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We performed high-frequency (0.4–1.7 MHz) measurements of the internal friction (IF) on 14 bulk metallic glasses (MGs). It is found that 12 of these MGs display relaxation IF peaks at temperatures ≈ 400–500 K, which are weakly affected by heat treatment within the amorphous state. The corresponding relaxation time is about 0.3 μ s. This fast relaxation is reported for the first time in the literature. The apparent activation enthalpy for 4 MGs is determined. It is shown that if measured at a low frequency of 1 Hz, these IF peaks would appear near room temperature or by 30–50 K below it. Thus, the IF peaks found in the present investigation are direct analogues of low-temperature/low-frequency β ′ - and/or γ -relaxations described in the literature. It is argued that the origin of these IF peaks is related to the relaxation of structural defects similar to dumbbell interstitials, which are frozen in solid glass from the liquid state upon melt quenching. These defects can be considered as elastic dipoles and their re-orientation in the applied stress provides anelastic deformation and corresponding IF peak. After correction for temperature dependence of the shear modulus, the true activation enthalpy (0.62–1.08 eV) and activation entropy (4 ≤Δ S ∕ k B ≤15) for defect re-orientation are determined. • High-frequency (0.4–1.7 MHz) internal friction (IF) measurements are performed. • IF peak located at 400–500 K is found in 12 metallic glasses. • The relaxation time corresponding to this peak is about 0.3 μ s. • Corresponding activation enthalpy and activation entropy are determined. • The origin of the IF peak is supposed to be due to defect re-orientation. [ABSTRACT FROM AUTHOR]

Refractory high entropy alloys (RHEAs) are promising candidates for high-temperature structural materials due to their excellent high-temperature performance. However, the room-temperature brittleness of most alloys results in poor plastic formability, thereby limiting their engineering applications. In this study, Nb 25 Ti 35 V 5 Zr 35 alloy with cold-rollability was developed, and its phase stability, tensile mechanical properties, elastic properties, strengthening mechanism, and deformation mechanism were investigated by combining experiments, CALPHAD, DFT and molecular statics (MS) methods. The results demonstrate that Nb 25 Ti 35 V 5 Zr 35 alloy possesses good phase stability, with both the as-cast and annealed states maintaining a single-phase BCC structure without undergoing phase transformation. The tensile yield strength of the alloy reaches its peak at 1152 MPa in the cold-rolled condition, while its annealed state exhibits an optimal balance of strength and plasticity, with a yield strength of 836 MPa and an elongation of 22.45 %, respectively. Solid solution strengthening is the primary source of its high strength, with V and Zr playing key roles in this strengthening mechanism. Dislocation slip plays a dominant role in plastic deformation. Additionally, compared to traditional BCC alloys, the significance of edge dislocations in the deformation process is notably enhanced, with the { 112 } plane serving as the preferred slip plane for dislocations. DFT results indicate that the alloy exhibits significant anisotropy in both Young's modulus and shear modulus. This work contributes to understanding the material properties of the Nb 25 Ti 35 V 5 Zr 35 alloy and provides a reference for the design of new ductile RHEAs. • Nb 25 Ti 35 V 5 Zr 35 RHEA with excellent strength and ductility was designed. • The cold-rolled alloy shows a high tensile yield strength of 1152 MPa. • Solid solution strengthening is the primary origin of the strength. • Dislocation slips on {112} plane is the main deformation mechanism. [ABSTRACT FROM AUTHOR]

Stacking fault energy (SFE) is a crucial property influencing the deformation mechanisms of multi-principal element alloys (MPEAs). However, experimentally measuring SFE and exploring composition space of MPEAs is challenging. This study explores the SFE in NbMoTaW by integrating machine learning force fields (ML-FF), molecular dynamics simulations (MD), neural networks, and symbolic regression (SR) methods. A SFE dataset containing 2000 different NbMoTaW compositions were generated by combining ML-FF and MD. Then the neural-network model was developed for SFE prediction with an accuracy of 0.981 and a mean absolute error of 0.020. Using SR, the valence electron concentration (VEC), average shear modulus (G), radii gamma (γ) were identified as the key descriptors to determine SFE with the relationship of SFE=0.307·VEC+0.352·(G+γ). This work demonstrated a significant impact of chemical composition on SFE and established an accurate mathematical expression for SFE prediction, enhancing the understanding and alloy design of MPEAs. • Exploring the stacking fault energy (SFE) in NbMoTaW by machine learning. • High accuracy machine learning model for SFE prediction with an accuracy of 0.981. • Determining SFE by valence electron concentration (VEC), average shear modulus (G), and radii gamma (γ) descriptors. • Mathematical expression of SFE = 0. 307 ·VEC + 0. 352 · G + γ between descriptors and SFE. [ABSTRACT FROM AUTHOR]

The cell structures and mechanical properties (i.e., hardness, Young's modulus, shear modulus, and Poisson's ratio) of (Hf 0.2 Zr 0.2 Ti 0.2 Nb 0.2 Ta 0.2)C (HEC) and (Hf 0.2 Zr 0.2 Ti 0.2 Nb 0.2 Ta 0.2)N (HEN) high-entropy ceramics were simulated by special quasi-random structure (SQS) and general random structure (GRS) with atomic occupation preference based on the first-principles density functional theory. The results show that compared to SQS, the cell structure constructed by GRS is more realistic, which is verified via scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive spectroscopy. The mechanical properties simulated by GRS were also determined by microhardness and dynamic elastic modulus testers. The hardness, Young's modulus，shear modulus and Poisson's ratio predicted by GRS are 23.07 GPa, 449.71 GPa, 183.28 and 0.227 for HEC and 22.96 GPa, 413.71 GPa, 162.47 and 0.241 for HEN, which are in a reasonable agreement with the measured results (i.e., 22.05 ± 0.32 GPa, 433 ± 12 GPa, 172 ± 18 GPa, 0.21 for HEC and 22.12 ± 0.13 GPa, 372 ± 23 GPa, 158 ± 11 GPa, 0.23 for HEN). This work can provide a promising reference for preparing high-entropy non-oxide ceramics via the prediction. • Atomic occupancy-based structure is used to analyze atomic preference occupancy within high-entropy non-oxide ceramics. • Crystal structure of high-entropy non-oxide ceramics is predicted besides experimental validation. • Simulated and measured mechanical properties of high-entropy carbide and nitride bulk ceramics are analyzed. [ABSTRACT FROM AUTHOR]

The emergence of lithium-ion solid electrolytes greatly increases the safety risk of liquid electrolytes. Among the many solid electrolytes, aluminum-doped Li 1.3 Al 0.3 Ti 1.7 (PO 4) 3 (LATP) has become a research hotspot due to its high ionic conductivity and good air stability. However, the traditional high-temperature sintering process has the problems of lithium volatilization and secondary phase formation. Therefore, it is very difficult to prepare high-quality LATP solid electrolytes. The X-ray diffraction pattern and analysis showed that the LATP samples prepared in this paper showed rhombohedral structure and could be indexed by the R 3 c space group, and a new method of excess lithium compensation sintering was proposed, in which lithium compensation (LiNO 3) could well reduce the impact of lithium volatilization. It can be used as a sintering additive to promote the sintering densification of LATP. In this paper, the optimal sample for sintering at 900°C was determined by measuring the microstructure and electrochemical properties of the electrolyte, and lithium doping was studied. The LATP solid electrolyte with 10 wt% lithium doped has a conductivity of 7.2× 10−4 S/cm and a low activation energy (0.278 eV). Its mechanical properties (elastic modulus and hardness) are the best, which are 103.024 GPa and 8.053 GPa, respectively, and the value of its elastic modulus is much greater than that of lithium metal shear modulus of 4.25 GPa, which can effectively inhibit the growth of lithium dendrites. And the magnitude of the grain boundary conductivity and particle size of the lithium-doped sample correspond to the dielectric constant results. • The appropriate sintering temperature is a key factor in obtaining high-performance LATP solid electrolytes. • The ionic conductivity of the prepared LATP solid electrolyte is as high as 7.2×10−4S/cm. • The elastic modulus and hardness of LATP reach the maximum of 103.024 GPa and 8.053Gpa. [ABSTRACT FROM AUTHOR]

In order to improve the room-temperature strength and hardness of Ta-W alloys, Zr was chosen for alloying and strengthened Ta-W-Zr alloys were developed. The strengthening effect of Zr alloying was investigated based on first-principles calculation and experimental verification. Calculations revealed that the doped of Zr atoms increased the shear modulus G and Young's modulus E of the alloys and promoted the formation of metallic and ionic bonds, which improved the hardness of the alloys. To verify the calculated results, hardness and compression tests were carried out for Ta-W-Zr alloys. The results showed that the compressive strength and hardness of the alloys increased with increasing Zr content, which was consistent with the trend predicted by the calculations. Among them, the maximum compressive strength of Ta-11.3 W-11.2Zr alloy was as high as 1850.53 ± 6.8 MPa and the maximum hardness was up to 478.40 ± 8.3 HV, which was almost twice that of the Ta-10 W alloy. It was indicated that Zr alloying can effectively strengthen Ta-W alloys, which provided a guidance for the development of high-performance Ta-W alloys. • Ta-W-Zr alloys were designed and alloying Zr elements obviously strengthened Ta-W alloys. • The addition of Zr promoted the formation of metallic and ionic bonds in Ta-W alloys. • Compressive strength and hardness of Ta-W-Zr alloys increased with increasing Zr content. • The calculated results were consistent with the trend presented by the experimental results. [ABSTRACT FROM AUTHOR]

The rapid surge in sales of electronic devices and electric vehicles has created an ever-increasing demand for batteries that excel in terms of both safety and energy density. Solid-state batteries (SSBs), as compared to conventional liquid electrolyte-based lithium-ion batteries, have emerged as pioneers at the forefront of the transformation of lithium-ion battery technology, distinguished by their exceptional safety features and elevated energy density. Among the numerous candidate materials in the realm of solid-state electrolytes (SSEs), the garnet-type Li 7 La 3 Zr 2 O 12 (LLZO) stands out due to its exceptional ionic conductivity, shear modulus, and chemical stability. However, inadequate contact between LLZO and the cathode, anode, and even within LLZO itself have been a substantial impediment to the practical application of solid-state batteries. In this review, we delve deeply into the diverse types of interfaces and the associated challenges they present, providing a meticulous analysis of improvement strategies tailored to each specific issue. Finally, we offer an extensive discussion on the challenges and prospective future developments of LLZO in the realm of SSBs, with the aim of contributing to the sustainable advancement of energy storage technologies. [ABSTRACT FROM AUTHOR]

Effects of W solution (3 at.%) on the structure, elastic properties, and structural phase transition of Co under pressure were investigated in this paper by first principles calculations. The lattice constants of pure Co and Co–W alloy, both with fcc and hcp structure, gradually decrease with the increasing pressure. In general, the bulk modulus(B), shear modulus(G) and Young's modulus(E) of pure Co and Co–W alloy increase approximately linearly with the increasing pressure. W solution brings almost negligible impact on B of fcc and hcp Co, however, effect of W solution on G and E can not be neglected. It is worth to mention that B , G , and E for fcc Co and Co–W alloy are always higher than those for hcp Co and Co–W alloy at the same pressure. According to the calculated results, W solution can improve the ductility and thermodynamic stability of Co, and increase the hcp to fcc phase transition pressure from 102 GPa to 130 GPa. • Effects of W solution on properties of Co phase under pressure was investigated. • Effect of W solution on lattice constants of Co under pressure is very limited. • W solution brings almost negligible impact on bulk modulus of fcc and hcp Co. • Ductility and thermodynamic stability of Co can be improved by W solid solution. • Transition pressure from hcp to fcc is 102 GPa for Co and 130 GPa for Co–W alloy. [ABSTRACT FROM AUTHOR]

The equiatomic HfNbTaTiZr solid solution is currently regarded as a model disordered body-centered cubic high-entropy alloy. Therefore, the temperature dependence of its elastic moduli is of prime importance to improve our understanding of the mechanical properties of this refractory alloy. In this study, the alloy was found to be single phase, fully recrystallized with a slight texture along the normal direction after thermomechanical processing at room temperature. Elastic moduli were determined over the temperature range [293 K-1100 K]. Image 1 • The elastic moduli of HfNbTaTiZr have been studied between 293 K and 1100 K. • Evolutions of the elastic moduli have been quantitatively determined. • The shear modulus is undergoing a weak decrease in the studied temperature range. • A damping relaxation peak is observed between 700 K and 950 K. • This damping relaxation peak is likely associated to the presence of interstitials. [ABSTRACT FROM AUTHOR]

Although Nb Ir compounds are promising high-temperature structural materials due to the high melting-point, moderate density and excellent thermal stability, the structural stability and mechanical properties of Nb Ir compounds are unclear. Here, we investigate the influence of Ir concentration on the structure, elastic modulus, elastic anisotropy and brittle-or-ductile behavior of Nb Ir based compounds by using the first-principles calculations. Six Nb Ir compounds are considered. The results show that the structural stability of Nb Ir compounds strongly depends on the Ir concentration. In particular, NbIr 3 is more thermodynamically stable than the other Nb Ir compounds. The calculated elastic modulus of Nb Ir compounds (except for Nb 5 Ir 3) increases with increasing Ir concentration. The calculated bulk modulus, shear modulus and Young's modulus of NbIr 3 are much larger than that of other Nb Ir compounds. It is found that the high elastic modulus of NbIr 3 is attributed to the strong and symmetrical Nb Ir and Ir Ir metallic bonds. Compared to other Nb Ir compounds, Nb 3 Ir and NbIr 3 have the smallest percentage anisotropy in compressibility. However, Nb 3 Ir 2 has the highest percentage anisotropy in shear. Finally, our work indicates that NbIr 3 is a promising high-temperature structural material, which is potential used in advanced aerospace and automotive applications. Image 1 • The influence of Ir on the structure and mechanical properties of Nb Ir compounds is studied. • NbIr 3 is more thermodynamically stable than that of the other Nb Ir compounds. • The elastic modulus of Nb Ir compounds depends on the Ir concentration. • The elastic modulus of NbIr 3 is much stronger than that of the other Nb Ir compounds. • Nb 3 Ir and NbIr 3 have the smallest percentage anisotropy in compressibility. [ABSTRACT FROM AUTHOR]

Abstract Amorphous-crystalline nanolaminates (ACNLs) composed of CuZr metallic glass layers and single crystal copper layers were constructed, and the anisotropy of the material deformation behaviors were investigated by conducting shear loadings on the ACNL sample in parallel deforming and serial deforming directions using molecular dynamics method. In parallel deforming mode, the yielding of the material was mainly triggered by generation of dislocations and slips in crystalline layer, and both crystalline and amorphous phases participated in the subsequent plastic deforming. In serial deforming mode, the results showed that the yielding and plastic deforming of the material was induced by shear localization of amorphous layers only. Amorphous-crystalline interfaces (ACIs) served as stress resistance weakness and dislocations breeding cradle in the former deforming mode while a strong connection of two phases in the later deforming mode. Furthermore, the increasing of crystalline layer thickness would promote the material shear modulus and shear strength in both deformation modes. The promotions and incentives varied and had dependence on the coupled deforming mechanisms. For the serial deforming mode, the shear moduli obtained from our simulations fitted the predicted ones from rule-of-mixture very well, while in the parallel deforming mode, the simulated shear moduli were much higher than predicted ones, which could be explained with the size effect induced by reduction of crystalline layer thickness surround with ACIs. Highlights • The anisotropies of ACNL were reflected in yielding and plasticity behaviors. • ACI served as structural weakness and dislocations breeding cradle in P-direction. • ACI served as strong connection of two phases in S-direction. • The increase of t c/ d would improve the ACNL shear moduli in both directions. • C-layer thickness has size effect on the ACNL shear modulus in P-direction. [ABSTRACT FROM AUTHOR]

In the present paper, a Ti-39Nb (wt.%) was employed to illustrate the feasibility of designing β-type titanium alloys with low Young's modulus through concurrently reducing shear moduli C 44 and C'. The solution treated and quenched alloy exhibits a dual (β+α") phase due to the insufficient Nb content, implying the intrinsically low β-phase stability. After severe cold rolling and annealing treatment at 523 K for 30 min, the martensitic transformation was suppressed by high density of defects. As a result, a nearly single β-phase alloy with a low Young's modulus of 39 GPa and a high ultimate tensile strength of 745 MPa was successfully fabricated. The single-crystal elastic constants of the cold rolled plus annealed Ti-39Nb alloy were extracted from its polycrystalline specimen by using an in-situ synchrotron X-ray technique. It is indicated that the alloy has an anomalously low C 44 of 21.4 GPa as well as a low C′ of 17 GPa, both of which contribute to the low Young's modulus. This suggests that it is a feasible approach to concurrently reduce C 44 and C′ through composition design and microstructure optimization. Our findings provide a new strategy of designing β-type titanium alloys with ultralow Young's modulus. [ABSTRACT FROM AUTHOR]

We performed high precision shear modulus and calorimetry measurements on a model Pd-based glass subjected to different annealing treatments below the glass transition temperature T g . Applying the Interstitialcy theory, we found that structural relaxation-induced heat release/absorption below and near T g can be precisely described using shear modulus data confirming thus the generic relationship between the heat and elastic relaxation effects in metallic glasses. The same approach is used for the reconstruction of underlying activation energy spectra. It is found that the spectra derived from calorimetry and shear modulus data are very close. Integration of these spectra gives the change of the concentration of frozen-in defects and its absolute value for different stages of structural relaxation. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate in-depth the effect of Co 2+ ions doping on ZnFe 2 O 4 nanoparticles in term of morphology, magnetic and optical properties. Zn 1-x Co x Fe 2 O 4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) powders were prepared by co-precipitation method. X-ray diffraction (XRD) and Energy Dispersive Spectroscopy (EDS) confirmed the incorporation of Co 2+ ions within ZnFe 2 O 4 host lattice, and an increase of the crystallite size from 37 to 51 nm in agreement with TEM analysis. FTIR revealed a slight change in two main bands υ 1 and υ 2 in the frequency range of 400–4000 cm −1 , which caused by stretching vibrations at the A- and B-sites respectively. The elastic moduli such as stiffness constant, Young's modulus, rigidity modulus, bulk modulus, Poisson's ratio, wave velocity and Debye temperature have been calculated using FTIR data. VSM showed transformation of magnetic behavior from paramagnetic to ferromagnetic as a result of Co 2+ ions doping. With higher Co 2+ (x = 0.2 to x = 0.5) content, the saturation magnetization (Ms) increased rapidly from 5.7 emu/g to 82 emu/g respectively. The remanance magnetization (Mr) and coercivity (Hc) were influenced by Co 2+ content too and this was mainly related to the change in crystallite size. The optical band gap ( Eg ) of Co-Zn ferrite samples was determined by means of diffuse reflectance spectra. The optical band gap value estimated from Tauc plots was found to decrease from 1.89 to 1.31 eV with increasing Co 2+ content. [ABSTRACT FROM AUTHOR]

Applying the evolutionary algorithm for crystal structure prediction and first-principles calculations, a newly orthorhombic Cmcm structure of HfB 4 is predicted theoretically. The result shows that this new phase is much more superior to the early proposed YB 4 -, ReP 4 -, FeB 4 -, CrB 4 -, and MnB 4 -type structures. The calculations of the phonon dispersion curve and elastic constants verify that the predicted Cmcm phase is dynamically and mechanically stable. Moreover, the predicted large shear modulus (240 GPa) and high hardness (45.7 GPa) imply that the Cmcm -HfB 4 phase is a potential superhard material. At the same time, the dependences of the Young's modulus, bulk modulus, and shear modulus for HfB 4 on the crystal orientation are also systematically studied. Further analyses of the electronic structure and chemical bonding properties indicate that the strong B B and B Hf covalent bonds make great contributions to its high hardness and stability. [ABSTRACT FROM AUTHOR]

The first-principle calculations of density functional theory have been used to study the structural, elastic, electronic and magnetic properties of Mn 2 RhGe full-Heusler alloy. The present study reveals that the Mn 2 RhGe is stable in X a -type structure and exhibits a half-metallic ferrimagnetic feature at equilibrium lattice constant. In the Mn 2 RhGe, the ferrimagnetic behavior results from antiparallel coupling between Mn (1) and Mn (2) spin moments. The total magnetic moment of Mn 2 RhGe is 3μ B , which obeys to the Slater-Pauling rule. The Mn 2 RhGe keeps the half-metallic character for the lattice parameters ( a ) in the range of 5.73–5.95 Å, but at a = 6.05 Å this behavior destroyed and the compound becomes metallic in nature. Therefore, the Mn 2 RhGe is predicted to be better candidate to explore ferrimagnetic property for possible spintronics applications. [ABSTRACT FROM AUTHOR]

On the basis of the Interstitialcy theory, a method to calculate the fourth-rank shear modulus is suggested and verified. The estimates of this modulus for a number of metallic glasses are given. [ABSTRACT FROM AUTHOR]

In this paper, silver tellurovanadate 40TeO 2 -(60-x)V 2 O 5 -xAg 2 O, 0 ≤ x ≤ 50 mol%, glasses (abbreviated as TVAgx) are prepared by melt-quenching to study the correlation between structural and acoustical properties of TVAgx resulting from the substitution of V 2 O 5 by Ag 2 O. Elastic aspects of these glasses are investigated by measuring the longitudinal (U L ) and shear (U S ) wave velocities using the pulse-echo overlap technique at a frequency of 5 MHz at room temperature. Ultrasonic velocities showed non-linear trends: increasing behavior for 0 ≤ x ≤ 20 mol% and decreasing trend for 20 < x ≤ 50 mol%. The structural elucidation was achieved by studying the ultrasonic wave velocities and material density at room temperature. Longitudinal modulus L, shear modulus G, Young's modulus E, bulk modulus K, Poisson's ratio σ as well as other physical properties such as Debye temperature ϴ D have been determined and discussed up on the number of bonds per unit volume n b , oxygen ion packing density OPD and mean atomic volume V ¯ . All mentioned quantities are obtained as functions of Ag 2 O content, in which they show a behavior change at x = 20 mol% in excellent coincidence with the previously reported results of thermal stability (ΔT), optical band gap (E g ), and oxygen molar volume ( V O * ). The findings indicate the important role of non-bridging oxygens NBOs. The room temperature ultrasonic wave velocities, glass transition temperature and other mentioned quantities show a critical content of silver oxide as x = 20 mol%, indicating that the addition of a silver oxide modifier changes the compactness, rigidity and content of non-bridging oxygens (NBOs). Compositional dependence of all elastic and other mentioned properties, imply to two composition regions as: relatively strength structure for 0 ≤ x ≤ 20 and loose packing structure for 20 < x ≤ 50, which is attributed to the increase of NBOs in the second region. It is also inferred that the glass with x = 20 is more stable, in agreement with the data of calorimetric analysis. Moreover, the glass transition temperature T g , crystallization temperature T cr and thermal stability show a behavior change at x = 20, indicating that this glass as possess the highest thermal stability. Therefore, glass with x = 20 mol% of Ag 2 O has the a more rigid structure, the highest thermal stability, the highest elastic moduli, a narrower band gap, the highest OPD, and a lower V O * , which makes it an excellent and promising sample in optothermal and acousto-optic applications. Vickers microhardness of the samples vary with composition, indicating the highest value for the case of x = 20. The hardness testing results comply with those of acoustical, optical, thermal and structural tests. Also, the scanning electron microscopy (SEM) confirms the amorphous structure of the studied glasses and gives more light on their morphological aspects and their microhardness. [ABSTRACT FROM AUTHOR]

We have systematically investigated the structural and elastic properties of the zincblende-derived and wurtzite-derived structures of Cu 2 ZnSnS 4 (CZTS) under various pressures utilizing first principles calculations within density functional theory (DFT). The results revealed that the enthalpy-pressure curves of kesterite (KS) and stannite (ST) intersect at approximately 32 GPa, while the curves of wurtzite kesterite (WKS) and wurtzite stannite (WST) phases intersect at approximately 52 GPa, which suggests that the phase transitions or mixed crystals occur in the WKS and WST structures. Furthermore, in the KS and ST structures, shear modulus (G) and Young's modulus (E) decrease with an increase in pressure, which indicates that stiffness reduces with increasing pressure. However, in the WKS and WST phases, G and E first decrease and then increase with an increase in pressure. Moreover, owing to Pugh's ductility index (G H /B H ) being less than 0.57, all four CZTS structures are ductile in nature under different pressures. In the KS and ST phases, Poisson's ratios (γ) increase gradually, when the pressure increases. Whereas, in the WKS and WST structures, the Poisson's ratios (γ) are greater than the Poisson's ratios (γ) under the zero pressure, which indicates better plasticity. Furthermore, it is demonstrated that under gradual pressure increases, the elastic constants are unable to satisfy the mechanical stability in all four structures. [ABSTRACT FROM AUTHOR]

Compositionally graded samples of Ti- x Nb-7Zr- y O alloys (11 ≤ x ≤ 35, 0.49 ≤ y ≤1.01 wt%) were prepared from elemental powders and TiO 2 and compacted by the field-assisted sintering technique. By this approach, four layered samples covering together twenty four different chemical compositions were prepared. It allowed efficient sampling of alloys for potential biomedical use. Elastic constants of each layer (the shear modulus G and the Young's modulus E) were determined using resonant ultrasound spectroscopy. The results show that in the considered compositional space, elastic constants exhibit a dependence on the volume fraction of β- stabilizing niobium and interstitial oxygen. Minimum elastic modulus was achieved for the compositions close to the stability limit between parent β matrix and martensitic α″ phase, while maximum elastic constants were caused by the presence of isothermal ω particles. • Compositionally graded samples of Ti-Nb-Zr-O alloys were fabricated by powder metallurgy. • 4 sintered pellets covered 24 different chemical compositions, with α' , α″ , β and ω phases. • Elastic constants for each composition were determined by ultrasonic measurements. • The elastic constants exhibited systematic evolutions with the phase composition. • The ω phase strongly affected the elastic constants close to the stability limits of β and α″. [ABSTRACT FROM AUTHOR]

Recently, high-entropy carbonitrides (HECNs) have attracted extensive attentions due to their outstanding comprehensive properties. However, the underlying physical mechanisms responsible for their excellent properties are not well understood. In this work, the effects of nitrogen (N) on the material properties of the newly-developed (ZrHfNbTa)C 1- x N x (x = 0.0–0.5) HECNs are systematically studied by the first-principles calculations. The obtained results reveal that the calculated properties of the HECNs match well with experimental data. The mechanical properties of the HECNs are closely associated with their local lattice distortion. The lattice distortion is exacerbated with the increase of N. Increasing N content also leads to increase their mass density and ductility, but decrease their lattice parameter, Young's modulus, shear modulus, hardness, fracture toughness, acoustic velocity, Debye temperature, and thermal conductivity. The additive of N can promote the charge transfer between metal and non-metal elements, but decrease the strength of metal-carbon and metal-nitrogen bonds. • The effects of nitrogen on high-entropy carbonitrides (HECNs) are initially clarified. • Lattice distortion of HECNs is identified and evaluated by a new index. • Nitrogen plays a pivotal role in improving the comprehensive properties of HECNs. • The charge transfer and bonding mechanisms of HECNs are elucidated completely. [ABSTRACT FROM AUTHOR]

To pursue superior yield strength and maintain high ductility of CrCoNi medium entropy alloy (MEA) at room temperature, 1.0 at% W and 2.0 at% Mo were added to the CrCoNi alloy to ensure a single-phase solid solution strengthening in face-centered cubic structure. The effects of W and Mo additions on microstructure evolution and strengthening mechanism was investigated in detail. The results indicated that discontinuous dynamic recrystallization is the main recrystallization mechanism during annealing. The co-additions of W and Mo with a higher melting point can strengthen the interatomic bonding force and increase the activation energy of grain growth to 409.62 KJ/mol, which leads to sluggish diffusion and retards the recrystallization progress. The high activation energy for grain growth would restrain the grain growth and obtain significantly finer grains of (CrCoNi) 97 W 1 Mo 2 alloy than that of CrCoNi alloy under similar thermomechanical processing. Smaller grains can impose a stronger grain boundary strengthening and dominate the yield strength enhancement. The strength improvement resulting from grain boundary is 252 MPa for this alloy with the grain size of 1.20 µm. Besides, the co-additions of W and Mo increase the lattice parameter to 0.3610 nm owing to their larger atomic radius and higher shear modulus, then intrinsic lattice friction calculated by the Hall-Petch equation is significantly increased to 289 MPa, which indicated a stronger solid solution strengthening effect (~47 MPa) by severe lattice misfits. Above all, the comprehensive effect of the above aspects of W and Mo additions has developed superior yield strength of 698 MPa and ultimate tensile strength of 1141 MPa. The yield strength of this new alloy enhances by nearly 300 MPa and maintains a high ductility compared with CrCoNi alloy followed under similar thermomechanical processing. [Display omitted] • A novel designed (CrCoNi) 97 W 1 Mo 2 alloy exhibits superior strength of 698 MPa and elongation of 52% respectively. • The effects of W and Mo additions on the microstructure evolution and strengthening mechanism were summarized in detail. • The contribution of grain boundary strengthening and solid solution strengthening to yield strength were systematically analyzed. [ABSTRACT FROM AUTHOR]

Within the framework of the Interstitialcy theory it is shown that the amount of heat released during structural relaxation of metallic glasses must be proportional to the room-temperature change of the shear modulus. This prediction is verified by using experimental data taken on seven bulk metallic glasses. It is found that the kinetics of exothermal heat flow upon structural relaxation is determined by shear modulus relaxation. The released heat per one kinetic relaxation unit (“defect”) for all glasses practically coincides with the “defect” formation enthalpy calculated using the Interstitialcy theory providing further support for the description of structural relaxation on the basis of this approach. [ABSTRACT FROM AUTHOR]

High entropy alloy NiFeCrCo was systematically studied in the range of near-equal atomic concentrations, i.e., 10–40 at.%, by first-principles tools and high throughput calculations. Enthalpy of mixing, lattice parameter ( a 0 ), bulk modulus ( B ), and shear modulus ( G ) were calculated by the exact muffin-tin orbital method combined with coherent potential approximation (EMTO-CPA) for over 2700 compositions of the NiFeCrCo alloy as a single-phase solid solution in paramagnetic state. It was found that certain elements have the most significant influence on each property, namely, Cr on enthalpy of mixing, Co on a 0 , Fe on B , Co on G , and Cr on the ratio of B / G . An equation to predict the enthalpy of mixing by use of binary enthalpy data was evaluated and was found to have a good accuracy with a root-mean-square deviation (RMSD) of 42 meV per formula unit in the prediction. A similar equation to predict bulk modulus with weighted contribution from first–shell interaction is proposed and tested on all alloys. This equation was also found to be accurate with a RMSD of 6 GPa. Finally, it was found that shear moduli of all tested alloys are largely dependent on C 44 , while the concentration of Co has a noticeable control on C 44 . Spin polarized calculations were performed for a select group of alloys with both EMTO-CPA and the Vienna ab-initio Simulation Package (VASP) with special quasi-random structure models for comparison. Good agreement was found between these methods. [ABSTRACT FROM AUTHOR]

The influence of various transition alloying elements (X's) on the elastic properties of W-based alloys has been studied via first-principles calculations on the basis of density functional theory. Here, nineteen transition metal alloying elements (X) are considered: Ti, V, Cr, Fe, Co, Ni, Y, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, Re, Os, Ir, and Pt. It is found that (i) the bulk modulus of the dilute W-X alloy decreases with increasing its equilibrium volume, particularly, for the alloying elements in the same period; (ii) all of the alloying elements decrease the shear modulus of BCC W; and (iii) the largest decrease of elastic properties of W is due to alloying element Y. In addition, it is shown that the changes of elastic properties of W caused by the alloying elements are traceable from the electron charge density distribution, resulting in a bonding distortion between W and the alloying atoms. Using the quasi-static approach based on the Debye model, the elastic properties of these W-X alloys at finite temperatures are predicted. Calculated properties of BCC W and the W-X alloys are in favorable agreement with available experimental measurements. [ABSTRACT FROM AUTHOR]

The lattice parameters, electronic structures, elastic constants, Vicker's hardness and thermodynamics properties of SrAuSi 3 were systematically investigated by using first-principles and the quasi-harmonic Debye model. The calculated lattice parameters are in excellent agreement with the experimental data. The calculated elastic constants C ij reveal that SrAuSi 3 is mechanically stable but anisotropic. The elastic anisotropy is further illustrated by the three-dimensional (3D) of bulk modulus and Young's modulus. The polycrystalline elastic modulus: shear modulus, Young's modulus, Poisson's ratio are derived from the obtained single-crystal elastic constants. In addition, the temperature dependence of the expansion coefficient, specific heat and Debye temperature are investigated through the quasiharmonic Debye model. Finally, Using the McMillan formula the T c ∼ 9.94 K, which is conflicts with the experimental data (1.54 K). Presumably, the T c suppression phenomenon due to the presence of an antisymmetric spin–orbit coupling (ASOC) as a consequence of the lack of inversion symmetry. [ABSTRACT FROM AUTHOR]

First-principles calculations were performed to study the structural, elastic, electronic properties and Debye temperature of D0 22 -Ni 3 V under pressure. The obtained structural parameters are in accord with previous data. The calculated elastic constants manifest that Ni 3 V binary compound is mechanically stable. Using the Voigt–Reuss–Hill method, elastic properties such as bulk modulus B , shear modulus G , Young's modulus E and Poisson's ratio υ are calculated. And results indicate that pressure can improve the hardness of Ni 3 V compound. Moreover, the density of states as a function of pressure is analyzed, and Population analysis explain the improvement of hardness by pressure from the view of chemical bonds. The Debye temperature Θ D calculated from elastic constants goes up with the increasing pressure. [ABSTRACT FROM AUTHOR]

The effect of tin on the microstructure and creep behavior of as cast magnesium MRI153 alloy was investigated in the present study. Creep behavior of the alloys were studied using impression creep test under shear modulus normalized stress ranging from 0.025 to 0.04 at temperatures of 152–217 °C. Results showed that adding tin to MRI153 alloy reduces the amount of Al 2 Ca via forming CaMgSn phase, whereas the continuity and value of Mg 17 Al 12 phase are increased. Solubility of calcium in Mg 17 Al 12 phase is also reduced in the presence of tin. It was shown that adding tin to MRI153 alloy decreases the alloy creep strength, which can be attributed to the reduced value of Al 2 Ca phase and formation of CaMgSn phase instead as well as reduced thermal stability of Mg 17 Al 12 phase and its increased value and continuity. By calculating creep activation energy and stress exponent, it was shown that although climb-controlled dislocation creep is the dominant mechanism in the creep of these alloys, the creep activation energy is decreased with increasing the amount of tin. [ABSTRACT FROM AUTHOR]

First-principles method is performed to systematically investigates structural, phase stability and mechanical properties for the Laves phases MCo 2 (M = Sc, Ti, Y, Zr, Nb, Hf, Ta) with C15-type structure. The calculated equilibrium structures and formation enthalpies are very close to the available experimental and HfCo 2 has the highest phase stability. The elastic properties, including elastic constants, Poisson’s ratio and anisotropy index are also calculated. Shear modulus and hardness of MCo 2 have the same variation tendency; the degree of the elastic anisotropy for MCo 2 is in the order: ScCo 2 < TiCo 2 < YCo 2 < NbCo 2 < TaCo 2 < ZrCo 2 < HfCo 2 . Finally, Debye temperatures and sound velocities are also investigated. [ABSTRACT FROM AUTHOR]

First-principles calculations were performed to investigate the phase stability, magnetism, elastic properties and hardness of four main binary iron nitrides: FeN, ζ-Fe 2 N, ε-Fe 3 N and γ′-Fe 4 N. The linear relation Δ H f = −65.912 x − 11.154 kJ mol −1 was found between the formation enthalpies and their nitrogen content x . Based on this linear approximation, the formation enthalpies of ε-Fe 3 N 1.1 , ε-Fe 3 N 1.3 and γ″-FeN 0.91 were estimated as −28.95, −31.59 and −42.56 kJ mol −1 , respectively. The values were consistent with the experimental results. The calculated elastic constants indicated that the FeN and γ′-Fe 4 N phases were significantly anisotropic, the ζ-Fe 2 N exhibited some anisotropy to a certain degree. While the ε-Fe 3 N showed a relatively strong isotropic character. The ratios of bulk modulus ( B ) to shear modulus ( G ), 3.41 for FeN, 2.69 for ζ-Fe 2 N, 2.39 for ε-Fe 3 N and 3.09 for γ′-Fe 4 N, indicated their ductile nature. Magnetism calculations showed that the FeN was antiferromagnetic, the ζ-Fe 2 N, ε-Fe 3 N and γ′-Fe 4 N were paramagnetic. Besides, the Vickers hardness of these iron nitrides were calculated, and the strong Fe–N covalent bonds were found to play important roles in the hardness of iron nitrides. [ABSTRACT FROM AUTHOR]

Samples of Ni 3 Al, Ni 3 Al:B and Ni–Al–Cr super alloys were prepared by directional solidification method and their effect of alloying with ternary elements on the mechanical properties was investigated. In-situ X-ray diffraction studies were carried out on undoped Ni 3 Al, Ni 3 Al:B with boron 500 ppm and Ni–Al–Cr with 7.5 at.% of chromium super alloys at high pressure using diamond anvil cell. The results indicate that micro-alloying with B forms γ′-phase (L1 2 structure), similar to the pure Ni 3 Al, while Ni–Al–Cr alloy consists of γ′ precipitates in a matrix of γ-phase (Ni-FCC structure). The crystal structure of all three alloys was stable up to 20 GPa. Micro alloying with boron increases bulk modulus of Ni 3 Al by 8% whereas alloying with chromium has the opposite effect decreasing the modulus by 11% when compared to undoped alloy. Further, the elastic modulus and hardness of Ni 3 Al, Ni 3 Al:B and Ni–Al–Cr alloys were determined using the nano-indentation technique, in combination with compressibility data which enabled the estimation of shear modulus and Poisson’s ratio of these alloys. [ABSTRACT FROM AUTHOR]

We measured the heat flow, shear modulus and density changes occurring upon heating of bulk glassy Pd 41.25 Cu 41.25 P 17.5 , which polymorphically crystallizes into tetragonal Pd 2 Cu 2 P with simultaneous decrease of the density. It was found that the heat release (well below the glass transition temperature T g ) and heat absorption (near and above T g ) are uniquely linked to the relaxation of the shear modulus through the relaxation change of the concentration of internal “defects” frozen-in upon glass production. The two models suitable for a quantitative description of this interrelationship are discussed in detail. The obtained results clearly demonstrate an intrinsic connection of the shear moduli of glass and maternal crystal. [ABSTRACT FROM AUTHOR]

In this work, the effect of Sb addition on the microstructure and mechanical properties of Mg 2 Si phase in Mg 2 Si/AZ91 composites are investigated by experimental research and first-principles calculation. The experimental results show that the coarse dendritic shape is modified to blocky polygonal shape, and the size of primary Mg 2 Si, is successfully refined with the Sb addition. With enhancing Sb addition contents, the doping concentration of Sb in Mg 2 Si phase keeps increasing, which accounts for the morphology and size modification. Besides, nano-indentation tests reveal that the Young's modulus of Mg 2 Si phase exhibits less reduction, while the hardness is significantly improved when introducing 2.0 wt%Sb. The calculated results indicate that the structure stability of Mg 2 Si crystal is enhanced, and the mechanical modulus including bulk modulus, shear modulus and Young's modulus of Mg 2 Si are decreased with the increase of Sb concentration, agreeing well with experimental observation, but the hardness reduces, which is contrary to the experimental results. Mg 2 Si phase doping with Sb atoms, however, exhibits improved ductile behavior compared with undoped Mg 2 Si due to the increased Poisson's ratio and B/G ratio. In addition, Sb doping can weaken the bond strength and reduce the population of Mg-Si covalent bonds, as well as generate new Mg-Sb bonds with lower strength based on the electronic structure analysis, which contribute to the decrease of mechanical modulus. • The morphology of Mg 2 Si is modified with increasing Sb. • Sb doping reduces Young's modulus but enhances the hardness of Mg 2 Si. • The structure stability of Mg 2 Si crystal is enhanced by Sb doping. • Sb doped Mg 2 Si exhibits reduced mechanical modulus and improved ductility. • Newly formed Mg-Sb covalent bonds account for evolution of mechanical properties of Mg 2 Si. [ABSTRACT FROM AUTHOR]

Two dimensional (2D) Ruddlesden Popper perovskites have been extensively studied for their exceptional optical and electronic characteristics while only a few studies have shed light on their mechanical properties. The existing literature mainly discusses the mechanical strength of single crystal perovskites, however a study of structure tunability of 2D perovskite thin films is still missing. In this study, we report the effect of number of inorganic layers ' n ' on elastic modulus of 2D, quasi-2D perovskites and 3D perovskite thin films using nanoindentation technique. Our studies indicate the role of orientation of the inorganic layers in perovskite films in tailoring their mechanical response. The experimental results have been substantiated using first principle density functional theory (DFT) calculations. We also report other important mechanical parameters namely, shear modulus, bulk modulus, Poisson's ratio, Pugh's ratio, Vickers hardness, yield strength and the universal elastic anisotropic index using DFT simulations. Anisotropy is observed in the elastic modulus of the materials under study and has been discussed in detail in the manuscript. Understanding the mechanical behavior of 2D Ruddlesden Popper perovskites thin film in comparison with conventional 3D perovskite offers intriguing insights into the atomic layer dependent properties and paves the path for next generation mechanically durable and novel devices. • Nanoindentation of Ruddlesden Popper perovskite thin films having different n-values. • Elastic modulus increases with increasing 'n′, indicating rigidity of 3D perovskites. • Density functional theory (DFT) validates experimental findings. • All perovskite samples show strong elastic anisotropic behavior. [ABSTRACT FROM AUTHOR]

• Composition-dependent elasto-plastic properties of Co–Ni–W alloys were measured. • Elasto-plastic property databanks of Co–Ni–W system was built by machine learning approach. • Composition-dependent Peierls stresses of Co–Ni–W alloys were estimated. • Co–(0–7.8) at% Ni–(9.1–9.5) at% W alloys have high moduli and high hardness. [Display omitted] Co–Ni–W alloys are widely employed in aviation aerospace and power industries, and their elasto-plastic property data are very useful for the design and development of novel alloys. Electron probe microanalysis and nanoindentation tests were performed on 7 groups of Co–Ni–W diffusion couples annealed at 1373 K for 120 h, and a home-made MATLAB program based on the reverse analysis algorithms was used to obtain the composition-dependent elasto-plastic property data in a wide composition space of Co–Ni–W system. And the databanks of Young's modulus, hardness, and yield stress over the whole face-centered cubic phase zone were then obtained by using machine learning approach. Subsequently, bulk and shear moduli of Co–Ni–W alloys were extrapolated from the experimental Young's modulus and the constant Poisson's ratio. Moreover, Peierls stresses varied with the compositions were calculated with the aid of shear modulus data to analyze the dislocation motion in the Co–Ni–W lattices. This work reveals the construction of composition-dependent elasto-plastic property databanks for multicomponent alloys, and the results indicate that Co–(0–7.8) at% Ni–(9.1–9.5) at% W alloys have high moduli and high hardness. [ABSTRACT FROM AUTHOR]

● (V, M)C (M = W, Mo and Cr) carbides are thermodynamically and mechanically stable. ● V 0.5 Cr 0.5 C exhibits an excellent combination of hardness and ductility. ● The bonding nature is unveiled to rationalize the multi-alloying effect on physical properties of (V, M)C carbides. ● Nano-indentation measurements of mechanical properties of (V, W)C carbides agree well with by first-principles calculations. Vanadium carbides (VCs) usually function as reinforced phases of metallic materials, and their elastic and ductile-brittle properties are essential for mechanical properties of bulk materials. In this work, a multi-alloying method is adopted to modify physical properties of VCs. The stability, mechanical and electronic properties of multi-component (V, M)C (M = W, Mo and Cr) carbides were investigated by both first-principles calculations and nano-indentation experiments. The results show that W stabilizes (V, W)C while Cr destabilizes (V, Cr)C as demonstrated by the calculated formation energy. Doping with an appropriate amount of W, Mo and Cr may produce larger ratios of bulk modulus to shear modulus (B/G) and thereby enhance the ductility of (V, M)C carbides according to the Pugh's criteria while retaining high hardness. The nano-indentation measurements confirm the W doping effect on mechanical properties and agree well with the calculations. The physical properties of doped (V, M)C carbides can be rationalized by the evolution of intrinsic chemical bonding as suggested by the electronic structures. [ABSTRACT FROM AUTHOR]

• Studied systems are direct band gap earth abundant double perovskites. • First-ever thermoelectric properties for these double perovskites are reported. • Moderate thermoelectric and optoelectronic performance. • Moderate photoconversion efficiency (PEC), 26.8%, using SLME of Ba 2 SbNbO 6 is approaching to that of reported for state-of-the-art inorganic PV cells (29.1%). [Display omitted] We report the structural, mechanical, electronic, optical, thermoelectric properties and spectroscopic limited maximum efficiency (SLME) of oxide double perovskite structure Ba 2 SbNbO 6 and Ba 2 SbTaO 6 compounds. All the investigations were performed through the first-principles density functional theory (DFT). The results obtained for the elastic constants affirms the mechanical stability of the studied double perovskite compounds. The calculated data of bulk modulus (B), shear modulus (G), and Young's modulus (E) for Ba 2 SbTaO 6 are found to be greater than those of Ba 2 SbNbO 6. The obtained ratio of Bulk to shear modulus (B/G) shows that Ba 2 SbNbO 6 and Ba 2 SbTaO 6 are ductile in nature and are suitable for the device fabrications. The electronic properties of studied compounds are explained in terms of their energy bands, total and partial density of states. The computed electronic band structure reveals the direct band gap semiconducting nature of both compounds. The energy dependent optical properties such as, dielectric tensor, optical conductivity, absorption, reflectivity, refraction and energy loss for both the studied compounds are investigated and are explained in order to highlight the potential of studied compounds for the photovoltaic applications. In addition to electronic and optical properties, we have also studied the electron relaxation time-dependent thermoelectric properties, such as Seebeck coefficient, electronic thermal conductivity, electrical conductivity, thermoelectric power factor, and the thermoelectric figure of merit as a function of chemical potential at various temperatures for p-type and n-type charge carriers. The high absorption spectra and good thermoelectric figure of merit reveal that both the studied compounds, Ba 2 SbXO 6 (X = Nb, Ta) are promising materials for photovoltaic and thermoelectric applications. The calculated SLME of 26.8% reveals that Ba 2 SbNbO 6 is an appealing candidate for single-junction solar cells. [ABSTRACT FROM AUTHOR]

• The fluctuation mechanism of the internal friction near phase transitions in the Na 0.875 Li 0.125 NbO 3 lead free ferroelectric. • Ferroelectric domains contribution to attenuation of low-frequency sound. • The amplitude dependences of internal friction. • Friedel's dislocation model for amplitude dependences of internal friction. The temperature and amplitude dependences of internal friction Q −1 and shear modulus G for the Na 0.875 Li 0.125 NbO 3 solid solution were studied in the temperature range of 300–700 K. It was found that the material undergoes two structural phase transitions near temperatures T 1 ≈ 620 K and T 2 ≈ 559 K. Both low-temperature phases are ferroelectric one, whereas the phase above the temperature T 1 is paraelectric one. It is shown that the main contribution to mechanical losses below T 1 is related to the motion of domain walls. The Q −1 maxima observed near temperatures T 1 and T 2 are satisfactory described within the framework of the low-frequency fluctuation mechanism of internal friction. The amplitude dependences of Q −1 are in agreement with the Friedel dislocation model. [ABSTRACT FROM AUTHOR]

• Magnetic, pseudo-gap, topological, and phase transformation behaviorin Mn3Sb with a potential application in spintronics. • The ferrimagnetic nature due to localized and delocalized magnetism resulting in different magnetic moments on Mn atoms. • Unique magnetostructural properties exhibited by nonequivalent Mn atoms with their variable valence states. • Characteristics of band topology (opening of a gap in Dirac-like band features) and pseudo-gap in Mn 3 Sb. Magnetic, pseudogap, topological, magnetostructural, and elastic behaviors of Mn 3 Sb have been unraveled. The ferrimagnetism (FIM) is described by localized and delocalized electron magnetism resulting in different magnetic moments on Mn atoms, confirming the neutron diffraction data. The identified magnetostructural properties are due to the non-equivalent Mn atoms in its lowest symmetry structure. The electronic structure is also unique due to variable valance states of Mn atoms. The magnetic moment (4.10 μ B) of non-equivalent Mn1 atom is antiparallely aligned with the magnetic moments (2.34 μ B) of Mn2 and Mn3 atoms. The estimated Curie temperature, T C , is higher than the room temperature, which may have above the room temperature applications in spintronic devices. The band structure and density of states (DOS) show the characteristics of band topology (opening of a gap in Dirac-like band features) and pseudo-gap, respectively, around the Fermi level. While expanding the unit cell, the tetragonal FIM ground state transforms to the cubic primitive FIM phase, however, the contraction transforms it to the L1 2 ferromagnetic (FM) phase. The estimated elastic constants, bulk to shear modulus ratio, and elastic anisotropy factor indicate that Mn 3 Sb exhibits mechanically stable, ductile, and anisotropic behaviors, respectively. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) simulations based on the embedded atomic method (EAM) are used to study the annealing effect on elastic and structural behavior for different cooling rates of binary Mg 25 Al 75 metallic glasses (MGs). Firstly, we examine the cooling rates effect (5 × 10 11 K / s , 10 12 K / s , 5 × 10 12 K / s and 10 13 K / s) on the atomic locale structure of Mg 25 Al 75 MG through a variety of local structure analysis methods such as bond angle distribution (BAD), total and partial radial distribution function (RDF), Voronoi tessellation analyses (VTA) and coordination numbers (CNs). Our results confirm that the Mg 25 Al 75 glass formation is proved by a splitting of the second peak in the RDF upon quenching process. The < 0 , 0 , 12 , 0 > , < 0 , 1 , 10 , 2 > and < 0 , 2 , 8 , 4 > Voronoi polyhedrons (VPs) have been depicted as the most dominant polyhedrons in the system, and we have found that the < 0 , 0 , 12 , 0 > , < 0 , 1 , 10 , 2 > clusters increase while the < 0 , 2 , 8 , 4 > cluster decreases as a function of the decrease of the cooling rate. Via the Went-Abraham parameter, our numerical results show an increase of the glass transition temperature (T g) with increasing of cooling rate. Finally, we heat-treated the binary Mg 25 Al 75 MG samples at the aging temperature 450 K during period varying from 0 to 5 ns for four different quenching rates. We observed that the elastic constants C 11 and C 44 increase while C 12 decreases as the annealing time increases and the quenching rate decreases. This has been correlated with the elastic moduli, where Young's modulus (E), bulk modulus (B) and shear modulus (G) increase, which suggests the improvement of the elastic behavior, the resistance to compression and the resistance to the shear bands (SBs), respectively. We also found that at the atomic level in the short-range order (SRO), the < 0 , 0 , 12 , 0 > and < 0 , 1 , 10 , 2 > clusters and the degree of the five-fold symmetry increase as a function of the increase of annealing time. • The < 0 , 0 , 12 , 0 > , < 0 , 1 , 10 , 2 > and < 0 , 2 , 8 , 4 > Voronoi Polyhedrons have been depicted as the most dominant clusters in the Mg 25 Al 75 binary metallic glass; • The < 0 , 0 , 12 , 0 > , < 0 , 1 , 10 , 2 > clusters increase as a function of the decrease of the cooling rate; • The glass transition temperature increases with the increase of cooling rate; • The Young's modulus, bulk modulus and shear modulus increase as a function of the increase of annealing time. [ABSTRACT FROM AUTHOR]

The microstructure of the nanoscale precipitates (especially the β phase) formed in the primary a-Al grains of a cast Al–7Si–Mg alloy during ageing at different temperatures, and the strengthening effects of them on the mechanical properties have been systematically investigated by transmission electron microscopy (TEM) and tensile test. The interactions of dislocations with different types of precipitates were analyzed in depth. It was found that the GP zones and β″ phase can be easily sheared by dislocations along the close-packed {111} Al planes, leading to good deformation compatibility and elongation. The step-like planar defects were found in the deformed β″ phase, indicating that this needle-shaped precipitate can be sheared not only along the short axis but also along the long axis. The β phase and nanoscale Si particles are usually bypassed by dislocations, showing a typical Orowan strengthening mechanism, leading to the highest strength. This may be related to their large size (about 100 nm in diameter), high shear modulus and modest number density. In addition, the moiré fringes and FFT pattern of β phase were discussed by calculation of diffraction vectors. The moiré fringes with about 2.389 nm and 2.664 nm spacing displayed in HRTEM image results from the interactions between the 004 Al /006 β and 2 ¯ 22 Al / 3 ¯ 33 β diffraction respectively. The corresponding complex FFT pattern is caused by strong double diffraction of [110] β and [110] Al reflections. Furthermore, an interesting phenomenon that the β phase tends to nucleate and grow on the surface of Si particle was firstly observed and discussed in depth. • The β phase and nanoscale Si particles result in the highest tensile strength. • The dislocation can shear the β″ phase along its short and long axes. • The moiré fringes and complex double diffraction pattern of β phase are well explained. • The β phase tends to nucleate and grow on the surface of the Si particle. [ABSTRACT FROM AUTHOR]

• Successful fabrication of borate glasses through replacement of B 2 O 3 by TiO 2. • These glasses may have applications as optical filter devices because of their full band UV Blocking tendency. • T5 glass was found to be best shielder for fast, thermal neutron and gamma rays. The glasses of series xTiO 2 -xCeO 2 -(30-x) PbO-(70-x) B 2 O 3 where 2 ≤x ≤ 10 mol% were made using conventional melt-quench method and X-ray diffraction technique has been used to ascertain the amorphous nature of these glasses. The analysis of the compositional dependence of the physical parameters like density, molar volume and oxygen packing density along with the elastic parameters (Young's modulus, shear modulus, Vickers hardness number) of the studied glasses has been done. Infrared (IR) spectra revealed BO 3 and BO 4 units as main glass forming groups in these glasses but at higher concentrations of TiO 2 , Ti3+ and Ti4+ ions get significantly incorporated in glass matrix thereby creating TiO 4 and TiO 6 structural units. Optical spectral studies indicated that the band gap energy values decreased with increasing TiO 2 content and these glasses had good UV-blocking efficiency which could be exploited for their use as transparent UV shielding materials. The radiation shielding parameters such as Half Value Layer, Linear Attenuation Coefficient, Exposure Buildup Factor, Mean Free Path including thermal and fast neutron cross section were deduced which indicated that the attenuation performance of these glasses improved with the addition of TiO 2. Lower values of Exposure Buildup Factor and higher values of thermal and fast neutron removal cross section reflect the proficient shielding ability of these glasses. [ABSTRACT FROM AUTHOR]

• Homogeneous and dense Ta x Hf 1−x C solid solution were prepared using arc melting. • Ta 0.75 Hf 0.25 C leads to excellent comprehensive mechanical properties. • The electronic structures of Ta x Hf 1−x C were analyzed by the first-principles. • Relation between mechanical properties and chemical bonds were summarized. Ta x Hf 1−x C can withstand extreme environments, but the challenges in their densification prevent them from being used for many applications. In this paper, a method to prepare dense homogeneous Ta x Hf 1−x C solid solutions with a cubic structure is prosed. Moreover, mechanical properties of Ta x Hf 1−x C are characterized, including the elastic modulus and Poisson ratio. The hardness and Debye temperature are estimated by using empirical equation. The properties related to the electronic structures of Ta x Hf 1−x C (x = 0, 0.25, 0.5, 0.75, 1), including the density of states and Mulliken populations, are systematically calculated by using the first-principles method. From the calculation, we found that all Ta x Hf 1−x C are thermodynamically stable at room temperature. Moreover, Ta 0.5 Hf 0.5 C has a higher Young's modulus and shear modulus comparing to Ta 0.75 Hf 0.25 C and Ta 0.25 Hf 0.75 C. Ta 0.75 Hf 0.25 C possesses the highest bulk modulus, suggesting that it has greater comprehensive mechanical properties than the others. In addition, the compositions of their chemical bonds are discussed according to their density of states, population analysis and Debye temperature. We found that the number of valence electrons of transition metals significantly affects their mechanical properties. Finally, the relation between the mechanical properties of Ta x Hf 1−x C (x = 0, 0.25, 0.5, 0.75, 1) and the chemical bonds are summarized. [ABSTRACT FROM AUTHOR]

• Bi 12 GeO 20 (BGO) compound was investigated by density functional theory calculations. • The mechanical and anisotropic elastic characteristics of BGO were reported. • DFT studies presented shear and Young's moduli, linear compressibility, hardness. • Hardness and Young's modulus were also obtained by performing nanoindentation experiments. The present study reports the mechanical and elastic characteristics of Bi 12 GeO 20 (BGO) compound by experimental nanoindentation measurements and density functional theory (DFT) calculations. X-ray diffraction pattern of BGO was plotted and revealed diffraction peaks were associated with Miller indices of cubic crystalline structure with lattice constant of a = 10.304 Å. Two- and three-dimensional representations of Young's modulus, linear compressibility, shear modulus and Poisson's ratio were presented according to DFT calculations. The calculated elastic constants pointed out the mechanically stable and anisotropic behavior of the BGO. The hardness and Young's modulus ranges of the BGO calculated from DFT studies were found as 3.7–6.3 GPa and 61.7–98.9 GPa, respectively. Hardness and Young's modulus of BGO single crystal were also obtained by analyzing force-dependent nanoindentation experimental data. It was observed that hardness and Young's modulus decrease with increase of load in the low applied loads and then reaches saturation in the high applied loads. This behavior is known as indentation size effect. True hardness value was determined from proportional specimen resistance model as 4.1 GPa. The force independent region presented the Young's modulus as 114 GPa. [ABSTRACT FROM AUTHOR]

• Study of structural, mechanical, electronic, and magnetic properties of new series of Fe-based quaternary Heusler alloys. • Interesting properties like spin-gapless semiconducting (SGS) behavior and half-metallicity are realized. • Discrepancies observed in electronic and magnetic properties of Fe based quaternary Heusler alloys containing Yttrium is redressed. This paper presents a detailed investigation of FeCr-based quaternary Heusler alloys. By using ultrasoft pseudopotential, electronic and magnetic properties of the compounds are studied within the framework of Density Functional Theory (DFT) by using the Quantum Espresso package. The thermodynamic, mechanical, and dynamical stability of the compounds is established through the comprehensive study of different mechanical parameters and phonon dispersion curves. The meticulous study of elastic parameters such as bulk, Young's, shear moduli, etc. is done to understand different mechanical properties. The FeCr-based compounds containing also Yttrium are studied to redress the contradictory electronic and magnetic properties observed in the literature. The interesting properties like half-metallicity and spin-gapless semiconducting (SGS) behavior are realized in the compounds under study. [ABSTRACT FROM AUTHOR]

• Interdiffusion coefficients and activation energies are obtained from the measured composition profiles. • Hardness and Young's modulus of Ni-Zn IMCs have been obtained. • The β1 phase has been found in the diffusion couple. In this paper, the solid-solid diffusion reaction and growth kinetics of Ni-Zn system were investigated using diffusion couple technique. Three intermetallic compounds (IMCs), β 1 (NiZn), γ (Ni 2 Zn 11) and δ (Ni 3 Zn 22) were observed at the diffusion zone with the annealing temperature range between 598 K and 673 K. The results indicate that the growth process of reaction zone was dominated by volume diffusion. And the growth constants, integrated diffusion coefficients, growth activation energies and diffusion activation energies of γ and δ were evaluated based on thickness of the phases, reaction temperatures and annealing times. The Young's modulus and Vickers hardness of the three phases were evaluated from the displacement-loading curve by nanoindenter testing. The Young's modulus and hardness of the IMCs increased firstly and then decreased with the increasing of Zn concentration, where γ phase has the highest Young's modulus (183.3 GPa) and highest hardness (6.05 GPa) among the three phases. Finally, the bulk modulus (B), shear modulus (G), Young's modulus (E), and Poisson's ratio (v) of the Ni-Zn IMCs were calculated by the first-principles calculations. The tendency of calculated Young's modulus varying with the composition of Zn was consistent with that of experimental results. [ABSTRACT FROM AUTHOR]

• A new technique was used to study grain boundary (GB) internal frictions under tens of kilohertz. • The GB internal friction peaks of polycrystalline Al and Mg were observed near the melting point for the first time. • The torsional GB internal friction peak is about 1.5 times higher than longitudinal peak. • Quantitative evaluation on several existing GB sliding models were made based on the experimental results. By using a modified piezoelectric ultrasonic composite oscillator technique (M-PUCOT), the temperature dependence of Young's modulus, shear modulus and related internal frictions of 4 N polycrystalline aluminum and magnesium were measured from room temperature to 900 K at longitudinal and torsional resonance under several tens of kilohertz. The grain boundary internal friction peaks (K e ˆ peaks) accompanied by large moduli relaxations were observed near the melting point (~0.86 T m and 0.78 T m for Al and Mg respectively) in both vibration modes. The activation energy of grain boundary relaxation is almost the same for the two vibration modes, which is 31.2 kcal/mol for aluminum and 36 kcal/mol for magnesium. The peak values of grain boundary internal frictions are significantly dependent on the vibration mode, and for both materials, the torsional peak is about 1.5 times higher than that of longitudinal peak. Finally, the experimental results were evaluated by using existing grain boundary slipping models (including 3D and 2D Zener's model, Budiansky and O'Connell's model and Ghahremani's model). Results show that the periodic hexagonal grains sliding model (Ghahremani's model) can reproduce the experiments best. [ABSTRACT FROM AUTHOR]

• Internal friction and shear modulus data are presented for a 7 orders of magnitude frequency range. • A law describing the imaginary compliance component in this range is determined. • A new method for the determination of the Gibbs activation energy of relaxation is suggested. • It is argued that relaxation origin is related to the interstitial-type defects inherited from the melt. • It is assumed that at least defect-related three mechanisms of energy losses are operating. We report measurements of the internal friction and shear modulus of glassy Cu 49 Hf 42 Al 9 at sub-hertz frequencies (0.03–1 Hz) and at a high frequency of 560 kHz at temperatures from the room one up to well above the glass transition temperature T g. It is found that an increase of the frequency in this range results in a drastic decrease of the internal friction and shear modulus relaxation both below and above T g. The relaxation kinetics is analyzed within the framework of a classical phenomenological approach in terms of the real and imaginary parts of the dynamic shear compliance both for the initial and relaxed states of the glass under investigation. A law describing the frequency dependence of the imaginary compliance component in the whole frequency range investigated is determined. A new method for the determination of the Gibbs activation energy of relaxation is derived. The underlying activation energy spectrum determined on this basis is found to smoothly increase with the activation energies accessible in the experiment. A change of the activation energy with temperature below and above T g is determined. The phenomenological analysis is combined with a physical interpretation of the relaxation, which is assumed taking place due to the activation of interstitial-type defects (essentially elastic dipoles) frozen-in from the melt upon glass production. It is argued that there exist at least three mechanisms of energy losses, which are related to changes of the dipoles' orientation in the same energy states and transitions between their low- and high-energy states. [ABSTRACT FROM AUTHOR]

In the present investigation, key mechanical design parameters and the thermoelectric performance of powder ball milled spark plasma sintered P -typ e Bi 0 · 4 Sb 1 · 6 Te 3 material was determined. In particular, the effect of the powder preparation technique on the powder surface oxide layer as well as both the mechanical and thermoelectric properties were determined. All measurements were performed on identically prepared sintered samples in both parallel and perpendicular to the applied sintering pressure. The mechanical properties determined included relative density, uniaxial tensile strength, coefficient of thermal expansion, Young's modulus, Poisson's ratio, and shear modulus. The thermoelectric properties measured included the Seebeck coefficient, electrical resistivity, and thermal conductivity. A mechanically agitated reduction facility built in-house was used to reduce the powder surface oxide at 380 °C for 24 h using dry 5% H 2 95% Ar. To separate between the annealing and the reduction effects, the P -type (Bi , Sb) 2 Te 3 powder was annealed using highly purified Ar at the same temperature and time as the reduction process. The oxygen content in the sintered P -type samples was then measured using the inert gas fusion technique. The oxygen content was found to be decreased by 35 wt% after 24 h of reduction but did not change significantly after annealing with Ar only relative to the dried powders. The reduction of the surface oxides increased the relative density of the sintered parts from 97.1% to 99.2%. Consequently, the characteristic uniaxial tensile strength increased from 13.9 MPa to 26.3 MPa and from 16.3 MPa to 30.6 MPa in the parallel and the perpendicular directions to the sintering pressure, respectively, for the sintered bodies from the reduced powder. Both the Young's modulus and the shear modulus increased from 44.3 GPa to 48.7 GPa and 17.8 GPa–19.5 GPa in the parallel direction, respectively, after the reduction treatment and sintering. The figure of merit, ZT, increased from 0.35 to 0.80 and from 0.42 to 1.13 at room temperature (25 °C) in the parallel and the perpendicular directions, respectively, after the surface oxide reduction treatment. • Powder pre-treatment enhanced both mechanical and thermoelectric properties. • Powder surface oxide reduction increased the tensile strength by 89%. • The figure of merit (ZT) increased by up to 170% at room temperature (25 °C). • An anisotropy in the tensile strength and ZT was observed. • Superior performance in the direction perpendicular to the sintering pressure. [ABSTRACT FROM AUTHOR]

We have carried out a first-principles investigation of mechanical, electronic, thermodynamic and optical properties of the recently predicted thermodynamically stable MAX phase boride Hf 3 PB 4 for the first time. The calculated lattice constants of the optimized cell volume are consistent with those found earlier. Mechanical properties characterized by parameters such as C 44 , B (bulk modulus), G (shear modulus), Y (Young's modulus), H macro (macro-hardness) and H micro (micro-hardness) of Hf 3 PB 4 boride are compared with those of existing 211, 312 and 413 MAX phases. None of the MAX compounds synthesized so far has higher H macro and/or H micro than that of the predicted Hf 3 PB 4 nanolaminate. Calculations of stiffness constants (C ij) indicate that Hf 3 PB 4 is mechanically stable. The extraordinarily high values of elastic moduli and hardness parameters are explained with the use of density of states (DOS) and charge density mapping (CDM). The high stiffness of Hf 3 PB 4 arises because of the additional B atoms which results in the strong B–B covalent bonds in the crystal. The band structure and DOS calculations are used to confirm the metallic properties with dominant contribution from the Hf-5 d states around the Fermi level. The technologically important thermal parameters such Debye temperature, minimum thermal conductivity, Grüneisen parameter and melting temperature of Hf 3 PB 4 are calculated. The important optical constants are calculated and analyzed in detail and their relevance to possible applications in the optoelectronic sectors is discussed. Our study reveals that Hf 3 PB 4 has the potential to be the hardest known MAX phase based on the values of C 44 , H macro and H micro. ga1 • The physical properties of Hf 3 PB 4 have been studied using first-principles technique. • Hf 3 PB 4 exhibits the highest values of hardness parameters among the MAX phases. • The charge density mapping and bond population analysis disclose the existence of very strong B–B covalent bonds in Hf 3 PB 4. • Hf 3 PB 4 has the highest melting temperature and might be an efficient candidate as thermal barrier coating material. • Hf 3 PB 4 has the potential to be used as reflecting coating to diminish solar heating. [ABSTRACT FROM AUTHOR]