Analysis of Friction Stir Processed Surface Quality of AA2098 Aluminum Alloy for Aeronautical Applications

FSP is a relatively new technique that changes the microstructure on the surface of the material to improve mechanical properties in the desired zone. This study aimed to investigate the surface quality of AA2098 sheets after being subjected to friction stir processing under different conditions of feed rate and rotational speed. A DoE analysis was developed with two factors, feed rate and rotational speed, and three different levels of 75, 100, 125 mm/min and 1000, 1250, 1500 rpm respectively, in order to assess the processed surface quality. The Sa parameter was used to represent the surface quality in different zones of the process, near entrance tool, middle and near exit tool, and ANOVA analysis was conducted. The results indicated that only the position and feed rate have a statistical influence on surface roughness. Additionally, the surface quality is strongly affected by the position relative to the entrance of the tool and the side (retreating or advancing sides). The roughness was found to be significantly lower on the advancing side rather than on the retreating side

ASPETTI METALLURGICI SULLE TECNICHE DI AFFINAMENTO DEL GRANO CRISTALLINO NEGLI ACCIAI

Gli acciai ferritici a grano ultrafine UFG sono degli acciai da costruzione per uso generale con basso contenuto di carbonio. Sono chiamati così perché la loro microstruttura è costituita da grani di dimensione inferiore a 3 ?m, di solito contengono anche piccole quantità di elementi microleganti come Nb, V e qualche volta il Ti; questi elementi giocano un ruolo importante sull’affinamento del grano. Comunque acciai che contengono tali elementi fanno parte di una sottocategoria degli acciai generali da costruzione denominata HSLA (High Strength Low Alloy) [1-2]. Il motivo dell’enorme importanza di questi acciai è dovuto al fatto che l’affinamento del grano ferritico è l’unico metodo di rafforzamento dei metalli che oltre ad aumentare la resistenza meccanica migliora allo stesso tempo la tenacità alle basse temperature [3]

ASPETTI METALLURGICI SULLE TECNICHE DI AFFINAMENTO DEL GRANO CRISTALLINO NEGLI ACCIAI

Gli acciai ferritici a grano ultrafine UFG sono degli acciai da costruzione per uso generale con basso contenuto di carbonio. Sono chiamati così perché la loro microstruttura è costituita da grani di dimensione inferiore a 3 ?m, di solito contengono anche piccole quantità di elementi microleganti come Nb, V e qualche volta il Ti; questi elementi giocano un ruolo importante sull’affinamento del grano. Comunque acciai che contengono tali elementi fanno parte di una sottocategoria degli acciai generali da costruzione denominata HSLA (High Strength Low Alloy) [1-2]. Il motivo dell’enorme importanza di questi acciai è dovuto al fatto che l’affinamento del grano ferritico è l’unico metodo di rafforzamento dei metalli che oltre ad aumentare la resistenza meccanica migliora allo stesso tempo la tenacità alle basse temperature [3]

Sustainability Study of a New Solid-State Aluminum Chips Recycling Process: A Life Cycle Assessment Approach

Nowadays, reducing greenhouse gas emissions in all human activities has become crucial. This article presents a life cycle assessment (LCA) investigation conducted to evaluate the environmental benefits of a newly developed solid-state recycling process for aluminum chips, involving two steps: direct rolling and accumulative roll bonding. A comparison was made between this process and two current industrial methods of recycling aluminum scraps to obtain wrought products, which involve melting, casting, and subsequent rolling. The LCA analysis considered a scenario where 50% of the total electric requirement was met by photovoltaic energy. The results of the study indicate that in all examined impact categories, direct rolling has a lower environmental footprint compared to both traditional recycling and twin-roll cast technology. These results suggest that this new solid-state recycling procedure has significant potential to replace environmentally harmful melting processes

Effects of process parameters on the deformation energy in a sheet-bulk metal forming process for an automotive component

The present study investigates the effects of the process parameters on cold forming process of an automotive component in AISI 1006 low carbon steel. The material formability was characterised up to 250°C. The material flow behaviour and the related thermal distributions during the geometrical transformations were analyzed. Coining and forming operations were investigated by using a coupled 3D Thermo-mechanical FEM with different die geometries and friction conditions in order to optimize the final die geometry and to reduce the energy consumption. FEM simulation results were validated by comparison with the experimental trials. The detailed study of the component allowed defining the energy required by the severe bending of the initial thick plate. The FEM predictions led to a reduction of deformation energy of about 20%, a mass reduction of 28% on the final product and permitted avoiding secondary machining operations

Bonding of similar AA3105 aluminum alloy by accumulative roll bonding process

Accumulative roll-bonding (ARB) is a novel plastic straining process aimed at bonding of similar and dissimilar metal combinations. Moreover, it is used recently to produce ultrafine grain materials and metal matrix reinforced composites to enhance mechanical, electrical, and corrosion resistance properties. This work presents an experimental study of roll bonding and accumulative roll bonding of similar AA3105 aluminum alloy at 300°C with a final thickness of 1.2 mm, focusing especially on bond strength evaluation and layers continuities. Tensile tests and three-points bending were performed to mechanical characterize the produced sheets in the various steps and based on the number of the cycles. The maximum strength was reached after 3 ARB cycles. After 4 cycles, the bonding interfaces have a uniform distribution through the sheet thickness, it is possible to distinguish only the interface formed in the last pass in the fracture surface, and no significant enhancement in strength was observed. Starting from 2 ARB cycles, micro-cracks were observed at the outer surface for bending angles greater than 90 deg, and at 180 deg all ARBed samples except A1 were failed

STUDIO DELLE VARIAZIONI MICROSTRUTTURALI DURANTE LA DEFORMAZIONE A CALDO DELLA LEGA Al-4.5%Zn-1.8%Mg

La lavorabilità a caldo a 500°C di una lega Al-4.5%Zn-1.8%Mg, è stata studiata utilizzando prove di torsione condotte secondo una nuova procedura (a velocità crescente di deformazione) che prevedeva una variazione lineare della velocità angolare ø secondo la legge ø =Kè in cui è era l’angolo di rotazione. In particolare sono state condotte prove con valori di K variabili fra 0.05 e 2 s-1. A titolo di confronto sono state quindi condotte prove di torsione con velocità di deformazione costante. Le curve tensione equivalente - deformazione equivalente per le prove condotte a velocità crescente erano caratterizzate da un aumento monotonico della tensione con la deformazione, senza che si arrivasse ad un regime di saturazione. Le curve ottenute con velocità di deformazione costante a 500°C erano caratterizzate invece da un aumento della tensione fino ad un valore di picco seguito da una modesta diminuzione della tensione di flusso che raggiungeva successivamente il valore stazionario, comportamento tipico dei materiali che non esibiscono ricristallizzazione dinamica. Comunque questa semplice analisi qualitativa della forma delle curve tensione-deformazione non poteva essere considerata un prova conclusiva per escludere l’instaurarsi della ricristallizzazione dinamica. La microstruttura dei campioni deformati è stata analizzata tramite le usuali tecniche di microscopia ottica ed elettronica in scansione SEM/EBSD

Mechanical and microstructure characterization of hard nanostructured N-bearing thin coating

Tools for machining are made of hard steels and cemented carbide (WC-Co). For specialized applications, such as aluminium machining, diamond or polycrystalline cubic boron nitride are also used. The main problem with steel, is that it exhibits a relatively low hardness (below 10GPa) which strongly decreases upon annealing above about 600K. Thus, the majority of modern tools are nowadays coated with hard coatings that increase the hardness, decrease the coefficient of friction and protect the tools against oxidation. A similar approach has been recently used to obtain a longer duration of the dies for aluminium die-casting. Multi-component and nanostructured materials represent a promising class of protective hard coatings due to their enhanced mechanical and thermal oxidation properties. Surface properties modification is an effective way to improve the performances of materials subjected to thermo-mechanical stress. Three different thin hard nitrogen-rich coatings were mechanically, microstructurally, and thermally characterized: a 2.5 micron-thick CrN-NbN, a 11.7 micron-thick TiAlN, and a 2.92 micron-thick AlTiCrxNy. The CrN-NbN coating main feature is the fabrication by the alternate deposition of 4nm thick-nanolayer of NewChrome (new type of CrN, with strong adhesion and low coating temperature). All the three coatings can reach hardness and elastic modulus in excess of 20, and 250 GPa, respectively. Their main applications include stainless steel drawing, plastic materials forming and extrusion and aluminum alloys die-casting. The here studied TiAlN (SBN, super booster nitride) is one of the latest evolution of TiAlN coatings for cutting applications, where maximum resistance to wear and oxidation are required. The AlTiCrxNy combines the very high wear resistance characteristic of the Cr-coatings and the high thermal stability and high-temperature hardness typical of Al-containing coatings. All the coatings were deposited on a S600 tool steels. The coatings were subjected to two different thermal cycling tests: one for 100 thermal cycles consisting of 60 s dwelling time, respectively at the high- (573 to 1173 K) and at the room-temperature, a second for 100 thermal cycles consisting of 115s dwelling time, at same temperatures of the first test, followed by 5s dwelling at room-temperature. The investigated coatings showed a sufficient-to-optimal thermal response in terms of stability of hardness, elastic modulus, and oxidation behavior. The temperature induced hardness and elastic modulus coating variations were measured by nanoindentation.NPRP grant # NPRP5–423–2–167, from the Qatar National Research Fund (a member of Qatar Foundation

Analysis of adiabatic heating and its influence on the Garofalo equation parameters of a high nitrogen steel

Torsion tests at high temperatures and high strain rates were conducted on a high nitrogen steel (HNS). Under these conditions, adiabatic heating influences its flow behavior. This work focus on a new algorithm for conducting the adiabatic heating correction of stress-strain curves. The algorithm obtains the stress-strain curves at quasiisothermal conditions from those at adiabatic conditions. The corrections in stress obtained can be higher than 15% and increase with increasing strain rates and decreasing temperatures. On the other hand, an upper bound for the temperature rise was found using a dynamic material behavior approach. Finally, the influence of adiabatic heating correction on the Garofalo equation parameters of HNS was analyzed. High values of activation energy and stress exponent were attributed to reinforcement by dispersed carbonitrides and the high amount of alloying elements.The work was carried out through the Projects PBC-05-010-1 from JCCM (Castilla- La Mancha, Spain) and MAT2006-13348 from CICYT. Thanks are given to Prof. E Evangelista for valuable assistance.Peer reviewe