Al2Cu Phase Research Articles

Structure-property correlation in directionally solidified in-situ microwave cast of AA 2024 alloy irradiated at 2.45 GHz

The electric (E) and magnetic field (B) components of microwaves interact with materials at molecular level through various mechanisms, which demonstrate unique processing capabilities. In the present study, the AA 2024 alloy was melted using susceptor-assisted microwave heating, and the molten alloy was then directionally solidified in-situ at five solidification rates (50, 100, 150, 200, and 250 μm/s) under microwave irradiation. The effect of solidification rates on microstructure evolution and mechanical properties of directionally solidified AA 2024 alloy was investigated considering the specific influences of E and B components of microwaves. It was found that the eutectic phase gradient was formed along the solidification direction, becoming more pronounced at high solidification rates. Results showed a significant refinement in the microstructure with the increase in solidification rate. Hardness was observed to be higher at the bottom of the solidified alloy and varied along the solidification direction. The tensile properties of the AA 2024 alloy were found to increase with the increase in solidification rate up to ~125 μm/s. The alloy solidified at ~125µm/s exhibited the highest yield strength (314MPa), ultimate tensile strength (389MPa), and elongation (14.82%). The XRD analyses confirmed the presence of AlCu, Al2Cu, and Al2CuMg secondary phases. It was postulated that microwave interaction with the AA 2024 alloy during solidification played a significant role in tailoring the microstructure.

Investigation of Wetting Behavior and Brazing Reliability of Zn-15Al-xGa Filler Metals in Cu/Al Joints

Ga elements with different contents (0.1-1.5wt.%) were melted into the Zn-15Al filler metal to change the microstructure and thus improve the properties of the Cu/Al joints. The results showed that the addition of Ga element reduced the solidus and liquidus temperatures as well as the surface tension of the Zn-15Al filler alloy. Low concentrations of Ga (≤0.5wt%) can effectively increase the wettability of the filler metal. With increasing Ga addition amount, the size and proportion of the CuAl2 phase within the Cu/Zn-Al/Al brazed joint microstructure were increased, and also guided the transformation of the interfacial constituent phases on the Cu side interface from Al4.2Cu3.2Zn0.7/Al3Cu5Zn2 to Al4.2Cu3.2Zn0.7/CuAl2/Al3Cu5Zn2, which effectively adjusted the crack propagation path and increased the shear strength during the fracture process of the shear strength test on the brazed joint. The shear strength test results indicated the Cu/Zn-Al-0.5Ga/Al joint have the highest shear strength (85.8MPa, 15% improvement over the Cu/Zn-Al/Al joint). Consequently, appropriate Ga addition (0.5wt%) enhanced both the meltability and wettability of Zn-15Al filler metal, which was suitable for obtaining high-quality Cu/Al brazed joints.

Magnetic response and hardness enhancement by spontaneous directional coarsening of Fe2AlB2 in quasicrystal-rich matrix

This study investigates the Al55Cu20Fe15B10 alloy system to understand the characteristics of the Fe2AlB2 (Cmmm) phase and its interactions with a quasicrystal-rich matrix. The alloy’s composition was chosen for its boron content, which promotes the formation of well-defined Fe2AlB2 crystals. We examined how different heat treatments affect the alloy’s microstructure, magnetic properties and hardness. Microstructural and Electron Backscatter Diffraction analyses revealed the stable icosahedral Al59Cu27Fe12B2 quasicrystalline phase and a metastable Al70Fe20Cu10 approximant that is isostructural with C2/m Fe4Al13. Additionally, the alloy contained Al-Cu phases known from meteorites, such as AlCu stolperite and Al2Cu khatyrkite. Heat treatments at 706∘C and 828∘C yielded favorable microstructure for ballistic armor, characterized by Fe2AlB2 lamellae embedded within the quasicrystalline matrix, reinforced by AlB2 precipitation on the grain boundaries. Vickers hardness improvements were attributed to Hall-Petch strengthening and grain orientation effects. Notably, annealing at 943∘C nearly tripled the magnetic entropy change. Quantum Diamond Microscopy confirmed that Fe2AlB2 significantly contributed to magnetization. The improvement of magnetic properties was found to be due to preferential orientation of Fe2AlB2 grains along the [010] zone axis, as a consequence of directional coarsening induced by annealing. The enhanced magnetocaloric properties observed at 943∘C are primarily due to intrinsic changes in the Fe2AlB2 phase rather than strain relaxation or phase contributions from the quasicrystalline matrix.

Effects of alloying elements on microstructure evolution, interfacial structure, and mechanical properties of Al/Cu laminate

Hot press sintering process was employed to fabricate the Al/Cu laminates with pure Al or 6061Al as interlayer, and the effects of alloying elements on microstructure evolution, interfacial structure, and mechanical properties were clarified. A good metallurgical bonding was achieved and intermetallic compounds layers consisting of Al4Cu9, Al2Cu, and AlCu phases formed at the Al/Cu interface. Mg element facilitated the enrichment of Cu atoms and provided the nucleation sites for Al2Cu, resulting in a thicker Al2Cu phase and numerous dispersed Al2Cu particles in 6061Al/Cu laminate. MgAl2O4 phase distributed along 6061Al/Al2Cu interface, and it exhibits a coherent relationship with both 6061Al and Al2Cu, which contributed to enhancing the resistance of dislocation movement and the effectiveness of load transfer. During the tensile deformation of Al/Cu laminate using pure Al as the interlayer, the cracks were more likely to propagate across the Al/Al2Cu interface into the Al layer. When 6061Al was used as interlayer, the overall higher tensile strength was achieved, and the tensile curves showed two distinct stress drops. Moreover, the cracks faced greater resistance when traversing the 6061Al/Al2Cu interface during the expansion, and they tended to extend along the 6061Al/Cu interface, showing a distinct delamination fracture morphology.

Kinetic study of a-Si crystallization induced by an intermetallic compound

The problem under study is concerned with amorphous silicon (a-Si) crystallization which is induced by an intermetallic compound, with this compound chosen to be Al2Cu, formed by a solid-state reaction between nanolayers of aluminum and copper in a Cu/Al/a-Si multilayer system. In the case of crystallization initiated by the intermetallic compound Al2Cu, the crystallization temperature of amorphous silicon was found to be ≈ 300°С (upon heating at a rate of 5–10 °C/min), which was significantly higher than in the case of pure Al (≈170°С), but lower as compared to using pure Cu (≈485°С). The higher crystallization temperatures in comparison with aluminium-induced crystallization are assumed to be caused by a decrease in the number of free electrons due to the presence of copper and formation of the Al2Cu phase. By kinetic modeling, it was revealed that the mechanism of a-Si crystallization induced by the intermetallic compound Al2Cu was similar to the mechanism of Al-induced crystallization of a-Si in multilayer (Al/a-Si)n films, i.e the process of a-Si crystallization occurred in two subsequent stages: Cn-X→Fn. Kinetic parameters of silicon crystallization for each reaction step were obtained. The enthalpy of a-Si crystallization initiated by Al2Cu was estimated to be ΔH = 12.3 ± 0.5 kJ/mol.

The effect of the Zn layer on the microstructural evolution of Al/Cu composite material joints during friction stir spot welding

This study introduced Zn interlayer at the Al/Cu interface to form an Al-Zn-Cu tri-layer composite joint. The growth of the interfacial layer was enhanced by the generation of the liquid phase with increasing rotational speed and heat input during the welding process. Among the phases formed in the Al-Zn-Cu joint, the Cu5Zn8 phase exhibited the highest growth constant, making it the primary phase at the interface. The growth sequence of the Al2Cu phase was found to be between that of the Cu5Zn8 and AlCu phases. As welding progressed, Al2Cu acted as an ‘anchor point’ for the subsequent formation of the AlCu phase and was gradually consumed in the process. No Al4Cu9 phase was observed in the joint.

60 Years' Marine Corrosion of Aluminium Alloy 24S (A2024) - Conservation and Treatment of Very Corroded Aluminium Alloys with 100% Carbon Vegetal Corrosion Inhibitors

Aluminium alloys forming the remnants of Lockheed P38 of Antoine de Saint-Exupéry was identified as the 24S aluminium alloy developed in 1930’s. After 60 years in seawater, thick corrosion layers composed of aluminium hydroxide, copper salts and nanometre pure copper particles. In addition, the ancient aluminium alloy has undergone a very important intergranular corrosion. After the synthesis of Al2Cu, Al7Cu2Fe and Al2CuMg intermetallic phases, the study of their electrochemical behaviour in NaCl medium explains the significant presence of pure copper, because all the phases undergo a dealloying process. Electrochemical impedance spectroscopy measurements show that the kinetic of dealloying is constant versus immersion time, and is not limited by diffusion which explains the complete formation of copper sponge in NaCl medium in the conditions of long-term corrosion on aluminium artefacts.Specific corrosion inhibitors (non-toxic and based on vegetal compounds) were developed to treat the artefacts in very corroded 24S alloys from Lockheed P38 to respect the specifications of conservation of cultural heritage.

Influence of Ag-18Cu-10Zn Filler Material on Microstructure and Properties of Laser-Welded Al/Cu Dissimilar Butt Joints.

Dissimilar welding between aluminum and copper poses significant challenges, primarily due to differences in their thermal and mechanical properties, resulting in brittle intermetallic compounds, limited joint strength, and high electrical resistivity. This study aims to overcome these issues by employing Ag-18Cu-10Zn filler material and optimizing laser power with a focus on improving joint strength and electrical conductivity. The results indicate that the incorporation of silver and zinc enhances the phase composition and microstructure of the weld. By forming solid solution phases such as Ag2Al and Cu5Zn8, the brittle Al2Cu phase commonly found in traditional Al/Cu welding is replaced. This not only promotes the heterogeneous nucleation of fine silver-rich grains but also restricts the excessive growth of silver-poor grains, resulting in a uniform distribution of fine grains throughout the weld. These modifications contribute to both fine-grain strengthening and dispersion strengthening. At an optimal laser power of 750 W, joint strength reaches 109 MPa, while joint resistivity decreases to 3.19 μΩ·cm, 12.6% lower than that of the aluminum alloy base material. This study proposes a process for achieving highly conductive, reliable Al/Cu dissimilar metal joints, potentially impacting the aluminum-copper connections in battery modules for new energy vehicles.

(Digital Presentation) Nanoscale Sculpturing of Al and Al Alloys for Heterogeneous Al-Cu Joints

Heterogeneous Al-Cu joints are nowadays generated in a huge variety of different techniques depending on the intended application, such as corrosion protection of Al components, electric connections with improved interfaces, or even lightweight current collectors for batteries. Four major techniques are commonly used that can be further subdivided into cladding (including roll cladding, thermo-compression bonding, friction welding etc.), vapor deposition (including PVD, CVD etc.), thermal spraying and chemical plating (including electroless and electrochemical plating). Each of the methods offers certain advantages and disadvantages for the formation of Al-Cu joints. Typically observed disadvantages are the formation of intermetallic Al-Cu compounds (IMC), higher electric resistivity, a rather low mechanical strength under static or cyclic mechanical load conditions.The present work follows the electrochemical route to form Al-Cu joints utilizing nanoscale sculpturing of the Al substrate [1] as a starting point to overcome these above described typically observed disadvantages of Al-Cu joints. The resulting nanoscale sculptured Al-Cu joint is intensively characterized with respect to its structural (see Fig. 1), chemical and mechanical properties. It was found that such Al-Cu joints offer a high mechanical load bearing capability because of the interlocking zone between Al and Cu offering a gradual change, so that an optimum stress transfer can occur without the risk of a stress pile-up at the interface between both metals.Furthermore, no intermetallic Al-Cu phases grow at the interface between Al and Cu during deposition which could mechanically weaken the joint due to embrittlement, especially under cyclic loading conditions. Another advantage is the absence of Al-Cu intermetallics in the joint, being of great importance if high current or high voltage applications are intended.Fig 1: Nanoscale sculptured Al surface with cubic interlocking surface structures in cross-section (left) and cross-sectional view on Al-Cu joint after electrochemical Cu deposition on nanoscale sculptured Al surface (right).[1] M. Baytekin-Gerngross, M.D. Gerngross, J. Carstensen, and R. Adelung, Nanoscale Horizon 1(6), 467 (2016). Figure 1

A low copper content alloy Al(1-x)Cux, x≤0.1: A joint computational and experimental study

Atomistic simulation of Al1-xCux (x ≤ 0.1) alloy is performed and the mechanical properties are calculated within the framework of the density functional theory (DFT) by using of the virtual crystal approximation (VCA). The elastic matrix is calculated within the DFT using the CASTEP code and the dependences of Young's, shear and bulk moduli, Vickers hardness, Poisson's ratio, plasticity coefficient and anisotropy indices on the amount of copper are obtained. Al0.9Cu0.1 alloy was synthesized by spark plasma sintering (SPS) method. As a result, the aluminum and intermetallic CuAl2 phases were identified in the obtained sample by X-ray diffraction patterns. The microstructure (SEM) and Vickers microhardness of the sample were studied. The results of the work compensate for the lack of data for the Al-Cu alloys with a low copper content.

Evaluation of Structural Transition Joints Cu-Al-AlMg3 Used in Galvanizer Hangers

The paper deals with the evaluation of the quality of Cu-Al-AlMg3 structural transition joints (STJ) made by explosion welding proposed for the renovation of galvanizer hangers. The three-layer joint consisted of electrolytic copper with a thickness of 25 mm, 2 mm of aluminium represented by the AW1050 alloy, and 25 mm of the EN AW 575 aluminium alloy. Light microscopy analysis confirmed the wavy pattern of both interfaces of the welded joint and significant plastic deformation in close proximity to the waves. Microhardness measurement revealed a partial strain hardening of the AW5754 copper-aluminium alloy near the interface and a significant increase in microhardness in the vortex zone of waves, reaching a value of up to 863 HV 0.025. Microcracks were also observed in these places. The intermetallic phase Al2Cu was identified in the vortex zones by XRD analysis. As a continuous layer of intermetallic phase was not observed in the interface of the welded joint, it is possible to consider the used welding parameters as appropriate. A semi-quantitative EDX analysis revealed a diversity of chemical composition in the vortex zones, which does not correspond to the phase composition based on the equilibrium binary Al-Cu diagram due to non-equilibrium conditions in the formation of the welded joint interface. The bond strength of three-layer welded joint evaluated by the strength test ranged from 151 to 171 MPa, which represented approximately a two-fold increase in comparison to the ultimate tensile strength of alloy AW1050, while the failure occurred in all samples at the AW1050-AW5754 alloy interface.

The Interfacial Reaction Traits of (Al63Cu25Fe12) 99Ce1 Quasicrystal-Enhanced Aluminum Matrix Composites Produced by Means of Hot Pressing

This study fabricated (Al63Cu25Fe12)99Ce1 quasicrystal-enhanced aluminum matrix composites using the hot-pressing method to investigate their interfacial reaction traits. Microstructure analysis revealed that at 490 °C for 30 min of hot-pressing, the interface between the matrix and reinforcement was clear and intact. Chemical diffusion between the I-phase and aluminum matrix during sintering led to the formation of Al7Cu2Fe, AlFe, and AlCu phases, which, with their uniform and fine distribution, significantly enhanced the alloy’s overall properties. Regarding compactness, it first increased and then decreased with different holding times, reaching a maximum of about 98.89% at 490 °C for 30 min. Mechanical property analysis showed that compressive strength initially rose and then fell with increasing sintering temperature. After 30 min at 490 °C, the reinforcement particles and matrix were tightly combined and evenly distributed, with a maximum compressive strength of around 790 MPa. Additionally, the diffusion dynamics of the transition layer were simulated. The reaction rate of the reaction layer increased with hot-pressing temperature and decreased with holding time. Selecting a lower temperature and appropriate holding time can control the reaction layer thickness to obtain composites with excellent properties. This research innovatively contributes to the preparation and property study of such composites, providing a basis for their further application.

A study on hot deformation behaviors and microstructures of 10 vol% SiCP/Al-Cu-Mg-Ag composite prepared by spray co-deposition and extrusion

Isothermal compression test is used to investigate the hot deformation behavior of spray co-deposited and extruded 10 vol% SiCP/Al-Cu-Mg-Ag composite. In this study, an accurate strain-compensated model based on Arrhenius constitutive equation is constructed with the corresponding R value of 0.9965 and AARE of 4.05%. The experimental results are in high agreement with the predicted flow stress. Hot deformation activation energy of the SiCP/Al composite (161.685 kJ/mol) is notably higher than that of Al-Cu-Mg-Ag alloy, which is attributed to the dislocations introduced by SiC reinforcement. The microstructure evolution of compressed specimens is characterized using EBSD and TEM. DRX, including CDRX and DDRX, is the main softening mechanism under the hot deformation conditions of high temperature, low strain rate and high strain. The softening mechanism transition from DRV to DRX is due to the subgrains consuming dislocations and then transforming into DRX grains. Comparing the microstructure under different hot deformation parameters, the recrystallization degree is significantly influenced by temperature, followed by strain rate and strain. In addition, the recrystallization process is impeded by the primary Al2Cu phases, T phases and SiC particles in the composite through hindering the migration of dislocations.

Improving strength-conductivity synergy of Al-Cu-(Sn/Er) alloy with nanoscale substructure

As a conductive material for power transmission, Al-Cu alloy is widely used in power engineering, microelectronics and other fields. In view of the contradiction between the conductivity and strength of aluminum alloy, Sn and Er elements were selected to micro-alloy Al-Cu alloy. Al-Cu, Al-Cu-Sn and Al-Cu-Sn-Er alloys were prepared by near-liquidus casting. After solution treatment, it was subjected to three-stage alternating process of rolling and aging. The effects of micro-alloying and alternating process on the microstructure and properties of Al-Cu alloy were studied. The results show that the precipitated phase Al2Cu of Al-1.12 Cu alloy is rod-shaped after the first-stage process, and the average size is about 278±87 nm. The precipitated phases in the Al-Cu-Sn alloy are Al2Cu (average size of about 206±79 nm) and nano-sized β-Sn particles. The fine β-Sn nanoparticles in the Al-Cu-Sn-Er alloy heterogeneously nucleated on Al8Cu4Er (average size of about 167±45 nm), making Al8Cu4Er grow into particles. After secondary processing, stacking faults (SFs) appeared in the substructures of the three alloys, and the precipitated phases were further refined. The size of most precipitated phases in Al-1.13Cu-0.12Sn and Al-1.01Cu-0.15Sn-0.22Er alloys is reduced to nanometer level. After the three-stage process, some of the Al2Cu precipitates in the Al-Cu alloy are also refined to the nanometer level, and the precipitates in the other two alloys are all refined to the nanometer level. Nanotwins also appear in Al-1.01Cu-0.15Sn-0.22Er alloy. The tensile strength of Al-1.13Cu-0.12Sn and Al-1.01Cu-0.15Sn-0.22Er alloys after three-stage alternating process is 303 MPa and 327 MPa, respectively. The elongations are 21.6 % and 23.3 %, respectively. The relative conductivity was 61.7 %IACS and 59.8 %IACS, respectively. The synergistic effect of microalloying of Sn and Er elements and three-stage alternating processing technology not only reduces the size of precipitates and twins in the alloy to the nanometer level, but also adjusts the distribution of dislocation tangles and stacking faults (SFs), improves the substructure configuration, and improves the mechanical and electrical properties of conductive aluminum alloys.

The evolution and dissolution mechanism of θ-Al2Cu phase and the analysis of precipitation of a novel AlCu phase during elevated aging

The evolution and dissolution mechanism of the θ-Al2Cu precipitates were investigated in this study by transmission electron microscopy (TEM) during the re-aging at high temperatures for a long time. The results advance the current knowledge of dissolution and its associated mechanisms of the θ-Al2Cu phase in AlCu alloys. In this study, the coarsening and dissolution of θ-Al2Cu phase in T6 heat-treated Al4Cu alloy during various times (0−1000h) of re-aging temperature 420 °C were studied experimentally and theoretically. The morphological characterization revealed that the θ-Al2Cu phases gradually increase in size and decrease in volume density during the aging process, which can be attributed to coarsening and dissolution phenomena occurring during re-aging. Additionally, a body-centered tetragonal AlCu phase is precipitated within the θ-Al2Cu phase during the high temperature re-aging process, which is a characteristic of this phase prior to dissolution. Moreover, the primary mechanisms responsible for the high temperature melting of the θ-Al2Cu phase are the formation of the AlCu phase and the initial melting of the Cu-poor region in the θ-Al2Cu phase. The Cu atoms in θ-Al2Cu phase dissolve and diffuse into the Al matrix, forming L12 ordered AlCu solute clusters through long-range diffusion.

Interfacial microstructure and fracture mechanism of Cu/Al composite plate jointing process assisted by pulsed current-melted Al spheres: Finite element analysis and experimental studies

In this work, a novel method based on pulsed-current-assisted vacuum sintering processes was employed to fabricate the Cu/Al laminated metal composites (LMCs) with outstanding mechanical properties. The microstructural evolution, interfacial characteristics, phase composition, mechanical properties, and fracture behavior of Cu/Al composites prepared by the melted Al spheres induced with high-frequency pulsed current were investigated. Results show that robust interfacial bonding without micropores and cracks, and the grain structure consists mainly of recrystallized and substructured grains characterized by high angular grain boundaries. Meanwhile, interfacial analysis identifies melted Al and Al2Cu phases within the transition layer, exhibiting distinctive features such as "Al+Al2Cu" corrugated interfaces and island eutectic structures. Additionally, mechanical properties demonstrate superior strength (210 ± 13 MPa) and elongation (27 % ± 0.7 %) in specimens with corrugated interfaces compared to those with flat interfaces. Finite element analysis further elucidates stress redistribution and fracture behavior, emphasizing the enhanced coordinated deformation in specimens featuring corrugated interfaces. These findings underscore the significance of interface engineering and microstructural refinement in optimizing the mechanical performance of Cu/Al composite materials, offering valuable insights for their application in diverse engineering domains.

Tailoring the coefficient of thermal expansion in a functionally graded material: Al alloyed with Ti-6Al-4V using additive manufacturing

Functionally graded materials enable the spatial tailoring of properties through controlling compositions and phases that appear as a function of position within a component. The present study investigates the ability to reduce the coefficient of thermal expansion (CTE) of an aluminum alloy, Al 2219, through additions of Ti-6Al-4V. Thermodynamic simulations were used for phase predictions, and homogenization methods were used for CTE predictions of the bulk CTE of samples spanning compositions between 100 wt% Al 2219 and 70 wt% Al 2219 (balance Ti-6Al-4V) in 10 wt% increments. The samples were fabricated using directed energy deposition (DED) additive manufacturing (AM). Al2Cu and fcc phases were experimentally identified in all samples, and aluminides were shown to form in the samples containing Ti-6Al-4V. Thermomechanical analysis was used to measure the CTE of the samples, which agreed with the predicted CTE values from homogenization methods. The present study demonstrates the ability to tailor the CTEs of samples through compositional modification, thermodynamic calculations, and homogenization methods for property predictions.

Effect of Ultrasound on Microstructure and Properties of Aluminum–Copper Friction Stir Lap Welding

In this paper, the influence mechanism of ultrasound on plastic flow and microstructure features of the aluminum–copper friction stir lap welding (Al/Cu-FSLW) process is systematically investigated by adjusting the welding speed and improving the shear rheology in the plastic stirring zone. Through adjusting the ultrasonic vibration and welding speed, the directional control of mechanical properties is realized. It is found that increasing the welding speed properly is beneficial to enhance the mechanical shear between the tool and the workpiece, thus forming more staggered layered structures at the copper side and improving the tensile strength of the weld. The acoustic softening enhances the viscoplastic fluid mixing and strengthens the mechanical interlock of the Al/Cu lap interface. As the welding speeds increase or ultrasonic vibration is applied, the thickness of Al/Cu intermetallic compound (IMC) decreases, and the tensile strength and elongation of the Al/Cu joints are enhanced. Compared with adjusting the welding speed, the ultrasonic vibration can further refine the copper particles which are stirred into the plastic zone, and the thinning effect of ultrasound on IMC layers is better than that of increasing welding speed. At the welding speed of 60 mm/min, the IMC layer thickness is reduced by 42% under ultrasonic effect. In three welding speed conditions, the UV reduced the absolute value of the effective heat of formation (EHF) for Al2Cu and Al4Cu9 and suppressed the formation of AlCu phase. Meanwhile, only when the welding speed is increased from 60 mm/min to 100 mm/min can the formation of AlCu be suppressed. Under the ultrasonic optimization, the stable improvement of welding efficiency is ensured.

Revealing the substantial impact of trace Mg addition on the microstructural configuration of a cast Al-Li-Cu-Zr alloy under various conditions

In this study, the impact of 0.2 wt% Mg addition on the microstructural configuration of a cast Al-2.5Li-2.5Cu-0.15Zr alloy under different heat treatment conditions was investigated using multiscale characterization. Results indicate that in the as-cast state, trace Mg forms the low-melting-point Al2CuMg eutectic phases and promotes grain refinement. In the natural aging state, trace Mg promotes the precipitation of fine Guinier-Preston (GP) zones independent of pre-existing δ′-Al3Li phases. In the artificial aging state, trace Mg mainly leads to the inducing of GP zones, suppression of θ′-Al2Cu phases, and promotion of T1-Al2CuLi phases. δ′ phases with slight diameter reduction and minimal S′-Al2CuMg phases with two variants are also observed. Atomic-level analysis of the two newly formed composite precipitates indicates that L12 structure phases on both sides of the GP zone have an anti-phase relationship. This study is expected to provide theoretical insights into the microstructural origins underlying the beneficial effects of Mg microalloying in cast Al-Li-Cu alloys.

Study on the mechanical properties and microstructures of Al-Cu-Mg alloy thick plates obtained by different hot rolling processes

Abstract In the research, the microstructures of large-scale 2324 aluminum alloy thick plates obtained through two different hot rolling processes are investigated by using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and Electron Backscatter Diffraction (EBSD). Additionally, the tensile properties of the plates are evaluated at room temperature. The results indicate that the thick plates produced by Process A exhibit higher tensile and yield strengths along the L (longitudinal) and LT (long transverse) directions. The higher proportion of deformed microstructures is an important factor contributing to their enhanced tensile and yield strengths. Meanwhile, the different rolling processes have minimal impact on the kind and distribution of the second phase in the hot-rolled thick plates, with the second phase primarily consisting of Al2Cu and Al2CuMg phases, which are distributed in a streamlined way along the rolling direction of the thick plates. The microstructures of the hot-rolled thick plates obtained from both hot-rolling processes are dominated by deformed structures. The thick plates produced by Process B have relatively smaller grain sizes and a higher degree of fragmentation, making their microstructure more susceptible to recrystallization transformation during subsequent solution heat treatment.