EN AW Research Articles

Characterization of laser-induced surface structures of aluminum in an oxygen-free atmosphere

Brazing of materials with high oxygen affinity, such as aluminum alloys, requires the removal of surface oxides. This is commonly achieved using chemical fluxes. The approach described here utilizes IR-pulsed laser radiation at a pulse duration of 45 ns to remove the oxide layer. To prevent reoxidation, an oxygen-free atmosphere is used by introducing monosilane (SiH4) into the process chamber, which binds the oxygen molecules. The laser-induced surface structuring that occurs during oxide removal of aluminum alloy EN AW-6082 was investigated. Pulse energies between 60 – 300 µJ and different pulse overlaps between 0 – 90 % were analyzed for topography and roughness based on the process atmosphere. The results suggest that the roughness increases significantly only at 90 % overlap. Additionally, laser structuring with high energy and overlap in the presence of O2 results in a porous surface layer, while in the absence of O2, it leads to pillar formation with higher roughness.

Analysis of the thermal expansion coefficient of glass- and carbon-fibre-reinforced composites

With the development of manufacturing processes, an increase in the importance of metal-fibre composites in materials engineering is observed. These are materials consisting of appropriately arranged layers of metal and various types of fibres. The very wide use of composite materials in the construction of machine and equipment components means they are often exposed to work in variable temperature conditions. The aim of this article was analysis of the thermal expansion of typical composites: carbon fibre-reinforced polymer, glass fibre-reinforced polymer, glass-reinforced aluminium laminate and carbon-fibre reinforced aluminium laminate. EN AW-6060 aluminium alloy was used as the reference material. The aim of the dilatometric tests was to determine the coefficient of thermal expansion and the dimensional stability of composite materials at elevated temperatures up to 100 °C. The EN AW-6060 aluminium alloy was characterized by the highest linear expansion coefficient (20.27×10−6 1/K). Composites containing glass fibres were characterized by the lowest positive linear thermal expansion coefficient. Among the composite materials tested, CARALLs exhibit the lowest thermal expansion coefficient.

The Influence of the Burnishing Process on the Change in Surface Hardness, Selected Surface Roughness Parameters and the Material Ratio of the Welded Joint of Aluminum Tubes.

This paper presents the effect of burnishing on the surface hardness, selected surface roughness parameters and material ratio of tubes made of an EN AW-6060 aluminum alloy after welding. The prepared specimens were subjected to a 141-TIG welding process, after which the surfaces to be burnished were given a finishing turning treatment with DURACARB's CCGT09T302-DL cutting insert to remove the weld face. After the turning process, the surface finish treatment was carried out by rolling burnishing, for which Yamato's SRMD burnishing tool was used. The surface hardness, selected surface roughness parameters and material ratio were then measured. An analysis of the results showed an increase in hardness in the surface layer, as well as an improvement in the analyzed surface roughness parameters and the material ratio of the native material and the weld.

Development of EN AW-6082 Metal Foams and Stochastic Foam Modeling for the Individualization of Extruded Profiles

AbstractLightweight design and hybrid components enable innovative and new component concepts, especially when combining structurally reliable metal components with individualized polymer components. In this research, a process for additive manufacturing polymers on the surface of extruded aluminum profiles is examined. The extrusion process is adapted to produce foamable aluminum profiles, which can be utilized to enable a form fit between the two materials and ensures sufficient bond strength. For this purpose, a novel aluminum block material based on the standard wrought alloy EN AW-6082 was developed. It consists of a solid EN AW-6082 core and powder metallurgically produced outer layer, which allows local foaming of the aluminum profile surface. The main objective of this study was to optimize the bond strength of the hybrid aluminum-polymer components. The methods employed include fabricating aluminum test specimens, performing mechanical tests, x-ray microscopy to analyze the pore structure and evaluating the 3D pore distribution and the wall thickness. Virtual foam models were created to numerically investigate suitable pore sizes and foam geometries for form-fit with the polymer. The porosity achieved as a function of the processing of the components are discussed and a comparison is made between the real and virtual pore structures.

Studies on the Use of Laser Directed Energy Deposition for the Additive Manufacturing of Lightweight Parts

Despite the numerous benefits of battery electric vehicles, their relatively short maximal range compared to internal combustion engine vehicles limits their attractiveness to the consumer. Implementing lightweight structures is one solution to reduce the mass of the vehicle, which in turn lowers the energy consumption and thus extends the maximal range. Additive Manufacturing processes, such as the Laser Directed Energy Deposition (DED-LB), offer great potential for the resource-efficient manufacturing of lightweight components because they allow producing near-net-shaped parts of variable sizes and geometries. Therefore, in this study, DED-LB was assessed concerning its use for the rapid manufacturing or modification of lightweight parts. The additive process was performed on EN AW 6060 aluminum extrusion profiles commonly found in battery electric vehicles and an AlSi10Mg wire was used as feedstock. The investigations included temperature and microhardness measurements. Furthermore, the effect of the deposition rate on the geometric quality of the part was investigated. The results indicate that DED-LB can be performed on thin-walled structures to produce defect-free components. Furthermore, the findings reveal a trade-off between a fast build-up and the surface quality of the parts. Notably, it was observed that the different deposition rates had no impact on the hardness of the produced parts. Further studies on heat management are needed to optimize the process for producing lightweight parts with improved mechanical properties.

Joining of EN AW 6060 Pipes by Plastic Forming

The article deals with an innovative, but not widely used type of joining of aluminum pipes through experiments. The joints are formed by plastic forming. The process is carried out in one step using the principle of pipe expansion, in order to bring the mating surfaces of the two pipes into a suitable position for the subsequent joining, which is created by means of plastic instability and simultaneous pressure flanging. Experimental tests were carried out with the tools designed to create most suitable joints. The length of the plastically formed pipe sections involved in the joint, the angle of the sharpened pipe ends, and the thickness of the formed joints were analyzed. One of the main goals of this study is to determine the proper joining parameters, such as tool distance or edge tapering for further investigations. As per the test results, it can be stated that the technology is suitable for joining aluminum tubes in a cost-effective way, and based on the promising strength results, further investigations will be conducted.

Influence of copper content on the structure and properties of aluminium alloys

Designing new aluminium alloys always requires an assessment of the influence of modified contents of the main alloying additions on the required properties for a specific application. The aim of this study was to develop a new alloy with a higher tensile strength than the tensile strength obtained in typical 6xxx series alloys, with a satisfactory hot extrusion ductility. The article presents the results of studies on the influence of copper additions, in three variants, on the structure and mechanical properties of extruded aluminium profiles in various heat treatment states. The base reference for the presented studies was the following aluminium alloys: AlMgSi (EN AW-6063) and AlCuMgMn (EN AW-2017). On this basis, three alloy variants with Cu contents of 2.5, 3.5 and 4.5 weight % were selected. These alloys were cast by vertical semi-continuous casting in the form of ingots with a diameter of 100 mm. Hot deformation studies were carried out in the process of co-extrusion on a semi-industrial line consisting of a horizontal 5 MN press together with auxiliary devices. The extruded profiles were free from defects that could have resulted from the process, such as overheating, cracks and blisters. The materials in the form of extruded profiles, in the heat treatment states T1 and T4, were characterised in terms of structure and mechanical properties. The variants with Cu contents of 2.5 wt% and 3.5 wt% had comparable structure and grain size, and the variant with 4.5 wt% Cu had a finer microstructure. For the studied alloys after heat treatment, higher the strength, higher the Cu content in the alloy, ranging from 445 to 543 MPa. It has been found that it is possible to develop modified aluminium alloys based on the 6xxx series with an increased copper addition (but still below the content typical for Al alloys of the 2xxx series) that will have a strength above 400 MPa. The first variant of the new alloy with a Cu content of 2.5 wt% meets the set goal and meets the requirements set at the beginning of the studies.

Mechanical Responses of Ductile Aluminum Alloy under Biaxial Non-Proportional Tensile Reverse Loading Patterns

This paper deals with the study of the mechanical responses of ductile metals under biaxial non-proportional cyclic loading tests. The biaxially loaded HC specimens manufactured from 4 mm thick aluminum alloy sheets (EN AW 6082-T6) are subjected to various loading paths, including monotonic and cyclic loading conditions. The aim is to investigate the plastic, damage, and fracture behavior of the material under these different loading scenarios. In terms of numerical aspects, a modified anisotropic two-surface cyclic plastic–damage continuum model is used to predict the material behavior in the load-displacement field and different strain fields. Numerically predicted stress states are analyzed in detail to gain a better understanding of the damage mechanisms. Moreover, the scanning electronic microscopy (SEM) pictures taken from the fracture surfaces confirm the dependency of the damage mechanisms on the loading histories. The present work indicates the importance of considering different loading conditions for the accurate prediction of material responses.

Modification of Epoxides with Metallic Fillers-Mechanical Properties after Ageing in Aqueous Environments.

The aim of this research was a comparative analysis of selected mechanical properties of epoxy compounds that were modified with metallic fillers and aged in aqueous environments. The tested epoxy compounds consisted of three components: styrene modified epoxy resin based on Bisphenol A, triethylenetetramine curing agent (resin/curing agent ratio of 100:10) and two types of metallic fillers in the form of particles: aluminum alloy (EN AW-2024-AlCu4Mg1) and tin-phosphor bronze (CuSn10P). Samples were subjected to ageing in 4 water environments: low-, medium- and high-mineralized natural water and in a sugar-containing solution for 1, 2 and 3 months. The epoxy samples were subjected to compressive strength tests in accordance with the ISO 604:2002 standard. It was observed that, among others, the compositions seasoned in low-mineralized water usually achieved the highest average compressive strength. As for filler type, using the bronze filler (CuSn10P) usually achieved the highest average compressive strength results.

MODIFICATION OF THE 5-AXIS TOOLPATH TO INCREASE THE TURBINE HUB SURFACE QUALITY

This industrial article focuses on the finishing machining of workpieces made of aluminium alloy EN AW 7075 with a freeform shape, utilizing minimal material stocks. These workpieces are widely used in sectors like aviation and the energy industry. In these sectors, there is a pressing demand for high-quality production in the initial attempt, eliminating the need for subsequent post-processing operations. The reason for this is to save material and reduce production time. The paper, therefore, deals with a method that involves analysing the shape of a spherical end mill in relation to surface roughness and quality, followed by a mathematical recalculation of the tool path. This approach allows to adjust the machining settings during the preparation phase in order to achieve satisfactory surface quality across the entire machined surface. This method was successfully validated during the final surface treatment of the turbine hubs.

Comparison of Measurement of Aluminium Alloy in High Strain Rate

Abstract This article describes the Split Hopkinson Pressure Bar test of aluminium alloy EN AW 7075-T6. This test is used for material testing at a high strain rate. Two approaches in measurement. In the first case was used one size of specimen and different initial pressure. In the second case was set one initial pressure and three different lengths of specimen. Based on measured data, constants of Johnson-Cook material model for FEM analysis were found.

A study of the erosion characteristics of an EN AE-6060 aluminium alloy processed using middle and high power continuous and modulated water jets

This study investigates the erosion performances of a high-speed modulated jet (MWJ) and continuous water jet (CWJ). Two sets of hydrodynamic nozzles (HDNs) and two circular water nozzles (CWNs) were compared for two levels of hydraulic power (26 and 62 kW), representing middle- and high-power energetic water jets. The HDNs and CWNs were selected based on their size equivalence factor. The erosion effects of modulated and continuous jets were compared using the aluminum alloy EN AW-6060. Owing to the anisotropy of the modulated jet, two orientation angles (0° and 90°) were used in the experiment with a traverse speed of v = 1 mm/s at an optimal standoff distance z (mm). The hydraulic power of the generated water jets was monitored online using a flowmeter and pressure sensor. Overall, 36 runs were performed for mutual comparison. Optical and scanning electron microscopy were employed to investigate the grooves created using these techniques. Achieving a sharper interface in a deeper groove is possible under certain conditions, thereby inducing the effect of the liquid saw blade. In addition, this phenomenon reduces the effect of lateral flow action, which causes significant extrusion of the material above the original plane of the surface when using a pulsating water jet.

Damage and fracture behavior under non-proportional biaxial reverse loading in ductile metals: Experiments and material modeling

This paper deals with a modified anisotropic stress-state-dependent plastic-damage continuum model incorporating combined hardening and softening rules to predict the plastic, damage, and fracture behavior of ductile metals under monotonic and reverse loading conditions. In the experimental part, a newly designed biaxially loaded cruciform flat HC-specimen of aluminum alloy EN AW 6082-T6 was subjected to biaxial non-proportional loading to generate a wide range of stress triaxialities during experiments. Thus, it is enabled to perform shear monotonic and reverse loading superimposed by various preloads without unloading processes. The experimental data reveal the Bauschinger effect, the strength-differential (SD) effect, and the change in the hardening ratio after shear reverse loading. This is captured by a Drucker–Prager-type yield criterion with an extended Voce isotropic hardening and modified Chaboche’s kinematic hardening rule. In addition, the damage surface is assumed to be translated in the direction of the rate of the damage strain. The numerically predicted global force–displacement curves and local strain fields are verified in terms of the digital image correlation (DIC) technique. Moreover, the scanning electron microscopy (SEM) is used to examine the fracture surfaces and to validate the proposed damage constitutive model.

Effects of Zn, Mg, and Cu Content on the Properties and Microstructure of Extrusion-Welded Al-Zn-Mg-Cu Alloys.

The study presents the results of research on the influence of different contents of main alloying additions, such as Mg (2 ÷ 2.5 wt.%), Cu (1.2 ÷ 1.9 wt.%), and Zn (5.5 ÷ 8 wt.%), on the strength properties and plasticity of selected Al-Zn-Mg-Cu alloys extruded on a bridge die. The test material variants were based on the EN AW-7075 alloy. The research specimens, in the form of 100 mm extrusion billets obtained with the DC casting method, were homogenized and extrusion welded during direct extrusion on a 5 MN horizontal press. A 60 × 6 mm die cross-section was used, with one bridge arranged in a way to extrude a flat bar with a weld along its entire length. The obtained materials in the F and T6 tempers were characterized in terms of their strength properties, hardness, and microstructure, using EBSD and SEM. The extrusion welding process did not significantly affect the properties of the tested materials; the measured differences in the yield strength and tensile strength between the materials, with and without the welding seam, were up to ±5%, regardless of chemical composition. A decrease in plasticity was observed with an increase in the content of the alloying elements. The highest strength properties in the T6 temper were achieved for the alloy with the highest content of alloying elements (10.47 wt.%), both welded and solid. Significant differences in the microstructure between the welded and solid material in the T6 temper were observed.

Thermodynamic and Microstructural Analysis of Lead-Free Machining Aluminium Alloys with Indium and Bismuth Additions.

The present study comprises an investigation involving thermodynamic analysis, microstructural characterisation, and a comparative examination of the solidification sequence in two different aluminium alloys: EN AW 6026 and EN AW 1370. These alloys were modified through the addition of pure indium and a master alloy consisting of indium and bismuth. The aim of this experiment was to evaluate the potential suitability of indium, either alone or in combination with bismuth, as a substitute for toxic lead in free-machining aluminium alloys. Thermodynamic analysis was carried out using Thermo-Calc TCAL-6 software, supplemented by differential scanning calorimetry (DSC) experiments. The microstructure of these modified alloys was characterised using SEM-EDS analysis. The results provide valuable insights into the formation of different phases and eutectics within the alloys studied. The results represent an important contribution to the development of innovative, lead-free aluminium alloys suitable for machining processes, especially for use in automatic CNC cutting machines. One of the most important findings of this research is the promising suitability of indium as a viable alternative to lead. This potential stems from indium's ability to avoid interactions with other alloying elements and its tendency to solidify as homogeneously distributed particles with a low melting point. In contrast, the addition of bismuth does not improve the machinability of magnesium-containing aluminium alloys. This is primarily due to their interaction, which leads to the formation of the Mg3Bi2 phase, which solidifies as a eutectic with a high melting point. Consequently, the presence of bismuth appears to have a detrimental effect on the machining properties of the alloy when magnesium is present in the composition.

Tolerance of Al–Mg–Si Wrought Alloys for High Fe Contents: The Role of Effective Si

Aluminum scrap is often contaminated with steel parts, leading to accumulation of Fe in recycled Al alloys. Consequently, low limits for Fe in Al wrought alloys are difficult to meet by recycling without dilution with primary Al. Wrought alloys with a higher tolerance for Fe could help overcome this problem and improve the sustainability of Al wrought products. Here we study the effects of increasing the Fe content in EN AW-6060, 6005A, and 6082 from 0.2 to 0.7 wt pct. The microstructure and mechanical properties of the alloys after extrusion and artificial ageing are compared to the standard alloys. We found that 6082 is more tolerant to above-standard Fe contents than 6005A, which in turn is more tolerant than 6060: the strength of the 6082-based alloy with increased Fe content is comparable to that of standard 6082 and the elongation at break is increased. In contrast, the artificial ageing potential of the 6060-based alloy with more Fe is drastically reduced compared to 6060. This data and literature values show that the effective Si content is a good overall predictor of alloy strength. Effective Si is not bound in AlFeSi-type phases and is available for precipitation hardening. Additional effects of increased Fe levels are discussed.

Analysis of the Combine ECAP's Heat Treatment for Creating Aluminum Chips, as Well as a Correlation and Regression Analysis of the solid-state data

The primary objective of this study is to provide a green solution for aluminum recycling. For the aluminum industry to become more circular, it is crucial that innovative recycling methods be developed to maximize the potential for scrap reuse and reduce CO2 emissions. In this article, we discuss how energy and material costs were reduced by recycling aluminum chip waste without first remelting the chips. Solid state recycling or direct recycling are common terms for the method shown here. Chips are cleaned, cold pre-compacted, and hot direct extruded in the solid state recycling process. This is followed by equal channel angular pressing (ECAP) and heat treatment. The effect of artificial aging time and temperature, as well as holding time during solid solution treatment, on the mechanical characteristics of recycled EN AW 6082 aluminum chips was studied. The studies were carried out using a response surface methodology and a design of experiments strategy. The effect of changing the settings of the heat treatment for the proposed solid state recycling process on the mechanical properties of the recycled samples was modeled using a regression analysis. When compared to commercially manufactured EN AW 6082 aluminum alloy in T6 temper condition, the mechanical properties of the recycled samples obtained using the innovative process were found to be comparable. The recycled samples were also analyzed using metallography. Models using regression and correlation analysis have been created to describe the impact of heat treatment settings on the mechanical properties of the generated samples reported in the statistical analysis. using MATLAB as analytical program to conduct correlation and regression.

Experimental and Theoretical Research on Welded Aluminium X‐Joints

AbstractAluminium provides many advantages as a construction material in civil engineering, such as for example light weight, functionality by extruded profiles and corrosion resistance. It is obvious to use these advantages also for trusses. However, most aluminium alloys develop zones of weakening due to welding. The so called heat affected zones (HAZ) reduce the load‐bearing capacity of welded aluminium joints by up to 50%. Consequently, the design and execution of welded X‐joints within lattice girders are challenging. Indeed, the design of welded aluminium X‐joints is not specifically treated in EN 1999. Until now, the calculation of aluminium welded X‐joints relies on the steel standard EN 1993‐1‐8, which does not take into account the characteristic of aluminium. This results in errors and inefficient design. Thus, in this experimental research project the behavior of welded X‐joints in real‐scale models is explored. To this purpose, tests have been carried out on lattice girders made from aluminium alloy EN AW 6082 T6. In total, six girders with varying coefficient β and shape of the hollow section of brace members have been investigated. Thereby, the girders were loaded vertically until the failure of the X‐joints. Strains at the brace and chord members were measured by strain gauges and respective stresses were derived. In addition, a comparative analysis between experimentally and theoretically ‐ based on Eurocodes (EN 1993 part 1‐8 and EN 1999 part 1‐1) ‐ obtained results has been made. The analysis shows that the reduction of the load‐bearing capacity of welded aluminium X‐joints due to the HAZ is not constant but varies with the value of coefficient β and the shape of the cross‐section of the brace member. Obviously, the design of welded aluminium X‐joints based on EN 1993‐1‐8 applying a constant value for the HAZ does not reflect the true behavior of these joints as it leads to a quite conservative design approach.

An analysis of longitudinal residual stresses in EN AW-5083 alloy strips as a function of cold-rolling process parameters

Abstract Various process nonhomogeneities in the cold rolling lead to an uneven distribution of deformation across the strip cross-section, resulting in the induction of residual stresses. This study investigates the longitudinal residual stresses in cold-rolled EN AW-5083 aluminum alloy strips using the finite element method (FEM) to achieve reliable predictions. The impacts of process parameters, including the reduction ratio, coefficient of contact friction, and front and back tensions, were analyzed. Changes in residual stresses, depending on the process parameters, were determined by the distribution of linear and shear strains, as well as the strain hardening conditions at the exit part of the deformation zone. An increase in the reduction ratio from 20 to 50%, as well as an increase in the friction coefficient from 0.1 to 0.2, resulted in decreased stress values. The residual stresses on the strip surface, determined by the experimental deflection method, were consistent with the results obtained by FEM simulation. Under the impact of back and/or front tensions, there is a reduction in longitudinal residual stresses, with the front tension exerting the greatest influence. The research results show that the FEM is a reliable tool for predicting residual stresses in cold-rolled strips.

Fracture Characteristics of EN AW 1200 Tensile Test Specimens Joined with FSW and SFSW Processes

The aim of the current study is to perform a preliminary analysis on specimens extracted from 4 mm sheets of EN AW 1200 alloys that were butt-joined using FSW and two SFSW processes. The purpose of this scientific investigation is to promote the suitability and advantages of new ecological joining processes by implementing SFSW in the automotive, naval, railway and aerospace industry. The papers authors performed destructive testing on specimens extracted from sheets joined with the above mentions processes, namely tensile strength test according to SR EN ISO 6892-1:2020. Researchers also performed topography analysis on samples extracted from the AW 1200 but-joined similar sheets using scanning electron microscopy – SEM, combined with energy dispersive X-ray analysis EDAX. Results from the tensile tests highlighted an improvement in the ultimate tensile strength of the welded butt-joint, if compared to regular FSW results. The highest tensile strength value resulted from the samples extracted from joints performed using the second version of SFSW process. Researchers also noticed that samples broke in the weld or transition area. There was also a change in the chemical composition of the sample performed using the first SFSW method, namely, a high concentration of oxide appeared (≥18%), leading to the conclusion that the module used induces rapid oxidation of joints. Experimental data doesn’t comply with automotive, railway, naval and aerospace-imposed compliances, thus further investigations should be done to improve the application of the technology.