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θ' -Al 2 Cu 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. [Display omitted] [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) technologies have been used to repair aluminum (Al) alloy components in many engineering structures. However, the use of AM technologies to repair Al-Cu alloys is still very limited, and the repair via electron beam directed energy deposition (EB-DED) has not been reported so far. In this work, the EB-DED repair was performed on AlCu4MgSi-O Al alloy substrate with the specially developed Al-Cu-Si wire (380D). The results show that wall structures with high metallurgical quality were successfully prepared. The deposit exhibits alternating fine grain zones and coarse grain zones. In the bottom layers of deposit, columnar grains growing along building direction dominate, while the middle and top layers mainly consist of equiaxed grains. In the AlCu4MgSi-O substrate, the heat-affected zone (HAZ) close to the fusion line undergoes recrystallization and completely transforms into fine equiaxed grains, while abnormal grain growth occurs and coarse grains are formed in the HAZ slightly away from the fusion line. From substrate to deposit, the intensity of texture gradually decreases. After EB-DED repair, the microhardnesses and strengths of the bottom layers and HAZ are significantly improved. The strengthening of HAZ is entirely attributed to precipitation strengthening, while the bottom layers are affected by both precipitation strengthening and dispersion strengthening. Tensile tests indicate that the repaired structure samples fracture from the interface between HAZ and base metal zone of the AlCu4MgSi-O substrate. EB-DED is demonstrated to be a promising technology to repair AlCu4MgSi alloy components, and this work can serve as a useful reference for the high-quality repair of Al-Cu alloy structural parts. • EB-DED was used for the first time to repair AlCu4MgSi-O alloy, with the specially developed Al-Cu-Si wire. • The evolution of grain morphology, precipitation behaviors and mechanical properties from substrate to deposit was studied. • After EB-DED process, the closer to the fusion line, the more are θ′ precipitates. • The thin-wall repaired structure exhibits higher strength than the AlCu4MgSi-O matrix. [ABSTRACT FROM AUTHOR]

Microstructural evolution and creep response were investigated in the cast Al-5.0Cu-0.3Mn-0.2Zr (wt.%) alloy with and without addition of slow-diffusing, intermetallic-forming elements Fe, Ni, or Co. Baseline Al-5.0Cu-0.3Mn-0.2Zr alloy exhibits high creep resistance at 300 °C, up to ∼75 MPa, which is attributed to high-aspect-ratio, intragranular θ′-Al 2 Cu precipitates that effectively suppress dislocation climb. However, θ′-Al 2 Cu precipitate-free zones form along grain boundaries upon heat treatment, whose extent is amplified during subsequent creep. Such weak regions experience dislocation creep, leading to strain localization and acceleration of grain-boundary sliding. Adding Ni and Co, individually or in combination, leads to the formation of grain-boundary precipitates (Al 9 Co 2 , Al 3 Ni 2) which are resistant to coarsening, thus suppressing the formation of θ′-Al 2 Cu precipitate-free zones. This microstructure provides high creep resistance at stresses up to 75–80 MPa, with strain rates much lower than in unmodified Al-5.0Cu-0.3Mn-0.2Zr. Adding Fe, which results in extensive decoration of grain boundaries with coarsening-resistant Al 7 Cu 2 Fe, and then increasing the Cu content to compensate for the Cu loss to this new phase, leads to a new Al-7.4Cu-1.6Fe-0.3Mn-0.2Zr alloy with creep resistance at 300 °C that surpasses known cast aluminum alloys. Adding Fe to improve the creep resistance of Al-Cu alloys is both cost-effective and sustainable. Our findings offer guidelines applicable to various alloy systems on controlling the evolution of precipitate-free zones and its ensuing effects on creep deformation. [ABSTRACT FROM AUTHOR]

Solute segregation at the interface between the aluminum (Al) matrix and the Ω ( Al 2 Cu) phase decreases the interfacial energy, impedes the coarsening of precipitates, and enhances the thermal stability of such precipitates. In this study, we employ density functional theory to systematically calculate solute segregation energies of 42 solute elements at the coherent and semi-coherent interfaces between the two phases, as well as mixing energies of these elements within the Al and Cu sublattices of the Ω phase. Using correlation analysis and machine learning methods, we establish the relationship between the solute segregation energy and 20 selected atomic descriptors. Metalloid and late transition metal elements are predicted as potential candidates for enhancing the thermal stability of Al–Cu alloys. We observe that the solute segregation energy at the interfacial site of the semi-coherent interface correlates with the atomic size of solute atoms and their solubilities within the Ω phase. The developed machine learning models exhibit the potential to predict solute segregation energies at various sites of the coherent and semi-coherent interfaces. Overall, our study provides valuable insights into the stabilizing potential of individual elements at the Ω /Al interface in Al–Cu alloys. [Display omitted] [ABSTRACT FROM AUTHOR]

Electric vehicles are a viable alternative for internal combustion engine cars to overcome transportation problems due to high fossil fuel consumption and greenhouse gas emissions. Due to their direct current motor and battery technologies' technological development, they have become an efficient transportation option in the last decades. However, the rapid spread of electric vehicles will bring huge dump problems for the environment. Thus, policies related to the recycling of their components must be carried out. In this study, an Al–Cu alloy is developed from the waste direct current motor's Cu rotor coils and pure Al for hydrolysis reactions. Then, 2 wt%, 4 wt% and 6 wt% Cu are added to pure Al to observe different Cu addition to Al–Cu alloy's hydrogen production performance to varying temperatures like 40, 60, and 80 °C. In 40 °C, 6 wt% Cu added Al alloy has around two-fold higher hydrogen production than pure Al. Moreover, the hydrolysis reaction's activation energy is decreased from 81.56 to 35.5 kJ mol−1 in 6 wt% Cu added Al alloy. [Display omitted] • Al–Cu alloy is developed from waste DC motor's Cu rotor coils and pure Al. • Activation energy is decreased from 81.56 to 35.5 kJ mol−1 in AlCu6 alloy. • In AlCu6 alloy, 0.17 ml s− 1 hydrogen generation rate is obtained at 40 °C. • Corr rate of the pure Al is changed from 28.78 to 86.56 ml g−1 min−1 by 6 wt% Cu addition. [ABSTRACT FROM AUTHOR]

During the solidification process, the recycled Al-Cu alloys form coarse Fe-rich phases, which seriously deteriorate the mechanical properties of the alloy. The study employed optical microscope (OM), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and synchrotron X-ray imaging to investigate the impact of cooling rate and Fe contents on the growth of Fe-rich phases, Al 2 Cu, and pores in recycled Al-Cu-Mn-Mg-Fe-Si alloys under synergistic effect ultrasonic melt processing (USMP) and Al-Ti-B. USMP can homogenize the distribution of TiB 2 particles and provides more nucleation sites for the formation of Fe-rich phases. Under the synergistic effect of USMP and Al-Ti-B, increasing the cooling rate,the volume fractions of Fe-rich phases in 0.7FeUB (0.7 wt%Fe + USMP + Al-Ti-B) and 1.2FeUB (1.2 wt%Fe + USMP + Al-Ti-B) alloys decreased from 8.92% and 16.52% to 8.03% and 14.73%, respectively. The volume fraction of Al 2 Cu increased from 4.06% and 3.13% to 4.37% and 3.54%, respectively. Furthermore, the three-dimensional (3D) morphology of Fe-rich phases and Al 2 Cu became more compact and uniform. The volume fraction of pores in the 1.2FeUB alloy decreased from 0.412% to 0.072%. In-situ synchrotron X-ray radiography revealed that increasing cooling rates led to increased nucleation undercooling of primary α-Al and Fe-rich phases. These phenomena can be attributed to the combined effects of ultrasonic cavitation, ultrasonic streaming, and an increased cooling rate. These factors serve to homogenize the alloy composition, ensure uniform distribution of TiB 2 particles, inhibit element diffusion, reduce solute segregation, and ultimately lead to the refinement of the grain size, α-Al, Fe-rich phases, and Al 2 Cu, while also inhibiting pore growth. • Increasing the cooling rate under the synergistic effect of USMP and Al-Ti-B, refine the grain size. • Under the synergistic effect of USMP and Al-Ti-B, increasing the cooling rate resulted in a more compact 3D morphology. • Increasing the cooling rate increases the nucleation undercooling and reduces the size of α-Al and Fe-rich phases. [ABSTRACT FROM AUTHOR]

The influence of different types of precipitates (either Guinier-Preston zones, θ ″ or θ ′) on the critical resolved shear stress and strain hardening was determined by means of micropillar compression tests in an Al - 4 wt% Cu alloy. The size, shape and volume fraction of the precipitates were measured in each case. It was found that size effects were negligible for micropillars with diameter ≥ 5 µm. Micropillars with Guinier-Preston zones showed strain localization due to precipitate shearing. The best mechanical properties were obtained with either a fine dispersion of the θ ″ precipitates or a coarser dispersion of θ ′. Both precipitate shearing and Orowan loops were observed around the θ ″ precipitates and the micropillar strength was compatible with the predictions of the Orowan model. In the case of the alloy with θ ′ precipitates, the strengthening contribution associated with the transformation strain around the precipitates has to be included in the model to explain the experimental results. Finally, the micropillar compression tests in crystals with different orientations were used to calibrate a phenomenological crystal plasticity. This information was used to predict the mechanical properties of polycrystals by means of computational homogeneization. [ABSTRACT FROM AUTHOR]

The mechanisms of dislocation/precipitate interactions were analyzed in an Al–Cu alloy containing a homogeneous dispersion of θ ′ precipitates by means of discrete dislocation dynamics simulations. The simulations were carried out within the framework of the discrete-continuous method and the precipitates were assumed to be impenetrable by dislocations. The main parameters that determine the dislocation/precipitate interactions (elastic mismatch, stress-free transformation strains, dislocation mobility and cross-slip rate) were obtained from atomistic simulations, while the size, shape, spatial distribution and volume fraction of the precipitates were obtained from transmission electron microscopy. The predictions of the critical resolved shear stress (including the contribution of solid solution) were in agreement with the experimental results obtained by means of compression tests in micropillars of the Al–Cu alloy oriented for single slip. The simulations revealed that the most important contribution to the precipitation hardening of the alloy was provided by the stress-free transformation strains followed by the solution hardening and the Orowan mechanism due to the bow-out of the dislocations around the precipitates. Image, graphical abstract [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of orientation and spatial distribution on CRSS is investigated. • Disk-shaped precipitates interact with the dislocation via an ellipsoidal potential field. • An orientation factor is proposed to describe the orientation related strengthening. • A modified Orowan model considering orientation distribution is suggested. • An extended model considering irregular spatial distribution of precipitates is suggested. Precipitates contribute significantly to the strength of many common engineering aluminum alloys. The stress orienting effect of disk-shaped θ′ precipitates in Al-Cu alloy may lead to varying orientation distribution of the precipitates and, thus, varying critical resolved shear stress (CRSS) and macroscopic mechanical properties. In this work, θ′ precipitates was incorporated into discrete dislocation dynamics (DDD) simulation software ParaDiS. This approach was applied to systematically investigate how CRSS is affected by the orientation distribution and spatial distribution of the θ′ precipitates which has a considerable effect on the CRSS but has received less attention in previous research. As a simplification, the orientation distribution of a one-dimensional equidistantly distributed sequence of precipitates are taken as the research object. By varying the orientation of each precipitate, DDD simulations with wide range of overall orientation distributions can be obtained. Based on this, we propose an orientation factor that can adequately define the relationship between the orientation distribution and the CRSS. A modified Orowan model considering orientation distribution with parameters calibrated by dislocation dynamics simulations is suggested in light of these investigations, enabling rapid prediction of CRSS. Subsequently, the spatial distribution of precipitates was described using the extreme distribution, and a spatial factor was created by examining the mean and variance. This model was extended to the case of complex precipitate distributions by considering the spatial factor. The accuracy of the extended model was verified through DDD simulation results for randomly distributed precipitates and the prediction accuracy was greatly improved. This work makes it possible to calculate precipitation strengthening in Al-Cu alloys quantitatively and precisely while accounting for specific orientation distribution and spatial distribution. [ABSTRACT FROM AUTHOR]

The influence of trace elements (0.01 at.% In/Sn) on the decomposition process of Al-Cu-(Mg) alloys during the very early stages of natural ageing has been investigated in situ by small angle X-ray scattering supported with differential scanning calorimetry and hardness measurements. In the binary Al-Cu alloy quenched-in vacancies are bound to In or Sn, resulting in a suppressed Cu clustering process. In Al-Cu-Mg room temperature hardening occurs much faster due to Mg entering the clusters. However, the influence of In or Sn is negligible. Cu and Mg possibly form complexes with quenched-in vacancies before they can reach a trace element atom. Unlabelled Image [ABSTRACT FROM AUTHOR]

This work describes the micro- and nanostructures of inert gas atomized Al-Cu alloy powder particles over a range of compositions. For cold spray deposition, the microstructure and elemental distribution within the feedstock powder play a critical role in determining the final microstructure and properties of the fabricated material. A series of Al-Cu binary alloy powders, ranging from 2 to 5 wt% Cu, were produced by inert gas atomization and were then thoroughly characterized using electron microscopy and X-ray diffraction. The gas atomized powder particles, nominally 20 μm in diameter, presented a cellular structure with θ (Al 2 Cu) phase forming along the cell boundaries. The continuity and phase fraction of the θ phase increased systematically with copper content. No Guinier-Preston zones were observed in the powders, but small, incoherent θ phase particles were observed in the matrix near the cell boundaries. The as-atomized particles were observed to be in a non-equilibrium state with a reduced amount of θ phase and altered lattice parameters for the α and θ phases. A mild, post-atomization annealing returned the θ phase fraction and lattice parameters to their equilibrium values. [ABSTRACT FROM AUTHOR]

In this study, the evolution of iron-rich intermetallics and their effects on room and elevated-temperature tensile properties of gravity die cast and squeeze cast 2A16 wrought Al alloys with high Fe content of 0.5% after T7 heat treatment were investigated by various methods. Compared to gravity die-cast alloys, squeeze cast 2A16 wrought Al alloys showed superior tensile properties at both room and elevated temperatures, especially in terms of elongation. This can be attributed to refinement in grain size and iron-rich intermetallics, which decreased porosity and raised dispersoids in α(Al) matrix. However, the increase in mechanical properties at high temperature resulting from applied pressure was lower than that obtained at room temperature. The results were attributed to the refinement in grain size and the weakness of grain boundary at elevated temperature. [ABSTRACT FROM AUTHOR]

Numerous previous researchers have used nucleation models as part of their simulation of droplet solidification. None of these have verified the nucleation portion of these models with experimental results. In this work, a heterogeneous nucleation model based on the classical nucleation theory was coupled with a thermal model of a falling droplet through a stagnant gas. The pre-exponential factor, which is usually unknown, was determined to obtain an undercooling similar to experimental results for a 196 μm droplet solidified in helium. A stochastic element was added by using a cumulative density probability function, leading to a range of possible nucleation undercoolings and nucleation points. The primary and eutectic undercoolings as well as the number of nucleation points were then compared with additional experimental results of Al-Cu alloy droplets. Good agreement was found between the calculated and the experimental undercoolings. Modeling results also suggest the presence of one nucleation point in the majority of cases and are in agreement with experimental observations. [ABSTRACT FROM AUTHOR]

A small amount of Zr and Ta are added to aluminium-copper (Al-Cu) alloys, and the evolution of strengthening phases with multi-step heat-treatment and their stability after prolonged thermal exposure at 250 °C has been studied. The L1 2 ordered (Al,Cu) 3 (Zr,Ta) precipitates were formed in the Al-matrix, followed by preferential nucleation of Cu-rich θ"/θ' plates on the L1 2 /matrix interfaces. Transmission electron microscopy and atom probe tomography studies established the segregation of Zr and Ta at θ' plate/matrix in the aged alloys. It is shown that Zr segregates at coherent broad interfaces of θ' plate and inhibits the growth of these interfaces. Segregation of Ta primarily occurs at the growing θ' plate interface in the lengthening direction (semi-coherent interface) along with Zr and restricts the lengthening of the plate. The restricted growth triggers sympathetic nucleation of newer plates at the plate edges to sustain the growth process. A yield strength of ∼475 MPa at room temperature is recorded due to the presence of ordered precipitates and the growth restriction of θ' plate. Segregation of slow diffusing elements (Zr and Ta) also enhances the thermal stability of the microstructure. [Display omitted] [ABSTRACT FROM AUTHOR]

A recent investigation has confirmed that solute atoms segregated to the interfaces between aluminum and θ ′-Al 2 Cu can extend the stability of metastable θ ′ to higher temperatures. Herein, we present an extensive first-principles database of the segregation energies of 34 elements to the Al/ θ ′ interface and identify key descriptors that can guide the design of higher temperature Al-Cu alloys. We find that the segregation energies are strongly correlated with the size and volume of solute atoms and their solubilities within θ ′. We provide a physical/chemical basis to the experimentally observed elemental hierarchy in terms of the ability of individual elements to stabilize the Al/ θ ′ interface. Finally, we suggest a new microalloying strategy that offers opportunities to further increase the critical temperature limit of Al-Cu alloys. [ABSTRACT FROM AUTHOR]

Laser remelting was employed to refine the interlamellar spacing (λ) to approximately 30 nm on an arc-cast Al-32.7 wt%Cu eutectic. λ scaled with A ′ (h) - ° 0.25 where h is the distance from the trace bottom, and A ′ is a factor dependent on laser processing conditions. A ′ increased with the laser power (at a constant spot diameter) but decreased with the spot diameter (at a constant laser power). The nanoindentation measured hardness increased up to 4.68 GPa with decreasing interlamellar spacing, following the Hall-Petch relation. The as-cast eutectics showed microcracks around indents, while cracking was suppressed in the laser remelted nanoscale eutectics. A dislocation theory based mechanism is proposed for the enhanced plastic co-deformation of fine scale laser-remelted Al-Al 2 Cu eutectics. [ABSTRACT FROM AUTHOR]

The present work deals with the effect of semisolid processing on microstructure and mechanical properties of Al-4.5% Cu – 5% TiB 2 in-situ cast composites. The composite was prepared by flux assisted synthesis in which TiB 2 particles were formed in-situ through an exothermic reaction between K 2 TiF 6 and KBF 4 halide salts. Al-4.5 wt% Cu alloy and Al-4.5% Cu-5% TiB 2 composite samples were forged in semisolid state with 0.3 vol fraction of liquid. Semisolid forging was carried out for two forge reductions (30% and 50% forge reductions). Microstructure studies show that the semi-solid forging results in uniform distribution of TiB 2 particles and Al 2 Cu particles in the composite. Further, TiB 2 particles play a dual role as grain refiners as well as reinforcements of composites. EBSD and nano indentation studies shows that semisolid forging results in dynamic recrystallization of grains in the composite with significant grain refinement which leads to a marked increase in hardness and elastic modulus of the alloy as well as the composite. [ABSTRACT FROM AUTHOR]

Porosity is a common casting defect induced by solidification shrinkage as well as gas segregation, nevertheless, it may exert a beneficial effect on reducing alloying element segregation. Unfortunately, the influence of porosity formation on alloying elements segregation in casting alloys have not been synthetically investigated by neither experiment nor theoretical analysis. In this regards, here a theoretical model, based on analyses of the redistribution behaviours of both gas element and the alloying elements, is proposed to simultaneously predict the porosity and segregation in as-solidified Al-based alloys. First, Al-4.5 wt pct Cu alloy with a columnar dendritic interface is selected to mathematically predict the porosity forming process. The modelling results show the same tendency with Poirier’s prediction, but the volume percentage of porosity calculated by the present model is lower than that of Poirier’s. Besides, the present model predicts a decrease in porosity fraction at late stage of solidification, and more than the previous studies, the gas escaped from eutectic liquid is also evaluated. Then, the impact of porosity formation on the velocity of interdendritic feeding flow is estimated, the porosity in the mushy zone apparently slow down the suction of interdendritic liquid. Finally, a mathematical model for element segregation is derived with consideration of porosity formation. Numerical results show that the solute enrichment in interdendritic liquid gets relieved slightly with porosity formation. Consequently, porosity will reduce the solute segregation. [ABSTRACT FROM AUTHOR]

We consider the effect of a mutual misorientation between two interacting equiaxed dendrites in polycrystalline materials on the scaling law of growth from undercooled melt. This effect is investigated by three-dimensional quantitative phase-field simulations of Al-Cu alloy solidification in thin samples. It has been found that the equiaxed dendritic growth kinetics changes due to the reduced solute interaction when considering mutual grain misorientation, and both the characteristic growth rate and primary dendritic arm length can be approximately correlated linearly to the misorientation of two dendrites. The scaling law, which originally uses the solute composition and the distance between two nuclei as physical parameters to describe the dynamics of primary dendritic arms, is then adapted with consideration of the misorientation. Compared with the previous scaling law that only concerns face-to-face growth of two dendrites, the predictions of the newly proposed scaling law taking the grain orientation in account are in better agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Creep mechanisms are studied in θ′-Al 2 Cu-strengthened Al-Cu-Mn-Zr alloys at 300 and 350°C for (i) ACMZ, a base alloy without further alloying elements and (ii) RR350, a commercial alloy with additions of Ni and Co forming distinct grain-boundary precipitates. At high stresses, creep is dominated by dislocations bypassing θ′ precipitates within grains via the Orowan mechanism, as evidenced by (ⅰ) very high stress exponent (n ∼20-25) and (ⅱ) α-Al and θ′ lattice strains (measured via in-situ neutron diffraction) evolving during creep in a manner consistent with load transfer from the plastically-deforming α-Al matrix to elastically-deforming θ′ precipitates. At intermediate stresses, both alloys exhibit a n ∼3 regime, where α-Al and θ′ lattice strains scale near-linearly with applied stress while remaining largely unaffected by strain accumulation, indicating that Orowan looping or dislocation pile-up around θ′ is now inactive within the grains. Rather, dislocation motion occurs solely in θ′-precipitate-free zones (θ′-PFZ) where high dislocation densities are observed via TEM after creep deformation. Plastic flow at θ′-PFZ and/or localized pipe diffusion are expected to enable grain-boundary sliding (GBS), which is proposed as the rate-limiting mechanism in the n ∼3 regime. Ni/Co-rich precipitates at RR350 grain-boundaries, with negligible θ′-PFZ around them, share load (as determined via neutron diffraction) with the α-Al matrix more effectively than θ-Al 2 Cu precipitates at ACMZ grain-boundaries, with wide surrounding θ′-PFZ. Thus, high creep resistance in the n ∼3 GBS regime of RR350 is enabled by coarsening-resistant grain-boundary precipitates, forming without concomitant development of weak θ′-PFZ, which effectively share load with the grains. [Display omitted] [ABSTRACT FROM AUTHOR]

The influence of large pre-deformation on the age hardening behaviors, tensile properties and precipitate characteristics in an Al-Cu alloy during artificial ageing was investigated using mechanical property measurements and electron microscopy. Room-temperature rolling of Al-Cu alloy with a thickness reduction of 80% plus a subsequent artificial ageing can result in a strength increase of 35% without sacrificing ductility compared with an alloy that is peak–aged using a conventional heat treatment process (T6). A large quantity of dislocations that accumulated during cold-rolling was retained in the alloy after post-ageing at 150 °C. Although dense dislocation walls and dislocation tangles that exist in cold-rolled Al-Cu alloys were expected to cause micro-structural heterogeneity, the plate-shaped precipitates on the {001} Al planes exhibited an exceptionally uniform distribution. Atomic-scale angular dark-field scanning transmission electron microscopy (ADF-STEM) revealed these precipitates are θ′–approximants with a crystal structure similar with the well–known tetragonal θ′ phase but with the body-centered position not fully occupied by Cu. In addition, the precipitate sizes were considerably refined as compared to the θ′ precipitates that were formed in the T6 peak-aged alloys. The microstructure–property relationships in the alloy are discussed to explain the observations. Our results suggest the deformation-modified precipitation may play a vital role in achieving better strength-ductility synergy. [ABSTRACT FROM AUTHOR]

An electrochemical method was developed for the formation of Al-Cu alloys. The electrodeposition of aluminum on Mo and Cu substrates was studied using cyclic voltammetry in molten LiCl-KCl-AlCl 3 (2 wt.%). During the cathodic scan of the cyclic voltammograms, three different Al-Cu alloys were observed before pure Al formed on the Cu substrate. The electrochemical formation processes were studied using square wave voltammetry and open circuit chronopotentiometry. The products of the different reduction processes were identified using XRD. The XRD results indicated that three different Al-Cu intermetallic compounds, Al 4 Cu 9 , AlCu, and Al 2 Cu, were obtained using electrochemical deposition in the molten salt system. [ABSTRACT FROM AUTHOR]

We report on the structure and mass transport properties of liquid Al–Cu alloys predicted by two recently-developed empirical many-body potentials: MEAM (Jelinek et al., 2012) and EAM-ADP (Apostol and Mishin, 2011), and by the well-known Gupta potential. Total and partial pair correlation functions, angular distribution functions, densities, coordination numbers and self-diffusion coefficients are compared with published experimental and ab initio results for a number of temperatures above the liquidus. Prevalent local orderings are characterized by means of Voronoi analysis. Densities and the temperature coefficient of density are compared with experiment for different compositions of the alloy. All three studied potentials, and EAM-ADP and MEAM in particular, display marked difficulty in describing mixed (Al–Cu) interactions. EAM-ADP mispredicts Cu-rich alloys to re-solidify at all temperatures studied, while MEAM’s predictions for the density and its temperature dependence are poor for Al-rich compositions. Overall, the best description of liquid Al–Cu is offered by the Gupta potential, which is found to give a reasonable picture of short-range order and predicts mass transport coefficients and densities in moderately good agreement with experiment. [ABSTRACT FROM AUTHOR]

Guinier-Preston (GP) zone is an important precipitate in Al-Cu alloys. In this work, atomic-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and first-principles calculations are combined to study paired GP zones and clustered GP zones that form frequently in samples of an Al-1.74at%Cu alloy under-aged at 120 and 160 °C. In addition to the well-known θ″-Al 3 Cu phase that comprises two Cu monolayers (GP zones) separated by three {002} layers of aluminium, a hitherto unreported θ′′′-Al 6 Cu phase, comprising two GP zones separated by six {002} layers of aluminium, is also frequently observed. Statistical counting indicates that the Al 6 Cu phase forms with a number density just below that of θ″-Al 3 Cu. The prolonged ageing at 120 °C and 160 °C leads to the formation of clusters comprising a mixture of θ″ and θ′′′ phases. First-principles calculations reveal that the origin of the regular and irregular stacks of GP zones is the enhanced Al-Al bonds induced by a pre-existing GP zone, which triggers a new GP zone to preferentially form at the position three or six {002} Al planes away from the pre-existing GP zone. The enhanced Al-Al bonds can not only explain the experimental observations made in the present work, but also rationalize previously reported precipitation phenomena associated with GP zone, θ″ or θ′ precipitate phase. All the relevant data are available from the corresponding author on request. • An unreported Al 6 Cu (θ''') precipitates are found in the under-aged Al-1.74at%Cu alloy. • GP zone clusters containing the mixture of Al 3 Cu (θ'') and Al 6 Cu (θ''') readily form. • Physical origin of GP zone stacking is the enhanced Al-Al bonds. • Such physical origin also explains the other θ'-associated precipitation phenomenon. [ABSTRACT FROM AUTHOR]

The effects of stress magnitude and crystallographic orientation on the mechanical properties of stress-aged Al–2Cu alloy single crystal specimens are investigated. The specimens with ( 1 - , 1, 6) plane orientation were stress-aged under 0, 15, 40, and 60 MPa. Specimens with five different plane orientations (( 1 - , 2 - , 6), (3, 1, 3), ( 1 - , 3, 3), ( 1 - , 1, 6), and ( 1 - , 4 - , 6)) were stress-aged under stress with the same magnitude of 40 MPa. The results of mechanical properties and TEM microstructure show that the yield stress of stress-aged specimens depends on the crystallographic orientation as well as the stress magnitude. A model based on crystallographic orientation describes the precipitation strengthening of stress-aged Al–2Cu alloy. The calculated yield stresses in the model fit well with the experimental observations. This model results not only provide important insight into solving the anisotropy problem attributed to precipitation strengthening, but also offer a benchmark for choosing the right range of stress in the manufacture of Al–Cu alloys. [ABSTRACT FROM AUTHOR]

• The first time applying in situ synchrotron imaging to Al-Cu alloy with La-Ce. • The real time solidification of Al-Cu alloy with La-Ce has been captured. • La-Ce decreases nucleation density of α-Al at a lower cooling rate. • La-Ce leads to grain refinement of α-Al at a higher cooling rate. The effect of La-Ce addition on the solidification behavior of hypoeutectic Al-Cu alloy was investigated using in situ synchrotron X-ray imaging with conventional casting experiments. The results show that La-Ce addition leads to a decrease in nucleation density and coarser grains at a lower cooling rate since La-Ce addition can suppress α-Al nucleation to a certain extent. At a higher cooling rate, melt undercooling can be increased by inhibiting early nucleation of α-Al on heterogeneous particles with large size, resulting in grain refinement. [ABSTRACT FROM AUTHOR]

In this study, Al-Cu alloy suitable for laser powder bed fusion (LPBF) is rapidly developed through casting and laser remelting. The microstructure of as-cast Al-Cu alloy is consisted of equiaxed grains, and it was significantly refined after remelting. The Vickers hardness in the remelted zone improved by approximately 33.7% compared with that of as-cast Al-Cu alloy. The effects of different element content on Al-Cu-Mg-Zr alloy were analyzed, and optimum alloy composition was obtained with Al-5Cu-2Mg-1Zr-0.3Mn-0.15Ti through comparing microstructure, the hardness and other properties after remelting. The nano-indentation hardness and Young's modulus of remelted Al-5Cu-2Mg-1Zr-0.3Mn-0.15Ti alloys were 1.86 and 86.7 GPa, respectively. The microstructure was dense without obvious crack after LPBF forming, and the tensile strength, yield strength and elongation values reach 483 MPa, 365 MPa and 13.4% after solution treatment. • The suitability of LPBF-fabricated alloys composition was judged by cast and laser remelting.. • The ultra-fine microstructure and Al2Cu dispersion distribution were observed in laser remelting alloy. • New composition Al-Cu alloy prepared by LPBF shows a dense structure and good mechanical behavior. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Al–Cu alloys modified by RE x O y have superior corrosion resistance than those unmodified alloys. [•] In 3.5wt.% NaCl solution, the corrosion resistance increases with the increasing RE x O y content. [•] In pH=4 acid solution, the corrosion resistance decreases with the increasing RE x O y content. [ABSTRACT FROM AUTHOR]

Combined effects of the cooling rate, alloy composition, and crystal-melt (CM) interfacial anisotropy on solidification of Al-Cu alloys are studied by integrating molecular dynamics and phase-field simulations. Capillary fluctuation method is used to determine the CM interfacial energy properties by molecular dynamics simulations for alloys ranging from 3 to 11 at% Cu. While the average CM interfacial energy decreases with increasing Cu content, its anisotropy does not present a clear trend with composition change. Primary and secondary dendrite arm spacings as well as θ-phase fraction are calculated by phase-field simulations, and validated against experimental measurements and analytical solutions at cooling rates ranging from 1 to 1250 K/s. Results show that the θ-phase fraction decreases with increasing the cooling rate, and this reduction is more drastic in alloys with a higher Cu content. Also, the microstructure features are influenced by the growth dynamics, where seaweed structure formation results in a more homogenous distribution of θ-phase and a finer microstructure. The effects of temperature gradient, Cu concentration gradient, and interfacial energy properties on the dendritic growth morphology of Al-Cu alloys are summarized by a map of supercooling versus the CM interfacial anisotropy to predict pattern formation. The results show that, irrespective of Cu content and cooling rate, the seaweed structure formation is halted at CM interfacial anisotropies larger than 0.005. As the anisotropy decreases, different seaweed structures can form regarding the constitutional supercooling. At low anisotropies (Al-3 and Al-8.4 at% Cu) and low supercooling (Al-3 at% Cu) fractal or degenerate seaweed is dominant while at high supercooling (Al-8.4 at% Cu) compact seaweed forms. This difference in supercooling stems from different solute atom transport rates. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights: [•] The effect of Fe-rich phases on squeeze cast Al–Cu alloys with high Fe content. [•] Four kinds of Fe-rich phases may present in Al–Cu alloys. [•] There is great tolerance to Fe impurities in squeeze cast Al–Cu alloys. [ABSTRACT FROM AUTHOR]

Abstract: In this study thin Al–Cu hypoeutectic alloys were mounted in a Bridgman furnace and solidified near isothermally from above the liquidus to below the eutectic temperature. The eutectic transformation is easily identified from the X-ray absorption contrast difference between the semi-solid mush and the fully solid phase in the field of view (FOV). By virtue of real time in situ X-radiography, and subsequent image analysis techniques, it was possible to directly observe and accurately measure eutectic nucleation, as well as transformation rate across the FOV. Post-solidified samples were then subjected to further microstructural analysis, whereby the lamellar eutectic spacings were measured at random locations across the FOV region. The lamellar spacings were correlated with the eutectic transformation rate and showed reasonable agreement with theoretical predictions. Some interesting observations, such as, for example, in situ observations of solidification shrinkage and the effect of liquid feeding through the semi-solid mush, are also discussed. [Copyright &y& Elsevier]

Abstract: Equal channel angular pressing (ECAP) is a material processing method that allows very high strains to be imposed, leading to extreme work hardening and microstructural refinement. Billets of nonhomogenized (as-cast) and homogenized Al–2 and 3wt.%Cu alloys were successfully processed by (ECAP) up to different number of passes at room temperature. The effect of the pre-homogenization treatment before the (ECAP) process on the fracture characteristics and wear properties was investigated. The pre-homogenization treatment has an obvious effect on the fracture mode and fracture surface morphology of the Al–Cu alloys. The homogenized alloys have higher wear resistance than the nonhomogenized alloys. The wear mechanism depends on the sliding distance, applied load and the homogenization treatment. The analysis of the worn surfaces indicates the transfer of higher Fe amount from the rotating disc into the sliding pin in the case of nonhomogenized alloys than that in the case of the homogenized alloys. [Copyright &y& Elsevier]

Abstract: The columnar - to - equiaxed transition (CET) was investigated in Al-Cu alloys (Al-1wt.%Cu, Al-4.5wt.%Cu, Al-15wt.%Cu and Al-33.2wt.%Cu) solidified directionally upward from a chill face. The CET occurs when the temperature gradient in the melt ahead of the columnar front reaches minimum and critical values. Two dimensionless numbers (Ω and Π numbers) that can relate the system parameters (cooling rate, local solidification time and liquidus temperature of the alloy) were defined. The Ω number which shows a linear relationship with the local solidification time and the Π number, that for the Al-rich region in the Al-Cu system, strongly depend on the macrostructure. These results are important to correlate the experimental values of physical quantities, which are relevant to describe the solidification process. [Copyright &y& Elsevier]

Abstract: Equal channel angular pressing (ECAP) is a material processing method that allows very high strains to be imposed, leading to extreme work hardening and microstructural refinement. Billets of nonhomogenized (ascast) and homogenized Al–2 and 3wt.%Cu alloys were successfully processed by ECAP up to different number of passes at room temperature. The microstructure was evaluated into ultrafine grained (UFG) microstructure with high grain boundary misorientation angle in the case of Al–Cu homogenized and nonhomogenized alloys due to imposed strain resulted. It was observed that more homogenized microstructures with smaller grain sizes and higher values of high grain boundary misorientation angle were obtained in the case of homogenized alloys. Higher improvement in the tensile properties and the microhardness values was noted in the case of Al–Cu homogenized alloys. The elongation% and uniform elongation% were observed to decrease with increase of the number of passes for all of the Al–Cu alloys except in the case of Al–3%Cu homogenized alloy. In the case of Al–3wt.%Cu alloy, the elongation% and uniform elongation% were decrease after the second pass then it increases with the addition of more passes. The microhardness distribution and the deformation homogeneity across the transverse direction of the billet were measured. The homogeneity of deformation was observed to increase with the increase of the ECAP number of passes and the copper content. Higher degree of the homogeneity of deformation was observed in the case of the homogenized alloys comparing to that in the case of the nonhomogenized alloys. [Copyright &y& Elsevier]

Abstract: The isothermal and non-isothermal ageing of an Al-2.4wt% Cu alloy have been studied using X-ray diffraction analysis and differential scanning calorimetry (DSC) at different heating rates. Quantitative metallography methods have been applied to measure the corresponding transformed volume fractions at various temperatures and times of precipitation. The variation of the heating rate using DSC technique has allowed us to calculate two kinetics parameters of precipitation which are the Avrami exponent and the activation energy of the process using Kissinger, Ozawa and Bosswell methods. These parameters are similar to those found for the precipitation reaction of θ′ and θ (Al2Cu) phases. [Copyright &y& Elsevier]

Abstract: Semi-solid deformation has been directly observed in an Al–12 wt.% Cu alloy through the combination of real-time synchrotron X-ray radiography and a bespoke high-temperature tensile tester over a range of fraction solid from 0.35 to 0.98. During deformation at low and moderate fraction solids, the X-ray radiographs indicate that there is significant feeding of interdendritic liquid in the region of strain localization prior to crack formation. Furthermore, the measured load required to initiate localized tensile deformation was found to be similar over the range of fraction solid 0.35 to 0.66. At higher fraction solids, the radiographic observations are consistent with classical hot tearing behaviour: limited liquid flow due to low permeability; void nucleation and coalescence; and final failure. Based on these results, a three-stage mechanism for semi-solid failure is proposed which includes the effects of liquid flow and micro-neck formation. [ABSTRACT FROM AUTHOR]

Abstract: Cu additions to Al alloys decrease pitting susceptibility provided that the Cu is retained solid solution. In this study, a range of electrochemical, surface analytical and electron microscopy characterization experiments were carried out with Al–Cu solid solution alloys to understand the origins of this inhibiting effect. Potential-controlled electrochemical polarization experiments carried out in dilute chloride solutions show that stimulation of alloy dissolution without inducing passive film breakdown significantly ennobles a subsequently measured pitting potential. Similar effects are not observed with high-purity Al or Al–Zn solid solution samples. The ennobling effect is more difficult to detect in large area electrodes due to pit initiation triggered by defects and inclusions that are more regularly encountered in larger electrodes. X-ray photoelectron spectroscopy of Al–Cu solid solution samples reveals no Cu enrichment above detection limits. However, scanning transmission electron microscopy and spectral imaging of specially prepared Al–Cu needle-type samples shows that Cu is enriched at the alloy interface by a range of exposure regimens including those that induce pitting. These results suggest the possibility of local Cu enrichment at incipient pit sites by metastable pitting, which can contribute to an ennoblement of the critical pitting potential under certain circumstances. [Copyright &y& Elsevier]

Abstract: This study was undertaken to investigate the machinability aspects of four new Al–Cu casting alloys with regard to the drilling and tapping processes; the base alloy is the 220 Al–2%Cu–1.3%Si–0.4%Mg alloy from which the other three alloys were prepared through the addition of TiB2 and Zr, Sn, and Bi. The machining performance was evaluated based on the calculation of the total cutting force and moment together with that of the tool life expressed as the number of holes drilled/tapped up to the point of tool breakage. The evaluation range was limited by a predefined targeted tool life of 2520 holes corresponding to 14 machinability test blocks. The results show that more than 2520 holes can be drilled for all the alloys studied without drill breakage. The addition of Sn and Bi decreases the total drilling force over the evaluation range by 14% and 25%, respectively, compared to the base alloy. The total drilling moment was reduced by almost the same ratios. All the alloys studied produce a fan-shaped chip which is considered to be the ideal chip for most drilling applications. The addition of Bi increases chip fragility considerably whereas no distinct change in chip characteristics was caused by the addition of Sn. No significant drill wear or any outstanding change in the built-up edge (BUE) to be observed with the progress of the drilling process. A comparative study was also carried out on the machining behavior of these new alloys, represented by their base 220 alloy, with that of the A206, 356, B319, and A319 alloys. Results revealed that the 220 alloy may be proposed as a promising cheaper and lighter alternative for the machining application of the A206 alloy. Furthermore, the machinability of the 220 alloy may be deemed an acceptable compromise between that of the 356 and B319 alloys, on the one hand, and that of the A319 alloy on the other. [ABSTRACT FROM AUTHOR]

Abstract: The pitting corrosion of Al, and two Al–Cu alloys, namely (Al–2.5% Cu) and (Al–7.0% Cu) was investigated in gluconic acid (HG) solution through linear polarization and cyclic voltammetry techniques complemented with ex situ EDX and SEM examinations of the electrode surface. Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) method of chemical analysis was used to study the effect of alloyed Cu on the rate of the uniform corrosion of Al in these solutions. Results obtained from ICP were compared with those obtained from polarization measurements. For the three Al samples, the anodic responses did not involve active/passive transition due to spontaneous passivation. Addition of HG induced pitting (confirmed from SEM) within the passive oxide film due to the aggressive attack of gluconate (G−) anions. Relationships between pitting potential (E pit), HG concentration, temperature, pH and potential scan rate were established. Alloyed Cu was found to enhance uniform corrosion, while it suppressed pitting attack. Local acidification model is employed to explain passivity breakdown induced by pitting corrosion as a result of the aggressive attack of G− anions. [Copyright &y& Elsevier]

Abstract: Equal channel angular pressing (ECAP) is a material processing method that allows very high strains to be imposed, leading to extreme work hardening and microstructural refinement. To investigate the deformation homogeneity in the transverse direction, rigid-viscoplastic 3D finite element simulations were conducted for the different numbers of ECAP passes of Al with Cu contents 0–5%. The simulation results indicated that the material on the outer side of the die channel undergoes less deformation than that in the inner side due to the formation of a corner gap. It was also found that the homogeneity increased with increasing the number of ECAP passes and the copper content due to the decrease in the size of the corner gap. To verify the 3D finite element simulation results, the microhardness homogeneity across the transverse direction of the billet was measured. The same trend was observed: the homogeneity in hardness increased with increasing the number of ECAP passes and Cu contents from 0% to 5%. The homogeneity of deformation indicated by microhardness and by FEM results was higher for route A compared with route Bc and increases with the number of ECAP passes. The homogeneity in route A was higher than that in route Bc by 10% after 2 passes up to 8 passes. [Copyright &y& Elsevier]

Abstract: Using a modified dispensed drop method, a decrease in contact angle on sapphire from pure aluminum to low-copper-containing Al alloys (7–12 wt.%) was found; with higher copper additions θ transitions to the non-wetting regime. Atomic force microscopy on long-term samples showed a significantly increased surface roughness beneath the drop. Using high-resolution transmission electron microscopy, the reaction product at the interface was identified as CuAl2O4 for Al–7Cu and Al2O3 for an Al–99.99 drop. X-ray photoelectron spectroscopy further confirmed the formation of CuAl2O4 under CuAl2 drops. Spinel formation is caused by reaction of the alloy with residual oxygen in the furnace that is transported along the interface as modeled by thermodynamic simulations. The formation of CuAl2O4 causes the reduced σsl and hence the improved wettability of sapphire by low-copper-containing alloys compared to pure aluminum. The main reason for the increase in θ with higher copper contents is the increasing σlv of the alloy. [Copyright &y& Elsevier]

Abstract: The phenomena involved during equiaxed growth, which is the most common growth morphology in metal casting, are dynamic. Therefore, in situ investigation is necessary to fully analyse the microstructure formation. Synchrotron X-ray radiography has become a major tool for in situ characterization of solidification in metallic systems. This paper reports on dedicated equiaxed solidification experiments carried out at the European Synchrotron Radiation Facility (ESRF) in Grenoble-France on Al–10wt.% Cu alloy. The analysis is based on the recorded images obtained through absorption radiography. Equiaxed growth is achieved in nearly isothermal conditions and observed continuously in real time from the early stages of solidification to the final state. The evolution of the dendrite arm lengths and the corresponding growth rates are analysed for two couples of grains in relation with their environment. This analysis suggests that the solutal interaction is dominant between equiaxed grains. [Copyright &y& Elsevier]

Abstract: There is a dearth of published experimental measurements of flow stress behaviour of semi-solids, yet it is critical for simulating phenomena ranging from the processing of metals to the flow of magma. In this paper, a method for calculating flow stress behaviour of semi-solids was developed using a combination of high-temperature compression testing, X-ray microtomography (XMT) imaging and direct finite element modeling (DFEM). This novel methodology was applied to columnar dendritic structures in semi-solid Al–Cu alloys via first quantifying the complex geometry of the semi-solid using XMT. Then these three-dimensional datasets were meshed and their behaviour was simulated using DFEM to derive the stress–strain relationship with a fraction solid (f S ) dependency term. The mechanical behaviour of the solid dendrites near the liquidus temperature was not available in the literature; therefore, samples were fabricated and compression tested using a Gleeble 3500 thermomechanical simulator. The resulting XMT–DFEM-derived constitutive equation predicts the flow stress behaviour of semi-solid in the range of f S equal to 0.1–0.9, showing good correlation to prior experimental data for both other aluminium and ferrous alloys. [Copyright &y& Elsevier]

Abstract: Creep behavior of the unmodified and modified cast Al–Cu alloys was investigated at temperatures from 393 to 483K in the tension test. The creep resistance ability of the Al–Cu alloy modified by Pr x O y is almost 3–5 times as high as that of the unmodified Al–Cu alloy, which is attributed to a large number of nano-scale θ′ precipitates with high thermal stability in the modified Al–Cu alloy restricting and impeding the dislocation movement during the creep. The induction of a threshold stress in the analysis leads to a stress exponent of 5, which suggests that the creep behavior of both the present alloys is associated with the lattice diffusion-controlled dislocation climb (n =5). [Copyright &y& Elsevier]

Tensile and compressive creep tests were performed at 300 °C on high-temperature Al–Cu–Mn–Zr (ACMZ) alloys with 6 wt% Cu (6Cu) and 9 wt% Cu (9Cu) to evaluate the effect on creep properties of micron-size θ-Al 2 Cu intergranular precipitates. For compressive creep, the increased volume fraction of θ-precipitates at grain boundaries (from ∼0.7% in 6Cu to ∼ 6% in 9Cu) does not affect deformation rates across the investigated stress range of 15–110 MPa, consistent with creep being controlled by submicron θ′-Al 2 Cu precipitates within grains, whose size and fractions are the same in both alloys. In contrast, for tensile creep, 9Cu creeps faster than 6Cu at stresses above 20 MPa, and this difference increases with the stress level. This discrepancy between tensile and compressive creep behavior is explained by cavitation during tensile creep, which is favored by higher volume fraction and larger size of intergranular θ precipitates in 9Cu. Conversely, larger precipitates impede cavity linkage resulting in improved creep ductility of 9Cu as compared to 6Cu at 300 °C. [ABSTRACT FROM AUTHOR]

Abstract: Non-isothermal ageing of an Al–4, 5% Cu alloy has been studied by using differential dilatometry, differential scanning calorimetry (DSC) and high-temperature X-ray diffraction (HTXRD). Six anomalies have been detected on the differential thermodilatometry curve (DTD). The GP zones formation and dissolution are traduced by two small contractions followed by one expansion. The precipitation of θ′-phase induces a big expansion and its dissolution reaction produces an important contraction. Moreover, θ-phase formation accompanies the precipitation, as well as the dissolution reactions of the θ′-phase. The θ-phase dissolution which dissolves the Cu atoms in the Al lattice is accompanied by a thermal dilatation of the Al lattice. The obtained values of the activation energy associated to the main precipitation reaction, by using Kissinger and Ozawa methods, are similar to that found for the precipitation reaction of θ′-phase. [Copyright &y& Elsevier]

Pre-stretching prior to ageing in Al-Cu alloys leads to preferential formation of precipitates in certain habit planes and produces anisotropic mechanical properties. In this work, we attempt to eliminate this problematic anisotropy by adding Sc and Zr to an Al-Cu alloy. When pre-stretching the binary Al-Cu alloy along the [001] Al zone axis, transmission electron microscopy (TEM) reveals that precipitation of θ ″ occurs mostly on the (001) Al plane (and not on the (100) Al and (010) Al planes). This "stress orienting effect" is caused by the local change in elastic strain energy induced by the pre-stretching. In the pre-stretched Al-Cu-Sc-Zr alloy, the presence of coherent Al 3 (Sc, Zr) dispersoids is found to promote equivalent nucleation of θ ′ precipitates in all three habit planes (at the expense of θ ″), resulting an isotropic precipitate distribution. The strengthening potential of these different precipitate distributions is analytically modelled and discussed. [Display omitted] [ABSTRACT FROM AUTHOR]