Alloy AA2024-T3 Research Articles

Machinability studies of AA2024-T351 alloy with uncoated carbide tool

AA2024-T351 alloys are widely used in aerospace and automotive industries due to their high strength to weight ratio and ductility. The present paper investigates the machinability of AA2024-T351 material with uncoated carbide tools. Orthogonal machining experiments were performed at varying cutting speeds and feed rates with a constant depth of cut. Machinability studies were done using cutting forces, coefficient of friction and chip morphology. As the feed rate increased both cutting force and feed forces were found to be increased whereas the coefficient of friction decreased. Chip formation process was significantly influenced by the operating conditions. In addition, the shear angle and contact length were determined analytically.

Simulating the Effect of Temperature Gradient on Grain Growth of 6061-T6 Aluminum Alloy via Monte Carlo Potts Algorithm

During heat treatment or mechanical processing, most polycrystalline materials experience grain growth, which significantly affects their mechanical properties. Microstructure simulation on a mesoscopic scale is an important way of studying grain growth. A key research focus of this type of method has long been how to efficiently and accurately simulate the grain growth caused by a non-uniform temperature field with temperature gradients. In this work, we propose an improved 3D Monte Carlo Potts (MCP) method to quantitatively study the relationship between non-uniform temperature fields and final grain morphologies. Properties of the aluminum alloy AA6061-T6 are used to establish a trial calculation model and to verify the algorithms with existing experimental results in literature. The detailed grain growth process of the 6061-T6 aluminum alloy under different temperature fields is then obtained, and grain morphologies at various positions are analyzed. Results indicate that while absolute temperature and duration time are the primary factors determining the final grain size, the temperature gradient also has strong influence on the grain morphologies. The relationships between temperatures, temperature gradients and grain growth process have been established. The proposed MCP algorithm can be applied to different types of materials when the proper parameters are used.

Parametric optimization of friction stir welding of Al-Mg-Si alloy: A case study

Al-Mg-Si alloys have wide applications in industries such as aerospace, marine, automobile, construction. In this work, newly developed friction stir welding (FSW) was utilized for joining of AA6082-T6 alloy. The effect of major FSW process variables like rotational speed, traverse speed, and shoulder diameter of tool is studied over microstructural and mechanical characteristics of friction stir welded (FSWed) joints. Experimental design was done using Taguchi method (L9 orthogonal array). Three factors viz. rotational speed, welding speed, and diameter of tool shoulder were taken at three levels each. Mathematical modelling was developed in order to optimize the tensile strength of weld joints. Analysis of variance (ANOVA) was utilized to determine the percentage contribution of input variables. The results of present study exhibits that shoulder diameter, rotation, and welding speed of tool significantly affect the mechanical strength of FSWed joints.

Fatigue analysis of the friction stir welded AA6061-T6 aluminum alloy

Investigation of mechanical and fatigue behavior is necessary to find out the long-term durability of the welded joints. The current work focuses on the mechanical and fatigue behavior of the joint formed when AA6061-T6 alloy plates were friction stir welded (FSWed) then joint was also analyzed as compared with parent material. The tensile strength and microhardness profile were obtained by the uniaxial tensile test and Vickers hardness test respectively. The maximum yield strength and ultimate tensile strength of the FSWed specimens were found to be 207.2 N mm−2 and 264 N mm−2 which are 72.2% and 80.3% of the parent metal respectively. The minimum value of hardness in FSWed specimen was equivalent to 63% of the parent material. The fatigue tests were carried out in a constant amplitude loading condition at a positive load ratio (R = 0.1). The limit of maximum stress applied during the fatigue tests was determined based on the results of the tensile tests. Microstructural and scanning electron microscope (SEM) examination of welded specimens was also carried out to understand the effect of FSW on microstructural development, commence of fatigue crack, and the way the crack spreads. The outcomes show the formation of a fine-grained microstructure in the center of the weldment. Results of the fatigue tests show that the fatigue strength of both types of configurations i.e. FSWed and parent material were almost the same at the low-stress level. At high-stress level, parent material exhibits superior fatigue strength than FSWed specimens. An effort has also been made to relate the fatigue resistance to the microstructural observations of the welded specimens.

Mechanical Properties and Microstructural Characterization of Dissimilar Friction Stir Welded AA5083 and AA6061 Aluminium Alloys

Solidification is one of the major issues that was faced during the fusion welding of dissimilar non-heat treatable and heat treatable aluminium alloys. To overcome this issue Friction Stir Welding played a very vital role, since it is a solid state welding process. In the current study, dissimilar friction stir welding was carried out between non heat-treatable aluminium alloy AA5083-H111 and heat-treatable aluminium alloy AA6061-T6. The microstructural analysis and the mechanical properties of the dissimilar friction stir welded aluminium alloy AA5083-H111 and AA6061-T6 have been investigated. Both optical microscopy and scanning electron microscopy was used to evaluate the microstructural features. The elemental analysis was carried out using SEM-EDX. The tensile properties are studied using Universal Testing Machine. Hardness at various zones of the welded joints was measured using Vicker’s Hardness Testing Machine. The mechanical properties of the friction stir welded joints were correlated with the microstructure of the dissimilar welded joints.

Interfacial effects on anticorrosive and tribological properties of electrodeposited amorphous carbon film on AA2024-T3 aluminum alloys using ethanol as carbon source

Amorphous carbon (a-C) films were prepared by electrodeposition technique on AA2024-T3 and proposed as an anticorrosive film. Ethanol (CH2CH2OH) was used as carbon source and the electrodeposition was carried under constant voltage of 1200 V or 800 V for 3, 8 and 24 h using a graphite bar as anode and an AA2024-T3 aluminum alloy as substrate.The morphology, structure and chemical properties of a-C films was investigated using Raman spectroscopy, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Raman spectra of 1200 V 24 h electrodeposited film showed the presence of characteristic peaks for a-C films, typical D and G bands at 1373 cm−1 and 1574 cm−1, which proves the formation of amorphous carbon film. Electrochemical measurements was carried in order to evaluate the anticorrosive behavior of a-C film over AA2024-T3 alloy. The interfacial effect (AA2024-T3 alloy /a-C film / Electrolyte) on electrochemical behavior shows a character of pores blockage of amorphous carbon film, which shows a pseudo resistance due to corrosion products into microcracks of film.

Investigation of Surface Corrosion Morphology and Mass Change of Three Aluminum Aerospace Alloys As It Pertains to Corrosion Rate at Various Atmospheric Exposure Sites

Replicate coupons of bare aluminum alloys AA2024-T3, AA6061-T6, and AA7075-T6 are being exposed at two coastal atmospheric test sites, Kennedy Space Center (KSC) and the US Naval Research Laboratory in Key West, FL (NRL-KW). Various analyses including mass loss/mass gain determinations, elemental composition analysis (via scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS)), as well as pit density and pit volume measurements (via 3-dimensional laser/optical microscopy) are being performed to determine if there is a correlation between corrosion rate, corrosion morphology, and surface chemistries of the coupons exposed at the outdoor sites. The sample coupons are being retrieved at 3-month intervals. The aluminum alloy coupons are cleaned until a consistent change in mass between cleaning cycles has been reached per ASTM G1 (Table A1). At this point of the investigation, a cumulative exposure time of 6 months will be discussed and presented. Mass loss data for the bare metal substrates at the two field locations indicate that different mass losses occur at the two locations for similar exposure lengths for all three alloys, but at overlapping time intervals. For the AA7075-T6 alloy, mass gain (negative mass loss values) was measured for the 1Q (3 month) and 2Q (6 month) exposure at the NRL-KW site, whereas mass loss values (positive mass loss values) were determined for the KSC site for similar time exposures; however, replacement replicate AA7075-T6 coupon exposures at the NRL-KW site for the same length of exposure but at a different time interval, exhibited mass loss values (Figure 1).While the observed corrosion rates were different, it was determined that the morphology and elemental composition of the alloy substrates were different as well. Due to the extreme localized pitting attack on the 6061 and 7075 alloys, optical analyses of the coupons indicate that the resulting variability of the mass determinations may be due to incomplete removal of corrosion product from within the subsurface horizontal exfoliating pits populating the exposed coupons. Indeed, the populating of the coupons with these occluded pits was observed to increase with field exposure time at both field exposure sites, resulting in increased variability in mass loss values. These results reinforce the importance of deploying more than a single sample coupon of these aluminum alloys for corrosion rate calculations using mass loss determinations. Pit morphology and elemental analysis of the exposed alloy coupons as a function of exposure time and location will also be presented and discussed.These findings are important in developing accelerated test protocols. In previous laboratory exposure tests it was found that similar mass losses were observed at an accelerated rate in the modified chamber for these alloys versus the field exposures, but the surface morphology of the substrates exposed in the chamber were markedly different from the substrates in the field. Therefore, it may be more informative to consider the elemental composition, pit density and pit morphology of the corroded surface in addition to the mass loss, rather than rely on mass loss alone. Figure 1. Plot of mass loss comparison for aluminum alloys coupons exposed at KSC and NRL-KW for 3 and 6 months. Figure 1

Modeling, Validation, and Application of Finite Element Models for the Galvanic Corrosion of Aluminum Alloy 6061-T6 Coupled to Non-Passivating and Passivating Alloys

Galvanic corrosion of aluminum alloys coupled to non-passivating and passivating alloys exposed in corrosive environments can cause severe corrosion damage in marine structures. The aim of this study is the development of a finite element model using COMSOL Multiphysics to predict the galvanic interaction of aluminum alloy AA6061-T6 coupled to noble materials.The numerical model is based on anodic dissolution kinetics of AA6061 and cathodic kinetics of Ti6Al4V, 316 stainless steel, and copper determined with potentiodynamic polarization. The model predicts that the cathodic material and the geometry of the galvanic couple both influence the corrosion rate of AA6061, and that the solution composition locally changes over time.In order to account for the time-dependent change in solution chemistry a thorough experimental investigation of the effect of pH and chloride ion (Cl-) concentration on the corrosion kinetics of AA6061 is presented using potentiodynamic polarization. Corrosion kinetics were obtained in sodium sulfate and sodium chloride solutions as a function of pH and chloride ion concentration and implemented in the numerical model.The validation of the model is in progress and will be compared to data of actual galvanic couples exposed in the laboratory and in different atmospheric environments. Acknowledgement: This material is based on research sponsored by the USAFA and University of Hawaii under agreement number FA7000-18-2-0004. The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon.

The effect of ultrasonic vibration on stress-strain relations during compression tests of aluminum alloys

Complete understanding of ultrasonic interaction with aluminum alloys is essential to promote application of ultrasonic-assisted friction stir welding process in manufacturing industry. In this study, the ultrasonic-assisted compression tests were performed to investigate the effect of ultrasonic vibration on the stress-strain characteristics of AA2024-T3 alloy. At the same time, AA6061-T6 alloy was also tested, and the stress-strain relations for both alloys were compared and analyzed to study the influence of material properties on the variation of stress-strain characteristics under ultrasonic assisted compression. It was found that on the stress-strain curves of AA2024-T3 there are an obvious and transient stress reduction concave point at the beginning of ultrasonic exertion, a hysteresis of stress recovery and a short-term small hardening phenomenon after the ultrasonic exertion stopped. The results laid foundation for process optimization of ultrasonic-assisted friction stir welding of AA2024-T3.

Mechanical and Abrasive Wear Properties of Friction Stir Welded Joints of Aluminum Alloy AA6061-T6 with/Without Nickel Coating

Abstract The purpose of this work is to examine the microstructure, mechanical and sand abrasive properties of friction stir welded joints of aluminium alloy AA6061-T6 with and without nickel coating. A total eighteen samples, six samples of AA6061-T6 plates, six samples of 10 μm thick Ni coated AA6061-T6 plates and six samples of 15 μm thick Ni coated AA6061-T6 plates were friction stir welded by using different tool rotation speed (710 rpm, 1000 rpm, 1400 rpm) and different welding speed (28 mm/min, 56 mm/min). The joints manufactured using 1400 rpm tool rotation speed and 56 mm/min welding speed generated the highest tensile strength and percent elongation with joint efficiency of 69.05% with 15 μm Ni-coated AA6061-T6 plates and joints manufactured from 10 μm Ni-coated AA6061-T6 plates using 1000 rpm tool rotation speed and 28 mm/min welding speed generated the highest impact energy and higher hardness in NZ compared to the other joints. The 15 μm Ni-coated AA6061-T6 plates exhibited better abrasive wear resistant properties than the 10 15 μm Ni-coated plates. Microstructure investigation showed the precipitate size variations and their distributions and after friction stir welding, these precipitates became slightly coarser in the HAZ but finer in the nugget region.

Effect of revolution speed on the mechanical properties of dissimilar Aluminum alloy joined by friction stir spot welding

Friction stir spot welding (FSSW) method was performed for welding of aluminum alloys AA6061-T6 with pure aluminum AA1100 sheets having thicknesses of 2.4 and 3 mm respectively. FSSW procedure was accomplished at varied tool rotational speeds (1000, 1600, and 2000 rpm). The dwell time was (2, 4, and 6 sec) and the geometry of the tool pin was threaded cylindrical pin with a cylindrical and straight shoulder.The aluminum alloy AA6061-T6 sheet was overlapped on the pure aluminum AA1100 sheet. The tensile shear test was investigated for all specimens. It was deduced that the value of the maximum shear force is 1.95 kN. This value was obtained at the following welding factors: 2000 rpm spindle rotational speed, 4 sec dwell time and threaded cylindrical pin profile, the two other factors which were pin length and plunging time were kept as constant parameters through the tests at 3.2 mm and 40 sec respectively. It was also concluded that the fracture happens in the nugget zone mode at the highest lap-shear load.

Numerical and experimental investigation of the effect of process parameters on sheet deformation during the electromagnetic forming of AA6061-T6 alloy

Abstract. Electromagnetic forming is a high-speed sheet metal forming technique to form metallic sheets by applying magnetic forces. In comparison to the conventional sheet metal forming process, electromagnetic forming is a process with an extremely high velocity and strain rate, which can be effectively used for the forming of certain difficult-to-form metals. During electromagnetic forming, it is important to recognise the effects of process parameters on the deformation and sheet thickness variation of the sheet metal. This research focuses on the development of a numerical model for aluminium alloy (AA6061-T6) to analyse the effects of three process parameters, namely voltage, sheet thickness and number turns of the coils, on the deformation and thickness variation of the sheet. A two-dimensional fully coupled finite-element (FE) model consisting of an electrical circuit, magnetic field and solid mechanics was developed and used to determine the effect of changing magnetic flux and system inductance on sheet deformation. Experiment validation of the results was performed on a 28 KJ electromagnetic forming system. The Taguchi orthogonal array approach was used for the design of experiments using the three input parameters (voltage, sheet thickness and number of turns of the coil). The maximum error between numerical and experimental values for sheet thickness variation was observed to be 4.9 %. Analysis of variance (ANOVA) was performed on the experimental results. Applied voltage and sheet thickness were the significant parameters, while the number of turns of the coil had an insignificant effect on sheet deformation. The contribution ratio of voltage and sheet thickness was 46.21 % and 45.12 % respectively. The sheet deformation from simulations was found to be in good agreement with the experimental results.

A new ductile fracture criterion considering both shear and tension mechanisms on void coalescence

A new ductile fracture criterion is proposed based on three stages of ductile fracture: void nucleation, growth and coalescence from the microscopic viewpoint. Based on the observation of SEM fracture surfaces of AA2024-T351 aluminum alloy sheet and bar samples under different stress states, it is assumed that the void aggregation is controlled by shear or shear-tension fracture mechanism according to the stress state. And the stress triaxiality is deemed as the only influence factor for controlling the void growth. The new ductile fracture criterion applied to a wide range of stress triaxiality is built. By fitting the available testing data of AA2024-T351 aluminum alloy and AISI 1045 steel, the fracture loci in the stress triaxiality, Lode parameter and equivalent fracture strain space ([Formula: see text]) built by the new criterion are compared with those by DF2014, Hu criterion, modified Mohr-Coulomb criterion (MMC) and Hosford- Coulomb (H-C) criterion. The fitting results prove better prediction accuracy for the new criterion. To further compare the stability of these criteria, the fracture loci in the space of ([Formula: see text]) for AA2024-T351 alloy are established by only fitting five tests. The new criterion can still well predict the equivalent fracture strain ([Formula: see text]). Compared with DF2014, Hu criterion, MMC and H-C criterion, the average errors of the new criterion are reduced by 26.72%, 20.07%, 31.78% and 34.62%, respectively. Furthermore, the maximum errors are reduced by 49.62%, 27.31%, 33.76% and 29.91%, separately. Therefore, the new fracture criterion has higher prediction accuracy and better prediction stability. Last but certainly not least, the new criterion can predict more accurately under high stress triaxiality conditions.

Dry Machining Performance of AA7075-T6 Alloy Using Uncoated Carbide and MT-CVD TiCN-Al2O3-Coated Carbide Inserts

The present study examines dry machining performance of AA7075 T6 alloy using uncoated and MT-CVD TiCN–Al2O3-coated carbide inserts. Machining performance is assessed with regard to tangential cutting force, tool tip temperature and depth of flank wear. The performance of coated tool is compared to that of uncoated insert. In addition, different modes of tool wear and chip morphology are studied in detail. It is experienced that coated tool causes lower tool tip temperature and lesser flank wear than untreated counterpart. Apart from abrasion, adhesion and built-up layer formation; attrition wear is distinctly visible in case of uncoated tool. On the contrary, in addition to common wear modes, coated tool also experiences diffusion wear.

Intergranular corrosion of AA6082 Al–Mg–Si alloy extrusion: The influence of trace Cu and grain boundary misorientation

In the present work, the influence of trace level Cu on intergranular corrosion (IGC) in AA6082 Al–Mg–Si alloy is studied using correlative accelerated corrosion testing and high resolution electron microscopy. Further, grain boundary structure and its correlation to IGC are also investigated using electron backscatter diffraction (EBSD) and transmission Kikuchi diffraction (TKD). It is found that in AA6082-T6 alloy with very low Cu content (0.06 wt%), about 13% of high angle grain boundaries have Al2Cu precipitates, which promotes IGC at the grain boundaries.

Enhancement of Anticorrosion Properties of Epoxy Based Primer Coating by Bis[[3,4-Dihydroxyphenylmethylene] carbonothioicdihydrazide] on AA2024-T3 Alloy

A corrosion inhibitor bis[[3,4-dihydroxyphenylmethylene]carbonothioicdihydrazide] (DCT) was synthesized and used to improve the corrosion resistance of an epoxy based primer coating on AA2024-T3 alloy in NaCl solution. The ability of DCT to inhibit the corrosion was evaluated by electrochemical studies. The compound exhibited an inhibition efficiency of 99%. The surfaces of the corroded specimens were characterized by field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The anticorrosion nature of the substrate coated with a commercial epoxy-based primer doped with DCT was evaluated by electrochemical impedance spectroscopy and a salt spray test. The results established not only the ability of DCT to improve the anticorrosion property of the epoxy based primer coating on AA2024-T3 alloy but also a sustained corrosion protection (1000 h) of the alloy.

Modification of the design of circular thin-walled tubes to enhance dynamic energy absorption characteristics: Experimental and finite element analysis

A thin-walled tube is an energy absorber device that functions to dissipate kinetic energy into another form of energy during impact. The design of thin-walled tubes is a significant factor which affects to the energy absorption characteristics. This paper provides a comparative study between the original thin-walled tube designs and several modified tube designs that have been proposed. The main objective is to improve the energy absorption characteristics, such as energy absorption capacity, initial peak load, specific energy absorption (SEA) and crush force efficiency (CFE). Throughout this research, aluminium alloy AA6061-T6 has been used as the material for all tubes. For comparison, all of the tubes are developed with a circular shape with the same diameter, thickness and length. In addition, they are also impacted at the same kinetic energy under dynamic axial loading. Validated LS-DYNA finite element (FE) models have been used to simulate the impact of the thin-walled tubes. Compared to the original tube design, the modified tubes have improved energy absorption characteristics. A conical tube with a flat end cap was identified as the best performing tube among the modified tubes because it had the lowest initial peak load, a moderate energy absorption capacity and an excellent CFE and SEA. The findings from this study can be used as a guidance in designing thin-walled structure.

Analysis of surface roughness and wear resistance in low plasticity burnishing process using multi-objective optimization technique

To improve the mechanical properties of components, low surface plastic deformation caused by low plasticity burning (LPB) process is studied. Multi-objective optimization of process parameters for low plasticity burning on aluminum alloy AA6061T6 has been performed in the present analysis. The burning process parameters are considered for each of four levels such as pressure, speed, ball diameter, ball material, and number of passes. Consideration is given to response parameters such as surface roughness and wear resistance. Experimentation was conducted by considering the Taguchi method design matrix and the orthogonal array L16.In the current research work, multi-objective optimisation was carried out using the Grey Relational Analysis (GRA) technique. The technique is found useful for minimizing roughness of the surface and maximizing wear resistance. After the roughness of the burning surface decreased from 0.688 μm to 0.2593 μm, wear rate also decreased from 4.3076 × 10–3 mm3/Nm to 2.1380 × 10–3 mm3/Nm. The results of the optimization showed that the roughness of the surface decreased by 62%, where the wear rate decreased by 50% compared with the surface turned. The results of multi-objective optimization showed that burnishing pressure and burnishing speed are the important parameters for minimizing surface roughness and maximizing wear resistance.

Laser-interference pulse number dependence of surface chemistry and sub-surface microstructure of AA2024-T3 alloy

The laser-based treatment of a metal surface is an intrinsically non-chemical technique that can alter both the topology and chemistry of surfaces. A laser-based treatment for coating and joining applications can offer alternative surface preparations to the chemically-based surface preparation techniques, which are subject to severe environmental protection and hazardous-waste management considerations. In this study, the surface chemistry and sub-surface microstructural changes are investigated for a novel surface processing method using laser interferometry produced by two beams of a pulsed Nd:YAG laser. The two-beam laser-interference allowed the structuring of the surface at length scales much less than that of the laser beam spot. Surface chemistry changes in the oxide layer of AA 2024-T3 aluminum alloy rolled sheet due to laser processing were investigated using x-ray photoelectron spectroscopy (XPS). Near surface microstructural changes have been investigated with scanning electron microscopy and energy dispersive x-ray spectroscopy (SEM/EDS), and scanning transmission electron microscopy (STEM) as a function of number of interfering laser shots. SEM microstructure pictures of the top surface shows the minimization of surface defects, as all of the sharp features from a rolled sheet surface were smoothed by laser-structuring. STEM images indicate that the laser-interference processing reduced the formation of CuMn-rich precipitates over a 500–800 nm depth from the top surface. XPS data indicated that the Al oxide layer is modified compared to that of the baseline specimen and that the oxide thickness increases with the number of shots per spot. The additional thicker oxide on Al alloys is expected to increase the corrosion resistance of the coated Al 2024.

Joining of Double Pre-Holed Aluminum Alloy AA6061-T6 to Polyamide PA using Hot Press Technique

The objective of this work is using a hot press technique to join a hybrid structure of aluminum alloy AA6061-T6 sheet of 1mm thickness together with polyamide PA sheet of 2mm thickness. The aluminum alloy specimen was pre-holed with two holes of 5mm diameter. The joining process was carried out with a lap joint configuration. Three different process parameters of the joining process were used: temperature (164, 172 and180°C), pressure (4, 7 and 10 bar) and time (1, 2.5 and 4 min.). The joints were tested by a shear test, macrostructure and scanning electron microscope (SEM) inspection. The design of the experiments (DOE) method was used to analysis the effect of the process parameters on the joint shear force. The DOE optimized the shear force of the joint with a maximum value of 1565 N at 177.5°C 4bar and 3.5min. The SEM examination indicated that the joining mechanism occurred by re-solidified the PA through the internal surface of the aluminum hole.