In this paper, an innovative sustainable method of producing metal foams was presented. The base material was aluminum alloy waste in the form of chips obtained by machining process. The leachable ...agent, used to create pores in the metal foams, was natrium chloride, which was later removed by leaching, resulting in metal foams with open cells. Open-cell metal foams were produced with three different input parameters: volume percentage of natrium chloride, compaction temperature, and force. The obtained samples were subjected to compression tests during which displacements and compression forces were measured to obtain the necessary data for further analysis. To determine the influence of the input factors on the selected response values such as relative density, stress and energy absorption at 50% deformation, an analysis of variance was performed. As expected, the volume percentage of natrium chloride was shown to be the most influential input factor because it has a direct impact on the obtained metal foam porosity and thus on the density. The optimal values of the input parameters with which the metal foams will have the "most desirable" performances are a 61.44% volume percentage of natrium chloride, a compaction temperature of 300 °C and a compaction force of 495 kN.
This paper deals with the direct recycling of EN AW 2011 aluminum alloy turning chips into semiproducts utilizing forward hot extrusion process. The main goal of this study is to obtain mathematical ...models that will relate the process parameters of direct recycling to mechanical properties of final semiproducts. Influence of chip size, compaction force, and extrusion temperature on mechanical properties was investigated using Box-Behnken experimental design. The study has shown that the most influential factor on mechanical properties was extrusion temperature. Chip size does not affect both ultimate tensile strength and yield strength and on the other hand, compaction force does not influence on both ultimate tensile strength and percent elongation. Optical microscopy revealed cracks and inhomogeneities for all samples extruded on 300 °C in contrast to those extruded on 500 °C which showed no voids or cracks. Optimal recycling process parameters that would give maximal mechanical properties were found.
The main aim of this research was to investigate the aluminum AlSi9Cu3(Fe) machining chips recycling possibility utilizing a direct hot extrusion process and thixoforming. The thixo feedstock was ...prepared directly from the aluminum alloy AlSi9Cu3(Fe) machining chips waste without any remelting step. The machining chips were compacted, and direct hot extruded to create the solid samples and thixo feedstock. The aluminum alloy AlSi9Cu3(Fe) machining chips had a high degree of plastic deformation and after extrusion and heating in the semisolid temperature range, the suitable globular microstructure was achieved, which is a precondition for a successful thixoforming process. This approach can be characterized as a semisolid recycling process with a lower energy consumption, a higher material yield, and reduced greenhouse gas emissions into the atmosphere compared with conventional casting and recycling. Optical metallography, scanning electron microscopy accompanied with energy dispersive spectroscopy, electrical conductivity, and mechanical properties investigation were performed on the reference casted sample with a dendritic microstructure, the extruded sample with a severely deformed microstructure, and finally the thixoformed samples with a globular microstructure produced with different parameters, according to the Taguchi L4 (23) experimental plan.
The main aim of this research is to mathematically describe the influence of the processing parameters of metal foam production from machining chip waste. Using this method, metal foams were produced ...without a remelting step, which should be both economically and environmentally effective. Firstly, expensive metal powders were replaced with waste in the form of machining chips. Secondly, machining chip waste was recycled without any significant material losses, which usually occurs during conventional recycling (using the melting process). To describe the innovative process and to relate metal foam properties to foaming temperature, the blowing agent weight percentage, and foam density (controlled by foaming height), response surface methodology, and the design of experiments were used. The quality of the produced metal foams was evaluated by determination of density, yield strength, compression strength, plateau stress, energy absorption, pore perimeter, and pore inhomogeneity for specimens obtained following the experimental plan. It was proven that pore inhomogeneity increased in the range from 1.41 to 4.81 mm with a higher temperature and the addition of a foaming agent. However, higher energy absorption and yield strength were obtained with a higher temperature but a lower percentage of TiH2. Despite the production from machining chips, pores were homogenous without significant cracks. These kinds of metal foams are comparable to commercial foams made of metal powders.
In the last few years, there is a demand for developing new technologies in order to increase scrap reuse potential and CO
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emission savings. In this paper, aluminum was recycled from chips obtained ...by machining without any remelting in order to reduce environmental pollution and to increase material yield during the process. This process is called solid-state recycling (SSR) or direct recycling. SSR process consists of chips cleaning, cold pre-compaction, and hot direct extrusion followed by equal channel angular pressing (ECAP) at different temperatures. Influence of direct extrusion temperature, ECAP temperature, and number of ECAP passes on electrical conductivity and microhardness of the recycled EN AW 6082 aluminum chips was investigated. Microhardness and electrical conductivity of the recycled samples were comparable with commercially produced EN AW 6082. Experiments were planned utilizing design of experiments approach. Both adaptive neuro-fuzzy interference system (ANFIS) and regression models were developed and compared to describe the influence of input SSR process parameters on electrical conductivity and microhardness. Density and metallographic analysis of the recycled samples were also performed.
The effect of temperature (from 288 to 308 K) and concentration of sulfide ions (up to 40 ppm) on the corrosion behavior of AISI 304L and AISI 316L stainless steels in seawater was studied with ...measurements of open-circuit potential, linear and potentiodynamic polarization, and electrochemical impedance spectroscopy. An increase in temperature and pollutant concentration negatively affects the corrosion stability of stainless steels at the open circuit (the resistance, compactness, and thickness of the surface layer decrease and the corrosion current increases), in the passive region (the passivation current increases, the depassivation potential decreases, and the passive potential region narrows), and in the transpassive potential region (the rate of metal dissolution increases). The occurrence of pitting corrosion on the surface of the samples was confirmed with optical microscopy and a non-contact 3D profilometer. A few large pits (depth 80–100 μm and width 100 μm) were formed on the surface of AISI 304L steel, while several smaller pits (depth 40–50 μm and width 50 μm) were formed on the surface of AISI 316L steel. With increasing temperature and sulfide ion concentration, the width, depth, and density of the pits increased on both steel samples. In the studied temperature and concentration range of sulfide ions, the AISI 316L steels exhibited higher corrosion resistance. Overall, the influence of sulfide ions on steel corrosion was more pronounced than the influence of temperature.
The main aim of this paper is to present an environmentally friendly method for aluminum recycling. Development of new recycling technologies in order to increase scrap reuse potential and CO2 ...emission savings are of the main importance for aluminum circular economy. In this paper, aluminum chips waste was recycled without any remelting phase in order to increase energy and material savings. The presented process is usually called solid state recycling or direct recycling. Solid state recycling process consists of chips cleaning, cold pre-compaction and hot direct extrusion followed by a combination of equal channel angular pressing (ECAP) and heat treatment. Influence of holding time during solid solution treatment and both artificial aging time and temperature on mechanical properties of the recycled EN AW 6082 aluminum chips were investigated. A comprehensive number of the experiments were performed utilizing design of experiments approach and response surface methodology. Regression models were developed for describe the influence of heat treatment parameters for presented solid state recycling process on mechanical properties of the recycled samples. Utilizing novel procedure high quality recycled samples were obtained with mechanical properties comparable with commercially produced EN AW 6082 aluminum alloy in T6 temper condition. Metallographic analysis of the recycled samples was also performed.
Main aim of this research was to investigate unconventional method for aluminium recycling. Recycling process presented in this research was performed in solid state and therefore is called solid ...state recycling (SSR) or direct recycling. Main aim of direct recycling approach is to reduce greenhouse gasses emission compared with primary aluminium production and conventional recycling. Other advantages are higher scrap material yield during recycling and energy savings. In this paper, SSR process consisted of aluminium chips hot extrusion and afterwards severe plastic deformation process at room and elevated temperatures. Mechanical properties of the solid state recycled samples obtained by presented process were comparable with samples obtained by conventional manufacturing. Furthermore, it was shown that additional plastic deformation after hot extrusion significantly improved mechanical properties of the recycled samples compared with those recycled only by hot extrusion. Analysis of both microstructure and density analysis was also performed.
Aluminium alloy foams are a form of porous metal whose structure resembles the shape of natural materials such as coral, bone, sponge, etc. Due to their structure, these materials retain good ...mechanical properties of the base material while being significantly lighter than non-porous metal. Metal foams can be used as energy and vibration absorbers, heat exchangers, insulators, and filters. The main disadvantage of this type of material is its high production cost. To reduce production costs, aluminium alloy chips are used as base material. Foams are made of A360 and AA 7075 aluminium alloys. To produce a porous structure, CaCO3 is used as a foaming agent while Zn and CaO were added as stabilizing agents. The main goal of the paper was to investigate the difference in the shape of pores and relative density after foaming with different stabilizing agents.
The main aim of this research was to simulate high-pressure die casting of A356 semi-solid aluminum alloy using casting process simulation tool. Taking into account the viscosity of the semi-solid ...slurry and the mold-filling characteristics in high-pressure die casting, the mold for semi-solid aluminum alloy had been designed. Also, the influence of the three input parameters (liquid fraction of slurry, plunger velocity at 2nd phase and mold geometry) on the casting time, shrinkage and bubble formation during semi-solid high-pressure die casting processes were investigated. The Taguchi-based ‘grey relational analysis’ approach was used to identify the optimal process parameters. A method used in this study for finding out the importance of the controllable parameter on the performance characteristic is called the analysis of variance. It was observed that the optimal parameters are the liquid fraction of 50%, the plunger velocity at 2nd phase of 1 m/s and the angle between the vertical plane and the cavity of 60°.
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