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The alloy composition and sensitization behavior are crucial factors that cannot be overlooked in Al–Mg alloys. The effect of Zn addition on mechanical properties and sensitization behavior of 5083 alloy was investigated by tensile tests, weight loss experiments, and first-principles calculation in this paper. The results show that Zn can significantly improve the strength and sensitization behavior of the alloy. The tensile strength of the cold-rolled alloy increased from 459 to 498 MPa with the addition of 1.5%Zn. Furthermore, by incorporating 2.0% Zn, the mass loss of the cold-rolled alloy after sensitization at 170℃/1 h decreased from 49.3 mg·cm−2 to 19.5 mg·cm−2. First-principles calculations indicate that Mg clusters can only exist stably near grain boundaries, while Mg–Zn clusters can exist stably both within and at grain boundaries. This reduces the number of corrosive media at grain boundaries and weakens their continuity. Moreover, the energy barrier that T-phase precipitation needs to overcome during precipitation is lower than β-phase, which transforms the stabilization schedule of the alloy from 240℃/12 h without Zn to that 210℃/4 h with 2.0% Zn-containing. The synergistic effects of Zn content and sensitization on the properties of the alloy were revealed, which sheds some light for the design of the composition and processing method according to application scenarios. [ABSTRACT FROM AUTHOR]

In this paper, the effect of deep cryogenic treatment (DCT) on the microstructure and properties of automotive 6063 aluminum alloy at different times was investigated with automotive 6063 aluminum alloy as the research object. The results show that under the conditions of deep cryogenic treatment, the lattice distortion occurs in the alloy matrix microstructure, and the resulting internal stress promotes the large proliferation of dislocations within the alloy and the increase of dislocation density; meanwhile, after the deep cryogenic treatment, the deformed grains are transformed into recrystallized and sub-crystals structural grains, the grains are refined, and the size of the grains is refined from the original 25.2 μm to 20.3 μm, with fine equiaxed crystals. Among them, the mechanical properties of the DCT36h specimen were the best, and its hardness, tensile strength, yield strength and elongation reached 142.44 HV, 328.32 MPa, 177.42 MPa, and 29.29%, which were 34.17%, 5.62%, 11.10%, and 32.77% higher than the original sample, respectively. We believe that the main mechanism for the increase in toughness is multiple reinforcement such as dislocation strengthening, grain refinement strengthening, precipitated phase strengthening and texture strengthening. [ABSTRACT FROM AUTHOR]

High frequency fatigue behavior of near surface of turbine disk are critical for its application and operation. High frequency indentation fatigue tests of GH4169 alloy under different load amplitudes, frequencies and mean loads at small length scale were conducted, and the dependence of load amplitude, load frequency and mean load on high frequency indentation fatigue property of GH4169 alloy are discussed in this paper. Depth amplitude (ha), mean depth (hm) and depth propagation rate (dh/dN) were employed as evaluation indicators of the indentation behavior. Results show that depth amplitude is only relevant with load amplitude, while mean depth is related to all the adopted influencing factors, ranked in an ascending order as load amplitude, mean load and frequency with a ranking relation of nm1=1.4 < nm2=1.71 < nm3=2.02. Furthermore, a modified Paris law was utilized to reveal the fatigue mechanism, and found the fatigue mechanism is dominated by intrinsic mechanism under the influence of mean load and load amplitude, while for the influence of frequency, the fatigue mechanism is governed by extrinsic mechanisms. Combined with SEM results and three-dimensional morphology analysis, it can be deduced that dislocation movement mode in high frequency indentation fatigue is dislocation slip. [ABSTRACT FROM AUTHOR]

The CuZr-based bulk metallic glass matrix composites have attracted great attention in recent years owing to their unique mechanical properties compared to bulk glassy samples. The vital effect of B2 CuZr phase on mechanical properties was previously confirmed in CuZr-based alloys with equiatomic concentrations of copper and zirconium. In this paper, the structures and mechanical properties of the Cu45Zr48Al7 alloy, which has hypereutectoid composition with respect to stoichiometric B2 CuZr phase, were studied. This alloy exhibits high glass-forming ability, but low tendency to form the B2 CuZr phase during solidification. However, we demonstrated that depending on the cooling rate during solidification, governed by sample diameter, either bulk metallic glass or bulk metallic glass matrix composite can be produced. In order to allow partial crystallization of the B2 phase during solidification with the volume fraction allowing to observe the strain hardening effect, the minimum cooling rate should be lower than 40 K/s. The composite consisting of a glassy outer layer and a crystalline core composed of the B2 phase exhibits fracture strength of the same level as the bulk glassy sample (above 1800 MPa) obvious work-hardening with a plastic deformation of about 6%. [ABSTRACT FROM AUTHOR]

In recent years, more attention to unique and complex structures, such as nature-inspired and porous structures for medical applications, has been strongly developed. Open-cell porous metal-based ones display more benefits than rigid ones since they facilitate the transformation of load between the bone and the implants and avoid the phenomenon of stress shielding and bone resorption. By being biodegradable and non-toxic, as well as having lower density and mechanical properties close to those of natural bone, Mg and its alloys are considered promising materials for porous scaffolds. However, a high corrosion rate is the main drawback of Mg alloys. The porosity of porous structures can also worsen it as it enhances the surface area exposed to the corrosive solution and negatively impacts the performance of porous structures, that these issues have not been addressed in detail so far. Since fabrication methods of Mg-based scaffolds can significantly affect the porosity-related properties (e.g., porosity percentage, type, size, and geometry) and, consequently, scaffolds' mechanical behavior and corrosion resistance, this paper reviews and compares the fabrication methods of porous structures and how they affect the resultant properties. However, among different methods, due to the expansion of additive manufacturing as a novel and exciting manufacturing technique, the paper's central focus is on using additive manufacturing in biomedical applications, discussing its advantages over other techniques. The effect of geometrical parameters on mechanical properties and corrosion rate, which strongly affects bio-application, are also given. Moreover, different strategies are briefly introduced for tailoring the high corrosion rate of Mg and its alloys, such as alloying elements and coatings. However, there is still less information regarding the additive manufacturing of porous Mg scaffolds and the optimum way of controlling the corrosion rate of Mg-based parts. [ABSTRACT FROM AUTHOR]

AA6101 Al alloy is widely used as a high-strength conductive aluminum alloy, and the contents and existence of Mg and Si can influence its electrical conductivity and mechanical properties obviously. In this paper, experiments were conducted to find the optimal Mg, Si additions and Mg/Si ratio and then combined with heat treatment to improve the EC and mechanical properties at the same time. Firstly, considering the proper Mg/Si ratio, two optimal Mg and Si additions were determined: Al–0.7Mg–0.5Si and Al–0.4Mg–0.7Si with EC of 51.5%IACS and 51.4%IACS, and through homogenization treatment, their EC improved to 57.0%IACS and 55.7%IACS, respectively. Then, appropriate Fe was added to further control Si to achieve the balance of EC and mechanical properties. Results showed that for AA6101 Al alloy the ideal Mg/Si mass ratio was 1.4 and high Mg and low Si can obtain good EC and mechanical properties. Besides, it can be found that at low Mg/Si ratio, the alloy conductivity takes longer to reach its peak hardness. So the best performance Al–0.7Mg–0.5Si–0.2Fe alloy was obtained within the range of AA6101 national standard. The EC of Al–0.7Mg–0.5Si–0.2Fe can reach 56.3%IACS, and hardness is 91.3 Hv. Based on the study, a schematic diagram was drawn to analyze the influence mechanisms of Mg, Si and Fe on EC and hardness of AA6101 Al alloy. [ABSTRACT FROM AUTHOR]

In this paper, perfect interface model of Al/AlCu alloy and defect interface model of Al/AlCu alloy after cracks were introduced at different positions of the interface were established by using cohesive zone modeling method. Classical molecular dynamics simulation was used to study the deformation behavior and microstructure evolution of Al/AlCu alloy interface model at a strain rate of 0.05 Å/ps and the temperature of 300 K. The simulation results show that perfect interface exhibits a uniform plastic deformation stage due to structural relaxation after yielding, while there is no structural relaxation during the deformation of defect interface and the tensile strength is much lower than that of perfect interface as well. In the process of deformation, stacking faults formed in perfect interface and cracks are generated and expanded in Al matrix, while there was no stacking faults forming along with the expansion and cracking at the position of introduced cracks in defect interface. Massive dislocation nucleation leads to the reduction in stress at the perfect and defect interfaces after yielding. The extension of Shockley partial dislocation and the nucleation of Stair-rod dislocation are the main mechanisms of interface deformation. Densities of Shockley partial dislocation and Stair-rod dislocation decrease with increasing strain before crack propagation. This study enriches the analysis of microstructure evolution of Al/AlCu alloy interface and similar interfaces during deformation. [ABSTRACT FROM AUTHOR]

A cross-scale analysis method for predicting the compressive mechanical properties of tin-based bearing alloy was proposed based on microstructure finite element simulation and molecular dynamics (MD) simulation. The actual metallographic microstructure of tin-based bearing alloy taken by optical microscopy was utilized to construct the representative volume element (RVE) model for the computational modeling. The compression stress–strain curves of β-Sn and Cu6Sn5 obtained by MD simulation were used as the input material property parameters of each constituent phase in RVE model for the microstructure finite element analysis. The compression simulation was carried out for the tin-based bearing alloy with the microstructure containing Sn matrix and Cu6Sn5 phase. The results show that the simulation analysis method can predict the compression strength and elasticity of the studied tin-based bearing alloy well by comparing the simulated results with the experimentally obtained data. It is hoped that this paper can provide a simulation method for realizing the prediction of the mechanical properties based on microstructure and revealing the microscope mechanism of materials, thus providing theoretical guidance for the micro-design of high-performance tin-based bearing alloy. [ABSTRACT FROM AUTHOR]

Flexible linear aqueous zinc-ion hybrid supercapacitors are considered as ideal materials for flexible and wearable electronic devices due to their advantages of safety, high flexibility and good wearable ability. Materials based on shape memory can satisfy the needs of fatigue resistance and deformation recovery, and have great advantages in the assembly of flexible wearable devices. In this paper, aqueous zinc-ion hybrid supercapacitor with shape-memory function was assembled by using PANI/NiTi shape-memory alloy wire as the cathode electrode and flexible zinc wire as the anode electrode. The device can be bent into different angles from 0° to 180°, after repeated bending for 200 times and heating to its deformation temperature, the original shape can still be restored, and the capacitance retention rate is up to 90%, with good mechanical resistance. By assembling with flexible zinc wire, the potential window can be expanded to 1.6 V, and the energy density has been greatly improved. Its energy density can reach 55.9 Wh kg−1 at 3 A g−1, which greatly improves its energy density and has great development potential in flexible and portable electronic devices. [ABSTRACT FROM AUTHOR]

Layered double hydroxide (LDH) films have attracted extensive attention in Mg alloy anti-corrosion due to their unique physical barrier function and ion exchange performance. However, most of the LDH films on Mg alloy have problems of harsh preparation conditions, poor anti-corrosion stability, and poor adhesion. In this paper, a typical Li–Al-alanine (Ala) LDH film has been successfully prepared on AZ91D Mg alloy surface under milder conditions using multi-arc ion plating and in-situ dipping for the first time. Then an improved vacuum impregnation further modified the Li–Al-Ala LDH film in an ethanol solution of stearic acid (SA) to improve its protective stability. The potentiodynamic polarization curves and electrochemical impedance spectra (EIS) showed that the Li–Al-Ala LDH/SA film's corrosion resistance is more than three orders of magnitude higher than that of the blank Mg alloy in 3.5 wt% NaCl, showing a highly increased corrosion resistance. The long-term immersion experiments found that the surface structure and corrosion resistance of the Li–Al-Ala LDH/SA film did not change much after immersion in 3.5 wt% NaCl for 432 h. The bonding force between the film and the Mg alloy substrate can reach grade 0 based on the standard from International Standardization Organization (ISO). And the hydrophobicity of the film can remain stable with the water contact angle (WCA) being steady at about 140° after a certain distance of external abrasion, showing excellent mechanical wear resistance. The study provides a new milder approach to fabricating superhydrophobic LDH films with durable anti-corrosion resistance, good adhesion, and mechanical stability on Mg alloy surface. [ABSTRACT FROM AUTHOR]

This paper focuses on finding an optimum composition for the TiTaHfNbZr quinary high entropy alloy (HEA) system with an elastic modulus close to that of bone in order to attain a better biomechanical compatibility between the bone and the implant in orthopedic applications. To obtain the composition providing the desired structural match, machine learning (ML) tools were implemented in the current work instead of conventional trial-and-error methods. The ML algorithms utilized in this study were trained using experimental data available in the literature and then utilized to predict the optimum HEA compositions with the lowest elastic moduli. Consequently, the Ti23Ta10Hf27Nb12Zr28 and Ti28Ta10Hf30Nb14Zr18 compositions were predicted as the optimum HEA compositions with elastic moduli of 83.5 ± 2.9 and 87.4 ± 2.2 GPa, respectively. The materials were manufactured, and the elastic moduli were validated with nanoindentation experiments. The samples were also exposed to static immersion experiments in simulated body fluid (SBF) for 28 days to gain insight and information regarding the ion release and ensure that the new HEAs are biocompatible. The findings of the work reported herein demonstrate that the proposed ML model can successfully predict HEA compositions for an optimized biomechanical compatibility for orthopedic applications and warrant further biomedical research on the two new HEAs prior to their utility as orthopedic implant materials. [ABSTRACT FROM AUTHOR]

The purpose of this paper was to design an Al–Cu–Ag–C material system to address the deterioration of mechanical properties caused by intermetallic compounds generated during Al–Cu sintering. The in situ pyrolytic C layer was encapsulated on the surface of the raw material particles, which prevented Al–Cu diffusion and reduced the generation of intermetallic compounds. The microstructure of the Al–Cu–Ag–C composites illustrates that several alloy phases of Al2Cu, Al4Cu9, and Ag2Al are formed. The addition of Ag significantly improved the mechanical properties of the composite due to the formation of the Ag2Al phase and Cu–Ag solution. The tensile strength and compressive strength of Al–52Cu–3Ag–C are increased by 123.9% and 64.9% over Al–52Cu–C, and the strain is also considerably improved. The strength enhancement derived from the Orowan strengthening contributed by Ag2Al, and the solid solution strengthening contributed by Ag–Cu solid solution, respectively. The presence of Ag2Al also enhances the hardness of the composite. [ABSTRACT FROM AUTHOR]

TiAl alloy becomes a promising high-temperature structural material due to excellent mechanical properties at elevated temperature. However, the inherent brittleness makes it difficult to be processed by traditional technologies. Therefore, an innovative twin-wire plasma arc additive manufacturing (TW-PAAM) process is developed to fabricate TiAl alloy. Substrate heating is indispensable during additively manufactured TiAl alloy, which can alleviate its crack tendency. In this paper, crack-free TiAl alloy samples are fabricated using TW-PAAM, and the effect of substrate temperature (560, 620 and 680 °C) on as-deposited TiAl alloy is investigated in detail. With the increase in substrate temperature, microstructural lamellar spacing and colony size exhibit the tendency of increase. Also, α2 phase content, recrystallization degree and high Schmid factor frequency present the decrease tendency. These variations of microstructure characteristics further lead to the decrease in both microhardness and tensile properties of the deposit. These findings provide a valuable reference for optimizing microstructures and mechanical properties of additively manufactured TiAl alloys. [ABSTRACT FROM AUTHOR]

Aluminum–lithium alloys are widely used in aerospace due to their excellent comprehensive mechanical properties. The key to accelerate the composition design of aluminum–lithium alloys is to generate accurate precipitate structure models at the atomistic scale and quantify the effects of the secondary phase on the properties of the alloy. In this article, the development process of high-strength composition design of aluminum–lithium alloys is reviewed. The T1 phase is considered to provide the highest strength in Al-Cu-Li alloys, and we further discuss the characteristics of the crystal structure, orientation relationship and morphology of the main strengthening phase. Additionally, this paper highlights the atomic structure model, microstructure parameters of T1 phase and the precipitate–dislocation interaction relationships. Practically, the widely accepted atomic model of T1 phase characterized with a corrugated Al-Li layer at the interface remains controversial. Moreover, the strengthening mechanism of Al-Li alloy is discussed. Based on the shearing and bypassing interaction mechanism between the T1 precipitates and the matrix dislocations, some quantitative contribution models to the strength of Al-Cu-Li alloys are concluded. These models can effectively predict the variation of yield strength of Al-Cu-Li alloy, but the transition of T1 phase from shearing mechanism to bypassing mechanism is not considered. However, the T1 diameter threshold that activated this transition has not been completely determined, which need to be further studied by obtaining a wider range of T1 microstructures. [ABSTRACT FROM AUTHOR]

This paper reports atomistic simulation studies of tensile and compressive behavior of nanowires of a model quinary high entropy face-centered cubic (FCC) alloy. The simulations employ empirical interatomic potentials and use massively parallel molecular dynamics techniques at the atomistic level to study the deformation mechanisms. The studies consider pristine cylindrical nanowires oriented along various crystallographic directions. The focus is the role that local composition fluctuations in the random alloy plays in the deformation response. The deformation behavior observed for the complex random alloy is compared with a corresponding "average atom" material that has the same average properties but no local compositional fluctuations. In all cases, deformation is governed by dislocations emitted from the free surface. Twinning was also found, depending on the crystallographic orientation and loading mode. We show that for all orientations, the high entropy alloy (HEA) wires show the onset of plasticity at lower stress levels than the average atom material. However, after the onset of plasticity, the HEA presents a higher strength, mostly driven by the fact that the dislocations emitted from the surface do not glide as easily in the random alloy as they do in the average atom material. [ABSTRACT FROM AUTHOR]

Al–Zn–Mg–Cu alloys can be fabricated by a series of thermo-mechanical processing methods (e.g., hot rolling, forging and extrusion), which is able to serve in aeronautic, automobile, and marine industries because of its excellent physical properties. However, reaching the balance between high strength and favorable ductility to present its high performance is still in progress, during which temperature and strain rate are two very important external variables. More importantly, the core lies in sophisticated microstructure evolution paths involved in hot deformation, which consists of different microstructure mechanisms and behaviors and can be expressed as various mechanical responses. Therefore, a fundamental review of microstructure mechanisms and behaviors, microstructure evolution and relevant mechanical responses of Al–Zn–Mg–Cu alloys during high-temperature deformation is of great significance. In present paper, first, various experimental methods have been introduced. Second, general trends of mechanical properties changing with temperature and strain rate have been summarized. Third, major microstructure mechanisms and behaviors have been discussed. Then, a schematic illustration originating from dislocations' movement has been depicted, which succeeding microstructure evolution and mechanical responses (including superplasticity) have been reviewed accordingly. Finally, further suggestions of hot deformation of Al–Zn–Mg–Cu alloys have been given. [ABSTRACT FROM AUTHOR]

Aluminum (Al) alloys are of great importance and interest because of their extensive applications in various engineering fields. Lightweighting of our infrastructure has been a driver for more than the last two decades as our need to reduce carbon footprint on a global scale has become an inevitable reality. As a result, we have witnessed much progress in alloy development in Al alloys, especially with the advent of Integrated Computational Materials Engineering (ICME) and other computational tools. However, the limitations of the properties one may attain through alloy development to date have relied on the traditional solvent/solute model, where the matrix is Al with additions of elements (solute) to the matrix. Despite making much progress, we are still locked-in to the strength-ductility curve without any appreciable increase in modulus (stiffness) of the alloy. High Entropy Alloys (HEAs) provide a new paradigm as they differ from conventional alloys in entropy-based mixing logic of various elements, which is different from the solvent/solute model. HEAs offer the opportunity to move out of the strength-ductility curve as well as the opportunity to increase the alloy's modulus. In this paper, we present a retrospective view of Al alloys, followed with an understanding of the principles of HEAs, and lastly, with the idea of applying high entropy concept to conventional Al alloys to develop a novel Al alloy category, which we have coined HEAl. Preliminary results with a commentary on potential future opportunities are also given. [ABSTRACT FROM AUTHOR]