Showing papers on "Aluminium alloy published in 2017"
TL;DR: The approach to metal-based additive manufacturing is applicable to a wide range of alloys and can be implemented using a range of additive machines, and provides a foundation for broad industrial applicability, including where electron-beam melting or directed-energy-deposition techniques are used instead of selective laser melting.
Abstract: Metal-based additive manufacturing, or three-dimensional (3D) printing, is a potentially disruptive technology across multiple industries, including the aerospace, biomedical and automotive industries. Building up metal components layer by layer increases design freedom and manufacturing flexibility, thereby enabling complex geometries, increased product customization and shorter time to market, while eliminating traditional economy-of-scale constraints. However, currently only a few alloys, the most relevant being AlSi10Mg, TiAl6V4, CoCr and Inconel 718, can be reliably printed; the vast majority of the more than 5,500 alloys in use today cannot be additively manufactured because the melting and solidification dynamics during the printing process lead to intolerable microstructures with large columnar grains and periodic cracks. Here we demonstrate that these issues can be resolved by introducing nanoparticles of nucleants that control solidification during additive manufacturing. We selected the nucleants on the basis of crystallographic information and assembled them onto 7075 and 6061 series aluminium alloy powders. After functionalization with the nucleants, we found that these high-strength aluminium alloys, which were previously incompatible with additive manufacturing, could be processed successfully using selective laser melting. Crack-free, equiaxed (that is, with grains roughly equal in length, width and height), fine-grained microstructures were achieved, resulting in material strengths comparable to that of wrought material. Our approach to metal-based additive manufacturing is applicable to a wide range of alloys and can be implemented using a range of additive machines. It thus provides a foundation for broad industrial applicability, including where electron-beam melting or directed-energy-deposition techniques are used instead of selective laser melting, and will enable additive manufacturing of other alloy systems, such as non-weldable nickel superalloys and intermetallics. Furthermore, this technology could be used in conventional processing such as in joining, casting and injection moulding, in which solidification cracking and hot tearing are also common issues.
1,670 citations
TL;DR: In this article, the authors used scan electron microscopy and X-ray diffraction techniques to study the fracture mechanism and phase identification of a composite specimen, which is characterized by ridges, voids, cracks, dimples, particle fracture and ridges.
154 citations
TL;DR: In this paper, a comparative evaluation on the mechanical and microstructural characteristics of aluminium-based single and hybrid reinforced nanocomposites was carried out, where three numbers of single reinforced nano-alumina particles were manufactured through stir casting with reinforcements preheated to different temperatures.
139 citations
TL;DR: In this article, the authors investigated the mechanical properties of AA 6082 composites reinforced with tungsten carbide particles and found that the tensile strength of the composites increased initially and then tends to decrease.
121 citations
TL;DR: In this article, the fabrication and characterisation of AA 6061/Al2O3 AMMC which was fabricated using stir casting process was studied using scanning electron microscopy, where the particles were observed to refine the grains and were distributed homogeneously in the aluminium matrix.
116 citations
TL;DR: In this paper, the presence of n-TiC particles had a marked influence on the powder morphology, average particle size and microstructure of the matrix during the milling process.
87 citations
TL;DR: In this paper, the tensile behavior of selective laser melted (SLMed) aluminium alloy A357 in the as-fabricated and heat-treated states is explained using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscope (TEM), and t-EBSD.
Abstract: In this work the tensile behaviour of selective laser melted (SLMed) aluminium alloy A357 in the as-fabricated and heat-treated states is explained using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and transmission electron backscatter diffraction (t-EBSD). The as-built sample has an ultrafine microstructure, with high residual stresses and non-equilibrium solid solute concentration of Si in the supersaturated Al matrix. Consequently, the tensile properties of the SLMed Al alloy A357 are comparable or better than traditional cast counterparts. The Al grains in the SLMed alloy consist of sub-micron sized Al cells, and both high angle and low angle boundaries are initially occupied by eutectic nano-sized Si particles, which are beneficial for strength but detrimental for ductility. With subsequent solution heat treatment, the Si particles on the low angle cell boundaries (LACBs) dissolve while those at the high angle grain boundaries (HAGBs) coarsen. Simultaneously internal stresses decrease, as does solute content in the matrix. The evolution of these microstructural features explains the improved tensile ductility (at its maximum >23%) and reduced tensile strength for the heat treated SLMed aluminium alloy A357 samples.
82 citations
TL;DR: In this article, micro cell structures of different sizes were patterned using a nanosecond near-infrared laser source on Al2024 aluminium alloy plates with 2 mm thickness, and the influence of laser parameters on the shape and size of the produced patterns were studied together with the evolution of wettability properties over time for different storage conditions.
Abstract: Micro cell structures of different sizes were patterned using a nanosecond near-infrared laser source on Al2024 aluminium alloy plates with 2 mm thickness. The influence of laser parameters on the shape and size of the produced patterns were studied together with the evolution of wettability properties over time for different storage conditions. Samples were found to be superhydrophobic from a single step laser patterning, requiring no further treatment. Exposure to ambient air was shown to be a key factor in the property changes of the samples over time. The produced surface patterns with different laser parameter settings were correlated with the contact angle measurements, revealing a great influence of the amount of recast material on the hydrophobic properties. X-Ray photoelectron spectroscopy was used to study the impact of surface chemistry changes on hydrophobicity, analysis of elemental composition proved that chemisorbed organic molecules present in the ambient air were responsible for the hydrophilic to superhydrophobic transition.
81 citations
TL;DR: In this paper, the fabrication methods and mechanical properties of Al alloy/SiCp based metal matrix nano composites (Al-MMNCs) have been reviewed and the Scanning electron micrographs indicate that the nano SiCp reinforcing particles are uniformly distributed in the matrix alloy.
80 citations
TL;DR: In this article, the relationship between intergranular corrosion and crystallographic pitting in AA2024-T351 aluminium alloy during immersion in 3.5% NaCl solution is investigated.
76 citations
TL;DR: In this paper, local stirring using a friction stir processing (FSP) tool is shown to very significantly increase the fracture strain of the Al alloy 6056 sometimes by more than a factor of two while making it more isotropic.
TL;DR: In this article, the corrosion behavior of aluminium alloy anode was investigated with urea and thiourea in 5M KOH solution. But the results obtained by Tafel polarization, electrochemical impedance spectroscopy and hydrogen gas evolution test techniques were in acceptable agreement with each other and shows this alloy can used in aluminium-air battery.
02 Jan 2017-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a detailed analysis of microstructure under different strain paths suggests the direction and texture dependent yield locus to be a significant factor for in-plane anisotropy.
Abstract: AA-6061 aluminium alloys are used extensively in automobile and aerospace industries owing to their excellent combination of mechanical and physical properties. This alloy exhibits prominent anisotropy in mechanical properties when produced as cold rolled sheets. In manufacturing, sheet metal anisotropy may have severe consequences for downstream processes such as stamping and deep drawing operations. In the present study, correlations among in-plane anisotropy, strain path and formability of AA-6061 sheet metal are investigated. Using limit dome height tests, forming limit diagrams (FLDs) were constructed for three different sheet directions by applying appropriate strain localization and fracture criteria. For each sheet direction and strain path, microstructure and texture evolution were also observed to identify the origin of in-plane anisotropy and formability of the AA-6061 sheet metal alloy. A detailed analysis of microstructure under different strain paths suggests the direction and texture dependent yield locus to be a significant factor for in-plane anisotropy. Intra-granular crack propagation in a particular sheet direction (transverse direction: TD) may lead to reduced formability of AA-6061. Formability, on the other hand, appears to be highly correlated to the relative fraction of specific texture components. Certain critical texture components such as Cube {001} and Brass {011} influence the forming behaviour of AA-6061 aluminium alloy significantly.
TL;DR: In this article, the effect of laser peening without coating on the hardness of an aluminium alloy was investigated and the Vickers micro-hardness test was used to study the hardness with different wavelengths and laser intensities.
TL;DR: In this paper, a three-dimensional finite-element model of a honeycomb-core structure was developed using the commercial code Abaqus, and experimental compressive tests were made to validate the numerical model and good agreement was found between the experimental data and the numerical results.
TL;DR: In this paper, the influence of trace Au (200ppm) additions on precipitation in an Al-Cu-Au alloy was investigated by using first principles calculations and relevant thermodynamic modelling.
TL;DR: In this article, the authors scrutinized aluminium alloy 6101-graphite composites for their mechanical and tribological behaviour in dry sliding environments, and the traditional liquid casting technique had not been used.
TL;DR: In this paper, four alloys with low/high Cu and various Mg/Si ratios were designed and investigated by accelerated corrosion test, electrochemical test and electron microscopy, and it was revealed that IGC susceptibility of alloys was the result of microgalvanic coupling between the noble grain boundary precipitates and the adjacent precipitates free zone.
TL;DR: In this paper, an attempt has been made to establish an empirical relationship between the FSW process parameters (rotational speed, welding speed, and axial force) and predicting the maximum tensile strength of the joint.
Abstract: Friction stir welding (FSW) is an important welding technique where in, and optimizing the process parameters will improve the joint strength of the welds. The FSW process and tool parameters play a major role in determining the joint strength. In this paper, an attempt has been made to establish an empirical relationship between the FSW process parameters (rotational speed, welding speed, and axial force) and predicting the maximum tensile strength of the joint. Statistical tools such as design of experiments, analysis of variance, and regression analysis are used to develop the relationships. A non-heat treatable aluminum alloy Aluminium Association 5059 of 4 mm thickness was used as the base material. Response surface methodology is employed to develop the mathematical model. Analysis of variance technique is used to check the adequacy of the developed mathematical model. The developed mathematical model can be used effectively at 95 % confidence level. The effect of FSW process parameter on mechanical property of Aluminium Association 5059 aluminum alloy has also been analyzed in detail.
TL;DR: In this paper, the effects of heat input on microstructure and mechanical behaviour of the joints were investigated, and the results showed a distinctive interaction layer at polymer/aluminium interface, consisted mainly of C, O and Al.
Abstract: Joining feasibility of aluminium alloy to polypropylene sheets via friction stir lap joining was examined. Effects of heat-input on microstructure and mechanical behaviour of the joints were investigated. A covering plate was used to confine flow of molten polymer. The results showed a distinctive interaction layer at polymer/aluminium interface, consisted mainly of C, O and Al. Shear strength of the joints decreased by enhancement of the heat-input due to increase in the thickness of the interaction layer as well as the gap width between this layer and both aluminium and polymer matrices. Maximum shear-tensile strength of 5.1 MPa (∼20% of polymer shear strength) was obtained, which was higher than or comparable to that of the joints produced by other processes.
TL;DR: In this article, a hot stamping process of heat-treatable aluminium alloy sheets using quick heating below the solution treatment temperature was developed to improve the formability and productivity in conventional cold stamping of high-strength aluminium aircraft parts.
TL;DR: In this paper, the Gurson-Tvergaard-needleman model was employed to predict the ductile fracture behavior in the forming of aluminium alloy 5A06 sheet.
TL;DR: In this article, the effect of physical and mechanical properties of three different flyers on the interface phenomena of partially overlapped explosive welds, using the same base plate material, was studied.
TL;DR: In this article, surface modification of aluminium alloy AA7075 by two types of atmospheric pressure plasma: dielectric barrier discharge (DBD) and atmospheric pressure plasminar jet (APPJ) with the purpose to enhance the adhesion of polyurethane coating on the alloy.
Abstract: This work deals with surface modification of aluminium alloy AA7075 by two types of atmospheric pressure plasma: dielectric barrier discharge (DBD) and atmospheric pressure plasma jet (APPJ) with the purpose to enhance the adhesion of polyurethane coating on the alloy. The surface characterization was performed by using water contact angle, roughness and surface free energy measurements. Quality of the coating was tested according to the adhesion tape test (ASTM D3359) and evaluated by electrochemical techniques. The aluminium alloy showed great improvement of the surface wettability after plasma treatments. While, the adhesion tape test presented excellent results with perfect adhesion, meaning that both plasma treatments were efficient in improving the adhesion of the polyurethane coating to the AA7075. The Fourier Transform Infrared Spectroscopy (FTIR) results demonstrated that the plasma treatment cleaned the Al alloy surface by removing hydrocarbon contaminations. Both polarization curves and Electrochemical Impedance Spectroscopy (EIS) results showed better characteristics of corrosion resistance for polyurethane-coated AA7075 than untreated coated samples.
TL;DR: In this paper, the authors examined the corrosion pathways in AA2024-T3, AA5083-O and AA6082-T6 alloys and found that the overall corrosion pathways are distinctively different and are influenced by the flow of anolyte solution.
TL;DR: In this paper, the effect of anodizing voltage on the sol-gel impregnation and the protection afforded by the layers was evaluated by means of electrochemical impedance spectroscopy (EIS) and salt-spray tests.
Abstract: Corrosion is a major problem for high strength aluminium alloys Thickening of the naturally formed oxide layer through anodizing is one of the main approaches to improve the corrosion resistance of these materials Chromate anodizing is extremely efficient to produce anodized layers with good corrosion resistance and painting adhesion, however chromate based surface treatments must be banished from industrial use The corrosion resistance of aluminium alloy 2524 (AA2524) anodized in tartaric/sulphuric acid (TSA) bath and protected with a hybrid sol-gel coating was evaluated by means of electrochemical impedance spectroscopy (EIS) and salt-spray tests The morphologies of the obtained layers were characterized by SEM-FEG while the chemical in depth distribution of the hybrid layers was evaluated by means of Rf-GDOES The effect of anodizing voltage on the sol-gel impregnation and the protection afforded by the layers was evaluated Electrical equivalent circuit fitting of the EIS data has shown that the anodized layer thickness plays an important role in the protection mechanism of the sol-gel layer Salt-spray tests highlighted the significant contribution of the sol-gel distribution in the anodized layer
TL;DR: In this article, a 24-hour immersion in a 1M NaCl solution in a 2024-T351 Al alloy was characterized using a combination of electron microscopy techniques and showed the dissolution of intergranular Cu-rich precipitates all along the corroded grain boundaries.
TL;DR: In this paper, the effects of laser texturing on the corrosion and wettability of AA2024-T3 using an IR Nd:Vanadate picosecond (ps) laser was studied.
Abstract: The effects of laser texturing on the corrosion and wettability of AA2024-T3 using an IR Nd:Vanadate picosecond (ps) laser was studied. Three types of texture patterns were generated: dimples with 5% and 50% area density (percentage of surface area textured); cross groove patterns with an area density of 64%; and concentric ring patterns with an area density of 70%. For the higher area densities, the surface character changed from hydrophilic to hydrophobic. The evolution of the open circuit potential over time, potentiodynamic polarization curves and electrochemical impedance spectroscopy were then investigated and analysed. The results revealed that ultrashort ps laser surface texturing did not modify the corrosion behaviour of AA 2024-T3 in the test solution.
TL;DR: In this article, the effect of B4C reinforcement on AMCs mechanical properties like tensile strength, strain, hardness, wear and fatigue is discussed in detail, major issues like fiber-matrix bonding, agglomerating phenomenon and the problems related to distribution of particles are discussed.
TL;DR: In this article, the effect of Sc content on microstructure and stress corrosion cracking behavior of medium strength Al-Zn-Mg alloy has been investigated by optical microscopy, scanning electron microscopy and electron backscatter diffraction.