Showing papers on "Aluminium alloy published in 2022"

Review of High-Strength Aluminium Alloys for Additive Manufacturing by Laser Powder Bed Fusion

Abstract: Laser powder bed fusion (LPBF) is one of the major additive manufacturing techniques that industries have adopted to produce complex metal components. The scientific and industrial literature from the past few years reveals that there is a growing demand for the development of high-strength aluminium alloys for LPBF. However, some major challenges remain for high-strength aluminium alloys, especially in relation to printability and the control of defects. Possible strategies that have been identified to achieve high strength with printability include the adaptation of existing high-strength cast and wrought alloys to LPBF, the design of new alloys specifically for LPBF, and the development of aluminium-based composites to achieve unique combinations of properties and processability. Whilst review papers exist for aluminium alloys in general for the related work up to 2019, the purpose of this paper is to review the latest developments related to high-strength aluminium alloys for LPBF up to early 2022, including alloy and process design strategies to achieve high strength without cracking. It aims to provide fresh insights into the current state-of-the-art based on a review of extensive yield strength data for a wide spectrum of aluminium alloys and tempers that have been studied and/or commercialised for LPBF.

Recent Developments and Future Challenges in Incremental Sheet Forming of Aluminium and Aluminium Alloy Sheets

Abstract: Due to a favourable strength-to-density ratio, aluminium and its alloys are increasingly used in the automotive, aviation and space industries for the fabrication of skins and other structural elements. This article explores the opportunities for and limitations of using Single- and Two Point Incremental Sheet Forming techniques to form sheets from aluminium and its alloys. Incremental Sheet Forming (ISF) methods are designed to increase the efficiency of processing in low- and medium-batch production because (i) it does not require the production of a matrix and (ii) the forming time is much higher than in conventional methods of sheet metal forming. The tool in the form of a rotating mandrel gradually sinks into the sheet, thus leading to an increase in the degree of deformation of the material. This article provides an overview of the published results of research on the influence of the parameters of the ISF process (feed rate, tool rotational speed, step size), tool path strategy, friction conditions and process temperature on the formability and surface quality of the workpieces. This study summarises the latest development trends in experimental research on, and computer simulation using, the finite element method of ISF processes conducted in cold forming conditions and at elevated temperature. Possible directions for further research are also identified.

Precipitation phenomena in impulse friction stir welded 2024 aluminium alloy

Abstract: Microhardness variations across the friction stir welded (FSW) and impulse friction stir welded (IFSW) AA2024–T351 joints have been elucidated by the transformations of the S–Al2CuMg phase with a special focus on a distinguished hardness peak within the heat-affected zone (HAZ) of the impulse welds. The increase in hardness within the stir zone (SZ) originated from the partial re-precipitation of the initial Guinier–Preston-Bagaryatsky zones (GPB) and metastable S needles, previously dissolved.) Formation and growth of stable S precipitates via coalescence accounted for the softening through the thermo-mechanically affected zone (TMAZ). The peak strengthening within the HAZ of the IFSW joints was mainly caused by the dense needle-shaped S particles, which can be explained by a mutual influence of the process specific temperature and strain cycles. Dislocations and subgrain boundaries introduced to the material due to plastic deformation facilitated the nucleation of strengthening S precipitates in the HAZ. It demonstrates that the impact of deformation should be considered by the characterization of the precipitation development in the HAZ.

Local and distortional buckling behaviour of aluminium alloy back-to-back channels with web holes under axial compression

Abstract: Aluminium alloy back-to-back channels are becoming popular in building structures. These back-to-back channels often include web holes for installation of services. No previous research, however, is available in the literature for compressive behaviour of aluminium alloy back-to-back channels with web holes. This paper presents an experimental and numerical investigation on the behaviour of screw fastened back-to-back built-up aluminium alloy stub and short columns with web holes under axial compression. Fourteen tests were conducted in total, the results of all are reported in this paper. Prior to compression tests, tensile tests were conducted to determine the material properties of test specimens and initial geometric imperfections were also measured using a laser scanner. A non-linear finite element (FE) model was then developed, and the results were compared against the experiment results showing a good match in terms of both the axial strength and failure modes. Based on 720 FE models, a comprehensive parametric study was conducted to investigate the effects of hole size, screw spacing, section thickness, column length and modified slenderness on structural behaviour of back-to-back built-up aluminium alloy channel columns. Furthermore, the performance of current design guidelines by Australian/New Zealand Standards (AS/NZS) and the American Iron and Steel Institute (AISI) standards was assessed by comparing the axial strengths obtained from the experiments and FEA. It is shown that the AISI & AS/NZS (4600:2018) are conservative by 10% on average, when compared against the test results. Parametric study results were used to propose the axial strength reduction factor equations for aluminium alloy back-to-back channels, and thereafter a reliability analysis was performed. The results of reliability analysis showed that the proposed equations could closely predict the reduced axial strength of aluminium alloy back-to-back channels with web holes.

Concrete-filled and bare 6082-T6 aluminium alloy tubes under in-plane bending: Experiments, finite element analysis and design recommendations

Abstract: The application of aluminium alloys in structural engineering is growing owing to their high strength-to-weight ratio, aesthetic appearance and excellent resistance to corrosion. However, the low modulus of elasticity of aluminium poses adverse effects on the flexural response of structural members made of aluminium alloys. In case of tubular members, the performance can be improved with the addition of concrete infill. Research on the flexural response of concrete-filled aluminium alloy tubes is still minimal. This study presents experimental and numerical investigations on the behaviour of concrete-filled and bare 6082-T6 aluminium alloy tubular members under in-plane bending. In total 20 beams, including 10 concrete-filled aluminium alloy tubular (CFAT) and 10 bare aluminium alloy tubular (BAT) specimens, were tested. The specimens comprised of square and rectangular hollow sections and were filled with 25 MPa nominal cylinder compressive strength concrete. The experimental results are reported in terms of failure mode, flexural strength, flexural stiffness, ductility and bending moment versus mid-span deflection curve. Compared to the BAT specimens, the counterpart CFAT specimens have shown remarkably improved flexural strength, stiffness and ductility due to the concrete infill and the improvement is more pronounced for the specimens with thinner sections. Finite element models of BAT and CFAT beams were developed by taking into account the nonlinearities in geometry and material and validated against the experimental data. A parametric study considering a broad range of cross-sections and different concrete grades was conducted based on the validated models. The FE results have shown that the flexural strength of the BAT and CFAT members increases with the increase of cross-sectional aspect ratio, wall thickness and concrete grade. The results obtained from experiments and numerical analysis for BAT members were used to assess the flexural capacity predictions and the applicability of the slenderness limits provided in the European standards. It was demonstrated that the slenderness limits provided by Eurocode 9 are conservative for Class A aluminium sections. Hence, revised Class 1, Class 2 and Class 3 limits are proposed which appear to be better applicable to Class A aluminium alloys. In the absence of design specifications for CFAT flexural members, the design rules for concrete-filled steel tubular flexural members provided by Eurocode 4 were adopted and the material properties of steel were replaced with those of aluminium alloy. It was shown that the proposed design methodology is suitable for the design of CFAT flexural members. Moreover, a slenderness limit for compact sections of CFAT flexural members is proposed based on Eurocode 4 framework.

Friction stir welding for manufacturing of a light weight combat aircraft structure

Abstract: Abstract This paper aims to validate the viability of friction stir welding process (FSW) to join high strength aerospace grade AA2014-T6 aluminium alloy for manufacturing light-weight combat aircraft (LCA) structure as a replacement to riveting process. FSW is used to overcome the heat input-related problems in fusion welding of AA2014-T6 aluminium alloy such as coarse grain fusion zone microstructure, softening in HAZ and lower joint efficiency. The 2 mm thick AA2014-T6 aluminium alloy sheets were used as the base material (BM). Friction stir butt (FBW) and friction stir lap (FLP) joints were developed, and its performance was compared with double cover riveted butt (DRB) joint in butt (RBJ) and lap (RLJ) joint configuration. Results showed that the load-carrying capability of FSW joints is greater than the riveted joints. The superior load-carrying capacities of FBW and FLW joints refers to evolution of refined grains and strengthening precipitates in stirred zone (SZ), which ensures superior metallurgical bonding between the joining surfaces. The riveted joints disclosed inferior load-carrying capacities due to the lack of metallurgical connection between the joining surfaces.

In-situ laser shock peening for improved surface quality and mechanical properties of laser-directed energy-deposited AlSi10Mg alloy

Abstract: In the recent decades, the laser-directed energy deposition (L-DED) of aluminium alloy has encountered significant challenges owing to the defects and tensile residual stress. In this study, the in-situ laser shock peening method is employed for the first time to improve the surface quality and mechanical properties of L-DED-fabricated AlSi10Mg alloy. The physical mechanism of the compressive pressure on the pore defects is accounted for using the finite element method. The numerical results indicate that severe plastic deformation driven by the shock wave contributes to defect healing, and the maximum pressure plays a crucial role. The effects of surface laser shock peening (SLSP) and layer-by-layer laser shock peening (LLSP) on the densification, surface quality, including the roughness and residual stress, microstructure, and mechanical properties of the samples are experimentally studied. After the LLSP treatment, the surface quality and mechanical properties of the samples exceed those of common aluminium alloys fabricated by laser powder bed fusion (L-PBF). After the SLSP treatment, a compressive residual stress with a maximum value of 30 ± 14 MPa is formed on the upper surface, and the LLSP treatment overcome the depth limitation of the affected zone. Furthermore, the LLSP treatment addresses the strength–ductility trade-off, and realizes an excellent combination of strength and ductility through grain refinement, dislocation strengthening, and compressive residual stress. Therefore, this work establishes the viability of in-situ laser shock peening for the rapid additive manufacturing of large-size aluminium alloys. The data used to support the findings of this study are available from the corresponding author upon request.

Observations on comparable aluminium alloy crack growth curves: additively manufactured Scalmalloy® as an alternative to AA5754 and AA6061-T6 alloys?

Abstract: Scalmalloy® has been proposed for use as additively manufactured (AM) replacement aluminium alloy parts for civil and military aircraft, and for AM aluminium parts for use in satellites and space structures. This study builds on the results of a prior investigation to reveal that Scalmalloy® has a crack growth curve similar to those associated with aluminium alloys AA5754 and AA6061-T6, which are widely used in the automotive industry and in maritime vessels. The R = 0.1 da/dN versus ΔK curve for small naturally occurring cracks in LPBF Scalmalloy® is also predicted and the additive manufacturing community is challenged to undertake testing to validate or disprove this prediction.

Microstructural changes and formability of Al–Mg ultrafine-grained aluminum plates processed by multi-turn ECAP and upsetting

Abstract: The article focuses on an evaluation of the microstructure, mechanical properties, anisotropy and formability of ultrafine-grained plates of commercial aluminium alloy 5754, with a main addition of Mg. For manufacturing plates, a hybrid Severe Plastic Deformation process is proposed that combines multi-turn Equal Channel Angular Pressing with upsetting, a conventional metal forming process. It was possible to acquire plates of an average grain size of around 0.4 μm and a fraction of high-angle grain boundaries reaching an average of 70%. Due to the high accumulated strain during the processing, it was possible to achieve a Yield Strength and Ultimate Tensile Strength equal to 430 and 450 MPa, respectively, which is a 200 and 120% increase over the initial condition. The anisotropy of the mechanical properties in plate's plane was negligible. The Lankford parameter was used to evaluate formability, and its values proved to be similar to those acquired from other processing techniques. This combination of a substantial enhancement of mechanical properties and typical anisotropy parameters values offers an attractive technology for the production of high-strength plates suitable for further metal forming.

Design of aluminium alloy channel sections under minor axis bending

Abstract: In recent years, numerous research works have been reported on the flexural response of aluminium alloy tubular cross-sections. However, studies on monosymmetric cross-sections and particularly channel (C-) sections are limited, albeit their increased usage in structural applications. This paper aims to address this knowledge gap providing an improved understanding about the minor axis bending behaviour of C-sections through an experimental and numerical investigation. In total 14 specimens made from 6082-T6 heat-treated aluminium alloy were subjected to four-point bending. Tensile coupon tests were also performed to determine the mechanical properties of the examined aluminium alloy. The obtained experimental results are analysed and discussed. A series of geometrically and materially nonlinear analyses were also carried out to study the flexural performance of C-sections in two aluminium alloys and two bending orientations over a range of cross-sectional aspect ratios and slendernesses. The experimental and numerical results are utilised to assess the European design standards. The applicability of the Continuous Strength Method and the Direct Strength Method is also evaluated. An alternative design method based on the plastic effective width concept is proposed for slender C-sections subjected to minor axis bending. This method accounts for the inelastic reserve capacity which is in accordance with the experimental and numerical observations.

Application of machine learning approaches to predict joint strength of friction stir welded aluminium alloy 7475 and PPS polymer hybrid joint

Abstract: Vehicle weight has been a critical concern in the aerospace and automobile industries for decades. Integrating dissimilar aluminium and polymer hybrid structures is beneficial for weight reduction without affecting structural performance. In the present work, aluminium alloy 7475 and polyphenylene sulfide (PPS) sheets were joined using the friction stir welding (FSW) technology in lap joint configuration. A series of FSW experiments have been performed by the design matrix developed using response surface methodology. Tensile lap shear strength (TLS) is calculated for each experimental run. In this study, an attempt has been made to assess the potential of machine learning algorithms to predict the TLS of the joint. It was found that the support vector machine (SVM) model with RBF kernel was the most effective for predicting the TLS. Furthermore, FSW process parameters are optimized by means of the desirability approach. The optimal set to attain maximum TLS is identified as the tilt angle of 2°, welding speed of 5.12 mm/min and tool rotational speed of 1185.92 r/min. Finally, a confirmation test was performed to validate the optimal set and the adequacy of the developed SVM model. From the confirmation test, the error percentage between experimental and prediction values is less than 5%. Metallographic analysis revealed that the joining mechanism is the macro and micromechanical interlocking assisted by chemical bonding.

Fatigue Analysis of the Microturbine Rotor Disc Made of 7075 Aluminium Alloy Using a New Hybrid Calculation Method

Abstract: Today, where the production of any kind of device may have a negative impact on the environment, it is crucial to produce machines that are as efficient as possible but that can also be strong enough to withstand harsh operating conditions for a long time. That is why this paper raises the issue of the fatigue analysis of high-speed axial-flow microturbines whose components are made of commonly used 7075 aluminium alloy. The paper presents different methods that can be used to estimate and increase the fatigue life of a turbine disc. The object of study is a 10-kilowatt vapour microturbine. The various mechanical, flow and thermal loads that can occur during the operation of the microturbine have been analysed so that the most important ones can be taken into account in the final considerations. Stress calculations were performed using analytical equations, and the finite element method (FEM) was also used. Using the stresses obtained and material characteristics, fatigue analysis was conducted. Then, new hybrid calculation methods were proposed, taking into account both analytical and numerical approaches that do not require the use of ready-made programs dedicated to fatigue analysis. To verify these methods, calculations were performed for two rotor discs with different geometries. These methods can be used by both engineers and scientists in the design process of various microturbines when fatigue calculations are performed.

Optimization of Process Parameters for Friction Stir Welding of Aluminium Alloy AA5052-H32 by Using Taguchi Method

Abstract: This research interacts with the impact on ultimate tensile strength in FSW operation of controllable variables, especially rotational speed of tool, table speed, and shoulder diameter. The experiments were performed through the Taguchi approach on a 3 mm thick AA5052-H32 aluminium alloy sheet. The welded joints were distinguished by their morphology, mechanical properties (tensile strength and microhardness), and microstructural characteristics. “A three-level, three-factor experimental design was carried out using Minitab software in accordance with Taguchi L9 array to determine the most significant variable and % participation of the specific tensile strength variable, analysis of ANOVA, and ratio of signal to noise (S/N)”. As a result, the optimal level for tensile strength was identified to be 1000 rpm of rotational speed of tool, 40 mm/min of table movement, and 12 mm of tool shoulder diameter. Weld joints had a higher tensile strength of 180.12 MPa at 1000 rpm of rotational speed and 40 mm/min of table movement, which was about 79% of the base Al alloy strength. Research on microstructure reveals that the grain size becomes lower in weld stir region than base Al alloy, as well as nugget region will have a significantly higher hardness than base aluminium alloy. As a result, with a contribution of 71.84%, welding speed seems to be the significant contributing factor.