Aerospace Grade Aluminum Alloy Research Articles

Surface etching-reconstruction effectively suppresses icing in jet fuel pipeline

In extreme weather, icing in aircraft fuel systems poses a serious threat to flight safety. Moisture in fuel can freeze inside pipes at high altitudes, risking engine operation and performance. This study explores the use of superhydrophobic technology to prevent icing. Aerospace-grade aluminum alloy (6061) was chemically etched with FeCl3 to create rough micro and nano structures. The surface was then modified with low surface energy perfluoropolyether (PFPE) to form a superhydrophobic coating. Tests showed that a 1.0 wt% PFPE coating exhibited excellent superhydrophobic and oleophobic properties, with a water contact angle of 154.79° and a jet fuel (RP-3) contact angle of 150.13°. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) analyses confirmed the presence of C-F3 and C-F2 bonds. The electrochemical corrosion resistance test shows that the coating has good corrosion resistance and the corrosion resistance rate is 0.61 mm/a. The coating also demonstrated outstanding waterproof performance, resisting grease and stain adhesion under jet fuel immersion. This approach offers a promising solution for surface protection and functional material design. Future research will further optimize its performance and explore broader applications.

Modelling and Characterisation of Orthotropic Damage in Aluminium Alloy 2024.

The aim of the work presented in this paper was development of a thermodynamically consistent constitutive model for orthotopic metals and determination of its parameters based on standard characterisation methods used in the aerospace industry. The model was derived with additive decomposition of the strain tensor and consisted of an elastic part, derived from Helmholtz free energy, Hill's thermodynamic potential, which controls evolution of plastic deformation, and damage orthotopic potential, which controls evolution of damage in material. Damage effects were incorporated using the continuum damage mechanics approach, with the effective stress and energy equivalence principle. Material characterisation and derivation of model parameters was conducted with standard specimens with a uniform cross-section, although a number of tests with non-uniform cross-sections were also conducted here. The tests were designed to assess the extent of damage in material over a range of plastic deformation values, where displacement was measured locally using digital image correlation. The new model was implemented as a user material subroutine in Abaqus and verified and validated against the experimental results for aerospace-grade aluminium alloy 2024-T3. Verification was conducted in a series of single element tests, designed to separately validate elasticity, plasticity and damage-related parts of the model. Validation at this stage of the development was based on comparison of the numerical results with experimental data obtained in the quasistatic characterisation tests, which illustrated the ability of the modelling approach to predict experimentally observed behaviour. A validated user material subroutine allows for efficient simulation-led design improvements of aluminium components, such as stiffened panels and the other thin-wall structures used in the aerospace industry.

Sustainable recycling of aluminum scraps to recycled aerospace-grade 7075 aluminum alloy sheets

The production of aerospace-grade aluminum alloy sheet is characterized by stringent demands, resulting in a low yield rate. The processing of this material generates considerable amounts of highly alloyed scrap, complicating its recycling due to the challenge of maintaining melt cleanliness. This study employed an aerospace-grade melt refining system to purify the recycled 7075 alloy melt obtained from comprehensive scrap remelting. The melt's cleanliness was assessed using Porous Disc Filtration Analysis (PoDFA) and Liquid Metal Cleanliness Analyzer (LiMCA) and Alscan. The microstructure of the ingots and sheets was examined through Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD), whereas the mechanical properties of recycled sheets were evaluated and benchmarked against those of primary sheet at an aerospace-certified testing facility. The findings indicate that the recycled 7075 sheet meets aviation standards, with no significant differences in microstructure or performance when compared to primary sheet. Furthermore, the study highlights the economic benefits of recycling scrap, revealing a potential cost saving of $4210.8 per ton of recycled sheet. The findings presented herein offer a theoretical framework and empirical evidence supporting the development of a recycling system for aerospace scraps and the certification of airworthiness for recycled aerospace aluminum alloy.

CHARACTERIZATION OF SURFACE, SUBSURFACE DAMAGE AND THEIR EFFECT ON FATIGUE LIFE AFTER MACHINING OF AEROSPACE-GRADE ALUMINUM ALLOY (Al 6082-T6)

Aluminum alloys are widely used in the automotive and aerospace industries due to their lower mass-to-strength ratio than other metallic alloys. Apart from their inherent properties, aluminum alloys like other metallic alloys show a significant change in their mechanical properties according to the machining parameters. The research literature on obtaining optimum mechanical properties of aluminum alloys that undergo machining is very limited. Moreover, the combined effect of several parameters on the machinability of aluminum alloys has not yet been explored. In this paper, the effect of three machining parameters (Depth of Cut (DoC)), feed rate (FR), and cutting speed (CS) on the subsurface damage and fatigue life of aerospace-grade aluminum alloy (Al-6082-T6) is observed. Samples are prepared using a full fractional approach to effectively capture the effect of all input parameters. Thereafter, samples were subjected to surface roughness, micro-hardness, and fatigue life tests. Results of surface roughness and micro-hardness tests are compared with fatigue life. The general linear model was employed to capture the percentage effect of each input parameter on the output parameters. The results showed that DoC was the main contributing factor that caused subsurface damage, while surface roughness and fatigue life were mainly affected by FR and CS. Optical microscope images showed a white layer formation that had higher hardness than the base metal. Overall, this research work proposes the input parameters that can be used to achieve minimum surface damage and fatigue life.

Role of stacking sequence, metal sheets, and nano particle on strength and toughness of FMLs

The effect of nano particle inclusion and the stacking sequence/metal volume fraction on the tensile strength and energy absorption properties of Fiber Metal Laminates (FML) is investigated. The FML structure is composed of lightweight thin sheets of aerospace grade aluminum alloy 7075 and unidirectional glass fiber composite sheets with Araldite LY5052 thermoset epoxy system as the matrix. The volume fraction of aluminum sheets in the FML structure was varied by increasing the number of aluminum sheets from 2 to maximum 4. In the second batch, the epoxy matrix is reinforced with of multi-walled carbon nano tubes and nano diamond particles together, each with 0.15 wt%. The purpose is to enhance the properties of the epoxy matrix to facilitate higher inter-laminate adhesion (FRP and aluminum). The results of the tensile testing show that with the increase of the metal volume fraction, the tensile strength as well energy absorbing capability (toughness) both are increased. The inclusion of the nano-reinforcements has increased the tensile strength and the toughness of the FML structure as compared to that of the FMLs without nano particles. The strength-to-weight ratio of FML structures is also increased after the inclusion of nano reinforced as desired for aerospace applications.

Mechanical response of reduced graphene oxide (rGO) reinforced epoxy adhesive joints

The present work aims at investigating the effect of adhesive modification on the lap shear strength of the adhesively bonded joints. The epoxy-based adhesive is reinforced with reduced graphene oxide (rGO) at different weight fractions. Single lap joints (SLJ) have been prepared by considering the commercially available aerospace-grade aluminum alloy AA8011 as the adherend material and Araldite 2014 A/B as the adhesive. Experiments showed that the addition of 0.5 wt.% graphene to the epoxy adhesive resulted an approximately 27% increase in the lap shear strength of the SLJ. Further increase in the reinforcement loading decreases the lap shear strength due to the agglomeration of graphene particles. A detailed analysis of the effect of reinforcement loading and overlap length on the shear strength has been presented and failure mechanisms are discussed.

3D printing of continuous carbon fibre reinforced polymer composites with optimised structural topology and fibre orientation

This study presents a sequentially coupled optimisation of structural topology and fibre orientation for 3D printing of continuous carbon fibre reinforced polymer composites. Topology optimisation was first performed to obtain the geometry of the structure under a specific load, and then continuous fibres were placed along the identified principal stress trajectories. Composite preforms were 3D printed by a material extrusion-based technique followed by post-processing with vacuum bagging using epoxy for infusion. The case of Messerschmitt-Bolkow-Blohm (MBB) beam under three-point bending test was studied and a path-based model was also built to analyse the effect of customised fibre placement and their lightweight performance. Experimental results showed that 3D printed composites with optimised fibre orientation achieved 305% and 256% higher strength and stiffness than Markforged® printed composites. By comparing with the traditionally-manufactured composites and aerospace-grade aluminium alloy, this study demonstrated the potential of manufacturing ultra-lightweight composite structures via 3D printing and the benefits of fibre orientation optimisation in lightweight design of composites with topology optimisation.

An experimental and simulation study of various geometric modifications effects in single lap joint

This research explores the effects of various local geometrical modifications on failure characteristics of single lap joint via an experimental study. The study was coupled with a numerical investigation by using a commercially available finite element software Abaqus®. Aerospace-grade aluminum alloy 6061-T6 was used as adherends in the fabrication of lap joints. The adherends were bonded with Araldite® 2011 structural adhesive. Geometric techniques ranging from the external taper, internal taper, adherend rounding, adhesive fillets, and a combination of internal taper with adhesive fillet were examined. Each geometric configuration was evaluated experimentally and numerically using a parametric methodology. The best-performing parameter of each geometric configuration was then compared with the others for the reduction in adhesive stresses and failure load. The geometric configuration of internal taper with adhesive fillet showed the highest reduction in both peel and shear stresses of 88.58% and 39%, respectively, which was subsequently reflected by the maximum improvement in failure load of 60.29% when compared to the base geometry without any modification.

Tailoring surface properties of aerospace-grade aluminium alloy through solid-state friction stir processing

Aerospace grade AA7075-T6 alloy was friction stir processed at different tool rotation speeds and traverse speeds with a square profiled pin and the resulting microstructural evolution, texture formation and mechanical properties were analysed in this study. Low-magnification optical macroscopy, electron back-scattered diffraction, and bulk-texture analysis were conducted to probe material consolidation, microstructural grain refinement and crystallographic orientation of the grains inside the stir zone. Mechanical properties such as microhardness and tensile strength analysis were further conducted and the results correlated. Macrostructural observations show better consolidation in the specimens processed at 1050 r/min with 30 and 60 mm/min traverse speeds, and 1200 r/min with 30 mm/min as traverse speed. Electron back-scattered diffraction results confirm significant grain refinement in the sample processed at 1050 r/min, 60 mm/min and having a minimum grain size of 3.49 μm. Bulk-texture analysis indicated the presence of randomized grain orientation with copper and S as major texture components. Maximum hardness and tensile strength of 147.1 HV and 432 MPa were exhibited by the specimen processed at 1050 r/min and 60 mm/min due to grain refinement, increased dislocation density and finely distributed strengthening precipitates. Unprocessed base material displayed bimodal ductile and brittle mode of failure, while ductile fracture behaviour was exhibited by the friction stir processed specimen.

Dispersion of CNTs into an Aerospace-Grade Aluminum Alloy

Dispersion of CNTs into an Aerospace-Grade Aluminum Alloy

Development of friction stir powder deposition process for repairing of aerospace-grade aluminum alloys

This paper presents development of a novel friction stir powder deposition (FSPD) process for potential repairing applications of aerospace-grade aluminum alloy AA6061-T6. Powder form of the deposition material was thermo-mechanically processed at a temperature below its melting point. Influence of various process parameters on thermal cycles, deposition quality, deposition height, microstructure, and mechanical properties have been studied. Higher degree of deformation resulted in a dynamically recrystallized fine-grained microstructure which gave better mechanical properties. EDS study revealed uniform distribution of the major alloying elements throughout the deposition. Best quality deposition showed maximum microhardness and wear rate 0.84 and 1.07 times respectively than the substrate AA6061-T6 alloy. FSPD process is found to be capable of depositing maximum height of 0.45 mm, maximum deposition efficiency of 22% with an energy consumption of 73.7 J/mm 3 per unit deposition material consumption. Moreover, it used current in the range of 5-7 Ampere. This research shows that FSPD process can provide considerable cost and energy savings over fusion-based additive manufacturing processes making it a viable alternative for repairing aerospace-grade aluminum alloys. • Developed friction-stir powder deposition as a solid-state AM process for aerospace-grade Al alloys. • Max. deposition height: 0.45 mm; deposition efficiency: 22%; Avg. peak temperature: 293 °C. • Higher deformation gave dynamically recrystallized fine-grained microstructure. • Uniform distribution of alloying elements in the deposition. • Deposition microhardness and wear rate are 0.84 and 1.07 times than substrate AA6061-T6.

Comparative analyses and investigations of chamfered and honed-edge tool geometries on tool wear, chip morphology, residual stresses and end-burr formation

Cutting simulations for chamfered-edge and honed-edge tools for rough-to-semi finishing operations in machining an aerospace grade aluminum alloy AA2024 have been presented in this work. A finite element based approach has been developed to comprehend and investigate the relative effects of various cutting edge geometries on chip morphology, end-burr and residual stresses. Additionally, the role of chip-breaker geometry in segmentation and fragmentation has been thoroughly examined. Moreover, to estimate the expected wear in different sections of the tool, stress fields have been plotted. Furthermore, effects of chamfered-tool' macroscopic parameters: chamfer-length and chamfer-angle on various aspects of cutting process have been discussed. Presented coupled temperature-displacement numerical model has been validated for various results concerning chip morphology, cutting forces and segmentation frequency with previously performed experimental work. Finally, recommendations are made for proper selection of tool-geometry for better tool life, surface integrity and lesser burr formation in machining AA2024.

Comparative Studies on Normal and Pulsed Cold Metal Transfer Welding of Aerospace Grade Aluminum Alloy 2024

Abstract Aluminum alloy 2024 (AA2024) sheets are mostly used in the fuselage and wings of the aircraft and structural applications; it is because of better fatigue resistance and high strength. The joining of AA2024 through gas metal arc welding (high heat input) is complicated because of hot cracking (solidification cracking), softening of the heat-affected zone (HAZ), and formation of porosity. However, these problems could be minimized by employing cold metal transfer (CMT) (low heat input) welding. The ultimate aim of the present research is to compare the metallurgical integrity and mechanical properties of the butt-welded AA2024 through normal CMT (N-CMT) and pulsed mode CMT (P-CMT) methods. The fine-grain structure observed in the P-CMT contributed better mechanical properties compared to N-CMT. The segregations of magnesium, silicon, and copper have revealed the intermetallic compounds such as aluminum-copper (2:1), Al2CuMg, magnesium silicide, and tetracopper silicide. This results in an intergranular fracture of both N-CMT and P-CMT joints. Besides, P-CMT exhibited a higher ultimate tensile strength and % elongation than the N-CMT. Also, the joint efficiencies of N-CMT and P-CMT were 64 % and 68 %, respectively. Furthermore, the hardness value in HAZ of N-CMT (93 HV) was inferior to P-CMT (126 HV). Hence, P-CMT is recommended for joining AA2024 compared to N-CMT.

Numerical Investigation into In-Plane Crushing of Tube-Reinforced Damaged 5052 Aerospace Grade Aluminum Alloy Honeycomb Panels.

This paper aims to investigate the crashworthiness performance degradation of a damaged 5052 aluminum honeycomb panels under in-plane uniaxial quasi-static compression and the possibility of improving it using reinforcement tubes. The in-plane crushing behaviors and energy absorption capacities of the intact, damaged, and tube-reinforced damaged panels with different damage sizes in both X1 and X2 directions are numerically simulated by using the nonlinear FE method Abaqus/Explicit, and the crashworthiness performances are compared with each other. The validation of finite element model involves comparing the obtained simulation results with theoretical and experimental ones. Very good agreement between numerical, experimental, and theoretical results is achieved. The first maximum compressive load and the mean crushing load of the different honeycomb configurations are analyzed and compared through the load–strain curves. The energy absorption capacity of the damaged and the tube-reinforced damaged panels is calculated and then compared with their corresponding intact ones. The deformation modes are explained in detail. The obtained results show that the crashworthiness performance degradation is directly proportional to the damage size as well as the insertion of reinforcement tubes considerably improves in-plane crushing resistance of damaged honeycomb panels.

Hot extrusion of an aerospace-grade aluminum alloy modified with rare earths

Hot extrusion of an aerospace-grade aluminum alloy modified with rare earths

Microstructure, Tensile and Flexural Strength of Boron Carbide Particles Reinforced Al2030 Alloy Composites

Objective: To synthesize and assess the mechanical behaviour of 12 wt. % of 80 to 90 micron sized B4C reinforced Al2030 alloy metal composites. Method: Al2030 alloy with 12 wt. % of B4C reinforced composites were developed by liquid melt stir cast method. These prepared composites were subjected to microstructural characterization by SEM, EDS and XRD. Mechanical properties like hardness, tensile and flexural strength were evaluated according to ASTM standards. Findings: Scanning electron micrograph of Al2030 alloy with 12 wt. % of B4C composites revealed the thorough distribution of boron carbide particles in the Al2030 matrix. EDS and X-ray diffractometer patterns confirmed the presence of boron carbide particles in the Al2030 alloy matrix. The addition of 12 wt. % of B4C particles enhanced the hardness by 74.8%, ultimate strength by 59.2%, yield strength by 64.8% and flexural strength by 44.2% with slight decrease in ductility. Novelty: Al2030 alloy is an aerospace grade aluminium alloy widely used for industrial applications. Advanced metal composites developed with the incorporation of 80 to 90 micron sized B4C particles in Al2030 alloy helps in weight reduction of aerospace components. Keywords: Al2030 Alloy; B 4 C Particles; Microstructure; Tensile Strength; Flexural Strength; Fractography

Microsecond Laser Texturing of an Aerospace Grade Aluminum Alloy to Synthesize Superhydrophobic, Anti-Water Clogging Surfaces

Traditionally superhydrophobic surfaces are prepared by applying liquid repellant organic coatings or nano-based coatings. These superhydrophobic coatings are prone to wear and can be easily damaged by abrasion and cleaning. Recently researchers are switching interest to more efficient and promising technology of pulse laser texturing for engineering sub-micron topographies to have superhydrophobic surfaces. In this research, the micro-second Laser Pulses are used to feature sub-micron textures on titanium nitride coated aluminum and polished aluminum surfaces in order to achieve the water contact angle greater than 150°. Titanium nitride coated aluminum surface with scan line separation of 50 µm shows superior hydrophobicity having a water contact angle of 156º. These superhydrophobic aluminum surfaces have applications for anti-water clogging and anti-corrosion use.

Fracture behaviour of friction stir welded dissimilar aluminium alloys

High strength aerospace grade aluminium alloys are considered difficult to be welded by conventional fusion welding processes but Friction stir welding (FSW) process can effectively join these alloys with good joint properties. FSW is being widely used in aircraft construction and tank of space shuttles. After successful joining of Aluminium alloys by FSW, the fracture behavior of the joint need to be investigated for analyzing the joint fracture. In the present paper, dissimilar aluminium alloys were welded successfully at a rotational speed of 710 rpm, traverse speed of 160 mm/min and tool shoulder diameter of 12 mm. The welded joint was tested on tensile testing machine and the fracture location was found to be at heat affected zone (HAZ) of advancing side. HAZ was found to be the weakest portion of the joint due to thermal softening which resulted in grain growth and large-sized coagulated precipitates. Cracking of large-sized coagulated Al2Cu precipitates resulted in the fracture of the welded joint.

Numerical Modeling the Effects of Chamfer and Hone Cutting Edge Geometries on Burr Formation

A finite element based numerical model to simulate orthogonal machining process and associated burr formation process has been developed in the presented work. To incorporate simultaneous effects of mechanical and thermal loadings in high speed machining processes, Johnson and Cook`s thermo-visco-plastic flow stress model has been adopted in the conceived numerical model. A coupled damage-fracture energy approach has been used to observe damage evolution in workpiece and to serve as chip separation criterion. Simulation results concerning chip morphology, nodal temperatures, cutting forces and end (exit) burr have been recorded. Model has been validated by comparing chip morphology and cutting force results with experimental findings in the published literature. Effects of cutting edge geometries [Hone and Chamfer (T-land)] on burr formation have been investigated thoroughly and discussed in length. To propose optimum tool edge geometries for reduced burr formation in machining of an aerospace grade aluminum alloy AA2024, numerical analyses considering multiple combinations of cutting speed (two variations), feed (two variations) and tool edge geometries [Hone edge (two variations), Chamfer edge (four variations)] have been performed. For chamfer cutting edge, the “chamfer length” has been identified as the most influential macro geometrical parameter in enhancing the burr formation. Conversely, “chamfer angle” variation has been found least effecting the burr generation phenomenon.

T-FSW of Dissimilar Aerospace Grade Aluminium Alloys: Influence of Second Pass on Weld Defects

The restoration of numerous aircraft structures is achievable with effective repair of welded joints. T-joints are often utilized in these structures to provide structural stability, keeping minimal body weight. Multi-pass friction stir welding (FSW) has proved to be useful for improving the quality of aluminium alloy welds employed in the aerospace sector. However, FSW of these alloys in T-configuration has not been sufficiently addressed yet. Even rarer is the discussion of efficacy of second FSW pass, with altered process parameters for improving the weld quality in T-joints. Hence, two commonly used aerospace grade aluminium alloys, namely, AA2024 and AA7075, were friction stir welded in T-configuration, varying three process parameters, i.e., tool rotational speed, welding speed and shoulder diameter. The effect of second FSW pass, performed at an optimum set of parameters, on kissing bond and tunnelling defect was studied in detail. A substantial reduction in the detrimental effect of these weld defects was discussed via tensile testing, micro-hardness and micro-structural observations.