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We reported the influence of Al contents on microstructure and elevated-temperature mechanical properties in Co-free FeCrMnNiV 0.2 Al x (x = 0, 0.2, 0.3, 0.35 and 0.4) high-entropy alloys (HEAs), which were prepared by conventional cast and annealing methods. The results indicated that FCC + BCC structure was transformed into BCC/B2 structure with an increase of Al in as-cast HEAs, leading to an increase in Vickers hardness. After annealing, the formation of network spinodal decomposition structure in FCC regions led to an increase of hardness and strength with a sacrifice in ductility. Noted that the enhanced yield strength at elevated temperature of the cost-effective FeCrMnNiV 0.2 Al 0.2 HEA can be ascribed to the stable strengthening phases, including sub-micron/nanoscale B2 phase in BCC regions and network FCC/L1 2 structure in FCC regions. The cracks prefer to propagate through either FCC regions or BCC regions with more secondary cracks. [ABSTRACT FROM AUTHOR]

AlCoCrFeNi high-entropy alloys (HEAs) have shown excellent mechanical properties and high-temperature oxidation resistance but poor corrosion resistance owing to the high contents of the aluminium passivation film. In this study, Si was added to these alloys with the aim of improving the composition and stability of the passivation films. The microstructure and corrosion behaviour of AlCoCrFeNiSi x (molar ratio x = 0, 0.1, 0.2, 0.3, and 0.4) HEAs were investigated. Dendritic and spinodal decomposition regions were observed in all five alloys. In the dendritic region, the dendritic structures transitioned from a petal shape to a dendritic shape with increasing Si content. Phase separation occurred in the spinodal decomposition region, which predominantly consisted of ordered body-centred cubic (B2) and disordered body-centred cubic (A2) phases. The size of the A2 phase decreased, and the amount of the A2 phase increased with increasing Si content. An optimised Si content could enhance the stability of Al and Cr passivation films, whereas excessive Si imposed an adverse effect by forming a Cr passivation film. The corrosion resistance of AlCoCrFeNiSi 0.2 HEAs was optimum with a passive current density of 3.2 μA/cm2, which was 0.2 times that of the obtained AlCoCrFeNi HEAs without Si. The type of corrosion changed from local corrosion of AlCoCrFeNiSi x (x ≤ 0.3) HEAs to general corrosion of AlCoCrFeNiSi 0.4 HEAs. The corrosion mechanisms of the AlCoCrFeNi HEAs with various Si contents were elucidated. • AlCoCrFeNi high-entropy alloys (HEAs) with varied Si contents prepared. • Corrosion resistance of the HEAs in 3.5 wt% NaCl solution investigated. • AlCoCrFeNiSi 0.2 HEAs has the optimal corrosion resistance. • Corrosion mechanism of AlCoCrFeNiSi x HEAs elucidated. [ABSTRACT FROM AUTHOR]

TiAlCN thin films have been known for their high hardness, favorable toughness and wear properties. Nevertheless, a comprehensive theoretical study conveying the mechanism for the effects of dissolved carbon on the mechanical properties, and thermal stability of TiAlN is still missing. Here, we studied the influence of carbon addition on the structure, modulus and thermal stability of TiAlN by first-principle calculations. The calculated formation energies indicate that carbon preferentially occupies nitrogen site and decreases the solubility of Al in cubic TiN. Furthermore, the enhanced ductility and decreased shear modulus by carbon addition revealed by our calculations, nicely explain the experimentally observed exceptional toughness of TiAlCN. The decomposition enthalpy calculations suggest that c-Ti(C,N) and c-AlN are the most probable decomposition products of TiAlCN. The reduced diffusion barriers of Al, the dominant diffusing atoms, indicate promoted spinodal decomposition process by carbon addition. • Ab initio calculations show the preferential substitution of C for N within TiAlCN. • C-addition into TiAlN reduces the solubility of Al in c-TiN. • C-addition has a beneficial effect on the ductility and toughness of TiAlN. • The spinodal decomposition of TiAlCN is promoted with increasing C content. [ABSTRACT FROM AUTHOR]

Spinodal decomposition can improve a number of essential properties in materials, especially hardness. Yet, the theoretical prediction of the onset of this phenomenon (e.g., temperature) and its microstructure (e.g., wavelength) often requires input parameters coming from costly and time-consuming experimental efforts, hindering rational materials optimization. Here, we present a procedure where such parameters are not derived from experiments. First, we calculate the spinodal temperature by modeling nucleation in the solid solution while approaching the spinode boundary. Then, we compute the spinodal wavelength self-consistently using a few reasonable approximations. Our results show remarkable agreement with experiments and, for NiRh, the calculated yield strength due to spinodal microstructures surpasses even those of Ni-based superalloys. We believe that this procedure will accelerate the exploration of the complex materials experiencing spinodal decomposition, critical for their macroscopic properties. [Display omitted] [ABSTRACT FROM AUTHOR]

The 17-4PH stainless steel serves as the main steam isolation valve in a light water reactor due to excellent comprehensive mechanical properties and corrosion resistance. Nonetheless, the thermal aging resulting from prolonged service poses a threat to the safe operation of nuclear power plants. The mechanism of thermal-aging embrittlement of 17-4PH stainless steel and its repairing behavior under the action of the pulsed electric current were studied using transmission electron microscopy and 3D atom probe tomography. The ductile to brittle transition occurred following the spinodal decomposition and G phase formation during the thermal aging of 5000 h at 673 K, resulting in a 100 HV increase in hardness of the 17-4PH stainless steel, of which 94.4 HV was attributed to the spinodal decomposition. Under the action of a pulsed electric current at 733 K, the hardness and impact energy can be restored to its original state, whereas heat treatment at the same temperature is unable to restore these properties. This is because the pulsed electric current treatment decreased the thermodynamic barrier to dissolution for the spinodal decomposition and G phases. The Kolmogorov-Johnson-Mehl-Avrami model was used to calculate the kinetics of spinodal decomposition dissolution. The results suggest that the pulsed electric current could increase the diffusion pre-exponential factor of Cr element and accelerate the elimination of spinodal decomposition. This process ultimately facilitates the quick regeneration of the 17-4PH stainless steel's performance. • The thermal aging embrittlement is repaired quickly in 17-4PH stainless steel using pulsed electric current. • Spinodal decomposition is the dominant factor of the ductile to brittle transition. • The thermodynamic barrier of spinodal decomposition is lowered by pulsed electric current. • The Cr diffusion was increased by the pulsed electric current. [ABSTRACT FROM AUTHOR]

For metastable β Ti alloys, it still remains a key challenge to enhance their limited yield strength (YS) while retaining good strain hardenability and ductility. Here we report a new strategy to evade this trade-off dilemma via introducing an uncommon hierarchical structure with the assistance of spinodal structures. The new Ti–11Mo–2V alloy exhibits high YS (693 MPa), high ultimate tensile strength (857 MPa) and large total elongation (31.8 %). Such excellent strength-ductility synergy originates from successive activation of multiple deformation mechanisms, including primary {332}<113> twins, secondary martensite and secondary {112}<111> twins. Importantly, the stress-induced secondary martensite is the desirable α′ martensite rather than the common α'' martensite. Spinodal decomposition in parent β grains is expected to facilitate the unusual hierarchical structure where primary {332}<113> twins ensure high YS while secondary α′ martensite and {112}<111> twins result in excellent strain hardening ability. • The new alloy exhibits high yield strength while retaining large ductility. • An uncommon hierarchical structure, including primary {332}<113> twins and secondary α′ martensite, is created. • The products of SIMT are the unusual α′ martensite due to the assistance of spinodal decomposition. [ABSTRACT FROM AUTHOR]

Adjusting the phase composition of high-entropy alloys is an effective approach to change its mechanical and magnetic properties. In this study, FeCoNiCr high-entropy alloys with Al addition (Al x FeCoNiCr; x = 0.0, 0.25, 0.5, 0.75, 1.0, 1.25, 1.75) were prepared by argon arc melting to obtain a special spinodal decomposition structure. There precipitated body-centered cubic (BCC) phase in the face-centered cubic (FCC) phase matrix for the samples with Al (x = 0.25, 0.5, 0.75) addition. Furthermore, the increase in the Al content (x = 1.0, 1.25, 1.75) transformed the alloy into a BCC phase, and resulted in a spinodal decomposition in the alloy. This spinodal decomposition created a low-misfit coherent nanostructure combining the enriching AlNiCo ordered B2 matrix with enriching Fe–Cr BCC disordered nanoprecipitates. The difference in the distribution of chemical elements of the two phases leads to different magnetic properties and induces the magnetoresistance (MR) effect. This provides a pathway for the design of advanced functional high-entropy alloys. [Display omitted] • Spinodal decomposition can induce magnetoresistance (MR) in AlFeCoNiCr alloy. • The magnetic and nonmagnetic phase is necessary condition for inducing MR effect. • The mechanical and MR properties can be controlled by spinodal decomposition. [ABSTRACT FROM AUTHOR]

We synthesized four Fe (67− X) Cr 31 Co X Si 2 (X = 9, 14, 19, and 24 at.%) medium-entropy alloys and investigated the effect of Co on the connection between magnetic properties and spinodal structure. When the value of X was increased from 9 to 14 at.%, both the volume fraction of α 1 phase and the composition difference between α 1 and α 2 phases increased, leading to an increase in coercivity. This increase also resulted in an increase in the size of α 1 phase, leading to a decrease in remanence. When the value of X was increased beyond 14 at.%, both coercivity and remanence were significantly enhanced, even though the volume fraction of the α 1 phase remained unchanged. We attribute this enhancement to (1) intensification of the composition fluctuation in the spinodal structure, (2) increase in lattice misfits, and (3) refinement of the α 1 phase. Our results will be valuable in future magnet design. [Display omitted] [ABSTRACT FROM AUTHOR]

Spinodal decomposition of Ti 1 − x Al x N crystal structure significantly impacts their physical properties, particularly at the atomic scale. In this study, we employed systematic three-dimensional molecular dynamics simulations to understand the process of material removal in TiAlN. Orthogonal simulations were conducted with cutting depth and Al content as variables to analyze their impact on the phase transformation mechanism and the resulting surface finish. The simulations reveal that the aluminum content and depth of cut significantly influence the phase transformation process of supersaturated TiAlN crystals through spinodal decomposition. It is observed that the aluminum content has a maximum stable solubility of approximately 0.6 in TiAlN crystals, above which the system undergoes significant spinodal decomposition during cutting to produce hexagonal phases with lower hardness. Increasing the aluminum content leads to wider phase change and deeper sub-surface damage in the system. On the other hand, the cutting depth will promote phase transformation by affecting the stress distribution, thereby increasing the root mean square roughness of the height profile. [Display omitted] • Simulate the nanoscale cutting and roughness creation in supersaturated TiAlN. • Explore the effect of phase transition in the material removal mechanism in TiAlN. • Investigate the effect of Al content and depth of cut (DoC) on the phase transition. • The specific energy and roughness are functions of Al content and depth of cut. [ABSTRACT FROM AUTHOR]

Just as fine precipitate dispersions are sought for high yield strength in alloys, nanoscale, mixed-phase microstructures are sought for high electromechanical performance in oxide ferroelectric materials. Spinodal decomposition is an effective route to fine-scale alloy microstructures and is exploited commercially, for example, in bronzes. Spinodal decomposition has been linked to nanoscale ferroelectric microstructures, but a comprehensive analysis is missing. Here spinodal decomposition in ferroelectric crystals is analysed in 3D including the local electric field using the ferroelectric multi-phase field model for polymorphic phase boundary (PPB) systems. A polarisation consulate temperature T s p is identified: in single phase ferroelectric, T s p = T c w , and, in PPB ferroelectrics, T c w , ζ = 0 < T s p < T c w , ζ = 1 . The stability of fluctuations in polarisation depends on temperature, is isotropic in wavevector k → , and corresponds to 2D waves in ceramics. General predictions are summarised and specific predictions for single phase and a PPB system (1 − x)Ba(Zr 0.2 Ti 0.8)O 3 - x (Ba 0.7 Ca 0.3)TiO 3 (BZT-xBCT) are made. At 284 K , the minimum wavelength is l c r i t B T = 166 nm in BaTiO 3 and l c r i t P Z T = 1.70 nm in Pb(Zr,Ti)O 3 , suggesting that spinodal decomposition is less likely to be observed in BaTiO 3. For BZT-40BCT, the minimum observable wavelength at T P P B is ∼ 22 unit cells l c r i t B Z T − 40 B C T = 8.72 nm and presents a viable route to nanoscale rhombohedral + tetragonal microstructures. Domain size engineering by spinodal decomposition with controlled grain structures and quenching in oxide and organic ferroelectrics is identified as a new route to optimise performance. [Display omitted] [ABSTRACT FROM AUTHOR]

Understanding the phase stability and precipitation mechanisms is crucial for engineering multiphase nanostructured alloys with optimal mechanical properties. In this work, we studied the formation and temporal evolution of nanoprecipitates and their effect on mechanical properties of an fcc/L2 1 eutectic high-entropy alloy through a combination of experiments and analytical modeling. Aging the alloy at 1023 K results in the precipitation of coherent L1 2 nanoparticles in the fcc phase and coherent bcc nanoparticles in the L2 1 phase, leading to the formation of an fcc/L1 2 + L2 1 /bcc hierarchical structure. Notably, the scanning transmission electron microscopy (STEM) results reveal that the precipitation in both the fcc and L2 1 phases is not through a one-step nucleation, but a two-stage transformation consisting of an initial chemical separation via spinodal decomposition and subsequent structural ordering/disordering. The Gibbs free energy diagrams of the fcc and L2 1 phases were modeled through numerical techniques, and the spinodal decomposition regions of the two systems at different temperatures were calculated. Based on the modeling results, we discussed the phase stability and thermodynamics of spinodal decomposition of the two phases. In addition, the formation of hierarchical structure substantially enhances the strength of the alloy. Modeling of the strengthening mechanisms reveals that the order strengthening of L1 2 nanoparticles plays a major role in enhancing the yield strength of the alloy, whereas the contribution from the bcc nanoparticles can be negligible. Our findings provide insights into the phase stability, precipitation and strengthening mechanisms of hierarchical-structured alloys. [Display omitted] [ABSTRACT FROM AUTHOR]

• Phase separation into niobium-rich and depleted regions were evident after aging for half an hour in the U-13 at.% Nb subjected to aging at 450 °C. • A lath-shaped Nb-rich phase was identified to be more discriminable than the α precipitate in a smaller size, supposing prior precipitation of γ to α. • Applying several recent thermodynamic assessments, a spinodal decomposition mechanism seems unlikely. • The non-classical nucleation theory is suggested to be responsible for the initial precipitation of the Nb-rich phase. Phase separation of the U-Nb (13 at.%) alloy at an aging temperature of 723 K was investigated through transmission electron microscopy. Chemical redistribution initiated from a supersaturated state was identified after aging for half an hour before the discontinuous precipitation (DP) process. Such redistribution was accompanied by a fine two-phase structure and non-lamellar morphology. Among the decomposition products at this early stage, a lath-shaped Nb-rich phase was confirmed to be the bcc (γ) phase, with Nb content in the range of 35∼45 at.%. Meanwhile, discrete regions of much smaller size were detected to bare an Nb content approaching the equilibrium of the α phase. It is envisaged that the γ precipitation was a preceding event of the α. Thermodynamic estimation was carried out to reveal the decomposition mechanism responsible for this unexpected behavior. The results were in favor of a nucleation and growth mechanism over the spinodal decomposition. These results provide a deeper understanding and a new sight into the aging phenomenon of U-13Nb alloys, which are also worth consideration in other binary systems slightly outside the coherent spinodal regions such as Fe-20Cr. [Display omitted] [ABSTRACT FROM AUTHOR]

Phase transition kinetics of aqueous hydroxypropyl cellulose solution was studied by using turbidimetric monitoring and mathematical modelling techniques. Based on the nonlinear Cahn-Hilliard equation with a mobility depending on the component concentration, the phase separation has been modeled on a simple one-dimensional Flory lattice. For value set of the interfacial energy parameter, data were obtained on the changing of the average values of the cluster sizes, their mass and concentration. The simulation results allow us to distinguish three stages of the spinodal decomposition: early, intermediate and final. It was found that for the intermediate stage, the kinetics of the cluster mass growth is described by a dependence that is characteristic of the usual diffusion mass transfer; the change in the average cluster size can be represented by a scaling function with an exponent close to 1/3, typical of the systems with a conserved scalar order parameter. It is shown that the concentration of clusters at the final stage is determined by the temperature dependence of the interfacial energy.

A metastable beta TMZF alloy was tested by isothermal compression under different conditions of deformation temperature (923 to 1173 K), strain rate (0.172, 1.72, and 17.2 s−1), and a constant strain of 0.8. Stress–strain curves, constitutive constants calculations, and microstructural analysis were performed to understand the alloy’s hot working behavior in regards to the softening and hardening mechanisms operating during deformation. The primary softening mechanism was dynamic recovery, promoting dynamic recrystallization delay during deformation at higher temperatures and low strain rates. Mechanical twinning was an essential deformation mechanism of this alloy, being observed on a nanometric scale. Spinodal decomposition evidence was found to occur during hot deformation. Different models of phenomenological constitutive equations were tested to verify the effectiveness of flow stress prediction. The stress exponent n, derived from the strain-compensated Arrhenius-type constitutive model, presented values that point to the occurrence of internal stress at the beginning of the deformation, related to complex interactions of dislocations and dispersed phases.

Refractory metal high entropy superalloys (RSAs) have been heralded as potential new high temperature structural materials. They have nanoscale cuboidal bcc+B2 microstructures that are thought to form on quenching through a spinodal decomposition process driven by the Ta-Zr or Nb-Zr miscibility gaps, followed by ordering of one of the bcc phases. However, it is difficult to isolate the role of different elemental interactions within compositionally complex RSAs. Therefore, in this work the microstructures produced by the Nb-Zr miscibility gap within the compositionally simpler Ti-Nb-Zr constituent system were investigated. A systematic series of alloys with compositions of Ti5NbxZr95−x (x = 25–85 at.%) was studied following quenching from solution heat treatment and long duration thermal exposures at 1000, 900 and 700 °C for 1000 h. During exposures at 900 °C and above the alloys resided in a single bcc phase field. At 700 °C, alloys with 40–75 at.% Nb resided within a three phase bcc + bcc + hcp phase field and a large misfit, 4.7–5%, was present between the two bcc phases. Evidence of nanoscale cuboidal microstructures was not observed, even in slow cooled samples. Whilst it was not possible to conclusively determine whether a spinodal decomposition occurs within this ternary system, these insights suggest that Nb-Zr interactions may not play a significant role in the formation of the nanoscale cuboidal RSA microstructures during cooling.

To study the thermal aging of nuclear primary pipe material 316LN stainless steel weld, accelerated thermal aging experiment was performed at 400℃ for 15000h. Microstructure evolution of weld after aging was investigated by TEM and HREM. Impact properties of weld thermally aged at different time was measured by Charpy impact test. Meanwhile, taking Charpy impact energy as the standard of thermal aging embrittlement, the thermal kinetics formula was obtained by the fitting method. Finally, the Charpy impact properties of the weld during 60 years of service at the actual operation temperature were estimated by the thermal kinetics formula. The results indicate that the spinodal decomposition occurs in the ferrite of the weld after thermal aging at 400℃ for 1000h, results in α (Fe-rich) and α'(Cr-rich) phases, and meanwhile, the G-phase is precipitated in the ferrite; the spinodal decomposition and the G-phase precipitation lead to the decrease in the impact energy of weld as time prolongs; the prediction results show that the Charpy impact energy of weld decreases quickly in the early 25 years, and then undergoes a slow decrease during the subsequent operation process.

The phase field model based on the nonlinear Cahn-Hilliard equation was applied to analyze the spinodal decomposition process in Al-Zn and Al-Zn-Cu alloys. Partial differential equations were solved using the explicit finite difference method for the Al- 20, and 35 at. % Zn alloys aged at temperatures between 25 and 100 °C for times from 10 s to 2000 s and Al-20at.%Zn-10at.%Cu and Al-20at.%Zn-5at.%Cu alloys at temperatures between 400 and 500 °C for times from 3600 to 360000 s. Thermo-Calc indicated that the copper addition extends the presence of the metastable miscibility gap up to a temperature of about 597 °C in comparison to the temperature of 350 °C for the binary case. This miscibility gap was calculated assuming that the equilibrium phases were not present and thus it is only existing at the early stages of aging. Simulation results pointed out that the phase decomposition process is much faster in the binary alloys than that in the ternary alloys in spite of the higher aging temperature for the latter case.

A critical thermodynamic assessment of the metastable c-TiAlZrN coatings, which are reported to spinodally decompose into triple domains, i.e., c-TiN, c-AlN, and c-ZrN, was performed via the CALculation of PHAse Diagram (CALPHAD) technique based on the limited experimental data as well as the first-principles computed free energies. The metastable c-TiAlZrN coatings were modeled as a pseudo-ternary phase consisting of c-TiN, c-AlN and c-ZrN species, and described using the substitutional solution model. The thermodynamic descriptions for the three boundary binaries were directly taken from either the CALPHAD assessment or the first-principles results available in the literature except for a re-adjustment of the pseudo-binary c-AlN/c-ZrN system based on the experimental phase equilibria in the pseudo-ternary system. The good agreement between the calculated phase equilibria and the experimental data over the wide temperature range was obtained, validating the reliability of the presently obtained thermodynamic descriptions for the c-TiAlZrN system. Based on the present thermodynamic description, different phase diagrams and thermodynamic properties can be easily predicted. It is anticipated that the present thermodynamic description of the metastable c-TiAlZrN coatings can serve as the important input for the later quantitative description of the microstructure evolution during service life.

Cellulose derivate phase separation in thin films was applied to generate patterned films with distinct surface morphology. Patterned polymer thin films are utilized in electronics, optics, and biotechnology but films based on bio-polymers are scarce. Film formation, roughness, wetting, and patterning are often investigated when it comes to characterization of the films. Frictional properties, on the other hand, have not been studied extensively. We extend the fundamental understanding of spin coated complex cellulose blend films via revealing their surface friction using Friction Force Microscopy (FFM). Two cellulose derivatives were transformed into two-phase blend films with one phase comprising trimethyl silyl cellulose (TMSC) regenerated to cellulose with hydroxyl groups exposed to the film surface. Adjusting the volume fraction of the spin coating solution resulted in variation of the surface fraction with the other, hydroxypropylcellulose stearate (HPCE) phase. The film morphology confirmed lateral and vertical separation and was translated into effective surface fraction. Phase separation as well as regeneration contributed to the surface morphology resulting in roughness variation of the blend films from 1.1 to 19.8 nm depending on the film composition. Friction analysis was successfully established, and then revealed that the friction coefficient of the films could be tuned and the blend films exhibited lowered friction force coefficient compared to the single-component films. Protein affinity of the films was investigated with bovine serum albumin (BSA) and depended mainly on the surface free energy (SFE) while no direct correlation with roughness or friction was found. BSA adsorption on film formed with 1:1 spinning solution volume ratio was an outlier and exhibited unexpected minimum in adsorption.

The multi-layer composite development primarily aims to develop and test the components of the next generation of hadron colliders (e.g., Large Hadron Collider - LHC) consisting of superconducting raw materials. Multilayer sheet is very similar to the commonly used NbTi wire products, a 2D version of the commercial wire. These composites consist of layers such as NbTi superconductor, Nb diffusion barrier (between NbTi and Cu) and Cu stabilizer. In β-NbTi superconducting alloys, α-Ti precipitates are primary flux pinning centers that maintain stable superconductivity. A multi-step series of heat treatments and cold-forming processes can develop the flux pinning centers. Practically, this process means three heat treatments of constant period and temperature and drawing or rolling between the heat treatments. The study aimed to describe the behavior of the cold-rolled (ε = 3.35) Nb53Ti47w% alloys during isothermal heating at 673 K as a function of heating time. The processes during the aging were investigated by the in-situ XRD method in the heating chamber. The X-ray diffraction patterns were evaluated by Rietveld refinement. The thermally activated spinodal decomposition and precipitation processes were described based on the phases identified at the individual heat treatment steps and their lattice parameters. The in-situ study also revealed an increase in α-Ti precipitation with time and decomposition that co-occurs. This is the basic study that prepares the applicability of the alloy., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Erzsebet Nagy reports financial support was provided by 10.13039/501100003825Hungarian Academy of Sciences. Viktor Karpati reports financial support was provided by 10.13039/501100015498Ministry for Innovation and Technology Hungary. Erzsebet Nagy reports financial support was provided by 10.13039/501100015498Ministry for Innovation and Technology Hungary. Valeria Mertinger reports a relationship with 10.13039/100012470CERN that includes: non-financial support. Non financial cooperation agreement between the University of Miskolc and CERN (2019) for the development and testing of components of the Large Hadron Collider - LHC, consisting of superconducting materials. Non financial cooperation between the Institute of Physical Metallurgy, Metalforming and Nanotechnology of the University of Miskolc and the MTA Wigner Physics Research Center on the development of functional multi-layer composite structures., (© 2024 The Authors.)

The best research-cell efficiency of perovskite solar cells (PSCs) is comparable with that of mature silicon solar cells (SSCs); However, the industrial development of PSCs lags far behind SSCs. PSC is a multiphase and multicomponent system, whose consequent interfacial energy loss and carrier loss seriously affect the performance and stability of devices. Here, by using spinodal decomposition, a spontaneous solid phase segregation process, in situ introduces a poly(3-hexylthiophene)/perovskite (P3HT/PVK) heterointerface with interpenetrating structure in PSCs. The P3HT/PVK heterointerface tunes the energy alignment, thereby reducing the energy loss at the interface; The P3HT/PVK interpenetrating structure bridges a transport channel, thus decreasing the carrier loss at the interface. The simultaneous mitigation of energy and carrier losses by P3HT/PVK heterointerface enables n-i-p geometry device a power conversion efficiency of 24.53% (certified 23.94%) and excellent stability. These findings demonstrate an ingenious strategy to optimize the performance of PSCs by heterointerface via Spinodal decomposition., (© 2023 Wiley-VCH GmbH.)

Nanoscale concentration modulation (CM) is a novel and effective approach of manipulating martensitic transformations (MTs) for developing next-generation high-performance shape memory alloys (SMAs). Spinodal decomposition is one of the most economic methods to obtain bulk compositionally modulated materials for practical applications. The wavelength, amplitude, and statistical distribution of CM generated by spinodal decomposition are tunable via adjusting the aging temperature, or the aging time. However, how these features influence the effect of CM on MTs still remains largely unexplored. In this study, theoretical analyses and computer simulations are combined to dissect the influence of these features on the kinetic process of MTs and mechanical properties of SMAs. The findings of this study provide insights and guidance on the design of SMAs for desired mechanical properties via CM engineering. Moreover, the findings are applicable to not only SMAs but also other materials that have MTs, e.g. steels and high-entropy alloys. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The phase and structural transformations of a powder hard magnetic alloy of the Fe–30% Cr–27% Co–1% Si–0.07% B system with a metastable α1 + α2 phase composition, elevated cobalt content, and high level of magnetic properties are studied. The density and variation coefficient of the concentration of main elements of sintered billets at a level of deformable analogs are attained by sintering in the α phase with contact melting in the presence of a "vanishing" liquid phase formed due to the addition of silicon and boron ferroalloys. A kinetic approach to the development of a competitive hard magnetic alloy with a high fraction of a strong magnetic phase is proposed. The influence of boron additives on the incubation period of the formation of the undesirable σ phase and the temperature range of the concentration stratification of the α solid solution into the strong magnetic α1 phase and weak magnetic α2 phase are established. Optical microscopy, X-ray phase analysis, and differential scanning calorimetry are used to determine the temperature–temporal parameters of the thermal treatment of the alloy, including quenching, thermomagnetic treatment (TMT), and final aging, which provide the required combination of Hc and Br due to an increase in stability of a metastable α phase up to 20 min in a temperature range of spinodal decomposition α → α1 + α2. The largest increase in magnetic properties after TMT observed at the first and second stages of final aging is associated with the supplementary decomposition of the α solid solution and the formation of subgrain boundaries. Elements of the formed structure have submicron and nanometer sizes that correlate with the results of studying the deformable alloys based on the Fe–Cr–Co system. The anisotropic α1 + α2 structural state attained by thermomagnetic treatment provides an increase in characteristics of magnetic properties of the studied 30Kh27KSRA powder alloy to 30% and squareness ratio of the magnetic hysteresis loop of 0.82. [ABSTRACT FROM AUTHOR]

Due to its excellent resistance to high temperature oxidation and steam corrosion, FeCrAl alloys have received much attention recently as a highly potential candidate cladding material for light water reactors. However, under the effect of thermal aging and neutron irradiation applied in reactor, the nanoscale brittle precipitates will occur in the ferritic FeCrAl alloys after spinodal decomposition due to the presence of Cr, which greatly increase the hardness and reduce the toughness of the material, thus seriously affecting the operation of the nuclear reactor. In this work, the alloy after heat aging was treated by pulsed electric current at room temperature. The micro-hardness and electrical properties of the aged alloy are greatly restored. In addition, compared with the heat treatment at the same temperature, the dissolution time of precipitates in aged alloys into the matrix is reduced by 10 times by electropulsing treatment with higher parameters. In comparison to the ex-situ conventional annealing treatment, this in-situ pulsed treatment can be used as a novel efficient and convenient method to repair the performance degradation of aged materials. Based on the thermodynamic and kinetics, electric pulses reduces the thermodynamic barrier for precipitation dissolution and increases the atomic diffusion rate. • The properties of the aged FeCrAl alloy after the pulse treatment were significantly restored. • Reducing the critical dissolution temperature of the brittle precipitates by a large margin under electropulsing. • Electropulsing treatment dramatically accelerate the dissolution of the precipitates. • Electric pulses reduces the thermodynamic barrier for precipitation dissolution and increases the atomic diffusion rate. [ABSTRACT FROM AUTHOR]

Elemental segregation to grain boundaries (GBs) can induce structural and chemical transitions at GBs along with significant changes in material properties. The presence of multiple principal elements interacting in high-entropy alloys (HEAs) makes the GB segregation and interfacial phase transformation a rather challenging subject to investigate. Here, we explored the temporal evolution of the chemistry for general high-angle GBs in a typical equiatomic FeMnNiCoCr HEA during aging heat treatment through detailed atom probe tomography (APT) analysis. We found that the five principal elements segregate heterogeneously at the GBs. More specifically, Ni and Mn co-segregate to some regions of the GBs along with the depletion of Fe, Co and Cr, while Cr is enriched in other regions of the GBs where Ni and Mn are depleted. The redistribution of these elements on the GBs follow a periodic characteristic, spinodal-like compositional modulation. The accumulation of elements at the GBs can create local compositions by shifting their state from a solid solution (like in the adjacent bulk region) into a spinodal regime to promote interfacial phase-like transitions as segregation proceeds. These results not only shed light on phase precursor states and the associated nucleation mechanism at GBs in alloy systems with multiple principal elements but also help to guide the microstructure design of advanced HEAs in which formation of embrittling phases at interfaces must be avoided. Image 1 [ABSTRACT FROM AUTHOR]

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We develop a phase-field model, integrating both micromagnetic and microelastic approaches. The model can capture the impact of eigen strain, applied stress and elastic inhomogeneity on the microstructure evolution in presence of an externally applied magnetic field. We use the model to simulate bicontinuous microstructure evolution during spinodal decomposition, with co-existing paramagnetic and ferromagnetic phases. The simulations confirm that the ferromagnetic phase tends to align itself in the direction of the applied magnetic field. Depending on elastic inhomogeneity, we also observe preferential alignment parallel or perpendicular to the applied stress. When these two fields are applied together, the alignment of the phases can precisely be controlled by changing strength and direction of either of the two. Image 1 • Microstructure evolution in a two phase binary alloy is studied using phase-field simulations. • The effect of magnetic and elastic fields on the microstructure evolution is investigated. • The interplay between these two fields, when acting simultaneously, provides an insight into controlling the microstructure evolution. • Detailed parametric analysis gives a complete picture of eigen strain, applied stress and elastic inhomogeneity contributions. [ABSTRACT FROM AUTHOR]

A solution may be in one of three states: stable, unstable, or metastable. If the solution is unstable, phase separation is spontaneous and proceeds by spinodal decomposition. If the solution is metastable, the solution must overcome an activation barrier for phase separation to proceed spontaneously. This mechanism is called nucleation and growth. Manipulating morphology using phase separation has been of great research interest because of its practical use to fabricate functional materials. The Cahn-Hilliard theory, incorporating Flory-Huggins free energy, has been used widely and successfully to model phase separation by spinodal decomposition in the unstable region. This model is used in this paper to mathematically model and numerically simulate the phase separation by nucleation and growth in the metastable state for a binary solution. Our numerical results indicate that Cahn-Hilliard theory is able to predict phase separation in the metastable region but in a region near the spinodal line. [ABSTRACT FROM AUTHOR]

Ti 1− x − y Al x Zr y N cubic alloys within the 25–70% Al composition range have high age-hardening capabilities due to metastable phase transition pathways at high temperatures. They are thus ideal candidates for ultra-hard nano-coating materials. There is growing evidence that this effect is associated with the elasto-chemical field-induced phase separation into compositionally-segregated nanocrystalline nitride phases. Here, we studied the microstructural evolution in this pseudo-ternary system within spinodal regions at 1200 °C by using an elasto-chemical phase field model. Our simulations indicate that elastic interactions between nitride nano-domains greatly affect not only the morphology of the microstructure but also the local chemical phase equilibria. In Al-rich regions of the composition space we further observe the onset of the transformation of AlN-rich phases into their equilibrium wurtzite crystal structure. This work points to a wide palette of microstructures potentially accessible to these nitride systems and their tailoring is likely to result in significant improvements in the performance of transition metal nitride-based coating materials. Image 1 [ABSTRACT FROM AUTHOR]

In recent years, nanolamellar aluminum-rich face-centered cubic (fcc) Ti 1-x Al x N coatings with x as high as 0.8–0.9 grown by thermal chemical vapor deposition (CVD) have been investigated extensively. However, detailed information about their microstructure characteristics, local chemical composition and phase stability at elevated temperatures is still missing. Thus, within the present work, the temperature-induced microstructural changes of a nanolamellar fcc-Ti 0.2 Al 0.8 N coating, synthesized by thermal CVD at ∼790 °C, were studied up to temperatures of 1300 °C. In situ high-temperature X-ray powder diffraction and differential scanning calorimetry were employed to follow the phase evolution at elevated temperatures. Scanning electron microscopy and electron backscatter diffraction, carried out ex situ for six different microstructural states after isothermal annealing, revealed the distribution of individual phases and morphology of different phase regions. Complementary atom probe tomography as well as transmission electron microscopy experiments were performed on the as-deposited, an intermediate and the final decomposed and transformed state. The results provided 3D elemental information as well as detailed morphology, phase and orientation information of the respective samples. In the as-deposited state, the coating was characterized by columnar, relatively large fcc grains exhibiting a nanolamellar microstructure. Decomposition of initially supersaturated fcc-Ti 1-x Al x N was detected at temperatures of ∼900–1000 °C. Transformation of metastable Al-rich fcc regions into the thermodynamically stable wurtzitic modification started at ∼1000 °C and persisted up to ∼1175 °C. In this temperature range, intact nanolamellar fcc areas coexisted with fully decomposed and transformed regions, leading to a constant reduction of the fcc fraction with increasing temperature. At temperatures above ∼1175 °C, the coating was fully decomposed and transformed into fcc-TiN and w-AlN. The obtained findings provide a detailed description of the decomposition and transformation behavior of nanolamellar CVD fcc-Ti 1-x Al x N coatings, which significantly contributes to the fundamental understanding of this complex coating system. Image 1 [ABSTRACT FROM AUTHOR]

In-service thermal aging of CF8M cast austenitic stainless steel was investigated in materials removed from the steam generator inlet and crossover elbows of the Ringhals 2 pressurized water reactor nuclear power plant unit after approximately 92kh of full operating time. The thermal aging of these materials was investigated using the double loop electrochemical potentiokinetic reactivation method, coupled with indentation hardness measurements and microstructural characterizations, to identify correlations between the electrochemical behavior and traditional methods of investigating thermal aging embrittlement effects in cast stainless steels. While this electrochemical method can be easily employed to quantify thermal aging effects in materials aged at higher temperatures (e.g. greater than 350∘C), this study highlights the difficulties encountered when electrochemically evaluating the aging of materials exposed to nuclear power plant operating conditions. [ABSTRACT FROM AUTHOR]

Brillouin and NMR spectroscopy were used to explore transitions in the structuring of liquid binary mixtures composed of water and a deep eutectic solvent (DES) known as malicine and composed of malic acid (MA) and choline chloride (ChCl). Malicine/H 2 O binary mixtures were studied for DES contents ranging from 100 to 40 wt%. Data representation of sound propagation velocities – obtained from Brillouin spectroscopy – versus DES content exhibited two well-differentiated linear regimes above and below ca. 70 DES wt% while transitioning from a "water-in-DES" system to a "DES-in-water" one along with dilution. Two linear regimes intersecting at ca. 70 DES wt% were also observed when representing the self-diffusion coefficients versus malicine contents, with MA and ChCl – and even water – exhibiting nearly identical self-diffusion coefficients for contents above 70 wt%, that diverged for contents below 70 wt%. Interestingly, further insights about this behaviour were provided by spin-lattice relaxation time of MA, also revealing the occurrence of hydrophobic hydration around non-polar moieties as in other aqueous binary mixtures of non-ionic H-bond co-solvents – e.g., DMSO:H 2 O or dioxane:water. Unlabelled Image • Two well-differentiated systems in aqueous dilutions of malicine • Water-in-DES system becomes a DES-in-water one along with dilution. • Brillouin and NMR spectroscopies point to the dilution range for transition. • Water as a secondary HBD molecule – besides ChCl – in the water-in-DES system [ABSTRACT FROM AUTHOR]

• Side bands in diffraction and striations in real space were recorded from Ti-15Mo. • Evidence for phase separation by spinodal decomposition has been established. • Spinodal waves of 1.3 nm appear in Mo-enriched regions. • The ω phase forms in regions without undulation, presumably Mo-lean regions. • Two different types of nano instabilities occur simultaneously in quenched Ti-15Mo. Electron diffraction effect associated with nano-scale periodic modulations observed in a quenched Ti-15 wt%Mo alloy within ω phase forming regime has been investigated in this study by analyzing selected area diffraction patterns and high-resolution phase contrast images. Crystallographic direction of the side bands in electron diffraction associated with the periodic modulation of wavelength 1.3 nm is established as [001] β which is an elastically soft direction for the body-centered cubic lattice. Characteristics of the side bands in the diffraction patterns, such as the correlation of spacing of satellite spots with real-space modulation wavelength and the constancy in the direction of satellites and modulations are interpreted as the proof of phase separation by spinodal decomposition. The striations associated with spinodal decomposition form only in Mo-enriched regions of dimensions ˜ 20 nm distributed throughout the β matrix. Accordingly, in this study, two varieties of compositional modulations that appear in the matrix are experimentally illustrated: (1) Mo-depleted and Mo-enriched domains of 10–20 nm size, and (2) The anisotropic compositional modulation by spinodal decomposition in [001] β direction with a modulation wavelength of 1.3 nm occurring in Mo-enriched pockets. It is confirmed that the structural modulations and ω phase formation occurs only in the regions without striations (Mo-lean regions). By analyzing the diffraction spots, it is also shown that the ω phase does not undergo any phase separation by spinodal decomposition. [ABSTRACT FROM AUTHOR]