Al-Cu Alloys Research Articles

Fresh insights into structure-function-integrated self-antibacterial Cu-containing Al alloys: giving Al alloys a new function.

Contact infection by bacteria and viruses is a serious concern to human health. The increasing occurrence of public health problems has stimulated the urgent need for the development of antibacterial materials. Al alloys are the fastest-growing mass-produced material group, a prerequisite for the lightweight design of vehicles, food containers and storage, as well as civil-engineering structures. In this work, the structure-function-integrated concept was used to design and produce self-antibacterial Al-xCu (x = 2.8 and 5.7) alloys for the first time ever. The antibacterial tests indicated that Al-2.8Cu and Al-5.7Cu alloys provided a stable and efficient bacteriostatic rate against S. aureus and E. coli, which was 87% for Al-2.8Cu and 100% for Al-5.7Cu against S. aureus at 24 h, and 89% for Al-2.8Cu and 94% for Al-5.7Cu against E. coli at 24 h. The antibacterial effect was similar to the commonly-used antibacterial materials with a similar Cu content. Furthermore, the mechanical properties and corrosion resistance of Al-2.8Cu and Al-5.7Cu were comparable to those of the current commonly-used commercial casting Al-Cu alloys. Structural insights into the performance and biomedical function by Cu-rich precipitates provided understanding of the mechanisms of these structure-function-integrated self-antibacterial Cu-containing Al alloys: (i) the Cu-rich precipitates produced strengthening, and (ii) the immediate contact with Cu-rich precipitates and the Cu2+ caused a synergistic action in improving antibacterial activity. This work gives Al alloys a new function and inspires fresh insights into structure-function-integrated antibacterial Al alloys.

Effects of laser cladding and plasma nitriding on microstructure and properties of Cu-Al alloy

Effects of laser cladding and plasma nitriding on microstructure and properties of Cu-Al alloy

Transfer learning for accurate description of atomic transport in Al-Cu melts.

Machine learning interatomic potentials (MLIPs) provide an optimal balance between accuracy and computational efficiency and allow studying problems that are hardly solvable by traditional methods. For metallic alloys, MLIPs are typically developed based on density functional theory with generalized gradient approximation (GGA) for the exchange-correlation functional. However, recent studies have shown that this standard protocol can be inaccurate for calculating the transport properties or phase diagrams of some metallic alloys. Thus, optimization of the choice of exchange-correlation functional and specific calculation parameters is needed. In this study, we address this issue for Al-Cu alloys, in which standard Perdew-Burke-Ernzerhof (PBE)-based MLIPs cannot accurately calculate the viscosity and melting temperatures at Cu-rich compositions. We have built MLIPs based on different exchange-correlation functionals, including meta-GGA, using a transfer learning strategy, which allows us to reduce the amount of training data by an order of magnitude compared to a standard approach. We show that r2SCAN- and PBEsol-based MLIPs provide much better accuracy in describing thermodynamic and transport properties of Al-Cu alloys. In particular, r2SCAN-based deep machine learning potential allows us to quantitatively reproduce the concentration dependence of dynamic viscosity. Our findings contribute to the development of MLIPs that provide quantum chemical accuracy, which is one of the most challenging problems in modern computational materials science.

Impact of Combined Zr, Ti, and V Additions on the Microstructure, Mechanical Properties, and Thermomechanical Fatigue Behavior of Al-Cu Cast Alloys

The effects of minor additions of the transition elements Zr, Ti, and V on the microstructure, mechanical properties, and out-of-phase thermomechanical fatigue behavior of 224 Al-Cu alloys were investigated. The results revealed that the introduction of the transition elements led to a refined grain size and a finer and much denser distribution of θ″/θ′ precipitates compared to that of the base alloy, which enhanced the tensile strength but reduced the elongation at both room temperature and 300 °C. Constitutive analyses based on theoretical strength calculations indicated that precipitation strengthening was the primary mechanism contributing to the strength of both tested alloys at room temperature and 300 °C. The out-of-phase thermomechanical fatigue test results showed that the addition of transition elements caused a slight decrease in the fatigue lifetime, which was mainly attributed to the reduced ductility and higher peak tensile stress at low temperatures. During the fatigue process, the transition element-added alloy exhibited a lower coarsening ratio, indicating higher thermal stability, which mitigated the negative impact of the reduced ductility on the fatigue performance to some extent. Considering their various properties, the addition of Zr, Ti, and V is recommended to improve the overall performance of Al-Cu 224 cast alloys.

Microstructure and radiation shielding capabilities of Al-Cu and Al-Mn alloys

In this study, the microstructure and elemental analysis of aluminum-copper alloy type-2024, Al-2024, and aluminum-manganese alloy type-3003, Al-3003, have been investigated by using a scanning electron microscope (SEM) equipped with Energy dispersive spectroscopy (EDS) detector. Experimental and theoretical radiation shielding studies were performed to assess the radiation shielding capabilities of the studied alloys. Considering the radiation shielding theoretical assessment, some reliable software tools were used, such as Phy-X/PSD, MCNP5, NXCom, and MRCsC. The microstructural observations and results have shown the presence of second phases rich with the main alloying elements in both alloys. Considering Al-2024 alloy, coarse second-phase particles, having a size range of 8–15 μm, were found aligning in lines parallel to the rolling direction, whereas smaller ones, having a size range of 2–8 μm, were found decorated the grain boundaries. Also, dark holes represent the pull-out large particles separated during preparation indicated poor adhesion with the main matrix that could be a result of losing particle coherency with the matrix where the misorientation in-between the atomic planes increase. However, better adhesion of the second-phase particles with the matrix, which were found possessing smaller particle size, have been observed in the Al-3003 alloy indicating good coherency and better manufacturing process for the non-heat-treatable alloy. The second-phase particles in case of Al-2024 alloy were found containing significant content of high-Z elements like Cu with greater volume fraction equals 7.5%. On the other side, Al-3003 alloy has possessed second-phase particles which lack of high-Z elements with only volume fraction equals 3.5%. All the former besides the higher density and content of high-Z elements like copper in Al-2024 alloy in compare to Al-3003 alloy and pure aluminum, led to relatively better radiation shielding capabilities against energetic photons, the highest in the low energy band and decreases with the increase of the photon energy, and slight superiority in the case of fast neutrons with only 3%inc. over pure aluminum. For instance, the radiation protection efficiency (RPE) values dropped from about; 23.2, 21.6, and 20.8% at 0.100 MeV to only 5.7, 5.9, and 5.6% at Eγ = 2 MeV, for; Al-2024, Al-3003, and Al-Pure, respectively."Please check and confirm that the authors and their respective affiliations have been correctly identified and amend if necessary.""confirmed"

Analysis of forming-ageing route on post-incremental forming microstructure, mechanical properties and residual stresses of an Al-Cu alloy

Analysis of forming-ageing route on post-incremental forming microstructure, mechanical properties and residual stresses of an Al-Cu alloy

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.

Optimal Arrangements and Local Anisotropy of {100} Guinier-Preston (GP) Zones by Parametric Dislocation Dynamics (PDD) Simulations.

Stress-oriented precipitation and the resulting mechanical anisotropy have been widely studied over the decades. However, the local anisotropy of precipitates with specific orientations has been less thoroughly investigated. This study models the interaction between an edge dislocation source and {100} variants of Guinier-Preston (GP) zones in Al-Cu alloys using the parametric dislocation dynamics (PDD) method. Concentric geometrically necessary dislocation (GND) loops were employed to construct a line integral model for thin platelets. The simulations, conducted with our self-developed code based on Green's function method and Eshelby inclusion theory revealed distinct strengthening behavior along the strong and weak directions for 60° GP zones, demonstrating anisotropic strengthening from the perspective of elastic interactions. Furthermore, the optimal inclined arrangement of the GP zone array was determined through elastic energy calculations, and these results were corroborated by TEM observations.

Al-Ti-C (CNTs) master alloys improve room temperature and high-temperature mechanical properties of ZL205A alloy

The insufficient high-temperature properties of Al-Cu alloys represent a significant obstacle to their further development. The use of master alloy refiners can enhance the mechanical properties while refining the grains. This paper describes the preparation and characterization of Al-Ti-C (CNTs) master alloys containing submicron TiC particles through the aluminum melt reaction method, utilizing graphite powders (GPs) and (CNTs) as carbon sources,respectively.The effects of these two types of intermediate alloys on the microstructures and high-temperature mechanical properties of the ZL205A alloy were investigated at varying additive amounts. The results indicate that the Al-Ti-C (CNTs) master alloys contain TiC particles measuring up to 183 nm and 480 nm, respectively, with the Al-Ti-CNTs demonstrating a superior effect on the refinement of the ZL205A alloy. The optimal mechanical properties were achieved upon the addition of 0.3 wt% of the master alloy to the ZL205A alloy. The mechanical properties improved from 341.53 MPa (yield strength), 371.68 MPa (tensile strength), and 3.3 % elongation without the addition of master alloys to 413.20 MPa, 471.82 MPa, and 11.2 % with the addition of Al-Ti-CNTs and to 440.85 MPa, 492.61 MPa, and 10.8 % with the addition of Al-Ti-C, respectively.At a high temperature of 300°C, the mechanical properties of the ZL205A alloy improved from 144.0 MPa and 10.8 % (Al-Ti-C) to 174.87 MPa and 11.2 %, and 195.1 MPa and 13.8 % (Al-Ti-CNTs). The TiC particles generated in situ under a different carbon sources demonstrated distinct mechanisms in the grain refinement of the ZL205A alloy. TiC (GPa) with a larger size primarily impeded the further growth of grains, while TiC (CNTs) promoted the formation of crystalline nuclei and heterogeneous nucleation sites, thereby achieving grain refinement. Large-sized TiC particles prepared using graphite as the carbon source hindered further grain growth, whereas TiC produced using carbon nanotubes promoted the formation of nuclei and heterogeneous nucleation sites, resulting in grain refinement. In addition, both types of TiC particles contribute to the densification and strengthening of the ZL205A alloy through fine grain strengthening, precipitation strengthening, Orowan strengthening, load transfer strengthening, the pinning effect, and thermal mismatch strengthening. However,TiC(CNTs) exhibits a greater contribution to strength due to its high quantity and small size.

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.

Grain refinement and mechanical properties improvement of additively manufactured Al-Cu alloy through pre-deformation in thermo-mechanical treatment

Inferior mechanical properties induced by porosity and coarse grains of wire-arc additively manufactured Al-Cu alloy restrict its industrial application. The inter-layer cold rolling, conventional heat treatment (T6) and thermo-mechanical heat treatment (T8) was applied to Al-Cu alloy, and the effect of pre-stretched strain in T8 treatment was investigated. The pre-stretched strain induces equal increments of hardness and YS for both the as-deposited and cold-rolled conditions before aging treatment, while the increments for cold-rolled samples are larger after aging treatment. The cold-rolled sample shows better tensile properties than the as-deposited sample with the same pre-stretched strain in T8 treatment, proving that T8 treatment further increased the strengths compared to the T6 treatment. It shows the best tensile properties with the pre-stretched strain of 5 %, exceeding the properties of 2219-T87 plate. With the increased pre-stretched strain, the density of the θ′ phases significantly increases; while further increase to 10 % pre-stretched strain induces severe coarsening of θ′ phases. Therefore, an optimized pre-stretched strain leads to high-density and tiny dispersed θ′ phases, thus resulting in the best tensile properties. Grain refinement induced by inter-layer cold rolling and uniformly precipitated phases resulted from proper pre-stretched strain both contribute to the strengths enhancement. The strengthening mechanism of hybrid additive manufacturing and inter-layer cold rolling followed by T8 treatment was discussed.

Influence of Mn Addition on the Evolution of Precipitates in Al-Cu Alloys

Influence of Mn Addition on the Evolution of Precipitates in Al-Cu Alloys

The many faces of θ'-Al2Cu precipitates: Energetics of pristine and solute segregated Al/θ' semi-coherent interfaces

θ'-Al2Cu precipitates in Al-Cu alloys have various distorted octagon shapes, which can be explained by the competition between {100} and {110} type semi-coherent interfaces with the Al matrix. While most prior studies on the semi-coherent Al/θ' interfaces have focused on the {100} orientation, little is known about the {110} interface. We have investigated the energetics of pristine and solute-segregated {110} semi-coherent Al/θ' interfaces with advanced characterization and first-principles studies. We report interfacial, strain, and solute segregation energetics of the {110} Al/θ' semi-coherent interface for 39 elements and compared them with previously reported values of the {100} interface. We discuss the atomic features and atomic local structures to identify similarities and differences between the two types of Al/θ' semi-coherent interfaces. The isotropy in pristine Al/θ' semi-coherent interfacial energy and the anisotropy resulting from solute segregation provide insight into the formation of different types of θ' precipitate “faces” reported in the literature.

Origins and optimization mechanisms of periodic microstructures in Al-Cu alloys fabricated by wire arc additive manufacturing combined with Interlayer Friction Stir Processing

Inter-layer Friction Stir Processing on Arc Additive Manufactured Components offers significant potential for performance enhancement, yet the homogenization of microstructures has become a challenge for industrial application. To address this, 2319 Al-Cu alloy components were fabricated through the Wire Arc Additive Manufacturing + Interlayer Friction Stir Processing (WAAM-IFSP)1 technique, and a systematic study was conducted on the effects of deformation degree, deformation temperature, and strain rate changes on the microstructural evolution, revealing three distinct periodic microstructures. An increase in deformation degree resulted in a uniform periodic microstructure, attributed to the more uniform internal deformation caused by the increased deformation degree. At a deformation degree of 24.1 %, higher strength and ductility were achieved, along with a notable bimodal grain structure (BGS). Further research indicated that this structure would distribute more widely within the matrix with increasing strain rate, aiding in further performance breakthroughs, ultimately reaching an ultimate tensile strength (UTS) of 404 MPa and an elongation (EL) of 32 %. However, imperfections in the process led to inhomogeneity in the structure. Focusing on the dynamic recrystallization (DRX) mechanisms during stirring can improve this phenomenon. The research revealed that the fine grains in the BGS were controlled by a synergy of dominant discontinuous dynamic recrystallization (DDRX) and auxiliary continuous dynamic recrystallization (CDRX) nucleation mechanisms. The findings are expected to provide a theoretical basis for the optimization of WAAM-IFSP processes and microstructural and performance regulation, which is crucial for enhancing the industrial application prospects of aluminum alloys.

A quantitative study of the solute diffusion zone during solidification of Al-Cu alloys via in-situ synchrotron X-radiography and numerical simulation

The solute diffusion zone plays a critical role in determining nucleation efficiency during heterogeneous nucleation. In this study, in-situ synchrotron X-radiography and numerical modeling were employed to investigate the Solute Suppressed Nucleation Zone (SSNZ) surrounding growing equiaxed grains in Al-13Cu alloys. Quantitative analysis of SSNZ and constitutional undercooling was conducted using image processing techniques. Solute concentration and SSNZ length in the <110> direction exceed those in the <100> direction, suggesting higher solute enrichment in dendrite centers. This causes greater undercooling in the dendrite growth direction (<100>) with faster dendrite growth rates. As equiaxed dendrites grow, SSNZ length in the <100> direction decreases while increasing significantly in the <110> direction. Utilizing data obtained from numerical simulations, we refined the analytical equation governing solute distribution preceding the solid–liquid interface under three-dimensional conditions, and the computational equation determining the SSNZ length. The SSNZ lengths derived from the optimized equation along the <100> and <110> directions demonstrate more agreement with both experimental observations and numerical simulation outcomes. Higher growth rates rapidly increase undercooling, limiting the development of nucleation-free zone. Additionally, SSNZ area growth slows at higher cooling rate, correlating with increased solute concentration and reduced area in SSNZ.

Research on the differences of mechanical properties between horizontal and vertical in al-cu alloy deposits fabricated by wire + arc additive manufacturing

Research on the differences of mechanical properties between horizontal and vertical in al-cu alloy deposits fabricated by wire + arc additive manufacturing

A phase field crystal model for real-time grain boundary formation and motion in complex concentration alloy

The complex concentration alloys exhibit the excellent mechanical property due to the dual roles of their heterogeneous compositions and microstructures. However, the formation and motion of grain boundaries to significantly regulate the mechanical properties remain unknown at several microsecond and nanoscale in the complex concentration alloys. Here, we utilize a phase field crystal model to investigate the real-time grain boundary formation and motion in complex concentration alloys, specifically, in comparison to traditional alloys, using the example of AlCu alloys. Our findings reveal that the low concentration alloys exhibit segregation primarily at grain boundaries with minimal compositional fluctuations over a long period of grain growth, and the complex concentration alloys display a high concentration gradient within the grains to cause rapid grain rotation and merging in a short time frame. In the complex concentration alloys, the large component fluctuations not only cause the local lattice distortion to hinder dislocation movement during the deformation process, but also lead to the occurrence from dislocation locking to self-unlocking, which is beneficial to improve the strength and ductility. The present work provides a real-time atomic-scale understanding of grain boundary evolution using in situ atomic-resolution simulations.

Nucleation-dependent early growth of dendritic grains in Al-Cu alloys: The real-time observations and large-scale phase-field simulations

Formation of a dendritic grain starts from nucleation and then growth propagation occurs. Through the in situ and real-time solidification experiments of Al-Cu alloys observed by synchrotron X-ray imaging, it is found that the early-stage free growth rate of dendritic grains goes far beyond the concept described by the classical crystal growth theory. The rate gradually drops down even though the liquid is continuously cooled down. Quantitative 3D phase-field simulations demonstrate that this abnormal early-stage growth behavior depends strongly on the nucleation. A critical nucleus can grow rapidly to a peak rate driven by the initial nucleation undercooling, and then its rate gradually drops down to a minimum before it approaches the steady-state free growth regime. This strong dependence of the early-stage growth on the nucleation is then supported by an analytical model, and this correlation enables the accurate identification of the nucleation undercooling for each grain in the experiment and thus allows for a large-scale quantitative simulation of the real-time observed polycrystalline growth. This progress provides a comprehensive understanding on the crystal growth kinetics from a critical nucleus to the growth end, and thus will provide a new theoretical framework to design novel technology to control the solidification microstructures.

Effect of multi-pass overlapping friction stir processing on fatigue behavior of Al-Cu alloy

More than half of mechanical breakdowns stem from fatigue failure, often occurring suddenly and without warning. Friction stir processing (FSP) enhances the material's toughness and resilience to fatigue by refining its grain structure. This study investigates how multi-pass overlapping technique impacts the fatigue crack growth rate of FSPed Al-Cu alloy. Microstructural analysis revealed that the stir region exhibited uniformly dispersed and fragmented precipitates and finely recrystallized ultrafine grains. The hardness and strength were reduced, and ductility was enhanced after FSP due to high thermal cycling. Fatigue testing demonstrated a significant increase in fatigue life and reduced fatigue crack growth rate attributable to the combined effects of precipitation and grain refinement during cooling-assisted FSP. SEM examination of fatigue fracture surfaces revealed dimples indicative of ductile failure in the rapid crack propagation zone, while the steady-state propagation region displayed striation markings and secondary fractures.

The structural stability and mechanical properties of doped Al2Cu precipitates with different elements by first-principles calculations

The Al2Cu precipitates (θ phase) is an important strengthening phase of Al- Cu alloy, which has a significant effect on the comprehensive mechanical properties of the material. This study employed first-principles calculations based on density functional theory to investigate the effects of doped elements X (X = Fe, Mn, Mg, Sc, and Zr) on the structural stability, mechanical properties, and electronic structure of the θ phase. The calculations of forming energy, cohesive energy, and phonon spectrum show that different doping elements have different substitution sites for Al or Cu in θ phase, and the doped θ phase has good structural stability. The calculation results of elastic constants show that doping Fe can enhance the hardness and stiffness of θ phase, reduced Mn content can improve its ductility, while the introduction of Mg can improve the shear modulus of θ phase. Sc is the most effective element to improve the anisotropy of θ phase, and the addition of Zr can makes θ phase better ductility. By electronic structure analysis, it is found that the incorporation of doping elements promotes covalent interactions with Al and Cu atoms, thus enhancing the stability of the θ phase. Charge density and Bader charge analysis reveal that the Fe and Mn atoms experience electron gain in the doped θ phase, whereas the Mg, Sc, and Zr atoms undergo electron loss. The results of this study provide useful information for the composition design and performance optimization of Al-Cu alloys.