Materials Science Forum Vol. 1130

Abstract: Recently, researchers have done a lot of efforts to develop new solid-state recycling processes, both experimentally and developing numerical models. This kind of process is energy-saving and environmentally friendly compared to the conventional aluminum recycling process because avoided the melting step. The purpose of this work is to evaluate the feasibility of an innovative solid-state recycling process through direct hot rolling in a non heat-treatable aluminum alloy for automotive applications. AA5754 chips have been produced by turning a bar without the usage of lubricants and compacted with a 150 kN load; the compacted billets were treated at 400 °C and directly hot rolled in several successive passes. Rolled samples are then analyzed in terms of Vickers microhardness and microstructure in both as-rolled and heat treatment conditions, this last was performed at 185°C simulating the process of paint-bake. The produced samples show an excellent bonding between chips.

Abstract: In this paper, a numerical simulation methodology has been applied to optimize the design of extruded aluminium products. The methodology, PRO^{3 TM} , incorporates product properties, production-and material costs as well as CO₂ footprint in an optimisation procedure. This allows for multi-objective optimisation and avoids sub-optimisation of for instance properties on the expense of production costs or CO₂ emissions. The outcome that follows from this multi-objective optimisation procedure, is that the resulting profile cross section will be different when the optimisation is based solely on property considerations, than when costs and CO₂ emissions are introduced in the optimisation procedure. The present methodology requires that the main processes and operations along the aluminium process chain are represented by physics based, predictive models of various types, including material-and mechanical models, in addition to cost-, and sustainability models. A standard multi-objective optimization algorithm is used to combine the models and for automatic running through-process simulations in iterations. In this article, the PRO^{3 TM} methodology has been applied for optimisation of the profile cross section in case-studies with various user requirements. It has been demonstrated that the resulting cross section geometry depends on the specified relative importance of conflicting requirements like the desire for high productivity on the one hand, and the desire for low material costs and low CO₂ emissions on the other.

Abstract: The heat-treatable EN AW-6005 and EN AW-6060 alloys are by far the most used alloys for manufacturing extruded parts for automotive, aerospace, food and healthcare industries. The strength of these alloys is usually achieved by T6 heat treatment, whose efficacy depends on the chemical composition and solubilization/aging times and temperatures. This study aims to evaluate the influence of aging parameters on the microstructural and mechanical properties of two extruded components made of the above-mentioned alloys and supplied by a healthcare company. Samples were drawn by both parts in as-received condition. Part of them was directly artificially aged at different aging times and temperatures, while the rest was subjected to tailored T6-type heat treatments. The microstructure was first analyzed by optical and scanning electron microscopy. The mechanical properties were then investigated by Brinell hardness and Vickers microhardness measurements. At last, all hardness data were compared to those obtained on specimens drawn from two other components made of the same alloys, which were heat-treated according to the parameters commonly used by the company. Based on the results, the microstructure of both components exhibited coarse grains plus lamellar and rounded intermetallic particles. Irrespective of the heat treatment route, no changes were detected in the microstructure. For each alloy, the heat treatment conditions that guarantee the best mechanical resistance were established.

Abstract: AA6xxx alloys are used for various automotive and architectural applications where microstructural characteristics are critical to have acceptable final properties. Abnormal Grain Growth (AGG) in these alloys, industrially termed as Peripheral Coarse Grain (PCG) is undesirable and Mn, Cr based non-coherent dispersoids are used to control the extent of PCG. Homogenization soaking temperature and time along with heating rates determine the size, distribution with grains and volume fraction of these dispersoids. In this study the heating rates are varied in lab and industrial setting to assess the effect of aforementioned dispersoid features using SEM and digital microscopy. It is found that higher heating rates lead to coarser and lower area fraction of dispersoids which finally results in markedly large PCG in industrial extrusion. Observed dispersoid features were described based on basic kinetics and Thermo-Calc^TM predicted trends of micro-segregation, fraction of dispersoids and fraction of potential nucleating sites (β’-Mg₂Si) of dispersoids. A static recrystallization model was used to calculate the driving and retarding pressures based on substructural (EBSD analysis) and dispersoid features (SEM+ image analysis). The predicted recrystallisation response and PCG grain size was in close agreement with the observed values. This study highlights the significance of homogenization heating rates in addition to soaking time and temperature for PCG control.

Abstract: This paper delves into further analysis of the best infill structure for mechanical applications in 3D printing. Infill plays a crucial role in determining the strength, weight, and overall mechanical properties of printed objects. This study aims to explore and evaluate different infill structures to identify the optimal choice for mechanical applications. Specifically, the focus is on investigating the gyroid infill pattern due to its unique properties and potential advantages. The research includes an assessment of the structural integrity and mechanical performance of objects printed with gyroid infill compared to other commonly used infill patterns. Experimental testing, including tensile strength and load-bearing capacity, will be conducted to quantify and compare the mechanical properties of the printed parts. The results of this study will provide valuable insights and guidance for selecting the most suitable infill structure in mechanical applications, contributing to enhanced design and manufacturing capabilities in the field of 3D printing.

Abstract: This research paper investigates the recent progress in using Powder Direct Energy Deposition (Powder DED) for fixing parts. Powder DED is a modern way of 3D printing that's gaining attention for its ability to mend and renew vital components. This study breaks down the latest improvements and trends in Powder DED technology, explaining how it works and the materials and tools involved. We also discuss how Powder DED can help industries save money and be more environmentally friendly when it comes to repairing parts, and we explore potential future developments. This paper shows how Powder DED is changing the way we approach part maintenance and repair, making it easier and more cost-effective.

Abstract: Polymers having thermal stability and thermal conductivity are taken as the hot cake in the market these days. Manufacturing industries are focusing over the functional polymers with thermal management in aviation, electronics and other heat sink applications. In this research, general purpose polystyrene (GPPS-550P) is melt extruded with modified boron nitride powder. The fabricated composite samples showed an increase of 67.43% in thermal conduction. An increase of 56 multiple also achieved in thermal stability of the newly developed composite. This might be a tangible addition to the industrial word for developing functional polymers that offers stability and heat management applications synergistically.

Abstract: The major concern of the polymers is their degradation in the presence of thermal, mechanical or oxidative stressors even in the normal operating conditions. Life prediction of polymers e.g. insulations, jackets is vital for the continuous working of power plants. In this novel study, the accelerated aging procedure for the life estimation of EPDM and silicone rubber blend (ESB) in thermo-oxidative environment has been proposed. The procedure used the Arrhenius model and laboratory accelerated aging to predict the life of ESB. 50% elongation at break (EAB) was declared as the end-of-life criterion for this study. Thermal stability of the ESB has been investigated by monitoring infrared spectrum, mass loss curve, activation energy, melting point, density, tensile strength and shore hardness before and after thermal aging. The investigation showed that in addition to a loss in EAB, a considerable decrease in the activation energy, tensile strength and shore hardness has been observed. The life was calculated at three accelerated aging temperatures i.e. 130,140 and 150 °C and then this data was extrapolated to lower temperatures. The estimated life at 100 °C was found to be 282 days. This predictive approach is useful in determining the life of various polymeric materials and to build confidence for the use of certain polymers in the required service conditions.

Abstract: This study examines the utilization of human hair as a reinforcing material in epoxy-based composites. By conducting a series of experiments, the research investigates how various proportions of hair impact the properties of these composites. The results indicate that increasing the amount of hair significantly improves the strength of the materials. This research not only contributes to material engineering by repurposing a waste product but also holds potential for applications in industries such as automotive and aerospace where strong and lightweight materials are crucial.