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High-entropy alloys (HEAs) have attracted widespread attention from scholars as a new type of material employed in extreme environments. However, as a main kind of HEAs, many face-centered cubic single-phase HEAs are restricted in industrial applications due to their lower yield strength and high cost when containing expensive elements such as Co. In this study, dispersion strengthening by heat treatment was introduced in low-cost Co-free Fe40Mn20Cr20Ni20 HEA to improve its strength, and its high-temperature tensile behavior and constitutive model were studied to explore its potential application at high temperatures. It is found that when subjected to quasi-static room-temperature stretching, the heat-treated sample exhibits a yield strength of 534 MPa and a tensile plasticity of 26.8%. In addition, the tensile behavior of samples after heat treatment was investigated at high temperature (573–873 K) and low strain rate (10−3–10−1 s−1). The results suggest that the yield strength decreases with increasing temperature and decreasing strain rate. Moreover, at 873 K and 10−3 s−1, the electron backscatter diffraction system and x-ray diffraction results of the deformed sample indicate that the softening curve is driven from the recovery of materials. Finally, the flow stress was predicted using the Arrhenius equation and Artificial Neural Network model (ANN), and the two models were assessed using the average absolute relative error and coefficient of correlation (R). The results showed that the ANN had higher accuracy. [ABSTRACT FROM AUTHOR]

Magnetocaloric properties of hexagonally structured Mn 5 − x Fe x Ge 3 (x = 0.15 , 0.3, and 0.5) alloys have been investigated using DC magnetization and heat capacity measurements. The maxima of entropy change, − Δ S m max ∼ 5.04 (5.57) J/kg K, along with an adiabatic temperature change of Δ T a d max ∼ 5.05 (7.25) K was observed for x = 0.15 (0.5) at an applied magnetic field H = 5 T. With the scaling analysis of − Δ S m , the rescaled curves collapse onto a single universal curve anticipated by the mean-field theory, revealing a second-order type of magnetic transition. Furthermore, − Δ S m max follows a power law of H n with n = 0.597 (3) , 0.591(3), and 0.586(3) for Mn 5 − x Fe x Ge 3 (x = 0.15 , 0.3, and 0.5) alloys, respectively. The refrigerant capacity (RC) is increased from 400 J/kg (for x = 0.15) to 420 J/kg (for x = 0.5) with Fe doping in Mn 5 Ge 3. Moreover, the coefficient of refrigerant performance (CRP) enhances with Fe doping from 0.06 (for x = 0.15) to 0.1 (for x = 0.5). Thus, high RC and reasonable CRP values for earth-abundant Mn-based Mn–Fe–Ge alloys promise the potential to replace the high-cost rare-earth (Gd) and heavy metal-based metallic magnetocaloric systems for use in environment-friendly magnetic refrigeration technology. [ABSTRACT FROM AUTHOR]

By employing a recently proposed Hubbard U density-corrected scheme within density functional theory, we provide design principles towards the design of materials exhibiting a spin crossover-assisted gas release. Small molecular fragments are used as case study to identify two main mechanisms behind the change in binding energy upon spin transitions. The feasibility of the proposed mechanism in porous crystals is assessed by correlating the change in binding energy of CO2, CO, N2, and H2, upon spin crossover, with the adiabatic energy difference associated with the spin state change of the square-planar metal in Hofmann-type clathrates (M = Fe, Mn, Ni). A few promising cases are identified for the adsorption of intermediate ligand field strength molecules such as N2 and H2. The latter stands out as the most original result as the strong interaction in low spin, as expected from a Kubas mechanism, results in a large change in binding energy. This work provides a general perspective towards the engineering of open-metal site frameworks exhibiting local environments designed to have a spin crossover upon adsorption of specific gas molecules. [ABSTRACT FROM AUTHOR]

L10-MnAl exhibits excellent magnetic properties and could be used as a candidate to fill the gap between hard ferrite and rare-earth based permanent magnet (PM) applications. However, one of the major problems with L10-MnAl is that the structure is metastable and decomposes to other structural phases at higher temperature. Therefore, enhancing the structure stability of L10-MnAl is essential for PM applications. We studied the prospect of improving the structural stability and increasing the uniaxial magnetic anisotropy energy (K u) of the L10-MnAl structure in this work. It is found that C-doping at the 1d interstitial site enhanced the structure stability of the compound. Moreover, Fe substitution on Mn sites shows a significant increase in the uniaxial magnetic anisotropy energy (K u). Therefore, the electronic structure and magnetic properties of L10-ordered Mn1−xFexAlC (x = 0, 0.125, 0.250, 0.375, 0.50, 0.625, 0.75, and 0.87) alloys are investigated by using the first-principles calculations. The results show that x = 0.375 Fe content in the L10-MnAl alloy and 6% doping of C maintained the structural stability and provided a maximum value of K u = 2.13 (MJ/m3), which is 25% higher than for the pristine L10-MnAl, making it suitable for permanent magnet applications. [ABSTRACT FROM AUTHOR]

Dynamic recrystallization (DRX) is a widely observed phenomenon in metals and alloys during hot deformation. However, a comprehensive understanding of the mechanisms and microstructural evolution of DRX at extremely high strain rates is still lacking. In this study, we present a new mechanism, termed planar fault-assisted dynamic recrystallization (pfDRX), which was identified by simulating the cold spray of copper (Cu) at high strain rates using molecular dynamics. Our findings indicate that planar faults, such as nanotwins, stacking faults, hexagonal close-packed martensites, and local slip, play a dominant role in the initial deformation of Cu during high velocity impacts in columnar-like quasi-two-dimensional samples where deformations are primarily limited to in-plane slip. Furthermore, subsequent slip events interact with pre-existing planar faults, triggering the formation of new grains via a common interaction-amorphization-nucleation-growth pfDRX mechanism. We systematically varied temperature and strain rates to determine the optimal conditions for pfDRX. This study offers valuable insights into novel DRX mechanisms in face-centered cubic metals at high strain rates and provides guidance for future experimental research. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the corrosion behavior of cold-rolled Fe35Ni20Cr12Mn(28-x)Alx high-entropy alloys (HEAs) using the potentiodynamic polarization technique in 1 M H2SO4 acid. Additionally, the influence of molybdenum (Mo) additions as inhibitors and the effect of variations in cold rolling reduction ratios and Al content on corrosion behavior are examined. Design/methodology/approach: Two cold rolling reduction ratios, namely, 50% (R50) and 90% (R90), were examined for the cold-rolled Fe35Ni20Cr12Mn28Al5 (Al5) and Fe35Ni20Cr12Mn23Al10 (Al10) HEAs. Mo inhibitor additions were introduced at varying concentrations of 0.3, 0.6 and 0.9 Wt.%. The potentiodynamic polarization technique was used to evaluate the corrosion rates (CRs) under different experimental conditions. Findings: The results indicate that the addition of 0.3 Wt.% Mo in 1 M H2SO4 yielded the lowest CR for both R50 and R90, irrespective of the Al content in the HEAs. However, the highest CR was observed at 0.6 Wt.% Mo addition. Furthermore, increasing the concentration of Al resulted in a corresponding rise in the CR. Comparatively, the CR decreased significantly when the cold rolling reduction ratio increased from R50 to R90. Originality/value: This research provides valuable insights into the intricate relationship between Mo inhibitors, cold rolling reduction ratio, Al content and the resulting corrosion behavior of Fe35Ni20Cr12Mn(28-x)Alx HEAs. The comprehensive analysis of corroded HEAs, including surface morphology, compositions and elemental distribution mapping, contributes to the understanding of the corrosion mechanisms and offers potential strategies for enhancing the corrosion behavior of HEAs. [ABSTRACT FROM AUTHOR]

Directed energy deposition (DED) provides the possibility of high-throughput synthesis by controlling the multi-channel powder feeders. However, the compositional accuracy of the targeted alloy is of concern due to the difficulty of adjusting the proportions. In this work, we present a method to improve the adjustment accuracy of the high-throughput DED technology by replacing the elemental powder with pre-alloyed powder, and binary Al–Mn alloys with different compositions were synthesized with a composition step of 1 wt.%. The effect of Mn content on the microstructure and mechanical properties of the alloys was characterized and analyzed, and the relationship between the Al6Mn phase and the yield strength was established. The results showed that the microstructures of DED-ed Al–Mn alloys are composed of Al and Al6Mn phases with Mn contents in the range of 2–10 wt.%. The Al–Mn alloy reaches a tensile strength of 165 MPa and maintains an elongation of 9% at Mn content of 4 wt.%. The improved controlling accuracy of composition step to 1 wt.% by pre-alloyed powder in this work provides a paradigm for high-throughput discovery of high-performance alloys. [ABSTRACT FROM AUTHOR]

The study systematically examined how Mn impacts the precipitates and mechanical properties of 6082 aluminum alloy during the peak state of artificial aging following various natural aging durations, elucidating the underlying mechanisms. It is found that α-Al(Mn,Fe)Si precipitated during homogenization is less in amount in the alloy with lower Mn content, resulting in the less consumption of Si and a lower real Mg/Si ratio to create a relatively Si-rich environment in matrix. The Si-rich environment promotes the nucleation of the precipitates, so that the low Mn alloy precipitates more and finer precipitates in the artificial aging process, and has higher strength than the high Mn alloy. Additionally, it is also found that with the increase of natural aging time, the precipitates of 6082 aluminum alloy are significantly coarsening, and the alloy with lower Mn content can better resist the coarsening process of the precipitates, so that the strength of the alloy decreases more slowly than that of higher Mn alloys, and the negative effects of natural aging are lighter. [ABSTRACT FROM AUTHOR]

The challenges posed by volatile organic compound (VOC) emissions in iron ore sintering flue gas are significant. La-based perovskite catalysts offer a promising solution for efficiently degrading VOCs. In this study, a series of LaBO3 (B = Cu, Fe, Cr, Mn, Co) perovskite catalysts were synthesized using the sol-gel method. The influence of various B-site elements on the catalyst's structure and surface chemical properties was thoroughly examined. Simulations were conducted to assess the VOC reduction capabilities of these catalysts under conditions mimicking sintering flue gas composition. It was found that the crystallite size of the perovskite catalyst decreases as the ionic radius of the B-site elements increases, while the specific surface area, total pore volume, and average pore size increase correspondingly. Notably, LaCoO3 and LaMnO3 demonstrated exceptional activity, attributed primarily to their elevated surface oxygen concentration and oxygen migration capability, positioning them as highly promising materials for further development. Furthermore, a proposed mechanism elucidates the La-based perovskite catalytic reduction of toluene, wherein lattice oxygen and adsorbed oxygen undergo mutual conversion during the oxidation process. This mechanism aligns with the L-H and M-v-K models, providing a comprehensive understanding of the catalytic process. [ABSTRACT FROM AUTHOR]

The alloy 50Ag−50Mn (wt.%) was prepared using ball milling. After 50 h of milling, the samples were isothermally annealed for 1 h at a time at three different temperatures ranging from 350∘C to 550∘C. By analyzing the X-ray diffraction data, Rietveld refinement structure analysis was used to measure the lattice strain and crystallite size. The introduction of lattice strain and the decrease in crystallite size as a function of milling time may both contribute to the increase in coercivity. The analysis of superconducting quantum interference devices demonstrates the soft ferromagnetic behavior of as-milled and annealed Ag−Mn alloy. After being annealed at 350∘C for 1 h, the 50Ag−50Mn alloy's maximum coercivity was discovered to be 253 Oe. [ABSTRACT FROM AUTHOR]

Soft magnetic high entropy alloys (HEAs) have great potential to be used as industrial material because of their good magnetic properties and balanced mechanical, electrical, and corrosion resistance properties. To further optimize high saturation magnetization (Ms) along with other functional properties, it is critical to understand the effect of Mn, Cu, and Al on the magnetic properties and phase evolution of FeCoNi-based magnetic HEAs. In the present study, a combinatorial approach is adopted to optimize the magnetic properties of Co35 Fe10Ni30Ti20M5 (M = Mn, Cu, and Al) HEA through the variation of a single alloying element and its effects on the phase evolution, microstructure, and magnetic properties. Co35Fe10Ni30Ti20Mn5, Co35Fe10Ni30Ti20Cu5, and Co35 Fe10Ni30Ti20Al5 high entropy alloys were synthesized through mechanical alloying, and the as-synthesized HEAs were comprised of fcc and bcc solid solution phases. The as-synthesized Co35Fe10Ni30Ti20Mn5, Co35Fe10Ni30Ti20Cu5, and Co35Fe10Ni30Ti20Al5 HEAs have the value of saturation magnetization (Ms)- 81, 85 & 79 emu/g and coercivity (Hc)- 18, 28 & 27 Oe respectively. The phase stability of the developed alloys was also investigated through vacuum annealing at 700°C for 2 h duration. After vacuum annealing, both the Ms and Hc increased to 90 emu/g & 37 Oe, 105 emu/g & 43 Oe, and 104 emu/g & 46 Oe, respectively, for Mn, Cu, and Al – containing Co35Fe10Ni30Ti20M5 (M = Mn, Cu, and Al) HEAs. The present study provides a detailed insight into how the variation of a single alloying element and the annealing temperature significantly affect the magnetic properties of CoFeNiTi-based HEA. [ABSTRACT FROM AUTHOR]

We report here the FTIR, optical, and magnetic properties of Sn 1-x-y Zn x M y O z ceramics with various x, y, and M. The pure samples are called S1, S2, and S3 for ZnO, SnO 2 , and SnZn. The co-substituted samples are called S4, S5, S6, and S7 for SnZnFe, SnZnCo, SnZnNi, and SnZnMn, with Zn = 0.50, Sn = 0.25, and M = 0.25. The Young's modulus, was decreased from 5.70 (D/cm2) for S3 to 4.59, 3.14, 2.59, and 3.05 (D/cm2) for S4, S5, S6, and S7. The E g was decreased from 2.13 eV for S3 to 2.16, 2,2, and 1.6 eV for S4, S5, S6, and S7. The pure samples (S1–S3) exhibit ferromagnetic behavior at 300 K, and combination of paramagnetic and ferromagnetic behaviors at 10K. In contrast, the samples (S4–S7) exhibit a combination of paramagnetic and ferromagnetic behaviours at both temperatures. The Curie temperature (T c) obtained through zero-field cooling (ZFC) and field cooling (FC) is close to 300 K for S1–S3, S5, S6, 200 K for S4, and 20 K for S7. The real saturated magnetization (M s) of the ZnO sample was decreased by the addition of SnO 2 , and then increased by the addition of Mn, Ni, Fe, and Co sequentially. M s was increased from 12.31 (emu/g) for S3 at 300 to 16.24, 31.04, 27.27, and 10.49 (emu/g) for S4, S5, S6, and S7, and from 16 (emu/g) to 87, 730, 83, and 29 at 10 K. Remnant magnetization (M r) decreases with the addition of SnO 2 to ZnO and is not affected by the addition of TMs, just in the case of Co, where it increases. The coercive field decreases, but the switching field increases markedly with the addition of Mn and Ni, transforming the system from a hard magnetization to a soft magnetization system. [ABSTRACT FROM AUTHOR]

The addition of alloying elements to the steel matrix during the preparation process can significantly affect the properties of TiC reinforced steel matrix composites. In this study, the effects of Mn on the electronic structure and crystal structure stability of Fe supercells, along with as well as the stability of the TiC/Fe(Mn) interface, were analyzed through first-principles calculations. Additionally, 8 vol% TiC/Fe–C composites were prepared through the master alloy method. The effects of Mn contents (0, 0.8, 1.2, 1.6, and 2.0 wt%) on the interface mismatch and mechanical properties of the composites were investigated. The results revealed that Mn formed a solid solution and generated a stronger Fe–Mn bond compared with the Fe–Fe bond, and no interface chemical reaction occurred. The addition of a small amount of Mn improved the interface bonding between TiC particles and the steel matrix. The TiC particles were uniformly distributed in the matrix at the grain boundaries, with only a small amount dispersed within the grains. The TiC particles and steel matrix exhibited excellent, continuous, and stable interface bonding. The addition of Mn reduced the interface mismatch between TiC particles and the matrix. As the Mn content increased, the tensile strength and elongation of the composites first increased and then decreased, while the hardness of the composites increased. The addition of 1.2 wt% Mn resulted in an increase in the tensile strength, elongation, and hardness of the composite by 1160 MPa, 7.3%, and 43 HRC, respectively. These values were 109.8%, 151.7%, and 31.1% higher than those of the composite without Mn addition. However, an excess of Mn led to severe distortion of the Fe lattice and clustering at the interface, resulting in the degradation of the mechanical properties in the composites. [ABSTRACT FROM AUTHOR]

Defect engineering via doping exhibits considerable potential for improving the performance of environment-friendly lead-free piezoelectric materials. Owing to the susceptibility to lattice vibrations and the micro-local chemical environment, the readily available Mn/Fe transition metal elements (TMEs) facilitate the construction of defect structures. However, the role of TMEs in shaping the domain structures and the corresponding promotional mechanism of piezoelectricity need to be further decoded. Herein, we propose the different influence mechanisms of Mn and Fe ions on the ferroelectric domain and piezoelectric properties. Different concentrations of (M n Nb/Ta ′ - V O • • ) • and (F e Nb/Ta ″ - V O • • ) × defect dipoles are obtained based on the synergy of Mn/Fe ions with oxygen vacancies. Diverse ferroelectric behaviors resulting from (M n Nb/Ta ′ - V O • • ) • and (F e Nb/Ta ″ - V O • • ) × defect dipoles are observed. Furthermore, the variation of the dielectric diffusiveness with the defect dipole concentration is investigated. Trace concentration of (M n Nb/Ta ′ - V O • • ) • generates strong diffusiveness. With the characterization of the ferroelectric domain, this strong diffusiveness is attributed to the lattice-like domain structure. Thereafter, the mechanisms of Mn/Fe defect dipoles on the formation of domain structures are clarified. Macroscopically, the dielectric and piezoelectric properties are measured with Mn/Fe ion components. Trace Mn doping and the resulting lattice-like domain significantly enhance the piezoelectric coefficient, resulting in an increase of nearly 50% for K(Ta,Nb)O3 single crystals. This work highlights the tremendous potential of TME-induced defect dipoles for modifying the ferroelectric domain and provides a reference paradigm for improving piezoelectricity through defect engineering. [ABSTRACT FROM AUTHOR]

In recent years, the demand for electronic materials has significantly increased, driven by industrial needs and the pursuit of cost‐efficient alternatives. This comprehensive study investigates the effects of Mn substitution on LaFeO3 through the implementation of the GGA approach in density functional theory. The research findings demonstrate remarkable consistency with the experimental outcomes reported in the existing literature pertaining to the studied compounds. However, this study unveils novel insights into the mechanical and optical characteristics of the doped structures, which have not been previously reported. The structural stability is rigorously examined through multiple stability criteria, encompassing structural optimization, tests of elastic stability, and enthalpy of formation calculations. Furthermore, the electronic and optical properties of the compounds exhibit exceptional improvements in conductivity and reflectivity as a result of the doping process. The band structure analysis reveals the presence of a Moss‐Burstein shift. Investigation of the magnetic properties indicates an increase in the magnetic moment value due to the Fe‐Mn degeneracy resulting from increased Mn content. Mechanical analysis of the elastic moduli B, G, and Y demonstrates an enhanced strength and metal‐like conductivity, attributed to the induced anharmonicity. Moreover, the internal strain factor suggests a higher degree of bond flexibility, implying potential applications of these compounds in flexible electronics. [ABSTRACT FROM AUTHOR]

This study describes the strengthening mechanisms of an ultrafine-grained (UFG) Fe35Mn27Ni28Co5Cr5 high-entropy alloy (HEA) processed by severe cold rolling (SCR) process at room temperature. Microstructural evaluations were performed by field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The findings demonstrated that the development of deformation microstructures consisted of a single face-centered cubic (FCC) phase with stretched grains along the rolling direction and lamellar deformation bands after a 90 % reduction in thickness. Using the Nix-Gao model, the dislocation density was determined by measuring the microhardness indentation size effect. The results indicated that an increase in rolling deformation leads to an increase in dislocation density. The dislocation density increased from 2.28 x 109 cm-2 for as-homogenized specimen to 8.65 x109 cm-2 after 90 % reduction in thickness. The yield strength of the UFG Fe35Mn27Ni28Co5Cr5 HEA was 5.2 times (1155 MPa) higher than that of the as-homogenized state (225 MPa). Finally, an assessment was conducted on the relative contributions of individual mechanisms, such as dislocation and grain refinement, to the strengthening of the Fe35Mn27Ni28Co5Cr5 HEA. [ABSTRACT FROM AUTHOR]

Multi-material additive manufacturing using heterogeneous powders as raw materials is one of the important development directions of metal additive manufacturing technology. The evaporation behavior of heterogeneous powders in the selective laser melting (SLM) process has a significant influence on the accuracy of chemical composition control and the quality of the final product. In this paper, the fusion process of Fe20Mn (80 wt.% Fe and 20 wt.% Mn) heterogeneous powder, Fe and Mn elemental powders, and Fe20Mn pre-alloyed powder is numerically simulated using FLOW-3D® software and partially validated through SLM experimental results. The morphology and the characteristics of the flow field and temperature field in the melt pool for four kinds of powder materials are analyzed. The influence of the elemental evaporation behavior of different powders on the mass loss of the Mn element is discussed. The results show that the excessive accumulation of heat increases the maximum temperature of the melt pool, thus increasing mass loss. The Fe20Mn heterogeneous powder has a wider heat-affected zone and a higher peak value of temperature, nearly 400 K higher than that of the Fe20Mn pre-alloyed powders, which exhibits an intensive evaporation behavior. The mass loss of the Mn element obtained from the SLM experiment for Fe20Mn heterogeneous powders forming parts is more than the Fe20Mn pre-alloyed powders' forming parts for different laser powers, up to 17 wt.% at P = 120 W. This tendency is consistent with the numerical analysis of the effect of evaporation behavior of Fe–Mn heterogeneous powder during the SLM process. This study provides the necessary theoretical reference and process guidance for realizing the precise control of the SLM composition of a heterogeneous powder in multi-material additive manufacturing caused by evaporation behavior. [ABSTRACT FROM AUTHOR]

Evaluating the substitution of Cd for Mn, Co, Ni, Cu, and Zn elements in the high entropy oxide structure (Mn,Co,Ni,Cu,Zn)Fe2O4, is the primary focus in this investigation. For this purpose, five different high entropy oxides (HEOs), namely (Cd,Co,Ni,Cu,Zn)Fe2O4, (Mn,Cd,Ni,Cu,Zn) Fe2O4, (Mn,Co,Cd,Cu,Zn)Fe2O4, (Mn,Co,Ni,Cd,Zn)Fe2O4, and (Mn,Co,Ni,Cu,Cd)Fe2O4 were synthesized using combustion solution synthesis (SCS) method. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), elemental mapping, and field emission scanning electron microscopy (FESEM) were used to analyze the synthesized samples. The analyses confirmed the formation of single-phase (Fd-3m) nanocrystalline powders with an increased lattice parameter. Fourier Transform Infrared Spectroscopy (FTIR) revealed the placement of Cd element in the tetrahedral sub-lattice (A-site). Vibrating sample magnetometer (VSM) was employed to assess the magnetic properties. The results indicated that, in most cases, substitution of Cd for Mn, Co, Ni, Cu, and Zn leads to an increase in both the saturation magnetization (Ms) and coercivity (Hc) of the nanocrystalline powder samples. [ABSTRACT FROM AUTHOR]

Half‐metallic ferromagnets (HMFs) exhibit semiconductor behavior for one spin projection and metal characteristics for the other, which have promising applications in spintronics. It is a great challengeable for HMFs to have wide spin energy gap, large saturation magnetization (MS), and high Curie temperature (TC) simultaneously. Here, we report the Sr1.5Mn0.5Fe0.5Hf1.5O6 (SMFHO) double perovskite compounds synthesized by solid‐state reaction and display a magnetic TC up to 804 K due to the strong Mn3+(↑)Fe3+(↑) spin interactions, which is the reported record in perovskite‐type HMFs so far. The measured MS value at 300 K was 4.87 μB/f.u., and it further increased up to 6.09 μB/f.u. at 2 K. The SMFHO powders exhibited butterfly‐shaped magnetoresistance (MR)–H curve at 2 K, and the MR (2 K, 7 T) value was measured as −3.86% due to the intergranular magnetic tunneling effect. Variation of the resistivity of the SMFHO ceramics versus temperature exhibits a semiconductor behavior, and the electrical transport properties of the SMFHO ceramics are well studied by Mott's range jump model, thermally activated semiconductor conductance model and small polaron jumping model, respectively. The optical absorption spectrum of the SMFHO powders demonstrates an indirect optical bandgap of 3.56 eV. Our present work demonstrates the intriguing properties of the SMFHO oxides where high TC, wide energy gap, and large MS value are preserved at the same time, which open the way to their promising applications in advanced spintronic devices at or beyond room temperature. [ABSTRACT FROM AUTHOR]

First-principles calculations have been performed to investigate the structural, electronic, and magnetic properties of Sr2BB′O5 (B = Fe, Co, Ni; B′ = Co, Ni, Mn) brownmillerite materials. By considering the atomic arrangements and the tetrahedral rotated modes, including typical magnetic configurations, the ground states are found by comparing their total energy. The thermodynamic and dynamic stability studies revealed that two compounds, Sr2FeCoO5 and Sr2NiMnO5, could be stable in the brownmillerite structure. Further electronic structure calculations show that the ground state of Sr2FeCoO5 is a G-AFM insulator, while the ground state of Sr2NiMnO5 is an A-AFM half-metal with a half-metallic bandgap of about 1 eV, exhibiting excellent half-metallic properties. In addition, the magnetic interactions are analyzed, which suggest that Sr2FeCoO5 could suffer from the influence of the B-site atomic disorder to maintain the G-AFM state, while Sr2NiMnO5 is more sensitive to atomic disorder, so its A-AFM state would be easily destroyed by the B-site disorder. These results would be helpful for further research. [ABSTRACT FROM AUTHOR]

The electrical properties of semi-insulating GaN substrates doped with iron (Fe), carbon (C), or manganese (Mn) grown by hydride vapor phase epitaxy are presented. Hall effect measurements were performed at temperatures ranging from 300 to 800 K. At all of the investigated temperatures, the Mn-doped samples exhibited the highest resistivity. The Fe-doped samples showed n-type conduction, whereas the C-doped samples and the Mn-doped sample with a Mn concentration of 1 × 1019 cm−3 showed p-type conduction. A detailed analysis of the temperature dependence of the carrier concentration showed that all of the impurities formed acceptor levels at EC −(0.59–0.61) eV for Fe, at EV +(0.90–1.07) eV for C, and at EV +1.55 eV for Mn. The Mn-doped sample with a Mn concentration of 8 × 1017 cm−3 showed a negative Hall coefficient (suggesting n-type conduction) at high temperatures, contradicting the formation of acceptor levels by Mn. We successfully explained the negative value by considering the conduction of both holes and electrons with different mobilities. On the basis of the results, we calculated the relationship between the resistivity and doping concentration for each dopant. The calculations indicated that the highest resistivity can be realized in Mn-doped GaN with an optimized doping concentration (depending on the residual donor concentration). All of the dopants can effectively realize high resistivity at room temperature. Mn is an effective dopant for attaining high resistivity, especially at high temperatures (e.g., 800 K). [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs), recently emerging alloys with numerous excellent mechanical performances, may have a wide application prospect in impact engineering. The ballistic impact response of Fe40Mn20Cr20Ni20 HEA was investigated under various loading conditions. Ballistic impact tests with spherical projectiles and 87 type 5.8 mm small caliber bullets (DBP87 bullets) were conducted on 10 mm thick Fe40Mn20Cr20Ni20 HEA plates with varying impact velocities, compared with 20Mn23AlV steel (high manganese low magnetic steel). The relationship between microstructural details and aspects of ballistic behavior governing performance was established through experimental explorations and theoretical models. According to the findings, dense dislocation structures led to distinguishing work hardening in the HEA, and the strain-hardening capacity of the HEA enhanced dramatically with increasing strain rate under dynamic tension. Meanwhile, under 500 m/s impact velocity, twinning and microbanding had outstanding strain-hardening capabilities for the current HEA, and the cooperation of the dislocation slip and stacking faults was critical for strain hardening in the HEA when the impact velocity was increased to 930 ± 15 m / s , whereas only a small amount of dislocation sliding and twinning occurred during the dynamic deformation process of 20Mn23AlV steel at different impact velocities. These findings demonstrated that the outstanding strain-hardening capabilities of Fe40Mn20Cr20Ni20 HEA made it a promising candidate for ballistic impact engineering compared with 20Mn23AlV steel. [ABSTRACT FROM AUTHOR]

[Fe(bpp)2][ClO4]2 (bpp = 2,6-bis{pyrazol-1-yl}pyridine; monoclinic, C2/c) is high-spin between 5–300 K, and crystallises with a highly distorted molecular geometry that lies along the octahedral–trigonal prismatic distortion pathway. In contrast, [Ni(bpp)2][ClO4]2 (monoclinic, P21) adopts a more regular, near-octahedral coordination geometry. Gas phase DFT minimisations (ω-B97X-D/6-311G**) of [M(bpp)2]2+ complexes show the energy penalty associated with that coordination geometry distortion runs as M2+ = Fe2+ (HS) ≈ Mn2+ (HS) < Zn2+ ≈ Co2+ (HS) ≲ Cu2+ ≪ Ni2+ ≪ Ru2+ (LS; HS = high-spin, LS = low-spin). Slowly crystallised solid solutions [FexNi1−x(bpp)2][ClO4]2 with x = 0.53 (1a) and 0.74 (2a) adopt the P21 lattice, while x = 0.87 (3a) and 0.94 (4a) are mixed-phase materials with the high-spin C2/c phase as the major component. These materials exhibit thermal spin-transitions at T½ = 250 ± 1 K which occurs gradually in 1a, and abruptly and with narrow thermal hysteresis in 2a–4a. The transition proceeds to 100% completeness in 1a and 2a; that is, the 26% Ni doping in 2a is enough to convert high-spin [Fe(bpp)2][ClO4]2 into a cooperative, fully SCO-active material. These results were confirmed crystallographically for 1a and 2a, which revealed similarities and differences between these materials and the previously published [FexNi1−x(bpp)2][BF4]2 series. Rapidly precipitated powders with the same compositions (1b–4b) mostly resemble 1a–4a, except that 2b is a mixed-phase material; 2b–4b also contain a fraction of amorphous solid in addition to the two crystal phases. The largest iron fraction that can be accommodated by the P21 phase in this system is 0.7 ± 0.1. [ABSTRACT FROM AUTHOR]

Manganese zinc (MnZn) ferrite is one of the most used ferrite materials, while the investigations on sintering behaviors and magnetic properties of MnZn ferrite with ultrahigh metal oxide components are important supplements to the preparation knowledge of MnZn ferrite. In the formula triangle of the Fe 2 O 3 –ZnO–MnO 2 system, four representative formulas including 50%Fe–25%Zn–25%Mn, 80%Fe–10%Zn–10%Mn, 10%Fe–80%Zn–10%Mn, and 10%Fe–10%Zn–80%Mn were selective in this work to stand for medium-Fe, high-Fe, high-Zn, and high-Mn systems. The thermogravimetric aspects, phase compositions, microstructure features, magnetic properties, electromagnetic parameters, and electromagnetic wave absorbing properties of four samples were compared via the TG-DSC, XRD, XPS, SEM-EDS, VSM, and VNA analyses. It's suggested that the phase compositions and microstructures were dramatically affected by the iron content. After sintering, the high-Fe and medium-Fe systems present single Zn x Mn y Fe 2 O 4 (0 < x, y < 1) phase and condense structure, while some free superfluous oxides are concomitant in the high-Mn and high-Zn systems. The pore structure and number are positively correlated with the MnO 2 content in the Mn–Zn–Fe oxide system owing to the decomposition deoxygenation reaction. The magnetism study indicates that all four samples present good soft magnetic properties and less coercive force, while the high-Fe system displays the highest magnetic saturation intensity of 102 emu/g and the lowest magnetic coercivity. Due to the uniform composition, dense structure, and sufficient iron ingredient, the as-prepared MnZn ferrite with the formula of 80%Fe–10%Zn–10%Mn (high-Fe system) sintered at 1300 °C for 6 h demonstrates strong electromagnetism performance with the minimum RL peak of −42.03 dB at a veneer thickness of 8 mm. It's suggested that sintered MnZn ferrite with high-iron content demonstrates superior electromagnetic wave absorption properties. This work provided a batching formula foundation for the preparation of high-performance MnZn ferrites with high metal oxide constituents from pure oxide reagents or mineral materials. [ABSTRACT FROM AUTHOR]

Refinement of intermetallic compounds (IMCs) through enhancing heterogeneous nucleation during casting process is an important approach to improve the properties of aluminium alloys, which greatly increases the economy value of recycled Al-alloys. However, heterogeneous nucleation of IMCs is inherently more difficult than that of a pure metal or a solid solution. It requires not only creation of a crystal structure but also the positioning of 2 or more different types of atoms in the lattice with specific composition close to that of the nucleated IMCs. Previous understanding on heterogeneous nucleation is based on structural templating, usually considering the small lattice misfit at the interface between the nucleating solid and substrate. In this work, we proposed a hypothesis and demonstrated that composition templating plays a critical role in heterogeneous nucleation of IMCs. The experimental results revealed that segregation of Fe atoms on the AlB2 surface, i.e., the Fe modified AlB2 particle, provides the required composition templating and hence enhances heterogeneous nucleation of α-Al15(Fe, Mn)3Si2, resulting in a significant refinement of the α-Al15(Fe, Mn)3Si2 particles in an Al-5 Mg-2Si-1.0Mn-1.2Fe alloy. [ABSTRACT FROM AUTHOR]

The influence of grain refinement by high-pressure torsion (HPT) on the corrosion behavior of CoCrFeNi alloys with varied Cr content was investigated in aqueous 0.5 M H2SO4 and 3.5% NaCl solutions. The results were compared with CoCrFeMnNi alloys. Both the alloys showed a single fcc phase after vacuum melting and HPT. Protective passivation capability and resistance to general corrosion in H2SO4 was higher than that of Fe–Cr alloys and became higher with increasing Cr contents, indicating that high corrosion resistance of Cr-containing HEAs is attributed to the incorporation of Cr with other supporting elements. However, the impact of the nanocrystalline structure by HPT on the general corrosion behavior in the H2SO4 solution was negligibly small while the resistance to the local attack as pitting in NaCl was improved for the CoCrFeNi alloy. This is contrasted with the CoCrFeMnNi alloy, which exhibited negligibly small change by HPT in both NaCl and H2SO4 solutions. X-ray photoelectron spectroscopy indicated the Cr enrichment in passive films, but its degree is smaller regardless of grain size and Mn content, as compared with that of Fe–Cr alloys reported in the literature. The small change in the Cr enrichment in the passive film and the resulting corrosion behavior by grain refinement through HPT could be attributed to an intrinsic nature of HEAs such as sluggish diffusion and intrinsic lattice distortion. The improved resistance to pitting corrosion in CoCrFeNi alloys could be explained by the homogenization effect of the ultrahigh strain deformation, which may not take effect in alloys containing the solute Mn. [ABSTRACT FROM AUTHOR]

The Al–Mn alloy heat exchanger fin production process includes a brazing treatment at s high temperature of 600 °C, in which coarse grains are preferred for their high resistance to deformation at elevated temperatures by decreasing the grain boundary sliding. In this study, Al-1.57Mn-1.57Zn-0.58Si-0.17Fe alloy foils cold rolled by 81.7% (1.1 mm in thickness) and 96.5% (0.21 mm in thickness) were annealed at 100–550 °C for 1 h to investigate their recrystallization behavior, grain sizes, and precipitates by increasing the annealing temperature, using micro-hardness measurement, electron back-scattered diffraction (EBSD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The micro-hardness results showed that the recrystallization finishing temperatures for the two samples were almost the same, 323 ± 2 °C. The EBSD results showed that when the annealing temperature decreased from 550 to 400 °C, the recrystallized grain sizes of the two samples were nearly identical—both increased slightly. Further decreasing the annealing temperature from 400 to 330 °C caused the grain sizes to increase more, with the thinner foil sample having a more significant increase. The SEM and TEM observations showed that the micron-sized primary-phase remained unchanged during the annealing process. The nano-sized secondary phase precipitates formed during the hot-rolling process experienced a coarsening and dissolving process upon annealing. The particle size of the secondary phase increased from 32 nm to 44 nm and the area fraction decreased from 4.2% to 3.8%. The nucleation analysis confirmed that the large primary-phase could act as a nucleation site through particle stimulated nucleation (PSN) mode. The relatively dense secondary phase precipitates with small sizes at lower temperatures could provide higher Zener drag to the grain boundaries, leading to fewer nuclei and thereafter coarser grains. The coarsening of the recrystallized grains in the foils could be implemented through thickness reduction and/or precipitation processes to form densely distributed nano-sized precipitates. [ABSTRACT FROM AUTHOR]

The detailed investigation of the microstructure evolution in the Al–3.4Si–0.6Mg–0.5Mn alloy, solution-treated at 530, 545, and 560 °C for 4 h, and its corresponding mechanical properties at the T6 heat-treated state, is presented in this study. It was found that the as-cast microstructure of the experimental alloys comprised α-Al, eutectic Si, π-Al8Mg3FeSi6(Mn), and α-Al15(Fe, Mn)2Si3 intermetallics. Throughout the solution treatment, the dissolution of blocky π-Fe intermetallics transpired, accompanied by the spheroidization of eutectic Si and precipitation of Mn-enriched dispersoids. As the solution temperature increased, the dissolution of π-Fe intermetallics became more pronounced, leading to their gradual transformation into spherical α-Al15(Fe, Mn)2Si3 intermetallics. The alloy subjected to T6 heat treatment, which had been solution-treated at 545 °C for 4 hours, effectively mitigated the deleterious effects of blocky π-Fe intermetallics and eutectic Si, resulting in a commendable elongation to fracture (7.4%). Furthermore, the precipitation kinetics of Mn-containing dispersoids in the Al–Si–Mg–Mn alloy were markedly influenced by the solution temperature. The elevating solution temperature bolstered the nucleation, growth, and coarsening of dispersoids. The increase in the precipitation of fine dispersoids augmented the resistance to dislocation movement during the strain process, thereby enhancing the yield strength of the alloy. [ABSTRACT FROM AUTHOR]

Randomly mixing ferromagnetic (FM) and antiferromagnetic (AFM) elements in high-entropy alloys (HEAs) can create fluctuating local magnetic moments that influence the energetics of point defects. In this study, we employed first-principles calculations to investigate the influence of magnetic properties on vacancy migration energy in Fe49.5Mn29.4Co10.1Cr10.1C0.9, alongside equiatomic NiCoFeCrMn alloy. By examining structures with paramagnetism, ferromagnetism, and no spin polarization, our study reveals significant impacts of magnetic interactions on vacancy migration barriers, potentially altering the sequence of elemental migration energies if overlooked. In Fe49.5Mn29.4Co10.1Cr10.1C0.9, the order of vacancy migration barriers is Co > Fe > Mn > Cr across all magnetic states, suggesting the dominant roles of atomic properties and inherent chemical bonding. Conversely, the NiCoFeCrMn HEA exhibits a pronounced magnetic state-dependent elemental migration energy order, indicating that magnetic interactions significantly influence vacancy migration behavior in this alloy. In addition, while FM elements generally exhibit higher migration barriers, AFM elements display lower barriers in the investigated Cantor alloys, with notable variations between the studied compositions. These findings underscore the critical role of magnetism in accurate migration energy calculations, which is important for studying chemically biased diffusion and radiation-induced segregation in HEAs. [ABSTRACT FROM AUTHOR]

Based on the first-principles approach, we have studied the martensitic, electronic, magnetic, thermal, and thermoelectric properties of Ni2Mn1-xGa1-yFex+y. The substitution of Fe for Ga in Ni2MnGa compound makes the magnetic moment. Debye temperature and heat capacity are sensitive to the doping of Fe atom. The computed transport parameters are evaluated and influenced by the substitution on Mn and/or Ga sites. The slight reduction of both the total magnetic and the thermal expansion coefficient of systems is observed in the case of diminution Mn concentration. Regard with the phase stability, the Fe-doped Ni2MnGa on Mn and/or Ga sites reduces the stability of austenite which transformed to the martensitic phase. The thermoelectric parameters are computed for a temperature range of 200–900 K intended to check the potential of these alloys for applications in thermoelectric devices. The doping on Ni2MnGa with transition metals could be an effective strategy to tuning c/a ratio of the martensite phase. [ABSTRACT FROM AUTHOR]

This paper mainly investigated the effect of the Mn/Ag ratio on the microstructure and room temperature and high-temperature (350 °C) tensile mechanical properties of the as-cast and heat-treated Al-6Cu-xMn-yAg (x + y = 0.8, wt.%) alloys. The as-cast alloy has α-Al, Al2Cu, and a small amount of Al7Cu2 (Fe, Mn) and Al20Cu2 (Mn, Fe)3 phases. After T6 heat treatment, a massive dispersive and fine θ′-Al2Cu phase (100~400 nm) is precipitated from the matrix. The Mn/Ag ratio influences the quantity and size of the precipitates; when the Mn/Ag ratio is 1:1, the θ′-Al2Cu precipitation quantity reaches the highest and smallest. Compared with the as-cast alloy, the tensile strength of the heat-treated alloy at room temperature and high temperature is greatly improved. The strengthening effect of the alloy is mainly attributed to the nanoparticles precipitated from the matrix. The Mn/Ag ratio also affects the high-temperature tensile mechanical properties of the alloy. The high-temperature tensile strength of the alloy with a 1:1 Mn/Ag ratio is the highest, reaching 135.89 MPa, 42.95% higher than that of the as-cast alloy. The analysis shows that a synergistic effect between Mn and Ag elements can promote the precipitation and refinement of the θ′-Al2Cu phase, and there is an optimal ratio (1:1) that obtains the lowest interfacial energy for co-segregation of Mn and Ag at the θ′/Al interface that makes θ′-Al2Cu have the best resistance to coarsening. [ABSTRACT FROM AUTHOR]

Medium-coarse-crystalline dolomite is a major variant of dolomite, and its structural heterogeneity inside and outside the crystals makes it an ideal vehicle for studies of dolomite genesis, fluid evolution and elemental migration. In this paper, the medium-coarse crystalline dolomite from the fifth section of the Majiagou Formation of the Lower Ordos Basin was systematically studied by petrographic, cathodoluminescence and related geochemical methods. The rock is developed in the context of mud powder crystal dolomite and granular dolomite, possessing significant ring band structure, fluorite and quartz intergrowth. Compared with other dolomites, it is characterized by Fe and Mn enrichment and low Na and Sr contents, as well as a negative δEu anomaly and a strong negative δ18 O offset. Combined with the evolutionary history of diagenesis, it is believed that the medium-coarse-crystal dolomite is the end product of a series of diagenetic effects such as early dolomitization-atmospheric freshwater leaching-secondary burial recrystallization-deep burial dissolution. Electron microprobe analysis reveals the structural and compositional heterogeneity inside and outside the crystals. The formation of mediumcoarse- crystalline dolomite is associated with an increase in Fe-Mn content, a rise in the Mn/Sr ratio, a decrease in Sr, and a first rise and then a fall in Na concentration. This study provides a valuable reference for further research on the genesis of the medium-coarse crystalline dolomite. [ABSTRACT FROM AUTHOR]

The modulation mechanism of iron (Fe) and manganese (Mn) in transition‐metal elements on the interface bonding and mechanical properties of bronze (Cu3Sn)‐based/diamond composites is investigated through first‐principles calculations. Transition‐elements‐doping scenarios are investigated employing six‐layer slab models. It is revealed that the doping of Fe or Mn can make the Cu3Sn/diamond interface more stable, which effectively improves the wettability of the Cu3Sn/diamond interface based on the calculation results and analysis of interface energy, differential charge density model, and density of states. However, co‐doping with both Fe and Mn weakens the wettability of the Cu3Sn/diamond interface. Finally, wettability tests and microstructure characterizations demonstrate that the doping of Fe and Mn represents an effective approach to controlling the interface bonding performance of bronze/diamond composites. [ABSTRACT FROM AUTHOR]

Fe-based superelastic alloys, which show both superelasticity and high damping capacity, can be divided into four alloy systems based on the characteristics of the martensite transformation that is responsible for these effects, viz., Fe-Pt, Fe-Pd, Fe-Mn-Si, and Fe-Ni-Co. Since 2010, Fe-Ni-Co-Al-based alloys that exhibit a large superelastic effect have attracted widespread attention. In this paper, the characteristics of the phase transformation from austenite ( γ ) to martensite ( α ') and the effects of the martensite variants in Fe-Ni-Co-Al-based superelastic alloys are summarized. The effects of alloying elements, precipitates and texture on the thermoelastic martensite transformation and the superelastic properties are reviewed. The factors affecting the superelastic effect and recoverable strain along with the related mechanisms are discussed. In addition, research progress on the damping performance, microwire structures, and modeling of Fe-Ni-Co-Al-based superelastic alloys are outlined. Finally, the challenges and future developments of the superelastic effect in Fe-Ni-Co-Al-based alloy are explored. [ABSTRACT FROM AUTHOR]

The probability of martensitic transformation in stable 316L austenitic steel obtained using a 3D laser printer is investigated. Compressive deformation of the studied samples was carried out at room temperature at a high rate (2 × 10–2 sec–1). The features of the martensitic transition and the conditions for formation of an intermediate phase of epsilon-martensite are considered. [ABSTRACT FROM AUTHOR]

The Al–Ce-based alloys have gained increasing attentions owing to their favorable properties of high castability and good thermal stability, as well as excellent mechanical performance. However, since Ce has high chemical activity, it tends to bond with other impurities from the raw materials and affect the properties. In the present study, the influence of Ti and Mn impurities on the microstructure and mechanical properties of Al–Ce–Mg alloys was investigated. Both Al–Ce–Mg and Al–Ce–Mg–Ti–Mn alloys exhibit good formability traits during directed energy deposition additive manufacturing. Mechanical testing indicated that Ti and Mn significantly reduce the ductility by forming rosette-shaped Al20Ce(Ti, Mn)2 ternary intermetallic compounds, which provide favorable sites for the crack initiation in Al–Ce–Mg sample with Ti and Mn impurities. Compared to traditional hot extrusion, the lower solidification rate of direct energy deposition additive manufacturing coarsens the Al11Ce3 precipitates that compromise the strength but enhance the elongation in the sample without Ti and Mn addition. [ABSTRACT FROM AUTHOR]

Herein, the magnetic properties and elastocaloric effects of Cu70Al19 + 0.5xMn11−0.5x (x = 0, 1, 2, 3) alloys are investigated. The resistance versus temperature curves indicate that the phase transition temperature increases as the Mn content decreases. In particular, the Cu70Al20.5Mn9.5 alloy exhibits a phase transition temperature close to room temperature. Therefore, the elastocaloric effects of this alloy are examined under stresses ranging from 200 to 500 MPa. The results show that the adiabatic temperature change of the alloy under a stress of 500 MPa reaches 9.8 K. Furthermore, the magnetization curves at 300 K reveal that the magnetic properties of the alloy significantly improve after undergoing low‐temperature aging treatment. The X‐ray diffraction patterns show that this improvement can be attributed to the transformation of the β1 phase to the ferromagnetic phase β3. Overall, the Cu70Al20.5Mn9.5 alloy demonstrates elastocaloric and magnetic properties comparable to those observed in certain Ni–Mn‐based alloys. [ABSTRACT FROM AUTHOR]

La–Y–Ni-based superlattice hydrogen storage alloys exhibit key technological advantages as negative electrode materials for Nickel-metal hydride (Ni-MH) batteries; however, the function of Co has not been studied systematically. A series of LaY 2 Ni 10- x Mn 0.5 Co x (x = 0, 0.3, 0.5, and 0.9) alloys with only A 2 B 7 -type phases were prepared in this study, and the effects of Co on the microstructure and electrochemical properties were studied. Co has a minor effect on phase composition; however, it increased cell parameters because of its larger atomic size compared to that of Ni. Co-substituted alloys exhibited excellent activation performance and achieved the maximum discharge capacity in the first cycle. Moreover, Co promoted the discharge capacities of the alloys, but aggravated cycling degradation attributed to the accelerated pulverisation of the alloy particles that leads to serious oxidation/corrosion. Furthermore, an appropriate amount of Co enhances the electrochemical kinetics performance by promoting the charge transfer rates on the alloy surface and the hydrogen diffusion rates in the alloy bulk. [Display omitted] • La–Y–Ni-based alloys with only A 2 B 7 -type phases are prepared. • Affecting mechanism of Co on La–Y–Ni-based alloys are systematically studied. • Phase abundance changes little, enabling focus on Co effects. • Appropriate Co addition increases discharge capacity and HRD. [ABSTRACT FROM AUTHOR]

Liquefied gas storage and transportation, as well as space propulsion, are driving increasing interest in the cryogenic temperature deformation behaviour of 316L stainless steels. This was investigated here during tensile deformation at 15, 50 and 173 K. Complex transformation pathways, including one-step γ-austenite → α′-martensite, two steps γ → ε-martensite → α′ transformation as well as twinning and stacking fault-assisted γ → α′ transformation, are observed. γ grains with a (111) plane normal direction aligned 50–65°from the loading direction appear more likely to form the ε phase. Further, high-resolution transmission Kikuchi diffraction mapping revealed that the nucleation process of α′ can be assisted by ε and stacking faults at all cryogenic temperatures, whereas twins can also serve as sites for α′ nucleation when deformed at 173 K. For two-step transformation, separate lenticular α′ nucleate following Kurdjumov–Sachs orientation relationship (OR) within the shear band, once grown out of the shear band, Pitsch OR is preferable. As for one-step transformation, irregular oval α′ nucleates directly at γ grain boundaries with Nishiyama–Wassermann OR. These findings provide new insights into the correlation between the various transformation pathways and deformation mechanisms, as well as their improved performance at low temperatures. [ABSTRACT FROM AUTHOR]

Secondary phase precipitation in Fe-22Mn-9Al-0.6C low-density steel was investigated during a continuous cooling process with different cooling rates through a DIL805A thermal expansion dilatometer, and the changes in microstructures and hardness by different cooling rates were discussed. The results showed that the matrix of the Fe-22Mn-9Al-0.6C was composed of austenite and δ-ferrite; moreover, the secondary phases included κ-carbide, β-Mn and DO3 at room temperature. The precipitation temperatures of 858 °C, 709 °C and 495 °C corresponded to the secondary phases B2, κ-carbide and β-Mn, respectively, which were obtained from the thermal expansion curve by the tangent method. When the cooling rate was slow, it had enough time to accommodate C-poor and Al-rich regions in the austenite due to amplitude modulation decomposition. Furthermore, the Al enrichment promoted δ-ferrite formation. Meanwhile, the subsequent formation of κ-carbide and β-Mn occurred through the continuous diffusion of C and Mn into austenite. In addition, the hardness of austenite was high at 0.03 °C/s due to the κ-carbide and β-Mn production and C enrichment, and it was inversely proportional to the cooling rate. It can be concluded that the presence of κ-carbide, DO3 and β-Mn produced at the austenitic/ferrite interface when the cooling rate was below 0.1 °C/s resulted in κ-carbide and β-Mn precipitating hardly at cooling rates exceeding 0.1 °C/s, which provides a guideline for the industrial production of Fe-Mn-Al-C low-density steel in the design of the hot working process. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of high‐manganese steel (HMnS) fabricated using laser‐directed energy deposition (LDED) with Fe–Mn–4Cr–0.4C alloys with Mn contents of 13, 18.5, and 24 wt% are investigated. Additionally, the effect of annealing heat treatment on the microstructure and mechanical properties of the deposited HMnS is examined. Regardless of the manganese content, the deposited HMnS exhibits a fine microstructure without any defects (cracks or voids) and a strong fibrous texture along the <001>//building direction of the primary austenite phase. In addition, regardless of the manganese content, the grain size increases during annealing heat treatment, and the hardness decreases as the annealing temperature increases. The strength tends to decrease as the Mn content increases in the as‐built state. In addition, regardless of the Mn content, the yield strength and ultimate tensile strength tend to decrease owing to the effect of annealing heat treatment. Although the maximum elongation of 18.5Mn and 24Mn does not change significantly upon heat treatment, the maximum elongation of 13Mn is greatly reduced by annealing. The deformation behavior of HMnS is characterized by transformation‐induced plasticity (TRIP) for 13Mn and both TRIP and twinning‐induced plasticity for 18.5Mn and 24Mn. [ABSTRACT FROM AUTHOR]

The phase stability, martensitic transformation, and magnetic and mechanical properties of (Ni2-xCoxMn1.5Ti0.5)1-yBy (0 ≤ x ≤ 0.625; y = 0.03 and 0.06) alloys are systematically studied through the first-principles calculations method. The Co and B atoms are inclined to be aggregated distribution in the Ni2Mn1.5Ti0.5 alloy, and the phase stability of the austenite and non-modulated (NM) martensite decreases by co-doping. The ferromagnetic activation effect in the austenite occurs when x = 0.03 and y = 0.625. The magnetism of the austenite changes from an antiferromagnetic to a ferromagnetic state, which is ascribed to the elongation of the nearest neighboring distance of Mn–Mn, the nearest Mn–Mn distance increases from 2.50–2.79 to 2.90–2.94 Å, while the NM martensite always shows antiferromagnetism. Additionally, the doped B accelerates the change from antiferromagnetic to ferromagnetic for the austenite, but B-doping decreases the stability of the whole alloy system. The Co and B co-doping increases the stiffness of the NiMnTi alloy but decreases toughness and plasticity. However, the toughness and plasticity of the NiCoMnTiB alloy are better than those of the NiMnTiB alloy, indicating that the Co doping increases the d-orbital hybridization in the NiMnTiB alloy. The above results are expected to support the performance design of the NiMnTi-based alloy. [ABSTRACT FROM AUTHOR]

The defining feature of high-entropy alloys (HEAs) is their unprecedented degree of compositional inhomogeneity which influences their dislocation movements. We demonstrate differences between a HEA (Fe40Mn40Co10Cr10) and a conventional solution alloy (316L stainless steel) using acoustic emission (AE) spectroscopy. AE measurements under tension show the coexistence of two avalanche processes in Fe40Mn40Co10Cr10 HEA, whereby one avalanche process relates to the movement of dislocations and the other to detwinning/twinning processes. These two avalanche processes exhibit two branches of the E ∼ A2 correlation. The dislocation movements in Fe40Mn40Co10Cr10 HEA show systematically longer durations compared with the equivalent dislocation movements in the 316L stainless steel and a bias toward faster waiting times for subsequent dislocation movements. The aftershock rate, as identified by the Omori law, is the same for the two materials. [ABSTRACT FROM AUTHOR]

It is well known that the plate-like Al13Fe4 intermetallics are detrimental to the mechanical properties of recycled Al alloys which have higher Fe levels than primary Al. In wrought Al alloys, it is difficult to avoid the formation of primary plate-like Al13Fe4 intermetallics due to its equilibrium nature during solidification and its adaptions of many impurities such as Si, Mn, and Cr to form complex substitutional (Al, Si)13(Fe, Mn)4 crystals during subsequent homogenization and hot deformation. In this study, the influences of hot processing with different Mn and Cr additions and subsequent homogenization and hot transformation have been investigated. When 0.3Mn is added to Al–0.9Fe–0.1Si alloy, the percentage of Al13(Fe, Mn)4 decreases from 0.75 to 0.45% after homogenization of 10 h. When both 0.3Mn and 0.3Cr are added, it will decrease from 1.57 to 0.65%. After 30% hot deformation, it further decreases to 0.40% and 0.35% in 0.3Mn and 0.3Mn + Cr alloy, respectively, resulting in an improvement in elongation by 11.15% and 49.35%. Combined with cold deformation by 20%, Al13(Fe, Mn)4 eventually decreases to 0.30% and 0.24% in 0.3Mn and 0.3Mn + Cr alloys, achieving complete conversion from Al13(Fe, Mn)4 to α-Al15(Fe, Mn)3Si2, and the tensile strength is increased by 23.52% and 19.90%, respectively. To reveal the transformation mechanisms of Fe-rich intermetallics, first-principle calculations are adopted to compare the interfacial energy of Al13Fe4 and α-Al15(Fe, Mn)3Si2 with the Al matrix. It is found that the Al13Fe4 shows a much more faceted nature than the α-Al15(Fe, Mn)3Si2 due to its higher Jackson's α-factor and greater interfacial energy but can be transformed into α-Al15(Fe, Mn)3Si2 at certain thermodynamic conditions. [ABSTRACT FROM AUTHOR]

Non-stoichiometric AB2 alloys with (Ti0.75Zr0.25)1.05Mn0.8CrTM0.2 (TM = Cr, Mo, and Nb) formulation were synthesized using an arc-melting method in an argon atmosphere to optimize storage, activation, and kinetic reaction properties of hydrogen. The structural, morphological, and hydrogen storage properties of the alloys were examined using X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray mapping, and volumetric method, respectively. The results indicate that the Mo sample exhibits the highest hydrogen storage capacity at 1.34 wt%. This result is due to the solid solution phase (TiMo), which acts as a catalyst and facilitates hydrogen absorption. The best value of the plateau slope for the Nb sample at room temperature was 0.65, and the hysteresis coefficient was 0.239 for the Mo sample. In addition, the dissociation enthalpy (∆HDES) and entropy (∆SDES) for the Nb sample were 31.04 kJ mol−1 and 103.93 J mol−1 K−1, respectively. From the analysis of the hydrogen absorption kinetic curves, it was found that the reaction kinetic behavior is consistent with the Jander model. Furthermore, activation energy values of the alloys were calculated at a pressure of 13 bar and the range of temperature from 298 to 328 K. We obtained Ea(Cr) = 14.02, Ea(Mo) = 10.92, and Ea(Nb) = 10.23 kJ mol−1. Based on the results, the Nb sample showed good absorption/desorption plateau pressure properties with small hysteresis and slope. [ABSTRACT FROM AUTHOR]

In this paper, we study and discuss the structural, and electronic properties of the RbXF3 (X = Co, Mn, V or Fe) Perovskite Materials using the Density Functional Theory (DFT). Also, the origin of both semi‐conductor (SM) and half‐metallic (HM) characters have been outlined. The density functional theory (DFT) has been applied to illustrate the physical properties of the RbXF3 (X = Co, Mn, Fe or V) perovskite materials. The generalized gradient approximation introduced by Perdew–Burke and Ernzerhof (GGA‐PBE) with Hubbard correction has been used for modeling the physical properties of the RbXF3 (X = Co, Mn, V or Fe) perovskite compounds. The total and partial densities of states of each solar perovskite RbVF3 (X = Co, Mn, Fe or V) material have been illustrated and discussed. In addition, the contribution of the different elements: Rb, Co, Mn, Fe, V and F, has been investigated revealing the most contributing ones in the valance and conduction bands. The magnetic behavior of the studied solar perovskites RbVF3 (X = Co, Mn, Fe or V) materials, has been outlined. It is found that the perovskites RbCoF3 and RbFeF3 are half‐metallic, while the materials RbMnF3 and RbVF3 exhibit a semi‐conductor behavior. [ABSTRACT FROM AUTHOR]

This investigation explores the solid-state hydrogen storage properties of two series of hydrogen storage alloys: (Ti 0.85 Zr 0.15) x Mn 0.8 CrFe 0.2 (x = 1.00∼1.10) and (Ti 0.85 Zr 0.15) 1.02 Mn y Cr 1.8-y Fe 0.2 (y = 1.00∼0.40) alloys. These alloys exhibit a single C14-Laves phase structure and demonstrate promising capabilities for solid-state hydrogen storage. The (Ti 0.85 Zr 0.15) x Mn 0.8 CrFe 0.2 (x = 1.00∼1.10) alloys display an increased hydrogen absorption capacity and a reduced plateau pressure at higher super-stoichiometric ratios of x. When x = 1.10, the alloy achieves a maximum capacity of 1.86 wt%. The hydrogen storage capacity of the (Ti 0.85 Zr 0.15) 1.02 Mn y Cr 1.8-y Fe 0.2 (y = 1.00∼0.40) alloys diminishes as the value of y decreases. Furthermore, the hydrogen absorption plateau pressure and hysteresis factor of the alloys increase with an escalating Mn/Cr ratio. The analysis of cyclic stability reveals that the primary factor contributing to poor cycling stability of the (Ti 0.85 Zr 0.15) 1.02 Mn 0.4 Cr 1.4 Fe 0.2 alloy is the compositional decomposition, rather than pulverization or alterations in the phase structure. In summary, this investigation enhances our understanding of the solid-state hydrogen storage properties of these alloys. It establishes a foundation for further research and development in this pivotal field of hydrogen storage. [Display omitted] • The alloys have a stable C14 single-phase structure as influenced by the size factor. • The alloys have a maximum hydrogen storage capacity of 1.86 wt%. • Cycling stability of the alloys is determined by compositional decomposition. [ABSTRACT FROM AUTHOR]