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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]

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]

The ordered γ′-(Ni, Cu)3Al is a crucial strengthening phase that improves the high-temperature resistance of Cu-based alloys, so it is important to predict the kinetic evolution of the composition and microstructure of the phase for high-temperature applications. Herein, this paper discusses the temporal evolution of the composition and coarsening of the γ′ phase in a model ternary Cu50Ni37.5Al12.5 (at%) alloy during isothermal aging at 600, 700, 800, and 900 °C for 1–36 h. It is found that the γ′ phase composition evolves linearly toward a binary γ′ phase as the aging time increases during the process of aging at 800 and 900 °C, which cannot be predicted by the ternary phase diagrams alone. Meanwhile, through the utilization of the aforementioned linear law, the γ phase composition can be predicted at a given temperature within the alloy by determining the volume fraction of the γ′ phase. Additionally, the activation energy for coarsening decreases, and the coarsening rate of the γ′ phase increases owing to the higher diffusion rate of Cu at high temperatures. The addition of microalloying elements with strong enthalpic interactions is beneficial for reinforcing the structural stability of the γ′ phase. This work provides a simple method for the compositional analysis and performance prediction of Cu–Ni–Al alloys at elevated temperatures and sheds light on the subsequent compositional design and optimization of Cu-based high-temperature alloys. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

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]

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]

This paper aims to unveil effects of α colony and α plate parameters on tensile properties and impact toughness of Ti-55531 alloy with multilevel lamellar microstructures. Microstructures with different α colony and α plate sizes were prepared using varied heat treatments and analyzed by X-ray diffraction, scanning electron microscopy, electron back-scattered diffraction, transmission electron microscopy. Relationships of microstructure and strength, plasticity and impact toughness were discussed. Results indicate that tensile strength increases, while plasticity and impact toughness of the alloy decline with decreasing effective sizes (width/length ratio) of α colony (dc) and α plate (dα) and increasing of volume fraction of α phase. Both dc and dα follow the Hall–Petch principle with strength, and dc was determined to be the critical controlling parameter of strength owing to higher interfacial strengthening effect induced by α colony. However, plasticity is primarily related to dα. Moreover, impact toughness for both dc and dα follows the linear relation, but the coefficient of dα is higher. Furthermore, impact toughness is more dependent on plasticity than strength. Larger α plates lead to more mechanical twins during impacting and result in higher plasticity and impact toughness. Therefore, the impact toughness should depend more on the size of α plates. In order to unveil the influence of α plate size on impact deformation and microcrack initiation behavior of Ti-55531 alloy, the microstructural deformation and crack nucleation characteristics in the impact crack nucleation region were detected by TEM in detail; then, the schematic illustration for microstructural deformation and crack nucleation characteristics was made according to experiment results. [ABSTRACT FROM AUTHOR]

The paper studies the wetting of grain boundary triple junctions (GB TJs) by the second solid phase (intermetallic) δ in the Cu–In alloys. In this system, the portion of grain boundaries in a copper-based solid solution (Cu), which are "wetted" by the second solid phase δ, changes non-monotonically with increasing temperature. At first, the portion of such completely wetted GBs increases from zero to almost 100% when the sample is heated, and then quickly falls back to zero. The condition of complete wetting for the GB TJs (σGB > 1.73 σSS) is less stringent than for the GBs (σGB > 2 σSS). Therefore, if the transition from incomplete to complete wetting occurs with an increase in temperature, then all GB TJs should become completely wetted at a temperature TWTJ, lower than the temperature TWGB, at which all GBs become completely wetted. In this work on the Cu–In system, it was found experimentally for the first time that the wetting of the GB TJs also behaves non-monotonously. The percentage of wetted GB TJs also increases to 100% at first and then falls with increasing temperature. In this case, the portion of wetted GB TJs exceeds the portion of wetted GBs not only when it increases with increasing temperature, but also then, with the subsequent disappearance of fully wetted GBs. Grain boundary triple junctions in (Cu-In) solid solution are "wetted" by the δ intermetallic in broader temperature interval than grain boundaries. [ABSTRACT FROM AUTHOR]

Stacking fault energy (SFE) is an intrinsic material property whose value is crucial in determining different secondary deformation mechanisms in austenitic (face-centered cubic, fcc) steels. Considerable experimental and computational work suggests that the SFE itself is highly dependent-in a complex manner-on chemical composition and temperature. Over the past decades, there have been a large number of efforts focused on determining the composition dependence of SFE in austenitic steel alloys by means of experimental, theoretical or computational methods. Unfortunately, experimental methods suffer from the indirect nature of the methodologies used to estimate the value of SFE, while computational and/or theoretical approaches are either limited by the physics that they can incorporate into the predictions or have more practical limitations associated, for example, to the size of the systems that can be modeled or the assumptions that must be made. In this paper, we review the major experimental and computational approaches to determine SFE in austenitic steel alloys, and we discuss their limitations. We then demonstrate a data-driven machine learning technique to mine the literature of experimental SFE data in steels, while algorithms at the fore-front of machine learning have been used to visualize the SFE data and then construct a three-class classifier. The classifier is used then to predict likely secondary deformation mechanisms of untested compositions, while the classifier itself is presented as a valuable tool for the further development of austenitic steel alloys in which the specific secondary plastic deformation mechanisms are a feature to design for. The data as well as the entire analysis workflow are made available to the wider community through a public github repository. [ABSTRACT FROM AUTHOR]

A modified thermodynamic approach to describe melting in isolated nanoscale materials is suggested. The Gibbs free energy change of nanoscale alloy particles is modeled as a function of composition, temperature and nucleus and particle sizes. Cu–Ni has been chosen as a model system due to the availability of thermodynamic data within the high-temperature interval 1300–1600 K. For the first time, "melting loops" in the temperature–composition phase diagram were calculated for nanoparticle of 25 and 80 nm, respectively. It is shown that such loops represent the equilibrium two-phase solid–liquid states and do not coincide with the limiting solubility curves—the solidus and the liquidus. This new finding leads to the "melting loop" concept concerning phase diagrams of nanoscale alloys introduced in this paper. It is found that Cu–Ni nanoparticles can melt in different ways, whereas the dominant transition mechanism is surface-induced melting that initiates from the surface and then proceeds toward the core region. The decrease in size causes also a change of the melting temperature, the temperature width of the phase transition, the solubility limit, the concentration width of the melting loop as well as a change of the shape and slope of the equilibrium curves of the two-phase region of the phase diagram. As expected, when the size of the nanoscale particle increases, the solidus temperature increases and the size-dependent phase diagram approaches the bulk phase diagram. [ABSTRACT FROM AUTHOR]

A comprehensive understanding of solidification behavior of Mg–Al–Zn–Bi alloys is necessary for designing novel casting Bi-modified AZ alloys. In this paper, 21 Mg–Al–Zn–Bi alloys were prepared to investigate the phase constituents, morphologies, grain sizes and area fractions of precipitates in as-cast microstructures, as well as their phase transition temperatures and solidification paths by using X-ray diffraction, scanning electron microscopy, optical microscopy and differential scanning calorimetric techniques. It was found that the Bi addition leads to the formation of α-Mg3Bi2 phase, which became coarse flake as Bi content increased. Besides, the Bi addition can modify the morphology of eutectic γ-Al12Mg17 phase and refine the grain size of primary phase. Moreover, the measured area fractions of precipitates increased steadily as Bi content increased, which were comparable with the model-predicated values. After that, the calculated liquidus projections in the Mg-rich corner of Mg–Al–Zn–Bi quaternary system were employed for demonstrating the effects of Bi addition on the solidification sequences. Additionally, the phase transition temperatures predicted via Scheil solidification simulations agreed well with measured values. The present work indicated that the combination of experimental investigations and thermodynamic calculations can serve as an efficient method to obtain accurate and comprehensive solidification behavior of Bi-modified Mg–Al–Zn alloys. [ABSTRACT FROM AUTHOR]

The effect of high-density electroshocking on the solid phase transformation of Ti–6.6Al–3.4Mo alloy was studied in this paper. The microstructure at the same position of the specimens before and after electroshocking treatment with different parameters was characterized by the optical microscopy and scanning electron microscopy. The experimental results reveal that the refined and spheroidized primary α phase can be obtained under the appropriate treatment condition. Meanwhile, the fine orthorhombic α″ phase at submicron was discovered by the X-ray diffraction and transmission electron microscopy in the transformation products. A physical model was established to analyze non-uniform current distribution at microscale and to explain the spheroidization mechanism. The phase transition process was interpreted from the point of view of thermodynamics. [ABSTRACT FROM AUTHOR]

The paper demonstrates the prospects of spark plasma sintering (SPS) for the high-speed diffusion bonding of the high-strength ultrafine-grained (UFG) near-α Ti–5Al–2V alloy. The effect of increased diffusion bonding intensity in the UFG Ti alloys is discussed also. The bonding areas of the UFG near-α Ti–5Al–2V alloy obtained by SPS are featured by high density, strength, and corrosion resistance. The rate of bonding in the UFG alloys has been shown to depend on the heating rate non-monotonously (with a pronounced maximum). At the stage of continuous heating and isothermic holding, the bonding kinetics was found to be determined by the exponential creep rate, the intensity of which in the coarse-grained alloys is limited by the diffusion rate in the crystal lattice α-Ti. In the UFG alloy, the exponential creep processes associated with gliding and climb of dislocations, the activation energy of which corresponds to the diffusion activation energy in the lattice dislocation nuclei, may take place simultaneously with the grain boundary sliding and Coble creep, the activation energy of which corresponds to the grain boundary diffusion activation energy. [ABSTRACT FROM AUTHOR]

This paper presents a new approach to modify the surface of the Ti–6Al–4V alloy fabricated by additive manufacturing. This method is particularly suitable for titanium or titanium alloy components with complex shapes (such as pipes, holes and internal flow paths) which are difficult to be polished by conventional methods. The corresponding electrochemical tests were carried out in Hanks' balanced salt solution. The results demonstrated that the chemical polishing of additively manufactured Ti–6Al–4V obtained a high-quality surface through the combination of oxidation corrosive action and polishing liquid flow by reducing the peak-to-valley spacing and smoothing the alloy surface. After chemical polishing, a passivation film consisted of rutile and anatase formed on the alloy surface, which showed n-type semiconductor characteristics and had a lower donor density, leading to the increase in the corrosion resistance. [ABSTRACT FROM AUTHOR]

The growing interest in nanocrystalline (nc) materials is driven by their outstanding combination of mechanical and functional properties. Electrodeposited nc Ni–Fe alloys have received considerable attention, thanks to their unique strength and to their thermal and magnetic properties. However, the research on the relationship between microstructure, mechanical properties and fracture behaviour, under both As-deposited and annealed conditions, is still rather limited. In this paper, 48 wt% Fe electrodeposited nc Ni–Fe alloy foils were tested, by means of tensile and nanoindentation tests, under both As-deposited and annealed conditions (300–800 °C). High-resolution FESEM images revealed that the As-deposited microstructure consisted of an unforeseen, evident anisotropic nested three-scale hierarchy nc structure, namely from the nanocrystalline (~ 10 nm) to the sub-micron (up to 250 nm) scale, across a mesostructure (155–165 nm), here denoted as the characteristic grain structure. Such a nested nc grain structure of the electrodeposited nc Ni–Fe alloy, which resembles the one of a corncob (corncob-like structure), explained the unique anisotropic mechanical properties of the foils after nanoindentation, tensile and oblique-bending fracture tests. The mechanical properties (i.e. tensile strength, elongation, yield strength and hardness) of the foils annealed up to 320 °C were found to be improved, in comparison with the As-deposited counterparts, whereas those annealed above 320 °C were deteriorated. [ABSTRACT FROM AUTHOR]

Ductility dip cracking (DDC) is a solid-state failure occurring during multi-pass solidification processes (e.g., welding, additive manufacturing) for FCC alloys that exhibit a distinct dip in their ductility at intermediate temperatures. While the phenomenon has been studied for over a century, the majority of current research focuses on a subset of DDC-susceptible FCC alloys (Ni–Cr–Fe). The review paper herein presents an analysis of published data to evaluate the current state of understanding regarding the materials mechanisms at work. Recent advances in test methods have permitted highly controlled approaches for testing and quantifying DDC, but the wide range of unique tests often provide conflicting results regarding the fundamental materials behaviors and underlying mechanisms. At present, three mechanisms have been proposed for DDC: grain boundary sliding, precipitate-induced strain, and impurity element segregation. While the majority of published studies support grain boundary sliding as the primary mechanism of DDC, an examination of the aggregate data available across multiple studies suggests combinatorial impact of simultaneous (and competing) mechanisms for DDC. Further, the long-held assumptions regarding the negative impact of key alloying elements become less convincing when comparing results across studies. There are considerable future opportunities for research on DDC behaviors in other alloy systems, and there are a lacunae of data when considering the effect of welding process parameters on DDC and the use of modeling and simulation approaches to understand the DDC behavior in the highly susceptible FCC alloy systems. [ABSTRACT FROM AUTHOR]

An approach of achieving high ductility as well as respectable high strength for low-Zn-containing wrought Mg alloy is presented in this paper. A low-cost and industry-compatible Mg–2Zn–0.3Mn–0.2La–0.1Ce alloy with highest yield strength (YS) of 289 MPa, ultimate tensile strength (UTS) of 300 MPa and excellent elongation (EL) of 32.7% is developed by traditional indirect extrusion. The microstructure and macro-textures of this alloy under various extrusion temperatures are characterized by OM, EBSD and XRD analysis. High quantity of dispersed elongated un-DRXed grains with various orientations form at relatively low extrusion temperatures, and many of them possess high basal Schmidt Factors (SFs) toward transverse directions. TEM analysis reveals a large number of networked dislocations passing through the deformation bands along transverse directions within the un-DRXed grains, which suggests the integral deformation (bending) is achievable by dislocation motion. It is believed that the high ductility along extrusion direction is induced by the bendable elongated un-DRXed grains during tensile deformation by embodying the easy-to-failure regions, preventing the subsequent generation of micro-cracks and accommodating the stress concentration. [ABSTRACT FROM AUTHOR]

In this paper, an Open-source code for Interfacial Energy Calculation (OpenIEC, https://github.com/openiec) was developed by following Kaptay's models (Acta Mater 60(19):6804–6813, 2012; J Mater Sci 53(5):3767–3784, 2018. 10.1007/s10853-017-1778-y). The coupling with the CALculation of PHAse Diagram thermodynamic and molar volume databases was facilitated in OpenIEC for providing the necessary thermodynamic information. With OpenIEC, the temperature- and composition-dependent interfacial energies in alloys with any arbitrary number of components can be conveniently evaluated. In order to demonstrate the applicability and validity of OpenIEC, the benchmark tests in several model alloys in Ni and Al alloys were carried out, and the calculated interfacial energies were found to be in good agreement with the literature data. After that, the OpenIEC was applied to predict the temperature- and composition-dependent interfacial energies of coherent γ/γ' interfaces in two Ni-based superalloys, including ternary Ni–Al–Cr and quaternary Ni–Al–Cr–Re alloys, as well as the temperature- and composition-dependent solid/liquid interfacial energies in Ni–Al–Cr and Al–Cu–Li alloys. [ABSTRACT FROM AUTHOR]

The solid/liquid interfacial energies of pure metals and metallic alloys are modelled in this paper. A simple model is offered for pure metals, showing that their solid/liquid interfacial energy (sigma) slightly increases with temperature. Sigma for metallic alloys is considered for the interface between solid and liquid solutions being in thermodynamic equilibrium, calculated by the CALPHAD method. The Butler equation is extended to find the equilibrium composition of the solid/liquid interfacial region and the solid/liquid interfacial energy at fixed temperatures. This method takes into account the segregation of low-interfacial energy components to the solid/liquid interfacial region. It is shown how the new method can be extended to multi-component alloys. The method is applied to calculate the solid/liquid interfacial energy of Al-rich solid solutions in equilibrium with eutectic liquid alloys of Al-Cu, Al-Ni, Al-Ag and Al-Ag-Cu systems. Good agreement was found with experimental values. For the Al-Ag-Cu system, the modelled value allows to select the more probable experimental value from the two contradicting experimental values published in the literature. The solid/liquid interfacial energy is calculated for the eutectic Ag-Cu system as function of liquidus composition (which determines both the equilibrium solidus composition and the equilibrium temperature). Finally it is claimed that using solely bulk thermodynamic data (melting enthalpy and molar volumes of pure components and molar excess Gibbs energies of equilibrium solid and liquid solutions) it is possible to provide meaningful values for the temperature and concentration dependence of solid/liquid interfacial energies of alloys. The method can be applied for simulation of solid/liquid phase transformation and also to solid/liquid equilibrium calculations of nano-alloys. [ABSTRACT FROM AUTHOR]

Martensite has a body-centered tetragonal (bct) structure in high carbon steels. However, body-centered cubic (bcc) {112} 〈111〉-type twins instead of bct twins always be observed as the substructure of martensite in high carbon steels. In this paper, martensitic substructure in a quenched high carbon Fe-1.4C (wt%) alloy has been investigated in detail using selected area electron diffraction (SAED) technique in a conventional transmission electron microscopy. The reciprocal lattice of martensite has been built based on the experimental SAED patterns. Two sets of diffraction spots (one face-centered cubic lattice and one hexagonal lattice) in the built reciprocal lattice suggest that two crystalline phases with bcc (or α-Fe) and hexagonal (ω-Fe) structure actually coexist in the twinned martensite. The two-phase diffraction spot patterns from the reciprocal lattice can match perfectly with the experimental results. The fact that the {0001} diffraction spot at the 1/3{222} position and the {0002} at 2/3{222} can support the ω-Fe existence in the twinned martensite. [ABSTRACT FROM AUTHOR]

Phase equilibria in Ti-Al-Mo ternary system are of fundamental importance to better acquire the phase-forming regulation of TiAl-based alloys. In this paper, phase relations in this system have been investigated with Ti-TiAl-Mo diffusion triples combined with key equilibrated alloys. Five isothermal sections of the Ti-Al-Mo ternary system at 1473, 1373, 1273, 1173, and 1073 K were experimentally determined by means of electron probe microanalysis, scanning electron microscope, and X-ray diffraction. The TiAl and TiAl phases show wide ternary composition ranges, while the solubility of Mo in the TiAl and αTi phases is relatively limited. The solubility of Al in the β(Ti, Mo) phase decreases from 49.0 at.% at 1473 K to 39.9 at.% at 1073 K while that of Ti in the AlMo phase decreases from 25.4 at.% at 1473 K to 20.8 at.% at 1073 K. Moreover, the ternary compound σ forms at a temperature between 1423 and 1373 K through a peritectoid reaction β(Ti, Mo) + AlMo → σ. A peri-eutectoid invariant reaction β(Ti, Mo) + AlMo → σ + TiAl at 1373-1273 K was further deduced and the existence of another invariant reaction β(Ti, Mo) + TiAl → σ + TiAl at a temperature between 1273 and 1173 K was also confirmed. The established phase equilibria of the Ti-Al-Mo ternary system may provide essential data required for the construction of reliable thermodynamic assessment of the Ti-Al-Mo system. [ABSTRACT FROM AUTHOR]

NiTi alloy is considered to have great application potential in the fabrication of metal implant materials. However, the NiTi alloy still suffers from some disadvantages, such as poor corrosion resistance and health hazards caused by the release of nickel ions. In order to improve the corrosion resistance of NiTi alloy, a healing composite coating was prepared on NiTi alloys by micro-arc oxidation doped with ZnO nanoparticles and sol–gel sealing with polyacrylamide. The surface morphology, composition, roughness, thickness, and electrochemical performance of the prepared coating were investigated by SEM, EDS, Eddy current thickness gauge, electrochemical workstation, and so on. The adhesion of the prepared coating was also tested using the pull-off method. The results show that compared with NiTi alloy substrate, composite coating of MAO–ZnO@PAM has a dense microstructure, a flatter surface, the largest inner and interfacial charge transfer resistances, outstanding corrosion resistance, and possesses the self-healing ability under the humid condition. [ABSTRACT FROM AUTHOR]

The present study conducted a detailed investigation to determine the effects of adding Sc and applying low-frequency electromagnetic casting (LFEC) on the bendability and ductility of hot-rolled 7A36 alloy using optical microscopy, electron backscatter diffraction, and scanning electron microscopy by two different solid solution heating rate treatments. Results showed that the rapidly solid-solution-heated rates specimen (R specimen) exhibited several micro-cracks, while the slow solid-solution-heated rates specimen (S specimen) displayed visible cracks and even fractures. Additionally, increasing the solid solution heating rate resulted in a decreased diameter of the second phase but larger average grain size. The coarse second-phase grains of the alloys most likely lead to the formation of microcracks; however, the coarse recrystallized grains prevent the further propagation of bending cracks. The strap-like and finer recrystallized grains of the R specimen lead to an improved bendability of the 7A36 alloy by coordinating plastic deformation and accommodating more dislocations. Further, adding Sc improves the bendability and tensile properties by refining grain size and improves the texture strength, while applying LFEC slightly increases the average grain size and the recrystallizing degree, which result in a high Schmid factor value and lower texture strength, and dislocation density benefits the bendability and ductility of the 7A36 alloy with a little strength reduction. [ABSTRACT FROM AUTHOR]

The microstructure, compressive properties and in vitro degradation behavior of as-cast Mg alloys with high Zn or Ca content were investigated. The results showed that the addition of Ca (1 wt%) to Mg–5Zn or Zn (1 wt%) to Mg–5Ca changed the shape, distribution, volume fraction and the type of second phase. When 1 wt% Ca was added to Mg–5Zn alloy, the second phase changed from Mg7Zn3 to Ca2Mg6Zn3 phase and it was distributed from granular formation to a continuous network structure. While the second phase was changed from Mg2Ca in Mg–5Ca alloy to the coexistence of Mg2Ca(Zn) and slight Ca2Mg6Zn3 phase in Mg–5Ca–1Zn alloy. The second phase exhibited a continuous network distribution in both of Mg–5Ca and Mg–5Ca–1Zn alloys, but the width of Mg2Ca(Zn) phase was reduced obviously after adding 1 wt% Zn to Mg–5Ca alloy. The compressive test revealed that Zn element was contributed to the promotion of ultimate compressive strength and fracture elongation, while Ca element was beneficial for improving the yield strength of Mg alloys. The immersion test proved that the weight loss of Mg–5Zn–1Ca was the highest, followed by Mg–5Zn, Mg–5Ca and Mg–5Ca–1Zn alloy. The Mg–5Zn-based alloys suffered severe pitting, while Mg–5Ca-based alloy exhibited a relatively uniform corrosion. The Ca addition accelerated the corrosion of Mg–5Zn alloy due to the expansion of potential difference between second phase and Mg matrix, while Zn addition reduced the micro-galvanic corrosion of Mg–5Ca alloy due to the lowest potential difference between Mg2Ca(Zn) phase and Mg matrix. [ABSTRACT FROM AUTHOR]

To conquer the trade-off between strength and ductility, a new strategy for preparing heterostructured (HS) 2024Al alloys with various heterogeneity levels through introducing submicro-Al3Ti particles and adjusting partial remelting duration of powder thixoforming was proposed. The results indicate that the difference in volume fraction between soft and hard domains of the resultant HS alloys gradually decreases from 0.27 to 0.02, while that of microhardness also decreases from 1.58 to 1.17 GPa, i.e., the heterogeneity level gradually decreases with prolonging the remelting time. The excellent strength–ductility synergy is simultaneously achieved by a moderate heterogeneity level (the differences in microhardness of 1.23 GPa and volume fraction of 0.02) in the HS alloy thixoformed at the partial remelting time of 80 min. This is primarily ascribed to the largest strain gradient caused by the accumulation of the highest density dislocations at the boundary during deformation, which produces the highest heterodeformation-induced (HDI) strengthening and hardening. In addition, the dislocations emitted from the submicro-Al3Tip during the later deformation stage also improve the strain strengthening and hardening, further leading to the improvement in strength–ductility synergy. [ABSTRACT FROM AUTHOR]

Introducing of thermodynamically stable strengthening phases is an important means enhancing the properties of magnesium alloys. To introduce a stable Al2Nd strengthening phase, the Mg-Al-Nd alloys were prepared with a fixed atomic ratio of 2:1 for Al and Nd. The total content of Al and Nd was varied at 1%, 3%, 5%, and 7%, respectively. The effects of Al2Nd phase on the microstructure and mechanical properties of the Mg-Al-Nd alloys were systematically studied in this work. The experimental results indicated that the as-cast alloy primarily consisted of the acicular Al11Nd3 phase as a secondary phase. After undergoing a homogenization treatment at 500 °C for 12 h, the secondary phase underwent a transformation, resulting in the formation of short rod shape Al2Nd structures. Simultaneously, layered Al2Nd precipitated within the α-Mg matrix. The formation of twinning was inhibited, while the Al2Nd phase promoted recrystallization and refined the microstructure through the mechanism of particles stimulated nucleation (PSN), as the Al and Nd contents increased during thermal deformation. At the same time, the increases of Al2Nd phase can enhance the strength and the plasticity of the alloy. The mechanical properties of extruded Mg-1.36Al-3.64Nd (AE5) alloy were excellent with yield strength of 175 MPa, ultimate tensile strength of 249 MPa, and the elongation of 15.4%. The enhanced performance can be primarily attributed to the refined microstructure and the presence of Al2Nd precipitates with small size, which contributed to effective fine grain strengthening and secondary phase strengthening. [ABSTRACT FROM AUTHOR]

Data-driven methodology has become a key tool in computationally predicting material properties. Currently, these techniques are priced high due to computational requirements for generating sufficient training data for high-precision machine learning models. In this study, we present a support vector regression (SVR)-based machine learning model to predict the stability of silicon (Si)–alkaline metal alloys, with a strong emphasis on the transferability of the model to new silicon alloys with different electronic configurations and structures. We elaborate on the role of the structural descriptor in imparting transferability to the model that is trained on limited data (~ 750 Si alloys) derived from the Material Project database. Three popular descriptors, namely X-ray diffraction (XRD), sine coulomb matrix (SCM), and orbital field matrix (OFM), are evaluated for representing Si alloys. The material structures are represented by descriptors in the SVR model, coupled with hyperparameter tuning techniques like Grid Search CV and Bayesian optimization, to find the best performing model for predicting total energy, formation energy and packing fraction of the Si alloy systems. The models are trained on Si alloys with lithium (Li), sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), and aluminum (Al) metals, where Si–Na and Si–Al systems are used as test structures. Our results show that XRD, an experimentally derived characterization of structures, performs most reliably as a descriptor for total energy prediction of new Si alloys. The study demonstrates that by qualitatively selection of training data, using hyperparameter tuning methods, and employing appropriate structural descriptors, the data requirements for robust and accurate ML models can be reduced. [ABSTRACT FROM AUTHOR]

The effect of grain size and second-phase distribution on the corrosion performance of metal inert gas-welded Al–MgSi–Mn–Cr alloy in different regions was investigated. Due to the welding heat, the transformation of the strengthening phase β″ (Mg5Si6) to B′ phase (Al3Mg9Si7) in heat-affected zone I leads to the reduction in strengthening ability of the joint. In comparison with the equiaxed grain of weld zone, base metal exhibits high grain boundary density of the fibrous grain and a large amount of second phases on the grain boundary, which increases the anodic dissolution site, leading to the highest pitting corrosion susceptibility. Additionally, the continuous distribution of β (Mg2Si) precipitate and Al(MnFe)Si dispersoid at grain boundary forms a corrosion channel, which promotes the corrosion propagation along grain boundary. [ABSTRACT FROM AUTHOR]

Hafnium (Hf) was added as an alloying element to enhance the strength in the NiCoCrAlYMoHf alloys, and the effects of Hf content on constituent phases, microstructural characteristics, and mechanical properties of the as-cast alloy were investigated. The experimental results showed that microstructure of the alloy with 1.0 wt.% Hf was composed of β phase and γ′ phase. The experimental results showed that microstructure of the alloy with 1.0 wt.% Hf was composed of β phase and γ′ phase. With increase in Hf content, the β phase content increased, while the γ′ phase content decreased, and σ phase gradually appeared and precipitated at grain boundary, which resulted in an increase in the hardness of alloys from 429 to 586 HV. The indentation hardness, Young's modulus, and compressive strength of NiCoCrAlYMoHf alloy with 4.0 wt.% Hf could reach 7.12 GPa, 185.52 GPa, and 2659 MPa, respectively, which means that more addition of Hf is beneficial for improving performances of NiCoCrAlYMoHf alloys. The microhardness value is 1.95 times higher than that of the Hf-free alloy. Furthermore, the nanoindentation hardness and Young's modulus are 1.05 and 1.75 times higher, respectively, than those of the Hf-free alloy. [ABSTRACT FROM AUTHOR]

In this study, the gradient microstructure of Mg-Y-Nd-Zr alloy processed by an ultrasonic surface rolling process (USRP) is characterized by electron backscatter diffraction analysis and transmission electron microscopy. The mechanism of microstructure evolution and its effect on mechanical properties of the alloy are discussed in detail. The grain size and orientation of Mg-Y-Nd-Zr alloy after USRP treatment changed gradually along the processing depth. The grain refinement mechanism was elucidated as follows: First, the coarse-grained matrix was subdivided by dislocation slip and twins and further refined into sub-structures by multiple techniques, such as mutual intersection and fragmentation between twins, the interaction between twins and dislocations, and the entanglement of dislocations. Finally, equiaxed nanocrystals with high-angle grain boundaries were formed by sub-grain rotation and recrystallization. The strength improvement of the alloy was mainly attributed to the contributions of grain refinement and dislocation strengthening. The synergistic deformation between the gradient structures is the main reason for the excellent strength and plasticity matching of the alloy. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are conducted to study the self-diffusion process along a < 100 > Σ5(210) symmetric tilt grain boundary in a model equiatomic FeNiCrCoCu high-entropy alloy (HEA), for the directions both perpendicular and parallel to the tilt axis. For comparison, the grain boundary diffusion process is also quantified for each of the pure components of the HEA. Most importantly, the results are compared with the diffusion along the same grain boundary using the corresponding "average atom" potential that has similar average bulk properties but no compositional randomness as in the HEA. These comparisons show that the self-diffusion in the HEA grain boundary is slower than in the average atom material as well as the average of pure components, suggesting that a "sluggish" diffusion effect exists for this special grain boundary in the HEA. This effect is significant at low temperatures but diminishes at higher temperatures, indicating that the grain boundary sluggish diffusion is likely temperature dependent. Interestingly, the grain boundary sluggish diffusion behavior is different from the bulk diffusion that was studied previously using the same methods and interatomic potentials, in which no significant sluggish diffusion effect was observed. Our further analysis suggests that the combination of the "trapping effect" by compositional complexity in the HEA and the confined 2-D diffusion paths at this special grain boundary is responsible for the observed grain boundary sluggish diffusion. [ABSTRACT FROM AUTHOR]

The effects of pre-twinning on the microstructure and dynamic compression properties of non-aged and artificially aged Mg–Y–Nd–Gd–Zr alloys were investigated in this study. Previous studies have shown that in the pre-deformed T3 alloy, precompression along the extrusion direction (ED) generates high-density < a > and < c + a > dislocations and deformation twins, such as the 10 1 ¯ 2 < 10 1 ¯ 1 ¯ > extension, the 10 1 ¯ 1 - 10 1 ¯ 2 double, and 10 1 ¯ 1 < 10 1 ¯ 2 ¯ > compression twins at 86°, 38°, and 56°, respectively. In the pre-deformed T8 alloy artificially aged at 200 °C for 12 h, the dislocation density was found to decrease, with β″ (Mg3Y0.85Nd0.15) and β′ (Mg12NdY) precipitates appearing at both ends of the twin boundary. Subsequently, the precipitates extended toward [0001]Mg and [0001]T in the matrix region and the twin, respectively. The orientation relationships (ORs) between the β″ and β′ precipitates and the matrix/twin were determined to be 01 1 ¯ 0 β ″ / / 0001 Mg / T , 2 1 ¯ 1 ¯ 0 β ″ / / 2 1 ¯ 1 ¯ 0 Mg / T and (001)β′//(0001)Mg/T, 2 1 ¯ 1 ¯ 0 β ′ / / 2 1 ¯ 1 ¯ 0 Mg / T , respectively, in contrast to the counterpart ORs between the β″ and β′ precipitates and the matrix/twin in the non-deformed T61 alloy. Evaluation of the dynamic compression properties showed that compared with the compressive yield strength (CYS) of the T61 alloy, that of the T8 alloy considerably increased from 220 to 339 MPa. However, their ultimate compressive strengths (UCSs) of 363 and 360 MPa, respectively, were similar owing to the synergistic effect between the dislocations, the twin boundaries, and the precipitates. These results suggest that the pre-twinning approach should be adopted to improve the strengths of magnesium alloys. [ABSTRACT FROM AUTHOR]

This study presents the results of an investigation into the magnetocaloric effect (MCE) in the Ni47Mn40Sn13 alloy under the influence of alternating magnetic fields. The study examines the dependence of the MCE on temperature (ranging from 80 to 350 K), magnetic field (up to 8 T), and frequency (1–20 Hz). The maximum values of the MCE observed near the phase transformation temperatures have different signs depending on the type of phase transition, with approximately equal values |ΔTad|≈3.2 K in a field of 8 T. The field dependence of the MCE in the vicinity of the magnetic phase transition is described by an expression of the form ΔTad ~ α⋅Tn, where n = 1 at T < TC, n = 2 at T > TC, and n = 2/3 at T = TC, which is consistent with theoretical predictions. The study also finds that the field dependences of the MCE in the region of the martensitic phase transition show the irreversibility of the phase transition in fields up to 8 T due to the wide temperature hysteresis. Additionally, a sharp, more than twofold decrease in the magnitude of the MCE near TC is found with an increase in the cyclic frequency of the magnetic field from 1 to 30 Hz. This behavior is explained by the influence of magnetic and microstructural inhomogeneities, as well as by the lagging of the magnetization behind the magnetic field in alternating magnetic fields (magnetic viscosity). Finally, the specific cooling power for the Ni47Mn40Sn13 alloy is found to increase as the magnetic field frequency increases, with a value of 0.32 W/g at f = 1 Hz and 4.53 W/g at f = 30 Hz. [ABSTRACT FROM AUTHOR]

The enhancing effect of low melting trace additions (Sn, Cd, In) on the precipitation hardening in the Al–Cu based alloys accounts for the great practical importance of this phenomenon. However, to date, the influence of Sn micro-addition, either separately or jointly with other ones, on the precipitation structure and hardening of the wrought 2219-type alloys based on the Al–Cu–Mn system remains unexplored. In this study, the effect of 0.1 wt% (0.02 at.%) Sn trace addition on the structure and mechanical properties of the new Al–4Cu–1.5Mn (wt%) alloy has been studied using computational (thermodynamic calculations) and experimental techniques. Analysis of microhardness has revealed that the peak hardness at aging of the wrought model Sn-containing alloy reaches ~ 120 HV which is about 43% higher than for the Sn-free alloy. Transmission electron microscopy analysis of the peak-aged hot-rolled sheet alloys has revealed that trace addition dramatically changes the precipitation structure leading to the formation of much finer precipitates (with an average length of 55–60 nm) with a higher number density. Uniaxial tensile tests of the wrought and peak-aged samples have revealed that the mechanical properties of the model Al4Cu1.5Mn0.1Sn alloy (UTS ~ 402 MPa, YS ~ 323 MPa and elongation ~ 9.7%) are very close to those of the industrial 2219-type alloy. However, the new alloy contains a much lower concentration of copper and a superior fraction of Al20Cu2Mn3 phase dispersoids the influence of which on the mechanical properties should be further studied in detail. [ABSTRACT FROM AUTHOR]

Exploring the chemical micro- and nanostructure of metal alloys is essential to understand their physical properties, such as magnetism or hardness. Additively manufactured (AM) materials, e.g. via laser powder bed fusion (LPBF) followed by various heat treatments, can raise further questions concerning the printed material. For the in-situ alloyed, spinodal Fe54Cr31Co15 system, the macroscopic magnetic behaviour is greatly influenced by subsequent homogenisation and heat treatment steps. Here we show that the decomposition takes place on the nanometre scale, resulting in ferromagnetic FeCo-rich particles embedded in a Cr-rich matrix. By studying phenomena like chemical homogeneity, grain structure, and texture of the in-situ alloyed material at different scales, we reveal correlations between the heat treatment and the resulting nanostructure and its ferromagnetic properties. We found that the isothermal heating conditions determine the degree of phase segregation and that a homogenization step can be omitted for additively manufactured, in-situ alloyed FeCrCo alloys. The approach thereby offers insight and a path for also tailoring specific manufacturing parameters to provide the right quality printed materials with desired functionalities. For example, magnetic FeCrCo alloys are often used in electric motors or magnetic sensors, and the flexibility of the presented approach can lead to optimal use of the material. [ABSTRACT FROM AUTHOR]

Recently, the HfNbZrTi high-entropy alloy (HEA) has received extensive attention due to its exceptional mechanical properties, which is ascribed to the significant lattice distortion and complex structural evolution induced by inherent chemical short-range order (CSRO). In this study, we employ molecular dynamics (MD) technique to study nanoscale CSRO phenomenon and its influence on the mechanical response of Σ5(210) and Σ5(310) grain boundaries (GBs) in HEA under shear loadings. Results reveal an apparent CSRO manifested by clustering of Hf-Nb and Zr-Ti pairs consistent with experimental observations. Further analyses on some representative Σ5 GB models unveil that the presence of CSRO can induce transformation of GB structure, which not only causes a transition in deformation behavior from migration-dominated to sliding but also raises the yield strengths. Moreover, after probing into the stress–strain curves and the relative sliding energy curves of massive GB models, we discover that the transition in GB behavior is ascribed to the CSRO impeded dislocation motion. The findings of this work promote atomistic understanding on the CSRO modulated shear response of GBs in HfNbZrTi HEA. [ABSTRACT FROM AUTHOR]

Various electrochemical techniques were used to study the corrosion behaviour of the CNT-reinforced NiAl alloys under NaCl and Na2SO4 environments. The potentiodynamic polarization curves revealed activation Tafel behaviour when the NiAl alloy specimens were immersed in NaCl solution while passivation followed by slight development of transpassivation resulted under Na2SO4 environment. The reinforcement of pure NiAl alloy with up to 1.0 wt.% CNT increased the corrosion rate from 0.10 to 0.63 mm/yr under NaCl environment, while under Na2SO4 environment, the corrosion rate increased from 0.04 to 0.12 mm/yr. The observed increase in corrosion rate with an increase in CNT reinforcement (under both NaCl and Na2SO4 environments) suggested that the reinforcement of NiAl alloys with CNT reduced the corrosion resistance of NiAl. The X-ray diffraction analysis revealed that the corrosion products consisted of oxides including Al2O3 under NaCl environment, while scanning electron microscope analysis showed a porous passive layer on the surface of the alloy specimens immersed in Na2SO4 solution. [ABSTRACT FROM AUTHOR]

The half-metallic and pressure-induced elastic properties of PdVSi, PdVGe, PdVSn, and PdVSb were investigated. First, FM phases were obtained energetically as the most stable. The semiconducting characters seemed in spin-down states. The band gaps were calculated as 0.807 eV, 0.676 eV, 0.481 eV and 0.370 for PdVSi, PdVGe, PdVSn, and PdVSb, respectively. Since the spin polarization value of PdVSb alloy is less than 100% in GGA method, it is nearly half-metallic ferromagnetic, while other alloys are true half-metallic ferromagnetic. However, in HSE method, the forbidden and half-metallic band gaps were also calculated for PdVSb alloy as 0.375 eV and 0.134 eV, respectively. HSE method has a direct effect on the band gap values. PdVSi, PdVGe, and PdVSn, alloys have 1.00 μB/f.u. total magnetic moments, while PdVSb alloy has 2.00 μB/f.u. total magnetic moment. According to elastic results, all alloys are elastically stable and ductile materials. Debye temperatures were obtained as 371.53 K, 317.71 K, 311.78 K, and 263.13 K at 0 GPa pressure. PdVSi, PdVGe, PdVSn, and PdVSb alloys have been obtained as very remarkable materials with their structural, electronic, magnetic and pressure-induced elastic properties. [ABSTRACT FROM AUTHOR]