Search Results (782)

The plastic deformation during equal-channel angular pressing (ECAP) can be affected by various material- and processing-related factors. For instance, the initial crystal orientation and grain size play an important role in determining the material flow, which may cause localized deformation in terms of macroscopic deformation banding. In this study, we use a continuous cast AA1080 aluminum alloy with coarse columnar grains to analyze the influence of casting texture on the local material flow during ECAP. Billets are extracted with their columnar grains inclined either in the same direction as the ECAP shear plane or opposite to it. Visio-plastic analysis is performed on split billets. The pass is interrupted halfway through the ECAP tool to accurately capture steady-state deformation conditions. Flow lines at several positions within the billet are identified based on the positions of deformed and undeformed marker points and fitted to a phenomenological model based on a super-ellipse function. For further characterization, hardness measurements, optical and electron microscopy are carried out on the ECAP-deformed samples. Significant differences in terms of local material flow and microstructure evolution regarding the resulting crystal orientation and deformation banding are observed. Our results confirm and emphasize the importance of initial grain size and texture effects for ECAP processing. Full article

Aluminium alloys are known for their high strength-to-weight-ratio offering a wide range of applications in the aerospace and automotive industries. However, challenges exist like porosity, oxidation, solidification shrinkage, hot cracking, etc., in joining aluminium alloys. To address these challenges, there is a necessity to understand the process parameters for the welding/joining of aluminium alloys. The present study aims to investigate the effect of cold metal transfer (CMT) welding process parameters (i.e., welding speed and wire feed rate) on mechanical properties for dissimilar AA6061-AA6082 alloys weld joints. Two different welding conditions viz. CMT1 (speed: 0.5 m/min with feed: 5 m/min) and CMT2 (speed: 0.3 m/min with feed: 3 m/min), were considered. The weldments were deployed for testing different mechanical properties such as tensile, impact, hardness, corrosion tests and bead profile geometries. The results reveal that CMT1 has better mechanical properties (tensile_233 MPa; impact_8 J; corrosion rate_0.01368 mm/year) than CMT2, showing the welding speed and wire feed rate play a significant role in the joint performance. The heat affected zone and fusion zone are narrow for CMT1 when compared with CMT2. The present study provides insights into the CMT process and dissimilar joining of aluminium alloys that might be helpful for additive manufacturing of dissimilar aluminium alloys as future research directions. Full article

This study investigates the combined effects of build planes and heat treatments on the micro- and nanoscale mechanical properties of additively manufactured AlSi10Mg alloy. The hardness and elastic modulus were examined across two principal planes, XY and XZ, under three conditions: as-built (AB), after solution annealing followed by water quenching (SA), and artificially aged after solution annealing (SA&AA). The results reveal that hardness is significantly affected by heat treatment, decreasing after SA and partially recovering upon subsequent artificial aging (SA&AA), while remaining largely unaffected by build planes, with average values differing by less than 2%. In contrast, the elastic modulus demonstrates a clear anisotropy, correlated with the microstructural changes from both additive manufacturing and thermal post-processing. The XY plane initially shows a modulus up to 29% higher than the XZ plane. However, after aging, the values of both planes converge to similar levels. While average values suggest general trends, localized measurements reveal notable spatial heterogeneity in both the hardness and elastic modulus—particularly after thermal treatments—arising from microstructural evolutions. These findings highlight the complex interplay between orientation and thermal history, underscoring that the mechanical performance of AlSi10Mg is governed by the synergistic effects that influence anisotropy and local mechanical behavior. Full article

The development of technology has driven a rising need for high-accuracy and high-efficiency manufacturing of low-volume products. Incremental forming technology, characterized by die-free flexibility and low production costs, can effectively replace stamping processes for manufacturing customized small-batch products. However, high-performance aluminum alloys generally exhibit poor room-temperature plasticity but excellent high-temperature plasticity, necessitating the integration of thermal-assisted methods for manufacturing such products. However, the temperature of the forming region will excessively rise without temperature control, which will affect the forming performance of the material in hot incremental sheet forming of AA2024-T4 aluminum alloy. This study focuses on AA2024-T4 aluminum alloy and proposes a uniform temperature control method for the electric hot tube-assisted incremental sheet forming process, incorporating an adaptive fuzzy PID algorithm. The temperature difference of the forming region is lower than 6% under the various temperatures. On this basis, the forming limit angle and the microstructure state of the material are analyzed, and the grain feature of the material exhibits significantly refined grains and the uniform fine grain distribution under 180 °C with the temperature control of the adaptive fuzzy PID algorithm. Full article

This study investigates the friction stir joining of AA6082-T6 aluminum alloy and Noryl GFN2 polymer in a buttstrap configuration, targeting the development of lightweight cylindrical-shaped structures where the polymer provides thermal, chemical, and electrical insulation, while the aluminum ensures mechanical integrity. A parametric analysis was carried out to assess the ability to produce friction stir buttstrap composite panels in a single processing step and assess the resulting tensile and flexural behavior. To that end, travel and rotating speeds ranging from 2150 to 2250 rpm, and 100 to 140 mm/min, respectively, were employed while keeping plunge depth and the tilt angle constant. A total of nine composite joints were successfully produced and subsequently subjected to both tensile and four-point bending tests. The tensile and flexural strength results ranged from 80 to 139 MPa, and 39 to 47 MPa, respectively. Moreover, the microstructural examination revealed that all joints exhibited a defect within the joining region and its size and shape had a significant effect on tensile strength, whereas the flexural strength was less affected with more uniform results. The joining region was also characterized by a decrease in hardness, particularly in the pin-affected region on the aluminum end of the joint, exhibiting a W-shaped pattern. Contrarily, on the polymeric end of the joining region, no significant change in hardness was observed. Full article

The formation of hot tearing during direct chill casting of aluminum alloys, specifically AA6111, is a significant challenge in the production of ingots for industrial applications. This study investigates the role of hydrostatic pressure and tensile stress in the formation of hot tearing during direct chill casting of rectangular ingots. Combining experimental results and finite element modeling with ABAQUS/CAE 2022, the mechanical behavior of the semi-solid AA6111 alloy was analyzed under different cooling conditions. “Hot” (low water flow) and “Cold” (high water flow) conditions were the two types of cooling conditions that produced cracked and sound ingots, respectively. The outcomes indicate that high tensile stress and localized negative hydrostatic pressure in the hot condition are the main factors promoting the initiation and propagation of cracks in the mushy zone, whereas the improvement of the cooling conditions reduces these defects. Full article

This study investigates the fabrication and residual stress behavior of a 0.5 wt.% graphene-reinforced AA2195 aluminum matrix composite, developed for advanced aerospace structural applications. The composite was synthesized via squeeze casting, followed by a multi-pass hot rolling process and subsequent T8 heat treatment. The evolution of residual stress was systematically examined after each rolling pass and during thermal treatments. The successful incorporation of graphene into the matrix was confirmed through Energy-Dispersive Spectroscopy (EDS) analysis. Residual stress measurements after each pass revealed a progressive increase in compressive stress, reaching a maximum of −68 MPa after the fourth hot rolling pass. Prior to the fifth pass, a solution treatment at 530 °C was performed to dissolve coarse precipitates and relieve internal stresses. Cold rolling during the fifth pass reduced the compressive residual stress to −40 MPa, and subsequent artificial aging at 180 °C for 48 h further decreased it to −23 MPa due to recovery and stress relaxation mechanisms. Compared to the unreinforced AA2195 alloy in the T8 condition, which exhibited a tensile residual stress of +29 MPa, the graphene-reinforced composite in the same condition retained a compressive residual stress of −23 MPa. This represents a net improvement of 52 MPa, highlighting the composite’s superior capability to retain compressive residual stress. The presence of graphene significantly influenced the stress distribution by introducing thermal expansion mismatch and acting as a barrier to dislocation motion. Overall, the composite demonstrated enhanced residual stress characteristics, making it a promising candidate for lightweight, fatigue-resistant aerospace components. Full article

The research presented herein investigates the impact of axial force and feed rate in the Friction Stir Welding (FSW) of aluminum alloy 6061-T6 in a GROB G552 horizontal 5-axis CNC machine with adaptive torque control enabled. The purpose of this study is to further advance the performance and characteristics of FSW aluminum alloys in 5-axis CNCs, particularly in conjunction with adaptive torque control. The Taguchi and ANOVA methods were utilized to define parameter tables and analyze the resulting data. Optical microscopy and tensile tests were performed on the welded samples to evaluate weld quality. The results from this study provide clear evidence that axial force has a significant effect on tensile strength in FSW AA6061-T6. The maximum UTS found in this study, welded with an axial force of 9.4 kN, retained 69% tensile strength of the base material. Conversely, a decrease in strength and an increase in void formation was found at higher feed rates with this force. Ideal welds, with minimal defects across all feed rates, were performed with an axial force of 8.3 kN. A feed rate of 300 mm/min at this force resulted in a 67% base metal strength. These findings contribute to improving joint strength and application efficiency in FSW AA6061-T6 performed in a horizontal 5-axis CNC machine where adaptive torque control is enabled. Full article

Friction stir welding (FSW) is a novel welding technique that produces a solid-state weld by generating frictional heat and plastic deformation at the weld spot with a revolving, non-consumable welding tool. Despite processing a wide range of industrial materials, FSW has concentrated on welding aluminum and its alloys because of its high strength-to-weight ratio and uses in the shipbuilding, aerospace, and other fabrication industries. Important FSW process factors that determine the mechanical qualities of the weldment are the tool tilt angle, tool traverse feed, tool pin profile, tool rotational speed (TRS), tool traverse speed (TTS), tool pin profile (TPP), and shoulder plunge depth. Variations in the required process parameters cause defects, which lower the weld quality of FSWed aluminum alloys (AA). Therefore, keeping an eye on and managing the FSW process is crucial to preserving the caliber of the weld joints. The current study aims to investigate the changes in the mechanical characteristics and microstructure of the FSWed AA5052-H111 and AA6061-T6 joints. To perform the FSW experiments, we varied TRS, TTS, and TPP on plates that were 5 mm thick and had a butt joint structure. Following welding, the microstructure of the weld zones was examined to observe how the grains had changed. The joint’s tensile strength reached a maximum of 227 MPa for the square-shaped TPP, and the micro-Vickers hardness test results showed a maximum of 102 HV at the weld nugget zone (WNZ). Full article

Graphene, a two-dimensional carbon material, possesses exceptional properties such as high electron mobility, exceptional strength that surpasses that of steel, chemical resistance, environmental friendliness, and a large specific surface area. In this study, we used the modified Hummer process to produce graphene oxide, which was applied to an aluminum alloy substrate as a corrosion-resistant coating. The aluminum alloy used in our study is AA2024, which is widely applied in industry and aircraft. The coating layer was characterized by micro-Raman spectroscopy and atomic force microscopy (AFM) before and after the reduction process. Micro-Raman spectroscopy provided information on the degree of reduction and the presence of functional groups in the coating layer. AFM images enabled the study of surface morphology and topography. After the reduction process, achieved by annealing in an argon atmosphere at 140 °C, micro-Raman spectroscopy and AFM were again used to assess structural and morphological changes. The reduction resulted in the formation of reduced graphene oxide (RGO), which exhibited improved conductivity and stability. The combination of micro-Raman spectroscopy and AFM characterization techniques provided detailed information on the properties and effectiveness of the coating layer. This research contributes to developing anti-corrosion methods using advanced materials and surface engineering techniques. Full article

This study investigates the shell hydroforming of 1.2 mm-thick AA5052 aluminum alloy sheets to produce hemispherical domes which possess inherent spatial symmetry about their central axis. Shell hydroforming is widely used in fabricating lightweight, high-strength components for aerospace, automotive, and energy applications. The forming process was driven by a spatially symmetrical internal pressure distribution applied uniformly across the blank to maintain balanced deformation and minimize geometrical distortion. Experimental trials aimed at achieving a dome depth of 50 mm revealed wrinkle formation at the blank periphery caused by circumferential compressive stresses symmetrical in nature with respect to the dome’s central axis. To better understand the forming behavior, a validated 3D finite element (FE) model was developed, capturing key phenomena such as material flow, strain rate evolution, hydrostatic stress distribution, and wrinkle development under symmetric boundary conditions. The effects of the internal pressure (IP), blank holding force (BHF), coefficient of friction (CoF), and flange radius (FR) were systematically studied. A strain rate of 0.1 s⁻¹ in the final stage improved material flow, while a symmetric tensile hydrostatic stress of 160 MPa facilitated dome expansion. Although tensile stresses can induce void growth, the elevated strain rate helped suppress it. An optimized parameter set of IP = 5.43 MPa, BHF = 140 kN, CoF = 0.04, and FR = 5.42 mm led to successful formation of the 50 mm dome with 19.38% thinning at the apex. Internal pressure was identified as the most critical factor influencing symmetric formability. A process window was established to predict symmetric failure modes such as wrinkling and bursting. Full article

This work explores the application of Hidden Markov Models (HMMs) for the classification and reconstruction of corrosion mechanisms in the aerospace-grade aluminum alloy AA2055 from the signals obtained by electrochemical noise (EN) analysis. Using the PELT algorithm to segment the signal based on relevant changepoints, distinct corrosion states within the segments are isolated and identified, including general, localized, and mixed corrosion based on statistical signal features, which are used to create the probabilistic structure of HMMs through the initiation, transition, and emission matrices. This study utilized a dataset composed of five electrolyte groups, each containing ten EN signals with 1024 data points per signal, totaling 51,200 data points. The model demonstrates that even with variability in signal quality, meaningful reconstruction is achievable, especially when datasets include distinct transient behavior. Full article

This study investigates the factors affecting the mechanical performance of conventional and impulse friction stir welded (FSW and IFSW) AA2024-T351 joints under static and cyclic loading. Emphasis is placed on the influence of fracture-inducing features such as oxide inclusions, constituent particle distributions, crystallographic texture, and precipitation state. A series of IFSW welds produced at varying impulse parameters were compared to conventional FSW welds in terms of microhardness, tensile strength, fatigue life, and Taylor factor distribution. IFSW joints demonstrated a significant improvement in tensile strength and elongation, particularly at higher impulse frequencies. Enhanced material mixing due to the reciprocating tool motion in IFSW resulted in finer particle distribution, more favorable crystallographic texture, and reduced weld pitch, all contributing to increased ductility and strength. Fractographic analyses revealed that fatigue failures primarily initiated in the stir zone, typically at unplasticized metallic inclusions. However, IFSW joints displayed longer fatigue lives, particularly when impulse parameters were optimized. These findings underline the complex interplay of microstructural and textural factors in determining weld performance, highlighting IFSW as a promising technique for enhancing the durability of high-strength aluminum welds. Full article

Understanding and optimizing the relationship between critical processing parameters (rotational speed and dwell time) and the resulting weld performance is crucial for the effective application of friction stir spot welding (FSSW) in joining aluminum alloys. FSSW is an increasingly important solid-state, clean technology alternative for joining lightweight alloys such as AA5052-H32 in various industries. To optimize this technique for lap joint configurations, the current study examines the influence of rotational speeds (500, 1000, and 1500 rpm) and dwell times (1, 2, and 3 s) on the heat input energy, hardness across weld zones, and tensile/shear load, using a full factorial Design-Expert (DOE) analysis. The FSSW responses of the numerical model were validated using the experimental results for the spot-welded joints. The findings indicate that the dwell time significantly affected the mechanical properties, while the tool rotational speed had a substantial effect on the heat input energy and mechanical properties. Fracture surfaces predominantly exhibited ductile failure with diverse dimple morphologies, consistent with the enhanced tensile properties under optimal parameters. The presence of finer dimples suggests a mixed-mode fracture involving shear. Full article

Variations in the warm formability of AA7075 sheets are primarily attributed to differences in precipitate morphology resulting from distinct thermal histories. To better understand this relationship, this study systematically investigates the influence of precipitate characteristics—quantified by the product of precipitate volume fraction and average radius—on forming limits across various thermal routes in warm forming processes. A modified Cockcroft–Latham ductile fracture model incorporating this microstructural parameter was developed, calibrated against experimental data from warm isothermal Nakajima tests, and implemented within a finite element framework. The proposed model enables the accurate prediction of forming limit curves with minimal experimental effort, thereby significantly reducing the reliance on extensive mechanical testing. Building upon the validated FE model, a practical methodology for rapid R-value estimation under warm forming conditions was established, involving the design of specimen geometries optimised for isothermal Nakajima testing. This approach achieved R-value predictions within 5% deviation from conventional uniaxial tensile test results. Furthermore, experimental results indicated that AA7075 sheets exhibited nearly isotropic deformation behaviour under retrogression warm forming conditions. Overall, the methodology proposed in this study bridges the gap between formability prediction and process simulation, offering a robust and scalable framework for the industrial optimisation of warm forming processes for high-strength aluminium alloys. Full article