Extruded Aluminum Alloy Research Articles

Fatigue strength of welded joints of marine aluminum alloy extrusion stiffened plate considering welding effects

Due to the low stiffness of thin-plate welded structure, the influence of welding effect on fatigue evaluation of thin-plate welded structure cannot be ignored. Extruded stiffened plates are tried to be used in hull structures because of their excellent forming technology, which can greatly reduce welding deformation and defects. By carrying out fatigue tests of extruded reinforced welded joints and traditional T-shaped welded joints, the S-N curves of typical T-welded joints are obtained and compared. Furthermore, the residual stress and welding deformation of stiffened model and traditional T-model are predicted by numerical simulation. The welding effects are introduced into the calculation of hot spot stress as the initial value, and the hot spot stress class curves of extruded reinforced welded joints and traditional T-welded joints are renewed. Compared with traditional welded joints, extruded welded joints are less affected by residual stress and welding deformation. The study revealed that residual stress and welding deformation exhibited a higher sensitivity to the fatigue strength of traditional thin-plate welded structures.

Simulation of taper heating and variable pressing rate to improve extrusion performance for high-strength aluminum alloys

The main process parameters of direct and indirect extrusion of aluminum alloys were studied using FE-modeling in this article. The subject of the study was the use of billets taper heating and variable pressing rate as compared to the standard extrusion conditions. Extrusion of AA2024 grade alloy and experimental Al-2%Cu-1.5%Mn-1%Mg-1%Zn alloy was considered. The flow stress-on-strain dependences within the 350 °C–450 °C range at strain rates of 0.1–10 s−1 were determined for the experimental alloy. Considering the time of billet transportation to the extrusion equipment, its optimum temperature gradient was determined to be 500 °C at the front end and 140 °C at the tail end. Direct extrusion of taper heated billets at the variable rate and elongation of 7 allowed increasing the process performance by 5.6 times (from 1.8 mm s−1 to an average of 10 mm s−1, in case uniformly heated billets are extruded at the constant rate). In case of pressing at high elongations (15 and 25), the performance increase was about 2 times. It was found that the use of taper heating, both in case of grade alloy and model alloy extrusion, in all the considered conditions, allows achieving a significant increase in performance. However, these results are considered to be most effective in case of direct extrusion at small elongation ratios.

An Innovative, Lightweight, and Sustainable Solution for the Integrated Seismic Energy Retrofit of Existing Masonry Structures

A large percentage of existing building stock in Italy and throughout Europe is ageing and no longer complies with current regulations, particularly in terms of sustainability. For these reasons, an urgent consolidation plan is needed to ensure an increase in both seismic response and energy response. Indeed, these constructions were built before the actual technical codes, and currently, they are not able to withstand seismic actions. Meanwhile, they are subject to thermal dispersions that could be due to the use of materials with poor properties or construction errors. Among the numerous consolidation techniques, an innovative solution consisting of a coating system has appeared on the construction market in recent decades. It is an integrated solution that simultaneously improves the seismic and energy behaviour of the building. The paper proposes the evaluation of this lightweight and sustainable solution through some experimental tests which were performed at the National Institute for Research and Development in Constructions, located in the city of Timişoara (Romania). The tests were aimed to investigate the out-of-plane behaviour of a masonry wall (1.20 m × 2.40 m × 0.60 m) obtained by combining two smaller panels with mortar and subjecting them to constant vertical force and pushing by an increasing horizontal one. Its response was assessed before and after the application of extruded aluminium alloy base profiles belonging to the system under study.

Mechanical responses and microstructure evolution of a 7A09 aluminum alloy extrusion profile during novel stretch bending

This paper proposes a new stretch bending approach for aluminum alloy extrusion profiles based on a novel pre-hardening forming (PHF) process. Tensile tests were carried out to examine the flow behavior and mechanical responses of a 7A09 extrusion profile in PHF process. Microstructure evolution was investigated through X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and small angle X-ray scattering (SAXS). It is interesting to find that the yield stress at 200 °C was higher than that at 185 °C. The quantitative analysis revealed that the higher volume fraction of precipitates (200 °C) played a greater role than the refinement of precipitate sizes (185 °C) in precipitation strengthening mechanism, thereby causing an enhanced hardening effect. This phenomenon indicated that there was a preferred temperature zone for the precipitation behavior in PHF process, and it also explained the lower yield stress at 185 °C than that at 200 °C. Additionally, similar results were also observed in strength of the warm-deformed alloys. The optimal strength (σ/σ0.2=589/517 MPa) can be achieved at 200 °C without subsequent heat treatment, which exceeded the typical strength of 7A09-T6 extrusion. The primary strengthening mechanisms in PHF process were strain hardening and precipitation strengthening, and the warm forming procedure caused a hardening effect, rather than a softening impact as in traditional warm/hot forming procedures.

Evaluation of crush performance of extruded aluminum alloy tubes based on finite element analysis with ductile fracture modeling

In this study, the crush performance of four aluminum extrusions are investigated through analysis based on finite element (FE) simulation incorporating experiment-numerical hybrid ductile fracture modeling. Tensile tests on standard and non-standard specimens, coupled with digital image correlation and FE analyses, are employed to establish constitutive models for the materials. The evaluation of crush performance is performed based on both axial crush test and corresponding 3-dimensional FE simulation, which could validate the employed plasticity and fracture laws and predict crush performance indicators with reliable accuracy. Additionally, FE modeling enables thorough analysis of highly non-proportional loading paths and potential crack initiation sites, with the crack formation mechanism elucidated through the evolution of a proposed damage variable. Furthermore, the modified crush performance indicators are newly suggested, which could explain the dependence on both the absorbed energy of tubular extrusion and properties of ductile fracture.

Experimental study on mechanical behaviour of friction stir welded aluminium alloy butt joints

The purpose of this paper is to understand the softening extent and stress-strain behavior of the normal-strength 6061-T6, 6013-T6, and high-strength 7075-T6 aluminium alloy butt joints using the novel friction stir welding (FSW) technique. A total of 107 monotonic tensile coupons and 33 Vickers hardness coupons were prepared from 8- or 12-mm thick welded plates using various tool rotation speed, welding transverse speed and tool configurations. The surface morphology, stress-strain curves and hardness distribution laws after welding were evaluated. The W-shaped hardness profiles were clearly observed, with the fracture location positively correlated at the lowest point of Vickers hardness near the edge of the weld toe. The strength reduction and softening extent of extruded aluminium alloys in T6 temper induced by FSW were superior to those of aluminium alloys using fusing welding process outlined in the Chinese and European standards, indicating the effectiveness and applicability of the FSW technique in the formation of components and connections for aluminium alloy structures. Additionally, the current widely used constitutive models generally yielded under-estimations on the strength under large strains. The developed three-stage Ramberg-Osgood model, using seven key input parameters, significantly improved the accuracy and consistent predictions in the full-range stress-strain curve of FSW aluminium alloys. Furthermore, the suggested model could still achieve a great balance between accuracy and practicality when using just three common available parameters with the employment of predictive expressions on other four parameters.

Effect of aging process on precipitated phase and properties of mechanical extruded aluminum alloy

As the industrial sector develops, the performance requirements for aluminum alloys are also constantly improving. The study explores how aging and rolling treatment affect aluminum alloys' precipitates and mechanical properties by controlling the parameters of aging process and rolling deformation variables. 7N01 aluminum alloy was selected as the experimental object, and the samples were treated with non-aging, natural aging, artificial aging, and rolling deformation. How aging processes and rolling deforming affected alloys’ mechanical properties was evaluated through performance testing (mechanical and tensile testing) and material fiber characterization methods (advanced electronic instruments). These results confirmed that the combination of three aging pre-treatments + R20 % + 120 °C re-aging could significantly improve the hardness of aluminum alloys and maintain high ductility. As the deformation decreased, the time for the sample to reach the hardness peak was shorter and the hardness was higher. The 20 % deformation sample’s strength was better than the 80 % deformation sample’s. This confirmed that appropriate aging process and deformation combinations could improve the strength and hardness of aluminum alloys. These results have certain guiding significance for optimizing the aging process of mechanical extruded aluminum alloys and provide reference for the study of related alloy properties.

A unified physically-based model describing complex unloading behavior in cold and hot deformation process of aluminum alloys

During the cold and hot deformation of metals, the nonlinearity in unloading is mainly caused by dislocation-associated behaviors and creates challenges for the prediction of springback law and residual stress distribution after springback. In this paper, a unified physically-based model for describing the dislocation density evolution in unloading after cold and hot deformation was proposed firstly by considering the combined effects of reverse slip of reversible mobile dislocations (under back stress and the static recovery) and recrystallization (after deformation) on the dislocation density evolution in unloading. Furthermore, an anelastic strain model associated with dislocation behaviors was established for predicting the microplastic strain in unloading after cold and hot deformation by considering the effects of strain-induced dislocation multiplication and the dislocation annihilation/consumption caused by dynamic recovery and dynamic recrystallization on the reversible mobile dislocation density evolution during deformation. The established dislocation density evolution model and anelastic strain model were evaluated using the experimental results obtained from the hot compression of homogenous aluminum alloys and the cold compression of extruded aluminum alloys. The results indicated that the established models are able to accurately predict nonlinear unloading behavior and nonlinearly varying microplastic strain. Meanwhile, it was also found that, for cold deformation, the reverse slip of reversible mobile dislocations driven by back stress is the leading reason for the nonlinearity of unloading, and the strain hardening and recovery during deformation are main factors affecting the anelasticity of unloading; for hot deformation, the reverse dislocation slip, static recovery and recrystallization collectively affect the nonlinearity in unloading, and the anelasticity is affected not only by strain hardening and dynamic recovery but also by dynamic recrystallization during loading process.

Corrosion behavior of riveted joints with electrophoretic treatment in neutral salt spray environment

AbstractThis study delves into the corrosion behavior of riveted joints with electrophoretic treatment in a neutral salt spray environment using tensile test and surface analysis. The results showed that the open‐circuit potentials of the dual‐phase steels (590DP and 780DP) exceeded those of the AlSi10MnMg‐T7 and JDA1b die‐casting aluminum alloys by 100 mV, and exceeded that of the AA6063‐T6 extruded aluminum alloy by 50 mV. AlSi10MnMg‐T7 and JDA1b die‐casting aluminum alloys were more susceptible to corrosion in contrast to the AA6063‐T6 extruded aluminum alloy. The corrosion mechanism of the steel/aluminum riveted joints was not only galvanic corrosion but also oxygen concentration polarization. Over the 720‐h corrosion period, the failure loads of the riveted joints were not reduced at all. On the contrary, they increased at least 17% for the two‐sheet self‐piercing riveting (SPR) joints, 6% for the three‐sheet SPR joints, and 4% for the flow drill screw joints.

Application of microindentation to the evaluation of strain distribution over the section of extruded aluminum alloy bars

The paper proposes to supplement the monitoring of strain uniformity over the cross-section of extruded aluminum alloy bars, based on the macro- and microstructure in the central part, at ½ radius, and in the surface zone in several cross-sections along the length of press products, with microindentation of these sections. For this purpose, the microstructure, the loading diagram, and the pattern of the distribution of micromechanical properties across the cross-section of extruded bars made of the AD33 and D16 aluminum alloys are comparatively analyzed. These alloys differ in that in one alloy, AD33, the alloying elements strengthen the aluminum-based solid solution without forming independent phases, and in the other, D16, they form strengthening intermetallic compounds Al2CuMg. The microhardness of the AD33 alloy is ~55 HV 0.1, that of the D16 alloy being 120 HV 0.1. The alloys differ in the distribution of micromechanical properties over both the transverse and longitudinal sections of the extruded bars. It has been found that maximum homogeneity is characteristic of the central part of the rods made of both alloys. The microindentation data correlate with the changes in the microstructure and the results of assessing the distribution of microstrains in the crystal lattice of an aluminum-based solid solution over the cross-section of extruded products by EBSD using recrystallization maps. This makes it possible to recommend the microindentation method for assessing the distribution of strains over the cross-section of extruded aluminum alloy bars.

Aluminum alloy extrusion scheme and model with reduction of basis metal waste

Aluminum alloy extrusion scheme and model with reduction of basis metal waste

Effect of assembling clearance on welding characteristics of laser-MIG hybrid welding for aluminum alloy extrusions

Effect of assembling clearance on welding characteristics of laser-MIG hybrid welding for aluminum alloy extrusions

Numerical investigation of the surface recrystallization during the extrusion of a AA6082 aluminum alloy under different process conditions

Numerical investigation of the surface recrystallization during the extrusion of a AA6082 aluminum alloy under different process conditions

Microstructure and Mechanical Properties of Al-11.3Zn-3.2Mg-1.3Cu-0.2Zr-0.1Sr-xTi Extruded Aluminum Alloy with Different Aging Process

Microstructure and Mechanical Properties of Al-11.3Zn-3.2Mg-1.3Cu-0.2Zr-0.1Sr-xTi Extruded Aluminum Alloy with Different Aging Process

Microstructure and properties of laser-MIG hybrid welded joints for aluminum alloy extrusions with different gap sizes

Microstructure and properties of laser-MIG hybrid welded joints for aluminum alloy extrusions with different gap sizes

Microstructure evolution and texture development during production of homogeneous fine-grained aluminum wire by friction extrusion

This study aims to understand the microstructure evolution and texture development during friction extrusion of aluminum alloys, focusing on AA7075 as exemplary alloy system. Electron backscatter diffraction technique has been employed to obtain crystallographic data from various regions in front of the die and in the wire. It can be deduced that the combination of continuous dynamic recrystallization and geometric dynamic recrystallization mainly govern the formation of a fine-grained structure, however discontinuous dynamic recrystallization may also play a role at high temperature. The global shear deformation during the process was characterized as a simple shear deformation with dominant B/B¯ simple shear texture components. The material flow is mainly driven by the in-plane shear strain and the extrusion-induced shear strain that are determined by die rotational speed and extrusion force, respectively. The in-plane shear strain strongly affects the formation of a homogeneous fine-grained microstructure in the aluminum wire. In this regard, a novel material flow model for friction extrusion has been proposed.

Mechanical Properties of 6061 Aluminum Alloy under Cyclic Tensile Loading

During the service process of an aluminum alloy structure, its complex deformation zone experiences repeated loading problems such as repeated tension, compression, bending and reverse bending. At the same time, the cyclic loading and heat treatment process also have a certain impact on the mechanical properties of aluminum alloy extruded tubes. Therefore, the study of heat treatment process parameters has important engineering and practical value for the mechanical properties of aluminum alloy extrusion tubes under cyclic loading conditions. The experiment takes 6061-T6 aluminum alloy extruded tubes as the research objects. In the study, heat treatment and cyclic tensile tests were carried out on 26 aluminum alloy specimens to study the effects of different heat treatment parameters (such as heating temperature, holding time, and cooling method) on the stress–strain hysteresis curves, stress characteristics, hysteretic energy, skeleton curves and failure characteristics of the alloy under the same loading system. In addition, different cyclic tensile tests were carried out on 20 aluminum alloy samples without secondary heat treatment to discuss the effects of different cyclic loading regimes on the mechanical properties of the alloy. The research results indicate that the effect of heating temperature on the cyclic loading performance of the alloy is greater than that of the holding time, and the effect of the cooling method on the cyclic loading performance of the alloy is not obvious. A cyclic tensile loading regime has a significant impact on the strength, elongation and hysteresis energy of the alloy. The hysteretic behavior of the alloy during cyclic tensile loading depends on the applied stress level and loading history. As the number of cycles increases, the shape of the hysteresis curve tends to be stable, but there is no monotonic relationship between the number of cycles loaded and the hysteresis energy.

Laser-MIG hybrid welding of aluminium alloy extrusions for high-speed trains: effects of gap width on microstructure and properties

6A01-T5 aluminum alloy extrusions with a thickness of 4.5 mm were welded by laser-MIG hybrid welding, and the effects of gap width on the microstructure and properties were studied in details. The results indicated that the priorities of the welding parameters on the tensile strength of joints were laser power, defocusing amount and arc current when the welding speed was constant. The gap tolerance of the optimal welding parameters could reach up to 1.1 mm. The morphology and size of the microstructures were similar when the gap width was no larger than 1.1 mm. The grain boundaries became obvious and even cracks appeared near the fusion line when the gap width increased to 1.5 mm. The microhardness distributions almost the same with the different gap widths: highest in the base materials zone, secondly in the heat-affected zone, then in the weld zone, and lowest near the fusion line. The microhardness values reduced in each zone except base materials when the gap width increased to 1.5 mm. The tensile strength reduced as the gap width increased, the specimens all fractured near the fusion line due to where had the lowest microhardness and the fracture showed ductile failure mode.

Modified plasticity constitutive model for extruded aluminum alloys

Aluminum alloys have been increasingly used in a wide range of construction applications, especially in important public buildings. A plasticity constitutive model that can accurately describe the elastoplastic behavior of aluminum alloys under complicated stress states is of great importance in precisely simulating aluminum alloy structures under complicated working conditions. Also, a precise plasticity model serves as the foundation for studying the ductile fracture of metals, and is therefore crucial for structural analysis involving large deformation, such as progressive collapse analysis. The classic J2 plasticity model based on the von Mises yield criterion is the most commonly utilized model for ductile metal materials. However, it ignores the effect of stress state on metal plasticity behavior, making it inapplicable to aluminum alloy materials under various complicated stress states. This study experimentally demonstrated that stress triaxiality and Lode angle have a noticeable effect on the plasticity behavior of extruded aluminum alloys (6061-T6, 6082-T6, and 6063-T5). Accordingly, a plasticity constitutive model suitable for extruded aluminum alloys under complicated stress states was proposed and validated, including a full-range hardening law and a new yield criterion. In addition, the parameter calibration method for this new model was detailed. Finally, comparisons between the experimental and numerical results proved the high accuracy of the proposed model in predicting the actual response of a structural extruded aluminum alloy under complicated stress states. Compared with previous studies, the proposed model can not only consider the effects of stress triaxiality and Lode angle, but it can also provide a more reasonable description of yield surface under considerably high or low stress triaxiality.

Optimization strategy for the indirect isothermal extrusion of high-strength aluminum alloy based on temporal fusion transformer

Optimization strategy for the indirect isothermal extrusion of high-strength aluminum alloy based on temporal fusion transformer