Industrial Aluminum Alloy Research Articles

Modeling of GP(I) zone formation during quench in an industrial AA7449 75 mm thick plate

The GP(I) zone formation during quench is simulated in an industrial Aluminum alloy AA7449 75mm thick plate by using a multi-class precipitation model. For this purpose, results of in situ SAXS experiments are reported. A methodology is presented that takes advantage of the collected data to derive i - a thermodynamic description for GP(I) zones from reversion heat treatments by using a solubility product and ii - the influence of excess vacancies on diffusion coefficients. This approach allows reproducing reasonably well the GP(I) zone formation measured during rapid cooling. Further, the simulated as-quenched surface yield strength compares well with experimental results reported in the literature.

Corrosion protection of aluminum alloy substrate with nano-silica reinforced organic–inorganic hybrid coatings

Organic–inorganic hybrid (OIH) thin films derived from the sol–gel process have emerged as sustainable metal pretreatment alternatives to toxic heavy metal-based systems. In recent years, such OIH systems based on Si, Zr, and Ti have been successfully developed and commercialized for pretreatment of aluminum alloys, galvanized steel, cold-rolled steel, and many other metals and alloys, for improving adhesion and corrosion resistance performance. A variety of approaches are being used to further enhance performance of such OIH systems to match or surpass that obtained from chromate-based systems. In the present study, a novel bis-silane compound has been synthesized and used as a primary sol–gel precursor for OIH coatings. In order to further improve their mechanical and corrosion resistance performance, colloidal nanoparticles have been incorporated. The microstructure of the deposited films as a function of their composition and formation of Si–O–Si structural network has been studied by Confocal Raman spectroscopic technique. The chemical structure of the OIH films has been characterized by FTIR analysis. Electrochemical impedance spectroscopy, DC polarization measurements, and accelerated neutral salt-fog test (ASTM B117) have been used to evaluate corrosion resistance performance of coatings on industrial aluminum alloy AA 3003 H14. Nano-indentation tests of these OIH films have been performed to study the effect of colloidal nanoparticles on coating micro/nano structure and their mechanical properties. The study reveals that colloidal nanoparticles improve the corrosion resistance of OIH coatings by formation of a protective barrier to diffusion of corrosive species to the metal surface. The optimum content of colloidal nanoparticles that can provide best corrosion protection has been determined. Electrochemical study provides useful insight into the significance of interaction between the sol–gel hybrid and silica particles in the corrosion protection mechanism.

Fatigue FEM analysis in the case of brazed aluminium alloy 3L59 used in aeronautical industry

The use, on a larger scale, of brazed aluminum alloys in the aerospace industry led to the need for a detailed study of the assemblies behavior. These are built from 6061 aluminum aloy (3L59) brazed with aluminum aloy A103. Therefore, a finit element simulation (FEM) of durability is necessary, that consists in the observation of gradual deterioration until failure. These studies are required and are previous to the stage of the producing the assembly and test it by traditional methods.

Application of a Pore Fraction Hot Tearing Model to Directionally Solidified and Direct Chill Cast Aluminum Alloys

Hot tearing susceptibility is commonly assessed using a pressure drop equation in the mushy zone that includes the effects of both tensile deformation perpendicular to the thermal gradient as well as shrinkage feeding. In this study, a Pore Fraction hot tearing model, recently developed by Monroe and Beckermann (JOM 66:1439–1445, 2014), is extended to additionally include the effect of strain rate parallel to the thermal gradient. The deformation and shrinkage pore fractions are obtained on the basis of the dimensionless Niyama criterion and a scaling variable method. First, the model is applied to the binary Al-Cu system under conditions of directional solidification. It is shown that for the same Niyama criterion, a decrease in the cooling rate increases both the deformation and shrinkage pore fractions because of an increase in the time spent in the brittle temperature region. Second, the model is applied to the industrial aluminum alloy AA5182 as part of a finite element simulation of the Direct Chill (DC) casting process. It is shown that an increase in the casting speed during DC casting increases the deformation and shrinkage pore fractions, causing the maximum point of pore fraction to move towards the base of the casting. These results demonstrate that including the strain rate parallel to the thermal gradient significantly improves the predictive quality of hot tearing criteria based on the pressure drop equation.

Recent trends in resistance spot welding of aluminium alloys in automotive industry

Recent trends in resistance spot welding of aluminium alloys in automotive industry

The effect of zinc on the microstructure and phase transformations of casting Al-Cu alloys

Copper is one of the main alloying elements for aluminum casting alloys. As an alloying element, copper significantly increases the tensile strength and toughness of alloys based on aluminum. The copper content in the industrial casting aluminum alloys ranges from 3,5 to 11 wt.%. However, despite the positive effect on the mechanical properties, copper has a negative influence on the corrosion resistance of aluminum and its alloys. In order to further improve the properties of Al-Cu alloys they are additional alloyed with elements such as zinc, magnesium and others. In this work experimental and analytical examination of the impact of zinc on the microstructure and phase transformations of Al-Cu alloys was carried out. In order to determine the effect of the addition of zinc to the structure and phase transformations of Al-Cu alloys two alloys of Al-Cu-Zn system with selected compositions were prepared and then examined using scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDX). The experimental results were compared with the results of thermodynamic calculations of phase equilibria.

Change in Dislocation Structure and Phase Composition of 1565Ч Alloy Exposed to Ion Irradiation (Cu + Pb)

Background/Objectives: Using electron microscopy, it was revealed that exposure to ion irradiation (Cu + Pb) with an energy of 35 keV of samples sized 25 × 25 × 3 mm of 1565ч industrial aluminum alloy after cold rolling, leads to a significant narrowing of the boundaries of intragranular cellular dislocation structure and increase in the extent of its regularity. Methods/Statistical Analysis: We have studied samples of 1565ч alloy sized 25 × 25 mm 2 cut from non-clad sheets of a thickness of 3 mm, a change in the structure of cold-worked 1565ч alloy exposed to the beams of accelerated ions (Cu + Pb) with an energy of 30 keV at the densities of ion current of 100, 200 and 300 μA/cm 2 and irradiation doses of 1016 and 1017 cm -2 . Irradiation with pulsed beams of ions (Cu + Pb) was conducted at the setup for ion beam implantation equipped with ion source based on plasma arc in vacuo. Electron microscopic study by the method of thin foils was conducted at JEM-2100 transmission electron microscope. Findings: It was found that irradiation of cold-worked clad 1565ч alloy with copper and lead ions does not lead to a fundamental change in its structure compared to the structure existing in the deformed condition: cellular dislocation structure remains. With increase in ion current density and irradiation dose, the cellular structure becomes more regular - well-formed cells are observed throughout almost the entire volume of the sample. The average width of dislocation-free regions reaches 2.5 μm at the width of the boundaries not exceeding 0.6 μm. The effect of accelerated ions (Cu + Pb) (E = 30 keV, j = 100 μA/cm 2 ) on the alloy without the cladding layer even at a dose of 1016 cm -2 leads to formation of the developed subgrain structure in initially deformed alloy. The average size of subgrains with interlacements of dislocations varies in the range of 0.6 - 2.2 μm. In other words, a polygonal structure forms in the alloy similar to the structure forming at the initial stages of recrystallization annealing. Applications/Improvements: This applies to many industries associated with the development of high-tech and energy-saving technologies as well as addressing environmental problems.

The Study of Industrial Aluminum Alloy as Anodes for Aluminum-Air Batteries in Alkaline Electrolytes

Aluminum is attracting interest due to the good application prospect as anode for metal-air batteries in alkaline solutions. In this paper, the corrosion behavior and electrochemical properties of industrial aluminum alloy are investigated using hydrogen collection method, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 4 M NaOH and 4 M KOH. Battery performances are tested by constant current discharge at different current densities. The results show 8011 Al alloy has better electrochemical properties, discharge energy and power density. Considering the cost and performance, 8011 Al alloy is one of the most promising low-cost and high performance Al anode for Al-air batteries.

Identifying the stress–strain curve of materials by microimpact testing. Application on pure copper, pure iron, and aluminum alloy 6061-T651

Abstract

The thickness of native oxides on aluminum alloys and single crystals

We present results from measurements of the native oxide film thickness on four different industrial aluminum alloys and three different aluminum single crystals. The thicknesses were determined using X-ray reflectivity, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. In addition, atomic force microscopy was used for micro-structural studies of the oxide surfaces. The reflectivity measurements were performed in ultra-high vacuum, vacuum, ambient, nitrogen and liquid water conditions. The results obtained using X-ray reflectivity and X-ray photoelectron spectroscopy demonstrate good agreement. However, the oxide thicknesses determined from the electrochemical impedance spectroscopy show a larger discrepancy from the above two methods. In the present contribution the reasons for this discrepancy are discussed. We also address the effect of the substrate type and the presence of water on the resultant oxide thickness.

Modelling of micro- and macrosegregation for industrial multicomponent aluminium alloys

Realistic predictions of macrosegregation formation during casting of aluminium alloys requires an accurate modeling of solute microsegregation accounting for multicomponent phase diagrams and secondary phase formation. In the present work, the stand alone Alstruc model, a microsegregation model for industrial multicomponent aluminium alloys, is coupled with the continuum model ALSIM which calculates the macroscopic transport of mass, enthalpy, momentum, and solutes as well as stresses and deformation during solidification of aluminium. Alstruc deals with multicomponent alloys accounting for temperature dependent partition coefficients, liquidus slopes and the precipitation of secondary phases. The challenge associated with computation of microsegregation for multicomponent alloys is solved in Alstruc by approximating the phase diagram data by simple, analytical expressions which allows for a CPU-time efficient coupling with the macroscopic transport model. In the present work, the coupled model has been applied in a study of macrosegregation including thermal and solutal convection, solidification shrinkage and surface exudation on an industrial DC-cast billet.

Microstructure and Mechanical Properties of Cold Metal Transfer Welding Similar and Dissimilar Aluminum Alloys

Integrating structures made from aluminum alloys in automotive industry requires a large amount of joining. As a consequence, the properties of the joints have a significant influence on the overall performance of the whole structure. Robot cold metal transfer welding is a relatively new joining technique and has been used in this work to join 6082-T4 and 5182-O aluminum alloy sheets by using ER5356 and ER4043 filler metals. Microstructure characterization was performed by optical microscopy and energy dispersive X-ray spectroscopy, and the mechanical properties were measured by tensile and hardness tests. A correlation is made between welding variables, mechanical properties and the microstructure of welded joints. Results indicate that robot cold metal transfer welding provides good joint efficiency with high welding speed, good tensile strength, and ductility. Owing to the low heat input of robot cold metal transfer welding process, the heat affected zone microstructure was quite similar to base metals, and weld metal microstructure was the controlling factor of joint efficiency. The best performing were the 5182/5182 joints welded with ER5356 and these had mechanical property coefficients of 100%, 98%, and 85% for yield strength, ultimate tensile strength, and elongation, respectively.

A new systematic framework for crystallographic analysis of atom probe data

In this article, after a brief introduction to the principles behind atom probe crystallography, we introduce methods for unambiguously determining the presence of crystal planes within atom probe datasets, as well as their characteristics: location; orientation and interplanar spacing. These methods, which we refer to as plane orientation extraction (POE) and local crystallography mapping (LCM) make use of real-space data and allow for systematic analyses. We present here application of POE and LCM to datasets of pure Al, industrial aluminium alloys and doped-silicon. Data was collected both in DC voltage mode and laser-assisted mode (in the latter of which extracting crystallographic information is known to be more difficult due to distortions). The nature of the atomic planes in both datasets was extracted and analysed.

Electromagnetic Braking of Natural Convection during Ohno Continuous Casting of an Industrial Aluminum Alloy

With the purpose of obtaining compositionally uniform ingots during Ohno continuous casting of a dilute industrial aluminum alloy through eliminating segregation due to convection, a magnetic field strength required to damp natural convection and suppress macrosegregation was numerically determined. This was achieved by solving conservation equations of continuity, momentum, energy and Maxwell’s equations in order to predict the magnetic field effects on flow field (determining macrosegregation). The electromagnetic field was applied orthogonally to the natural convection flow. Through this approach, the optimum magnetic field strength required to damp natural convection and establish diffusion controlled solute transport of the alloy during solidification was established.

Hydrogen Production for Fuel Cells in Reaction of Activated Aluminum with Water

The paper discusses the issues concerning producing of compact hydrogen resources for fuel cells. The suggested alternative is implementation of the reaction of activated aluminum with water. In the paper, as an activator Ga-In liquid eutectic alloy is used. One of the main features of the study is using various industrial aluminum alloys as basic materials. With the help of scanning electron microscopy investigation with local element analysis the process of activation of technical alloy on aluminum basis treated by Ga-In eutectic is studied. Such processing leads, on the one hand, to the intense embrittlement, on the other hand – to the sharp increase in material chemical activity in relation to water with hydrogen emission. It is demonstrated, that activated aluminum can be prospective energy carrier for small-scale hydrogen power energetics.

Fatigue Behavior of Dissimilar Aluminum Alloy Spot Welds

With the broader utilization of a variety of aluminum alloys in the automotive industry for structural lightweight applications, the need for resistance spot welding (RSW) of dissimilar aluminum alloys is increasing. General Motors (GM) has developed a proprietary RSW process using a multi-ring, domed electrode geometry that significantly improves the performance of the aluminum resistance spot welds. In addition, to enhance structural performance, epoxy adhesivesare also often applied prior to RSW to obtain weld-bonded joints.As a contribution, the load-controlled fatigue behavior of dissimilar aluminum alloy spot welds made of 2mm thick AA5754 wrought sheet and 3mm thick Aural2 die casting sheet with and without the addition of adhesive prior to welding was studied. The same GM proprietary resistance spot welding electrode and current schedule was applied to both welding conditions leading to a larger nugget size when using adhesive, but both weld configurations presented similar maximum load in tension-shear testing. X-ray computed tomography was used to detect internal welding discontinuities such as voids and also to follow the damage evolution and fatigue crack initiation and growth during interrupted fatigue testing of the spot welds. The results show that the main fatigue crack initiates at the edge of the nugget and penetrates through the Aural2 die casting sheet in the thickness direction. Using the structural stress concept, it was also found that the structural stress-fatigue life curve for AA5754 to Aural2 aluminum spot welds with and without adhesive falls into a master curve indicating that the nugget size which corresponds to the tensile and bending strength dominates fatigue life.

THE PRESENT AND FUTURE PROSPECTS OF FRICTION STIR WELDING IN AERONAUTICS

Since its invention friction stir welding as a solid state joining method was considered primarily for aluminium alloys in the aerospace industry. Years of intense research and development were necessary to introduce the process for fabrication of aerospace components. It was necessary to accumulate sufficient information about process parameters, tooling and machinery for process specification, certification and design allowables. Friction stir welding was first used in space vehicles and in military aircraft, later it was used in civil aviation. Aircraft manufacturers such as Boeing, Airbus, and Embraer use this technique for components such as floor panels, fuselage panels, and wing ribs among others. This process allows for the introduction of new structural solutions in the same way that the development of advanced alloys also permits similar advances.

Thermal and X-Ray Microanalysis of Alloys B-1461 Ingots Based on the System Al – Cu – Li

Results are provided for thermal analysis and x-ray microanalysis of specimens from industrial ingots of aluminum alloy B-1461 based on the system Al – Cu – Li. A two-stage regime homogenization is proposed for industrial aluminum alloy B-1461 ingots, providing formation of uniformly distributed dispersed phases of compact shape within the microstructure, an increase in relative elongation, and a reduction in alloy yield strength in the temperature range 440 – 460°C.

Tensile Properties and Hot-Tearing Tendencies of 3xxx Alloys

A set-up for tensile testing in the mushy zone allowing for studies of semi-solid mechanical behavior is available at SINTEF. A hot-tearing experimental set-up has recently been developed allowing for investigation of the hot-tearing susceptibility of industrial aluminium alloys and effects of e.g. alloying composition and grain-refiner. Load and temperature are registered during constrained solidification giving information on the mechanical behavior of the alloy during solidification. Two crack-prone alloys in the 3xxx-series (A and B) have been investigated using both techniques and the results analyzed using information about solidification path from a thermo-physical model. Alloy B is found to be mechanically weaker in the interval most susceptible to hot-tearing in agreement with cast-house experience. This study shows that the experimental techniques combined with thermo-physical modeling and characterization allow for a better understanding of the hot-tearing sensitivity of the alloys.

Refinement of intermetallic compounds and aluminum matrix in 3xxx aluminum alloys solidified by an electromagnetic vibration technique

The industrial 3xxx aluminum alloy was solidified in a superconducting magnet, in which electromagnetic vibration (EMV) was imposed throughout the entire solidification process. The microstructure was examined as a function of vibration frequency. It is revealed that the microstructure contains intermetallic compounds and aluminum solid solution (Al(ss)) regardless of solidification condition. For both structures, quantitative characterization shows that their average grain sizes decrease to minima when vibration frequency, f, increases and further increases of f leads to an increase of average grain sizes. Moreover, the general uniformity of intermetallic compound becomes poor when f goes beyond 1000Hz. The microstructure transition behavior can be elucidated when considering the electrical resistivities of phases, i.e., Al(ss), intermetallic compounds and remaining liquid that coexist in mushy zone. The different electrical resistivities of these phases produce different Lorentz forces and thus lead to different vibration amplitudes and eventually generate uncoupled movement between the leading phase and sluggish phase during vibration. The microstructure transition can be clarified when the distance covered by the leading phase is revealed as a function of frequency. The morphological appearance of intermetallic compounds is dependent on f in EMV processing; however, their phase species and volume proportion are independent of processing conditions.