuous growth of undesired elements can be mitigated by different technologies, preliminary operations and treatments, and by the optimization of the melting process. Downgrading and dilution are possible solutions to reduce the rate of impurities, but they are not sustainable if the final use of Al alloy continuously increases. The main objectives in the development of the Al recycling are shown and discussed. In particular, the evolution of preliminary treatments of the scrap, as sorting, comminution and de-coating, is reported and a review of the melting technologies is also presented. However, the choice of performing preliminary operations to the melting stage, thus improving the operating conditions during the furnace running, is a trade-off between costs and process efficiency.

The precipitation of primary Fe-bearing compounds in a secondary AlSi9Cu3(Fe) alloy has been investigated over three levels of iron (0.80, 1.00, 1.20 mass%) and manganese (0.25, 0.40, 0.55 mass%), and two levels of chromium (0.06, 0.10 mass%), as well as different cooling rates (2, 10, 20 °C min-1). Differential scanning calorimetry and metallographic techniques have been used in order to quantitatively evaluate the nucleation temperature and the phase fraction of sludge particles. The temperature of sludge formation increases by increasing the initial concentrations of Fe, Mn and Cr, while an increase in the cooling rate shifts the sludge nucleation towards lower temperature. The amount of sludge particles increases progressively with the sludge factor but even more by decreasing the cooling rate. The combination of Fe, Mn and Cr levels, as well as cooling rate, allows to determine a threshold value that prevents the sludge formation. In the analysed range of composition and cooling conditions, functional equations have been developed in order to accurately predict the precipitation temperature and the phase fraction of sludge in AlSi9Cu3(Fe) die-casting alloys

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The effect of the T6 heat treatment on the microstructure and hardness of a secondary semi-solid AlSi9Cu3(Fe) alloy have been investigated by using optical, scanning and transmission electron microscopy and hardness testing. The semi-solid alloy was produced using the swirled enthalpy equilibration device (SEED). The solution heat treatments were performed at 450, 470 and 490 °C for 1 to 6 h followed by water quenching and artificial ageing at 160, 180 and 220 °C for holding times ranging from 1 to 30 h. The microstructural investigations have revealed the spheroidization of the eutectic Si and the dissolution of the majority of Cu-rich compounds after all the solution heat treatments; moreover, the greater the solution temperature and time, the higher the hardness of the alloy. Unacceptable surface blistering has been observed for severe solution condition, 490 °C for 3 and 6 h. The artificial ageing at 160 °C for 24 h has led to the highest alloy strengthening thanks to the precipitation of β” and Q’ (or L) phases within the α-Al matrix. The hardening peaks at higher temperatures have been early achieved due to faster hardening kinetic; however, the lower number density of β” and Q’ (or L) phases and the presence of coarser θ’ precipitates result in a reduction of hardness values for peak aged condition at 180 and 220 °C, respectively.

The precipitation of primary Fe-rich intermetallics (sludge) in AlSi9Cu3(Fe) type alloys has been investigated for different Fe, Mn and Cr contents and cooling rates. Differential scanning calorimetry was used in order to assess the nucleation temperature and the enthalpy of sludge particles as well as to follow their evolution. The results show that the sludge nucleation temperature and the release of latent heat during sludge formation are functions of the initial concentrations of Fe, Mn and Cr in the molten alloy, i.e. the sludge factor, and the cooling rate. Being able to predict the temperature of sludge formation will support the foundries to set the right molten metal temperature in order to prevent sludge precipitation during the entire high-pressure die-casting process.

Andean textiles are products of one of the richest, oldest and continuous weaving traditions in the world. Understanding the knowledge and practice of textile production as a form of cultural heritage is particularly relevant in the Andean context due to erosion of clothing traditions, reuse of traditional textiles on commodities targeted at the tourism market, and loss of knowledge embedded in textile production. "Weaving Communities of Practice" was a pilot project that aimed to create a knowledge base of Andean weaving designed to contribute to curatorial practice and heritage policy. The research team gathered data on the chain of activities, instruments, resources, peoples, places and knowledge involved in the production of textiles, relating to over 700 textile samples. A major part of the project has been the modelling and representation of the knowledge of domain experts and information about the textile objects themselves in the form of an OWL ontology, and the development of a suite of search facilities to be supported by the ontology. This paper describes the research challenges faced in developing the ontology and search facilities, the methodology adopted, the design and implementation of the system, and the design and outcomes of a user evaluation of the system undertaken with a group of domain experts.

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The design of a permanent Step mold for the evaluation of the mechanical properties of light alloys has been reviewed. An optimized Step die with a different runner and gating systems is proposed to minimize the amount of casting defects. Numerical simulations have been performed to study the filling and solidification behavior of an AM60B alloy to predict the turbulence of the melt and the microshrinkage formation. The results reveal how a correct design of the trap in the runners prevents the backwave of molten metal, which could eventually reverse out and enter the die cavity. The tapered runner in the optimized die configuration gently leads the molten metal to the ingate, avoiding turbulence and producing a balanced die cavity filling. The connection between the runner system and the die cavity by means of a fan ingate produces a laminar filling in contrast with a finger-type ingate. Solidification defects such as shrinkage induced microporosity, numerically predicted through a dimensionless version of the Niyama criterion, are considerably reduced in the optimized permanent Step mold