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This work reported the influence of laser surface melting (LSM) pretreatment on the growth behavior, electrical insulation and corrosion resistance of plasma electrolytic oxidation (PEO) film on 6061 aluminum alloy. It is found that the LSM pretreatment refines the surface structure of original Al metal, generating defects that store excessive energy, thereby enhancing reaction kinetics and phase transition during the PEO process. By LSM pretreatment, uniform electrical discharge and film growth can be obtained, resulting in fewer defects and lower porosity in PEO layers. Additionally, a large amount of columnar crystals comprising of SiO 2 phase are observed, which transformed from the SiO 3 2− deposited on the surface, and the LSM pretreatment significantly improves the electrical insulation, corrosion resistance, and substrate adhesion of following PEO layer. Under the same PEO treatment duration, the breakdown voltage of coating increased by 100 V, and icorr decreased from 3.26 × 10−4 to 9.13 × 10−6 A cm−2. It is expected that the combination of LSM and PEO processes can not only enhance the surface properties of Al metal, but also expand the practical application of aluminum alloy in high-power electronic devices and related fields. [Display omitted] [ABSTRACT FROM AUTHOR]

The relative energetic stability, mechanical properties, and thermodynamic behavior of B2-AlRE (RE = Sc, Y, La-Lu) second phases in Al alloys have been investigated through the integration of first-principles calculations with the quasi-harmonic approximation (QHA) model. The results demonstrate a linear increase in the calculated equilibrium lattice constant a0 with the ascending atomic number of RE, while the enthalpy of formation ΔHf exhibits more fluctuating variations. The lattice mismatch δ between B2-AlRE and Al matrix is closely correlated with the transferred electron et occurring between Al and RE atoms. Furthermore, the mechanical properties of the B2-AlRE phases are determined. It is observed that the calculated elastic constants Cij, bulk modulus BH, shear modulus GH, and Young's modulus EH initially decrease with increasing atomic number from Sc to Ce and then increase up to Lu. The calculated Cauchy pressure C12-C44, Pugh's ratio B/G, and Poisson's ratio ν for all AlRE particles exhibit a pronounced directional covalent characteristic as well as uniform deformation and ductility. With the rise in temperature, the calculated vibrational entropy (Svib) and heat capacity (CV) of AlRE compounds exhibit a consistent increasing trend, while the Gibbs free energy (F) shows a linear decrease across all temperature ranges. The expansion coefficient (αT) sharply increases within the temperature range of 0~300 K, followed by a slight change, except for Al, AlHo, AlCe, and AlLu, which show a linear increase after 300 K. As the atomic number increases, both Svib and CV increase from Sc to La before stabilizing; however, F initially decreases from Sc to Y before increasing up to La with subsequent stability. All thermodynamic parameters demonstrate similar trends at lower and higher temperatures. This study provides valuable insights for evaluating high-performance aluminum alloys. [ABSTRACT FROM AUTHOR]

We report the crack growth on peak aged Al 7075 under tensile loading in a saltwater environment to investigate whether hydrogen plays a role in the initiation and the subsequent growth of the crack. As the hydrostatic stress is at a maximum ahead of the notch, it has been speculated that hydrogen would diffuse to region of maximum hydrostatic stress and initiate the crack. An elastic-plastic finite element (FE) model is developed to determine the stress distribution around the circular notch at the edge of the plate. The crack growth was monitored using a camera attached with an optical microscope, and various regimes corresponding to hydrogen evolution, pit formation and growth, crack nucleation and initial growth and rapid crack growth leading to failure have been identified. We observe the crack was nucleated in a region associated with the highest hoop stress instead of the maximum hydrostatic stress from the base of a pit at the circular notch. We demonstrated the crack growth rate in a salt water environment is governed mostly by the dissolution of grain boundary MgZn2 precipitate, rather than the hydrogen induced decohesion mechanism. [ABSTRACT FROM AUTHOR]

This study delves into a Bayesian machine learning (ML) framework designed to comprehensively characterize cutting force and residual stress in the micro end milling process across a diverse range of aluminum alloys. The foundation of this investigation rested on acquiring dependable training data through finite element method simulations, encompassing material properties and processing parameters as inputs, while the output targets included residual stress in both the transverse and cutting directions, as well as cutting force divided into feed force and thrust force. The outcomes were remarkable, unveiling high predictive accuracy for both residual stress and cutting force, with a slight advantage in residual stress prediction. Moreover, the study revealed the significant influence of output target values on the weight functions of input parameters, highlighting distinct dependencies between each output target and the corresponding input features. This investigation elucidated that predicting residual stress and cutting force in micro end milling represents a multifaceted process contingent upon the interplay of material properties and processing parameters. The intricate nature of this process underscores the Bayesian ML model's potential as a robust and highly accurate approach, adept at effectively encapsulating these complex objectives. [ABSTRACT FROM AUTHOR]

Due to their high specific strength and low density, 7075 Al alloys are widely used in aerospace applications. However, Al alloys are prone to corrosion and deterioration, and the service life depends on their corrosion resistance. To investigate the corrosion and strengthening mechanisms of the 7075 Al alloy subjected to cold rolling, x-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to characterize the sample microstructure. Compared to the homogenized samples, the ultimate tensile strength of a cold-rolled sample increased from 235 ± 4 MPa to 347 ± 3 MPa when the thickness reduction increased to 50%. The yield strength approached 305 ± 0.4 MPa, and the tensile ductility decreased up to 62.9%. The cold-rolling process resulted in a significant increase in dislocation density and a reduction in grain size. The increased density of grain boundaries and the fragmentation of the precipitates led to a reduction in galvanic coupling with the Al matrix, resulting in the improved corrosion resistance of the 7075 Al alloy. This study provides a suitable approach to enhance both the mechanical properties and corrosion resistance of Al alloys. [ABSTRACT FROM AUTHOR]

The wear and degradation of tools applied in the high-pressure die casting of Al alloys induce significant financial losses. The formation of failures on the surface of mold parts caused by erosion, thermal fatigue, corrosion, and soldering negatively affects the surface quality of castings. In this study, the lifetime of inserts protected by physical-vapor-deposited coatings (TiN, TiAlN, and CrAlSiN) is examined under real manufacturing conditions while considering requirements for the castings' surface quality (maximum average roughness Ra) defined by the customer. The goal was to identify the most suitable solution for HPDC in the foundry organization. After the deposition of PVD coatings on the inserts, the hardness (HRC) values increased from two to five depending on the coating used, and also the surface roughness was higher in the case of all inserts (Ra values increased from 0.24 to 0.36 µm). The lifetime of all PVD-coated inserts was higher compared to the uncoated insert. The highest lifetime was achieved by the application of a TiN coating, when 15,000 shots were achieved until the inserts' wear negatively affected (increased) the surface roughness of castings, considering the customer requirements for the maximum Ra value. SEM analysis was used to identify examples of wear and degradation on the surface of the TiN coated insert. [ABSTRACT FROM AUTHOR]

An advantageous approach for hydrogen production, without greenhouse gas emissions, consists of the reaction of Al alloys with water in alkaline media. This study investigates the rates involved in hydrogen production using directionally solidified Al-5Zn-XSn and Al-10Zn-XSn (X = 10 and 20) [wt.%] alloys, with a particular focus on microstructure-related effects. The results of hydrogen evolution tests in a 1 M NaOH solution demonstrate that an appropriate combination of solute content and microstructure refinement can lead to a 5.7-fold increase in the hydrogen generation rate. Novel experimental equations based on the Hall-Petch relationship are introduced, linking dendritic arm spacings with hydrogen generation rates. It is observed that an excessive amount of Zn in the interdendritic regions has a negative impact on hydrogen generation kinetics. The Al-5Zn-10Sn alloy promotes faster hydrogen generation, and finer microstructures within this alloy can increase the hydrogen generation rate by approximately 87 %. [Display omitted] • Microstructural refinement induces an 87 % increase in the hydrogen generation rate. • Hall-Petch type equations associate the microstructure with hydrogen generation rates. • Excessive Zn content in the alloy has an unfavorable impact on hydrogen production kinetics. • The Al-5Zn-10Sn alloy promotes favorable kinetic and yield aspects in hydrogen production. • A proposed mechanism clarifies the corrosion of Al-Zn-Sn alloys in alkaline medium. [ABSTRACT FROM AUTHOR]

Anodizing is a well-documented surface treatment that is inserted in a complex protection system against corrosion applied to Al alloys. In the scientific literature, there are many works about this topic, which are concentrated on: (1) anodic aluminum oxide (AAO) growth mechanism; (2) anodized alloys corrosion behavior, or (3) the influence of anodizing parameters on the following steps of corrosion protection of the anodized layer. However, the effect of the microstructure on the AAO formation is not yet well established. This paper aims to review the effect of the microstructure of Al and its alloys on the anodizing process by a historical, statistical, and electrochemical approach, considering the advantages in understanding the influence of intermetallics in this process. Besides, this review brings a comparison among the number of publications and the types of alloys studied by statistical analyses. Finally, it emphasizes the importance of anodizing in the aeronautical industry, in which a great number of studied alloys are applied, mainly the 2XXX (Al-Cu) and 7XXX (Al-Zn) series alloys. [ABSTRACT FROM AUTHOR]

This study investigates the influence of cobalt (Co) addition on the microstructural and wear properties of an aluminum (Al) scrap alloy containing high iron (Fe) impurity content (3%). Microstructural analysis using scanning electron microscopy and optical microscopy confirmed the presence of Co in Fe-rich intermetallics. Upon increasing the Co concentration, β-Al5FeSi phase was seen to be refined without significant morphological modifications. Furthermore, Co addition promoted the formation of a new quaternary phase Al32Si7Fe4Co phase, which was finely distributed throughout the microstructure and acts as a tribo-layer in the Al scrap alloy, offering enhanced wear resistance and improved stability against wear. Standard EN-31 steel disk with compositions chromium (Cr)-1.6%, manganese (Mn)-0.75%, silicon (Si)-0.35%, and carbon (C)-0.9% was used for the wear test. Microhardness and wear properties were evaluated for both the as-cast and heat-treated alloys, with the as-cast samples exhibiting superior wear resistance and a lower coefficient of friction compared to the T6 heat-treated samples. Addition of Co showed refinement in the β-Fe rich intermetallics over the morphological modifications. Similarly, Co addition enhanced the hardness and wear resistance in the as cast alloys. This work provides a detailed analysis contributing significant understandings into the wear mechanisms and potential applications of Co modified recycled Al in various industrial sectors. [ABSTRACT FROM AUTHOR]

Laser additive manufacturing (LAM) has attracted significant interest in developing Al alloys due to its potential to fabricate structural components at low cost and high efficiency. Nevertheless, LAM Al alloys still suffer many issues, including heterogeneous microstructure, various defects, and poor mechanical properties, significantly hindering the advancement of LAM Al alloys. This article seeks to provide a comprehensive overview of the current advancements made in the field of LAM Al alloys and attempts to establish an in-depth relationship between microstructural characteristics, defects, and performances. Development status and limitations of LAM technologies are described, microstructural characteristics of Al alloys in LAM are introduced, mechanisms of formed defects and corresponding mitigation measures are discussed, and current quality improvement strategies are summarized. Following the research of previous work, this review will provide an outlook on overcoming the existing challenges and provide a helpful resource and reference for the development of LAM Al alloys.

The mechanical properties and crack propagation behavior of aluminum alloys, both with and without corroded surfaces, were thoroughly investigated through molecular dynamic (MD) simulations. The study delved into the effects of corrosion depth and width on the mechanical properties of corroded aluminum alloys. It was found that as the corrosion depth increases, the yield strength experiences an initial decrease followed by a subsequent increase. This can be attributed to the impact of increased corrosion depth on the healing of surface roughness, which ultimately leads to significant changes in yield strength. Furthermore, the presence of corrosion pits was identified as a key factor in regulating the local microstructure evolution within the material, leading to pronounced differences in stress distribution localization. This, in turn, influenced the path of crack propagation within the material. These findings not only contribute to a deeper understanding of the behavior of aluminum alloys under corrosion, but also provide valuable insights for the development of aluminum alloys with enhanced mechanical properties. [ABSTRACT FROM AUTHOR]

In the present work, 6063 Al alloy was subjected to cross cryo-rolling (XCR) at liquid nitrogen and room temperature for producing the ultrafine grained Al alloy. The XCR and cross room temperature rolling (XRTR) were performed by doing a reduction of 90%. The mechanical properties were investigated by measuring the hardness and tensile properties of investigated alloys. The increases in the average ultimate tensile strength (332 MPa), yield strength (300 MPa), and ductility (11.66%) of the XCR sample were observed as compared to the XRTR sample. The increase in the strength of the XCR sample was due to the extensive dislocation strengthening as compared to the XRTR sample. The increase in the ductility of the XCR sample was due to the softening mechanism dominated during the rolling. The microstructural properties were reported with the help of transmission electron microscopy (TEM), scanning electron microscopy and X-ray diffraction analysis and correlated with the mechanical properties. The TEM investigation revealed that XCR promotes the formation of heavily deformed sub-grains, dislocation tangles, and fragmented initial grains. The presence of dislocations inside the XRTR sample was low as compared to the XCR sample. It was observed that cross rolling at liquid nitrogen temperature further helped in the accumulation of a large number of dislocations and further improved the strength of 6063 Al alloy by suppressing the dislocations annihilations. [ABSTRACT FROM AUTHOR]

This study explores the combined potential of severe plastic deformation (SPD) via differential speed rolling (DSR) and plasma electrolytic oxidation (PEO) to enhance the material performance of 6061 Al alloys. To this end, DSR was carried out at a roll-speed-ratio of 1:4 to obtain ~75% total thickness reduction and a final microstructure of <1 µm. The rest of the samples were annealed to obtain various grain sizes of ~1, ~25, and ~55 μm. Through DSR, the hardness of the material increased from ~64 to ~102 HV. Different grain sizes altered the plasma behavior which further influence the growth of the coating layer, where the fine grain size produced a compact structure beneficial for corrosion protection. This synergy offers tailored materials ideal for high-performance applications across diverse industries, combining enhanced bulk properties from DSR with optimized surface attributes from PEO. [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) of AA2219-T87 and AA6061-T6 is carried out under six process parameters: rotational speed, tool profile, welding speed, tilt angle, AA2219 location, and backing plate. Response Surface Methodology (RSM) was used to develop the mathematical models for the responses (tensile strength, percentage elongation, and yield strength), and branch and bound algorithm and augmented ε-constraint (AUGMECON) method were used to optimize single and multi-responses. Utilizing a Cu backing plate in FSW led to a superior dissimilar joint, achieving 72% tensile strength, 65% yield strength (YS), and 80% elongation of the base material under 800rpm rotational speed, 100 mm/min welding speed and 3° tilt angle. The position of the parent materials determined the trade-off between the extreme Pareto solutions. Visual inspection and radiography confirmed minimal flashing and superior surface finish with no internal defect in Cu-backed optimized weldments. Tool profile and backing plate type influenced the tunnel and incomplete fusion formation respectively. Microstructural studies showed that Copper backing promotes uniform intermetallic compound dispersion at grain boundaries, with intermetallic layers at dynamic recrystallization (DR) and onion ring pattern (ORP) zones. Temperature profiling of FSW confirmed the uniform heat dissipation characteristics of Copper backing by producing a weld center temperature profile that is closer to its peak temperature but achieved more gradually. The micro-hardness study highlighted the nugget zone's lower hardness compared to parent materials. SEM fractography revealed a mixed ductile and brittle failure mode due to the presence of deep dimples filled with cracked second-phase particles. EDS and XRD analyses confirmed strengthening intermetallics presence favoring strong phases over brittle under Cu backing. Corrosion studies showcased reduced galvanic corrosion with Cu backing. [ABSTRACT FROM AUTHOR]

The reaction of water with Al-based alloys presents a promising alternative for on-board hydrogen production. This method, free from carbon emissions, has the advantage of addressing issues related to hydrogen storage and logistics. Al-Sn-Fe alloys are potential candidates for this application. However, the current literature lacks an in-depth understanding of the role of microstructural evolution in the hydrogen generation performance of these alloys. The present work investigates the influence of the microstructural length scale on the hydrogen production behavior of an Al-9Sn-1Fe (wt.) alloy. Directionally solidified samples with different microstructural length scales were subjected to hydrogen evolution tests in a 1 M NaOH solution. The results revealed that the microstructure of the studied alloy comprised α-Al-phase dendrites with a plate-like morphology along with the presence of Sn-rich particles and Al13Fe4 intermetallic compounds (IMCs) in the interdendritic areas. In addition, the microstructural refinement induced a 56.25% rise in hydrogen production rate, increasing from 0.16 to 0.25 mL g–1 s–1, without affecting the hydrogen yield, which stayed around 88%. The corrosion process was observed to be stimulated by Sn-rich particles and Al13Fe4 IMCs at their interfaces with the α-Al phase, positively impacting the hydrogen production rate. An experimental equation based on the Hall–Petch relationship and multiple linear regression (MLR) is proposed to associate the hydrogen production rate with dendritic arm spacings. [ABSTRACT FROM AUTHOR]

Microalloying is of great importance for the property modulation of lightweight high-strength aluminum alloys. Little is known, however, about the properties and micromechanisms of Al–Mg–Si alloys microalloyed with Sn and Sc. In this work, the property changes of Al–0.5Mg–0.4Si (wt%) alloys induced by 0.1Sn and 0.1Sn–0.1Sc (wt%) additions and underlying alloying mechanisms are revealed by atomic-scale transmission electron microscopy and first-principles calculations. The results show that the Sn–Sc coaddition results in a decreased diameter and an increased number density of the Sc-containing constituent particles of Mg2Si and Mg2(Si,Sn), as compared to the sole Sn addition. The featured Si-site columns in β'', B′ and β′ structures can be occupied by Sn and Sc. Substantial peak-aging β'' needles with confined cross-sectional coarsening are observed for the Sn–Sc containing alloy compared to the Sn containing alloy. The modified constituent particles and precipitates improve the plasticity and strength of peak-aging Al–Mg–Si–Sn–Sc alloy. The elevated peak-aging corrosion resistance and over-aging thermal stability of Al–Mg–Si–Sn–Sc alloy are associated with the sparse Sc-containing Mg2(Si,Sn) grain boundary precipitates and low strain filed of Al matrix around the β′ containing Sn/Sc, respectively. The obtained results are hoped to guide the design of high-performance Al alloys.

Solid solution strengthening is a well‐known strengthening mechanism for Al (Mg, Si) alloys. The distribution of solute atoms plays an important role in the enhancement of the mechanical properties. As‐quenched, dilute, Al alloys are analysed by atom probe tomography (APT) and mechanical testing (microhardness, tensile testing) and these data have been employed in order to assess the 3D distribution of solute atoms in the solid solutions. An innovative approach is to abstain from the conventional logic of binary versus ternary alloys in data analysis in favor of a less‐concentrated versus more‐concentrated strategy. This approach enables for the first time that the integration of first‐principles Condon–Morse atomic interaction effects, APT, and mechanical testing, and first principles effects (field, proximity, chemical, and atomic size), which results in a novel empirical singleton‐cluster plot. The plot allows differentiation between singletons, solute clusters, and coclusters as well as between the less‐concentrated and more‐concentrated alloys. The plot also allows determination of the maximal yield strengths from cluster strengthening and from singletons in the absence of clustering. Most critically, this new approach in data analysis allows for the first time the determination of the dmax (maximal distance between solutes in a cluster) based on experimental results. [ABSTRACT FROM AUTHOR]

Recycled Al alloys not only offer environmental and economic benefits but also present a valuable base for the development of innovative materials, such as Al-Ni-Fe alloys. This work particularly focuses on the microstructural changes and hardness of an Al-5Ni-1Fe alloy (wt.%) solidified with an approximate 20-fold variation in cooling rates. For the various microstructural length scales obtained, only the eutectic regions exhibit a uniform pattern, with the eutectic colonies comprising an α-Al phase along with Al3Ni and Al9FeNi intermetallic compounds. It is shown that microstructural refinement can lead to a 36% increase in hardness. To represent this mathematically, hardness values are associated with the eutectic colony and intermetallic fiber spacings (λEC and λIF is, respectively) using experimental equations based on the Hall–Petch relationship and multiple linear regression. In addition, comparisons are undertaken with Al-5Ni and Al-1Fe (wt.%) alloy samples produced under the same conditions. The Al-5Ni-1Fe alloy exhibits higher hardness values than both the Al-5Ni and Al-1Fe binary alloys. Furthermore, the hardness of the ternary Al-Ni-Fe alloy is sensitive to microstructural refinement, a characteristic absent in the binary alloys. For λIF−1/2 = 1.56 µm−1/2 (coarser microstructure), the Al-5Ni-1Fe alloy exhibits a hardness of about 13% and 102% higher than that of the Al-5Ni and Al-1Fe alloys, respectively, while for λIF−1/2 = 1.81 µm−1/2 (finer microstructure), it demonstrates a hardness of approximately 39% and 147% higher as compared to that of the Al-5Ni and Al-1Fe alloys, respectively. Thus, this research provides experimental correlations that connect hardness, microstructure, and solidification thermal parameters, contributing to a better understanding for the design of as-cast Fe-contaminated Al-Ni-based alloys. [ABSTRACT FROM AUTHOR]

In present work, the monotonic and cyclic properties of a novel Al‐Mg‐Zn‐Cu‐Si compositionally complex alloy (CCA) are investigated. Microstructural studies reveal that a eutectic phase and fishbone‐type structures are embedded in the Al‐matrix. The mechanical properties of this CCA obtained under compressive loading are found to be promising. However, low ultimate strength and brittle behavior are seen under tension. The fatigue performance of the alloy in the low‐cycle fatigue (LCF) regime is poor. Microstructural features and fracture surface analysis point to the fact that the presence of brittle intermetallic phases and shrinkage defects are responsible for the poor tensile properties and inferior LCF behavior. Homogenization at 460 and 465 °C for 3 h, 6 h, and 24 h results in spheroidization of all coarse precipitates. However, the heat treatment used is unsuitable to enhance the mechanical properties of this CCA. [ABSTRACT FROM AUTHOR]

It is difficult to achieve high‐strength joints of metals to carbon‐fiber‐reinforced plastics (CFRPs) with high contents of continuous fibers with the poor fluidity. Herein, a special designed laser‐processing pretreatment is conducted on the surface of 5052Al, and friction‐lap joining (FLJ) is employed to join pretreated 5052Al to the CFRP with 50%–55% fiber content. The maximal tensile shear force and strength reach 4.06 kN and 18.04 MPa, respectively, with an increment of 72% compared to the untreated sample. It is the first time to achieve the high‐strength joint of Al alloys to CFRPs with high contents of continuous fibers via FLJ. The joining area and adhesion work are quantified by theoretical calculations, and the residual stresses are visualized by finite‐element analysis. The laser‐processing pretreatment changes the plain Al alloy surface structure into the rough and porous structure, largely increasing the mechanical interlocking effect of the joint, and also changes the Al alloy surface wetting behavior and increases the adhesion work from 59.66 to 81.17 mN m−1. That largely changes the chemical reaction feature between the CFRP and Al alloy, resulting in their tight bonding. In addition, the residual stresses weaken, which further improve the tight bonding effect. [ABSTRACT FROM AUTHOR]

ABSTRACTThe precipitation hardening is widely applied to strengthen Al alloys. Here, we report an alternative way to achieve high-strength Al alloys via forming the dislocation gradient through pre-torsion. Remarkably, the gradient Al alloys exhibit a sharp increase in ultimate tensile strength up to 605 MPa yet nearly without reducing the uniform elongation, thereby outperforming their counterparts. The superior strength–ductility combination is ascribed to the excellent strengthening and strain hardening effects stemming from the substantial hetero-deformation-induced hardening in the coarse-grained gradient Al alloys. Our study thus paves a new way to improve the mechanical properties of Al alloys.

The mechanical properties and crack propagation behavior of aluminum alloys, both with and without corroded surfaces, were thoroughly investigated through molecular dynamic (MD) simulations. The study delved into the effects of corrosion depth and width on the mechanical properties of corroded aluminum alloys. It was found that as the corrosion depth increases, the yield strength experiences an initial decrease followed by a subsequent increase. This can be attributed to the impact of increased corrosion depth on the healing of surface roughness, which ultimately leads to significant changes in yield strength. Furthermore, the presence of corrosion pits was identified as a key factor in regulating the local microstructure evolution within the material, leading to pronounced differences in stress distribution localization. This, in turn, influenced the path of crack propagation within the material. These findings not only contribute to a deeper understanding of the behavior of aluminum alloys under corrosion, but also provide valuable insights for the development of aluminum alloys with enhanced mechanical properties.

The present study investigated grain growth, recrystallization, and fatigue crack growth behavior of Al-Cu-Si alloy subjected to cryorolling and annealing treatment for 1 h. Temperature from 373 to 523 K was considered for this study. Cryorolling is used to produce ultra-fine-grained (UFG) structures, while annealing is used to study the recrystallization and grain growth. The fatigue crack growth (FCG) rate was measured in the low-stress intensity factor range (ΔK) (Stage II) and high-stress intensity factor ranges using the Paris equation and measuring the striation width. The results discovered that cryorolling led to a significant decrease in the fatigue crack growth resistance in the low-stress intensity factor range compared to coarse grain counterparts due to a decrease in the crack closure level in the cryorolled alloy. The results also showed that the fatigue crack growth resistance of the cryorolled alloy improved in the high-stress intensity factor range due to the formation of ultra-fine-grained microstructure, resulting in fine striations observed from the fractographic studies. The post-annealed samples at 373 K exhibited higher fatigue crack growth resistance in low and high-stress intensity factor ranges. High fatigue crack growth resistance in the annealed sample in low and high-stress intensity factor range is attributed to the fine semicoherent spherical phase θ . [ABSTRACT FROM AUTHOR]

In this study, ceramic coatings were grown on the surface of as-cast aluminum alloys via plasma electrolytic oxidation (PEO). The effect of the Si- and Ca-alloying elements in aluminum on the growth process, morphology, composition, mechanical, and corrosion properties of the PEO coatings was investigated. Uniform coatings with a minimum number of defects were formed on the surfaces of Al–Ca alloys. Increasing the Si content in Al led to an increase in the bulk and surface porosity of the coatings. The α-Al2O3 phase mainly formed in the coatings synthesized on pure Al and Al–Ca alloys, while an increased amount of Si in Al alloys hindered the formation of the α-Al2O3 phase. The coatings had a microhardness of 660–1180 HV, which was 20–30 times higher than that of the original as-cast alloy. Moreover, the coating on the Al–Ca alloys had the highest peak hardness, which was probably caused by the formation of a greater amount of the α-Al2O3 phase. Electrochemical studies in 3.5% NaCl have shown that PEO coatings reduce the corrosion current density. Of all PEO-treated alloys, Al and Al1Ca have the lowest corrosion current density and hence the highest corrosion resistance due to the composition and uniformity of the coating. [ABSTRACT FROM AUTHOR]

Aluminum alloyed with other metals, such as Sn and Zn, was synthesized via fusion to trace the impact of alloying elements on the electrochemical characteristics of Al anodes. The corrosion inhibition and electrochemical tests were performed in a 5 M KOH medium in the absence and presence of CO 2 for the Al–Sn, and Al–Zn anodes and compared to the commercial aluminum. Tafel polarization exhibited that the anodic and cathodic branches display lower current densities than Al metal in pure KOH. The steady state of the open circuit voltage (E corr.) for the studied alloys was shifted to a more negative magnitude than for Al. The corrosion current is sharply decreased, and potential is significantly shifted to less negative values in the presence of CO 2. This is due to forming of a protective layer from the carbonate of Al, Sn, and Zn on the surface. Amazing results were obtained and discussed in the case of CO 2. Electrochemical impedance spectroscopy (EIS) results exhibited that charge transfer resistance (R ct) values rise with alloying elements. The data of Tafel plots are consistent with those of EIS. The alloying of Al with Sn and Zn elements significantly affects capacitance, hydrogen evolution process suppression, and charge-discharge efficiency. This reveals that the highest potential value in the presence of CO 2 in the charging process is obtained for Al–Zn alloy, while the most negative potential is obtained for Al in the discharging process with CO 2. Moreover, the discharge time is higher in the alloys than in commercial Al in the absence and more in the presence of CO 2. The produced alloys are thought to provide good anodes for long-life rechargeable batteries. • The electrochemical behavior of Al, Al–Zn, and Al–Sn anodes was studied. • Al–Zn alloy has the most stability against corrosion. • Al–Sn has a higher discharging potential and time. • CO 2 enhances both corrosion resistance and charging-discharging behavior. • Hydrogen evolution reaction is suppressed by alloying and the presence of CO 2. [ABSTRACT FROM AUTHOR]

Aluminum–silicon alloys require modification due to their coarse-grained microstructures and resulting low strength properties. So far, research into the modification process has focused on the use of various chemical components and technological processes, the tasks of which are to refine the microstructure and, thus, increase the mechanical properties of the alloy. In this paper, the answer to the question of whether the form of the modifier influences the modification effect of the hypoeutectic silumin will be found. The tests were carried out using the popular silumin AlSi7Mg. To answer our research question, the alloy was modified under comparable conditions using the following elements: Ti, B, and master alloys AlTi1.5 and AlB1.5. Modifiers in the form of Sr and master alloy AlSr1.5 were also used. All mentioned modifiers were produced and introduced into the liquid alloy in the form of a powder and a rod. Master alloys AlSr1.5 were also produced via cooling from the liquid state through cooling in air and the second variant at a speed of 200 °C/s (in the form of powder and a thin strip). The microstructure and mechanical properties were analyzed based on the following measures: tensile strength, elongation, and hardness of silumin. Based on the conducted research, it was found that the form of the modifier also affects the modification effect visible in the form of changes in the microstructure and mechanical properties. For the powder-modified alloy, greater fineness in the eutectic phase (α and B phases) and an increase in all analyzed mechanical properties were obtained. [ABSTRACT FROM AUTHOR]

Low-temperature superplasticity (LTS) is crucial to reduce manufacturing cost and to enhance the applications of superplastic forming. It is well known that grain refinement is the key point to decrease the temperature at which superplasticity is attained. Therefore, ultrafine-grained (UFG) materials have become attractive for achieving LTS. Severe plastic deformation (SPD) techniques provide abnormal grain refinement, and thus they have been used to achieve LTS in metallic materials. This paper overviews and examines the reports of LTS in the severely-deformed metallic materials. It provides fundamentals of grain refinement via different SPD techniques in various classes of metallic materials including Al-, Mg-, and Ti-based alloys. It also gives a brief summary about the effect of microstructural requirements on LTS with an emphasis on grain size, type and chemical composition of grain boundaries and microstructural alteration during the superplastic deformation. In the last section of the manuscript, the main deformation mechanism of LTS were also explained. [ABSTRACT FROM AUTHOR]

In the last three decades, several severe plastic deformation (SPD) procedures have been developed and applied in materials science to create bulk, ultrafine-grained (UFG) structures. As a consequence of the SPD, not only submicron and even nanometer grain sizes can be obtained, but also new grain boundaries with non-equilibrium structures in a material may be formed. Therefore, both the strength and ductility of the UFG materials can change significantly compared to the coarse-grained counterparts. This review is focused on unusual mechanical behaviors of UFG Al and Al alloys, associated with grain boundary structure and segregations which are responsible for the modification of the Hall-Petch relationship and the so-called size-effect for UFG structure. Unusually high strain rate sensitivity, intensive grain boundary sliding and superplasticity at low temperature are described and surveyed. In addition, innovation potential of these phenomena is also briefly considered. [ABSTRACT FROM AUTHOR]

This paper presents an overview of fundamentals and potential applications of ultrafine-grained Al-based conductors developed with the help of severe plastic deformation (SPD) techniques. Based on deliberate formation of nanoscale features (such as nanoprecipitates, segregation of solutes along crystallographic defects and so on) within ultrafine grains, it is possible to optimise their mechanical and functional performance enhancing the combination of strength and electrical conductivity to produce advanced lightweight conductors required by modern industries. Guidelines related to SPD-driven development of Al alloys with properties superior to those exhibited by traditionally processed conductors are discussed. [ABSTRACT FROM AUTHOR]

In this work, the effect of an ammonium nitrate ionic liquid on the corrosion susceptibility of an Al-Cu-Mg alloy was investigated. The effect of the nitrate anion and the ammonium cation on the anodic and cathodic kinetics were studied separately using potentiodynamic polarisation testing, electrochemical impedance spectroscopy and scanning electron microscopy. The results revealed a significant anodic inhibition, associated with a cation/anion synergy. The cathodic kinetics however increase with the presence of nitrates, associated with nitrate reduction reaction. Conversely, longer alkyl chain seemed to reduce the effect of nitrates. Such findings are promising in the context of developing ecofriendly chromate alternatives.

In this study, white thermal control coatings were produced on a 6061 Al alloy using plasma electrolytic oxidation (PEO). The coatings were mainly formed by incorporating K2ZrF6. The phase composition, microstructure, thickness, and roughness of the coatings were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), a surface roughness tester, and an eddy current thickness meter, respectively. The solar absorbance and infrared emissivity of the PEO coatings were measured using a UV–Vis–NIR spectrophotometer and FTIR spectrometer, respectively. The addition of K2ZrF6 to the trisodium phosphate electrolyte was found to significantly enhance the thickness of the white PEO coating on the Al alloy, with the coating thickness increasing in proportion to the concentration of K2ZrF6. Meanwhile, the surface roughness was observed to stabilize at a certain level as the K2ZrF6 concentration increased. At the same time, the addition of K2ZrF6 altered the growth mechanism of the coating. In the absence of K2ZrF6 in the electrolyte, the PEO coating on the Al alloy surface predominantly developed outwards. However, with the introduction of K2ZrF6, the coating's growth mode transitioned to a combination of outward and inward growth, with the proportion of inward growth progressively increasing in proportion to the concentration of K2ZrF6. The addition of K2ZrF6 substantially enhanced the adhesion of the coating to the substrate and endowed it with exceptional thermal shock resistance, as the inward growth of the coating was facilitated by the presence of K2ZrF6. In addition, the phase composition of the aluminum alloy PEO coating in the electrolyte containing K2ZrF6 was dominated by tetragonal zirconia (t-ZrO2) and monoclinic zirconia (m-ZrO2). With the increase in K2ZrF6 concentration, the L* value of the coating increased from 71.69 to 90.53. Moreover, the coating absorbance α decreased, while the emissivity ε increased. Notably, at a K2ZrF6 concentration of 15 g/L, the coating exhibited the lowest absorbance (0.16) and the highest emissivity (0.72), which are attributed to the enhanced roughness resulting from the substantial increase in coating thickness caused by the addition of K2ZrF6, as well as the presence of ZrO2 with higher emissivity within the coating. [ABSTRACT FROM AUTHOR]

Arc-directed energy deposition using wire as feedstock is establishing itself as a 3D printing method capable of obtaining additively manufactured large structures. Contrasting results are reported in the literature about the effect of the deposition parameters on the quality of the deposited tracks, as it is highly dependent on the relationship and intercorrelations between the individual input parameters, which are generally deposition-technique-dependent. This study comprehensively analysed the effect of several deposition parameters and clarified their interactions in plasma metal deposition of Al alloys. It was found that, although no straightforward correlation between the individual input parameters investigated and the measured output deposition track's quality aspects existed, the input current had the greatest effect, followed by the wire feed speed and its interaction with the input current. Moreover, the greatest effect of changing the shielding gas atmosphere, including the gas mixture, flow rate and plasma flow, was on the penetration depth, and fine-tuning the frequency/balance ratio and the preheating of the deposition substrates reduced the amount of porosity. This study demonstrates that well-deposited multi-layer walls made out of Al alloys can successfully be achieved via plasma metal deposition. [ABSTRACT FROM AUTHOR]

The precipitation hardening is widely applied to strengthen Al alloys. Here, we report an alternative way to achieve high-strength Al alloys via forming the dislocation gradient through pre-torsion. Remarkably, the gradient Al alloys exhibit a sharp increase in ultimate tensile strength up to 605 MPa yet nearly without reducing the uniform elongation, thereby outperforming their counterparts. The superior strength–ductility combination is ascribed to the excellent strengthening and strain hardening effects stemming from the substantial hetero-deformation-induced hardening in the coarse-grained gradient Al alloys. Our study thus paves a new way to improve the mechanical properties of Al alloys. The gradient distribution of dislocations significantly increases the strength of the Al alloy with the neglectable reduction in uniform elongation, which enables exceptional mechanical properties that outperform the peak-aged counterpart. [ABSTRACT FROM AUTHOR]

Adhesion is a major element of the bonding technologies used today. This way of joining meets the requirements of mechanical load, with high reliability of the product, and in connection with the production and climatic conditions. Bonding is the process of making inseparable bonds in mechanical engineering with non-metallic material, through adhesion and cohesion forces, without significant impact on the structure of the parts to be joined. Gluing (adhesive joint), as a way of making joints in mechanical engineering, is gaining importance in the development of spacecraft and aircraft, as well as the automotive industry. This requires high load-bearing capacity and stiffness, with minimal weight, so alloys such as aluminum and titanium are used. Adhesive joining is increasingly displacing the dominant rivets when joining light metals, and is used to join thin sheets made of different types of materials. In this paper, the possibilities of adhesive joining and the characteristics of glued joints made of aluminum alloy AW-5754 were researched, using static tests, and their fractography was analyzed. [ABSTRACT FROM AUTHOR]

In aeronautics, additive manufacturing (AM) leads to specific benefits, mainly connected to topological optimization for weight reduction, the decrease in "buy-to-fly" ratio, and the operations of maintenance, repair, and overhaul. Al alloys processed by AM technologies are extensively investigated and play an increasing role in the production of aircraft structural parts. Based on the recent literature and research activity of the authors, this work examines advantages and drawbacks involved in the printing of Al alloys. Defects, microstructure, mechanical properties, development of new alloys, and postprocess treatments are described and critically discussed by focusing the attention on the effects of the specific alloy composition, AM process, and process parameters. [ABSTRACT FROM AUTHOR]

Herein, we report that the influence of annealing time on the microstructure and mechanical properties of Al-14.5Si alloys solidified under a super-gravity field. The results indicate that the coarsening of metastable eutectic Si and formation of precipitated Si could be observed at the early stage of annealing. A slight increase in yield strength and tensile strength could be observed in the sample annealed for 0.25 h, which can be ascribed to the formation of precipitated Si with limited size during the early stage of annealing. The intensified diffusion of Si atoms during annealing led to the coarsening and coalescence of the eutectic Si, as well as the coarsening of precipitated Si with further extension of the annealing time. [ABSTRACT FROM AUTHOR]