ABSTRACT Computer simulation as it applies to jewelry manufacturing technology has, in the last years, proven to have tremendous potential as a tool in helping to pre- vent casting defects. Nevertheless, many aspects of its use need to be... more
ABSTRACT Computer simulation as it applies to jewelry manufacturing technology has, in the last years, proven to have tremendous potential as a tool in helping to pre- vent casting defects. Nevertheless, many aspects of its use need to be widened to further improve results, including investigations into the precious alloys' physi- cal parameters, the properties of investment materials and the dynamics of the process itself. Regarding the latter, the need to understand and, most importantly, to be able to predict the "when," the "how fast" and "where" the molten metal travels is of crucial importance, particularly when the filling and the solidification times are of the same order of magnitude. The paper focuses on the study of the filling times (both in terms of simulation and experimental validation) of different types of objects, with particular care for the filigrees' process dynamics.
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Research Interests: Mechanical Engineering, Materials Science, Laser, Metallurgy, Metal Forming, and 14 moreMaterials, Metallic Glass, Surface modification, Annealing, Micro hardness, Composite Material, High Temperature, Thermal Stability, Thermal Stability of Laser Treated Steel, Elevated Temperature, Corrosion Resistance, Continuous Wave, Heat affected zone, and glazing
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Components in the field of automotive application produced by a modified squeeze casting process have been considered. This innovative process has been oriented toward the manufacturing of high resistance and high toughness automotive... more
Components in the field of automotive application produced by a modified squeeze casting process have been considered. This innovative process has been oriented toward the manufacturing of high resistance and high toughness automotive parts using A380 alloys and they have been subjected to T6 heat treatment. Standard samples have been machined directly from real automotive components for tensile properties evaluation and hardness values determination. Superior mechanical characteristics have been obtained thanks to the low porosity content and to the particular microstructure features. Fracture surfaces analysis have been realised on the fractured samples, identifying some minor defects, like the presence of carbon particles (with any dangerous effect on the mechanical performances) and some nano-sized oxide inclusion. Moreover, the same fracture surface analysis highlights the ductile natures of the fracture. On the polished transverse sections of the samples morphological analysis...
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High-strength EN AW 7075 Al-based alloy (Al-Zn-Mg-Cu) is currently employed in many industrial fields where excellent mechanical performances of structural components are required. In contrast to the many positive features this alloy... more
High-strength EN AW 7075 Al-based alloy (Al-Zn-Mg-Cu) is currently employed in many industrial fields where excellent mechanical performances of structural components are required. In contrast to the many positive features this alloy presents, it is not fusion weldable, because it is subjected to solidification and liquation cracking. In this paper, the possibility to weld low thickness plates, made of 7075 aluminum alloy, by the tungsten inert gas welding technique will be presented. Two types of welding have been performed: for the former one, welding involves only one surface, while for the second one, welding has been carried out on both faces of the plates. After welding, microstructural analysis and mechanical properties investigations have been carried out. The present research highlights that the mechanical properties evolution is affected by the welding procedure. In particular, the mechanical strength reached for the samples welded on both faces, in the proposed setting, i...
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Sintered iron-molybdenum alloys and steels are innovative materials that are expansively applied in the industry. The research project presents the production of structural parts for the motor car industry with the use of conventional... more
Sintered iron-molybdenum alloys and steels are innovative materials that are expansively applied in the industry. The research project presents the production of structural parts for the motor car industry with the use of conventional powder metallurgy; elemental powders of iron, molybdenum, and boron are mixed together, then compacted and sintered. Some modified sintered alloys of molybdenum were alloyed by adding boron in amounts of 0.2%, 0.4%, and 0.6%. The structural investigations were conducted, and mechanical properties of Fe-Mo-B samples were definied. Furthermore, the effect of molybdenum and boron added on the structure and properties of the alloys investigated, was also studied.
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New challenges for the Aluminium alloys used for the production of castings for automotive engine components are coming from the evolution trend of Internal combustion engines towards higher specific power output. Cylinder heads, in... more
New challenges for the Aluminium alloys used for the production of castings for automotive engine components are coming from the evolution trend of Internal combustion engines towards higher specific power output. Cylinder heads, in particular, have to withstand higher operating temperatures and stress levels. The present study is aimed to evaluate the mechanical properties at high temperature of Al-Si-Cu aluminium alloys traditionally used for the production of cylinder head castings. The obtained results are very promising, especially for what concerns the modified alloys. In fact, the resistance of base Al-Si-Cu alloy is fairly good up to 150°C, but drops at 250°C, while some interesting improvements have been achieved by modifying the composition of the base alloy with the addition of Mn and Ni, resulting in an increase of strength and ductility at both room and high temperatures. Further studies related to High Cycle Fatigue and creep resistance at high temperature are under wa...
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Functionally graded materials (FGM) are used for components with specific characteristics required by the considered area of application. In this research, functionally graded material is obtained with sequential casting process of two... more
Functionally graded materials (FGM) are used for components with specific characteristics required by the considered area of application. In this research, functionally graded material is obtained with sequential casting process of two different aluminum alloys. They are poured into the mould, aiming to obtain within the same component high thermal resistance and mechanical strength on one side and ductility and elongation on the other side.The new casting has high potential, especially in the production of automotive components, e.g., pistons. Usually, piston alloys are eutectic Al-Si alloys, with high percentage of other alloying elements which increases the thermal resistance of the material. However, this high concentration of alloying elements leads to a considerable reduction of the material’s elongation that is not always tolerable. The low ductility can be an issue for the inferior part of the piston that is more subjected to fatigue stress. To increase the elongation, in ad...
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Aluminum alloys are widely used in the automotive field, for the excellent relationship between mechanical strength and lightness. In the recent years, the request for cleaner, lighter and more powerful engines, has led to the design of... more
Aluminum alloys are widely used in the automotive field, for the excellent relationship between mechanical strength and lightness. In the recent years, the request for cleaner, lighter and more powerful engines, has led to the design of components subjected to higher thermo-mechanical stresses. Demanding exercise conditions can imply the presence of different properties that are never fulfilled by a single, homogeneous material. Various solutions have been developed using composites, surface modification techniques and Functionally Graded Material (FGM). This study has applied FGM concept to the traditional casting technology, in order to obtain a more performing product. To reach this goal, two different alloys were sequentially poured by gravity casting, each one delivering locally its properties to a specific volume of the casting. Beyond the morphological and microstructural analysis of the contact interface between the two alloys, the mechanical testing has shown promising results for future applications.
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Purpose of this paper is presenting an overview of alternative methods of production of enhanced performance Al-based alloys components for critical areas. The origin, development and current evolution of the semi-solid metal processing... more
Purpose of this paper is presenting an overview of alternative methods of production of enhanced performance Al-based alloys components for critical areas. The origin, development and current evolution of the semi-solid metal processing is illustrated with characteristics of real life components for automotive industry. Different techniques are presented to provide a general idea prevalently on the commercially available semi-solid metal processing techniques. Comparison with traditional methods in terms of process parameters and tensile properties are illustrated and discussed. Innovative semi-solid metal processing methods leads obtaining at least the same level of properties and performances of those obtained by conventional techniques, but their real and key benefits are given by a faster production rates at inferior cost. Based on the up to date achieved outcomes, it appears that the current competition is extremely relevant and some concurrent technologies are very competitive. New and recently developed semi-solid metal processing methods show high level of potentiality and at the same time there is a serious need for additional and more detailed rheological data. The continuous increase of Al-based alloys in different applications involves manufacturing high integrity and superior performance components using cost-effective and safely processes. In this direction the research communities together with manufacturing industries are focusing their attention to develop new products using innovative procedures, such as the semi-solid metal processing route. The central issue is the technological transfer to industry for affordable mass production
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Circular saw blades are used exclusively for cut-off work, ranging from small manual feed operations, up to very large power fed saws commonly used for sectioning stock as it comes from a rolling mill or other manufacturing processes for... more
Circular saw blades are used exclusively for cut-off work, ranging from small manual feed operations, up to very large power fed saws commonly used for sectioning stock as it comes from a rolling mill or other manufacturing processes for long products. The teeth profile, as well as the tooth configuration are of fundamental importance for the blade performances; through a combination of blade rigidity and grinding wheel condition a good quality surface finish is attained for tools of commercial standard. The materials used for the production of circular saw blades are ranging from high speed steel to cemented carbides. In particular, cemented carbides, being characterized by high hardness and strength, are used in applications where materials with high wear resistance and toughness are required. The main constituents of cemented carbides are tungsten carbide and cobalt. Tungsten carbide imparts the alloys the necessary strength and wear resistance, whereas cobalt contributes to the ...
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Normal 0 14 false false false IT X-NONE X-NONE In this paper evolution from hot forging to thixoforging process is proposed and talked over. A real-case study is presented, namely a steel-made steering piston produced by thixoforging... more
Normal 0 14 false false false IT X-NONE X-NONE In this paper evolution from hot forging to thixoforging process is proposed and talked over. A real-case study is presented, namely a steel-made steering piston produced by thixoforging technique is considered and analyzed. The transition between the traditional forging process and the new one involves several transformations and presents difficulties mainly due to the high working temperature. The targeted thixoforging technology allows obtaining near-net-shape components with good surface quality and mechanical properties provided along with a substantial reduction in material quantity, and implicitly of the involved amount of energy. According to the reported Finite Element based simulation results, the thixoforged component will weight 9.3 kg, which is 1 kg less than that obtained by hot forging technique. The overall material saving at the starting billet level with respect to the hot forging process corresponds to 2.3 kg.…
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ABSTRACT This paper presents an overview of alternative methods of production of enhanced performance Al‐based alloys components for critical areas. In particular, a new rheocasting system, suitable for the manufacturing of high... more
ABSTRACT This paper presents an overview of alternative methods of production of enhanced performance Al‐based alloys components for critical areas. In particular, a new rheocasting system, suitable for the manufacturing of high performance industrial components has been considered. The aforementioned method allows obtaining component quickly and results a more convenient process, from economical point of view than other innovative processes. Two series of components have been produced with A356 and A357 alloys, then have been heat treated using T5 and T6 treatments. On polished transverse sections of samples the microstructure of the alloy has been observed. Their soundness has been previously certified by non destructive tests. Samples for tensile and three point bending tests have been machined directly from the produced components. On the fractured samples, fracture surface analysis has been performed in order to analyze and evaluate the influence of the process and of the alloy on the fracture behaviour.
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Research Interests: Materials Science, Thermodynamics, Metallurgy, Materials Science and Engineering, Hardness, and 9 moreHigh Temperature Materials, Fatigue Testing, Thermal Fatigue, Laser Modification of Coating, Hot Work Tool Steel, Thermocouple, Mechanical Engineering Sciences, Tool Steel, and Vickers Hardness Test
Strontium-based modifier alloys are commonly adopted to modify the eutectic silicon in aluminum-silicon casting alloys by changing the silicon shape from an acicular to a spherical form. Usually, the modifier alloy necessary to properly... more
Strontium-based modifier alloys are commonly adopted to modify the eutectic silicon in aluminum-silicon casting alloys by changing the silicon shape from an acicular to a spherical form. Usually, the modifier alloy necessary to properly change the silicon shape depends on the silicon content, but the alloying elements’ content may have an influence. The AlSr10 master alloy’s modifying effect was studied on four Al-Si alloys through the characterization of microstructural and mechanical properties (micro-hardness and impact tests). The experimental results obtained on gravity cast samples highlighted the interdependence in the modification of silicon between the Si content and the alloying elements. After modification, a higher microstructural homogeneity characterized by a reduction of up to 22.8% in the size of intermetallics was observed, with a generalized reduction in secondary dendritic arm spacing. The presence of iron-based polygonal-shaped intermetallics negatively affects S...
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Research Interests: Materials Science, Thermodynamics, Metallurgy, Materials Science and Engineering, Hardness, and 9 moreHigh Temperature Materials, Fatigue Testing, Thermal Fatigue, Laser Modification of Coating, Hot Work Tool Steel, Thermocouple, Mechanical Engineering Sciences, Tool Steel, and Vickers Hardness Test
Premature failure of dies is a critical problem of manufacturers in hot-working processes, e.g. metal die casting, hot extrusion and/or thixoextrusion of aluminium/magnesium or steel. Typically, die material has to be resistant to heat... more
Premature failure of dies is a critical problem of manufacturers in hot-working processes, e.g. metal die casting, hot extrusion and/or thixoextrusion of aluminium/magnesium or steel. Typically, die material has to be resistant to heat cycling or corrosion environment, to plastic deformation and wear, especially when exposed to high temperature during continuous working cycle. The resistance of dies could be increased by the modification of their surfaces, i.e. by the application of an adequate coating. An improvement of the resistance of H11 steel substrate will be presented and discussed. Here, the coatings will be realized through both by High Velocity Oxy-Fuel coating spray method and by plasma spray method. Firstly, the measurement of the residual stress will be carried out on the un-coated and coated substrate. Secondly, morphological analysis by optical and scanning electron microscopy will be performed on the powders used for the coating and on the coated materials. Such inv...
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Purpose: of this paper was to examine the corrosion resistance of duplex stainless steels using electrochemical methods in 1M NaCl solution. The influence of powder mixes preparation and cooling cycle after sintering on corrosion... more
Purpose: of this paper was to examine the corrosion resistance of duplex stainless steels using electrochemical methods in 1M NaCl solution. The influence of powder mixes preparation and cooling cycle after sintering on corrosion properties was evaluated. Design/methodology/approach: In presented study duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements, such as Cr, Ni, Mo and Cu. In the studies behind the preparation of mixes, Schaeffler’s diagram was taken into consideration. Prepared mixes have been compacted at 800 MPa and sintered in a vacuum furnace with argon backfilling at 1260°C for 1 h. After sintering two different cooling cycles were applied: rapid cooling with an average cooling rate of 245 °C/min and slow cooling of 5 °C/min in argon atmosphere. Produced duplex stainless steels have been studied by scanning and optical microscopy and EDS chemical analysis of micro...
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An account is given of collapse of a section of an oil pipeline during its reinstatement after maintenance work. It is shown that the accident was caused by incorrect displacement of nitrogen from the line, leading to the formation of... more
An account is given of collapse of a section of an oil pipeline during its reinstatement after maintenance work. It is shown that the accident was caused by incorrect displacement of nitrogen from the line, leading to the formation of elastic pressure waves that burst the pipe at its structurally weakest portion.
Die-casting processes are commonly employed in the automotive area to cast aluminum alloys. These processes involve the use of steel dies, typically realized in AISI H11 or H13, with or without a coated surface. Mechanical and chemical... more
Die-casting processes are commonly employed in the automotive area to cast aluminum alloys. These processes involve the use of steel dies, typically realized in AISI H11 or H13, with or without a coated surface. Mechanical and chemical stresses and thermal cycles act producing stresses, plastic deformation, corrosion and metallization on the mold surfaces. Particularly, the interaction between the die and the molten aluminum causes the nucleation of intermetallic compounds at the interface. In this work the interaction between the hot work steel AISI H13 and the aluminum alloy EN–AB 46000 were evaluated in terms of adhesion strength for different roughness of the die surface. Two of the tested roughness were finally applied on the surface of die inserts; the use of injection pressure in a high pressure die casting (HPDC) machine, led to observe the possible variations in terms of soldering severity on the surface of the die in real operating conditions. The comparison between castin...