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M o 3 5 N i 1 5 R h 1 5 R u 3 5 , F e 1 4 M o 3 5 N i 1 5 R h1 5 R u 2 1 , M o2 5N i2 5R h2 5R u2 5, and F e 2 0 M o 2 0 N i 2 0 R h 2 0 R u 2 0 ( a t. % ) alloys were designed b y referring t o hexagonal close-packed ( h c p ) N b - M o - R u - R h - P d high-entropy alloys ( H E A s ) reported b y Liu e t a l., with the help o f Pearson ' s Crystal Data. X-ray diffraction profiles o f the F e 2 0 M o 2 0 N i 2 0Rh2 0 R u 2 0 and F e 1 4 M o 3 5 N i 1 5 R h 1 5 R u 2 1 alloys prepared via the conventional arc-melting and subsequent annealing a t 1700 K for 1 h show a n h c p structure. Further scanning electron microscopy observations combined with elemental mapping via energy-dispersive X-ray spectroscopy confirmed the single h c p structure. The F e 2 0 M o 2 0 N i 2 0 R h 2 0 R u 2 0 H E A annealed a t 1700 K for 1 h exhibited a mixing entropy (Sm i x) normalized b y the gas constant (R ) o f 1.846, 14% higher than the configuration entropy (Sc o n f i g) normalized b y R (Sc o n f i g/R = l n 5 ) . This study reveals two new ultrahigh-mixing-entropy alloys ( U H M i x E A s ) that satisfy Sm i x > Sc o n f i g, the F e 2 0 M o 2 0 N i 2 0 R h 2 0 R u 2 0 and F e 1 4 M o 3 5 N i 1 5 R h 1 5 R u 2 1 alloys. The evaluation o f Sm i x/Sc o n f i g for the present U H M i x E A s and referential Co-containing H E A s from early studies revealed that Sm i x/Sc o n f i g of the former are constant whereas those o f the latter increase a t the magnetic transition (Curie) temperature o r below.

Os-free alloys with compositions of Fe12Ir20Re20Rh20Ru28 and Ir25Re25Rh25Ru25 (at%) from an Ir-Re-Rh-Ru system with and without Fe are prepared via conventional arc-melting and subsequent annealing to examine their formation into a single hexagonal close-packed (hcp) structure as high-entropy alloys (HEAs). These alloys are derived by referring to Yunseko et al., who reported the formation of HEAs with a single hcp structure in a near-equiatomic composition (similar to Ir20Re20Rh20Ru20) achieved via a chemical reaction. The aim of the present study is to exclude Os from the prototypical HEA (the quinary exact equiatomic Ir20Re20Rh20Ru20 alloy) to prevent hazardous osmium tetroxide (OsO4) from volatilizing in a bulk sample. Fe12Ir20Re20Rh20Ru28 alloy is set as the target alloy by replacing Os with Fe0.6Ru0.4 in the prototypical HEA. The X-ray diffraction (XRD) profile of the Fe12Ir20Re20Rh20Ru28 alloy annealed at 2273 K for 1 h shows an hcp structure, and further scanning electron microscopy (SEM) observations combined with elemental mapping via energy dispersive X-ray spectroscopy (EDX) confirmed a single hcp structure. The XRD profiles of the other samples (the Fe12Ir20Re20Rh20Ru28 alloy in both as-prepared and annealed at 2000 K for 1 h states, and the Ir25Re25Rh25Ru25 alloy in both as-prepared and annealed at 2273 K for 1 h states) exhibit a combination of hcp structures, based on XRD, SEM, and EDX observations. The Fe12Ir20Re20Rh20Ru28 HEA yielded by the conventional solidification method reflects a significant development, as it is an Os-free alloy and the first single-phase hcp-HEA that includes an element from the 3d late transition metal.

© 2019 Acta Materialia Inc. A new Zr35Hf17.5Ti5.5Al12.5Co7.5Ni12Cu10 high-entropy bulk metallic glass with glass-forming ability up to centimeter scale (diameter of 18 mm) and configuration entropy of 1.77R was discovered. This high-entropy bulk metallic glass differs from previous ones because it was designed to possess a non-equiatomic eutectic composition and was free from Be. The high-entropy alloy exhibited excellent glass-forming ability despite its lower reduced glass transition temperature than those of prototypical glasses. Molecular dynamics simulations suggested that the excellent glass-forming ability was caused by the similar magnitude of the decrease in Hamiltonian from amorphous to crystalline phases to that of a reference ternary bulk metallic glass, as well as the sluggish crystallization of the high-entropy bulk metallic glass.

© 2019 The Japan Institute of Metals and Materials High-entropy alloys (HEAs) with a single hexagonal close-packed (hcp) structure were found in Ir26Mo20Rh22.5Ru20W11.5 and Ir25.5Mo20Rh20Ru25W9.5 alloys annealed at 2373 K for 1 h. These HEAs were designed based on a sandwich strategy for valence electron concentration (VEC) of the constituent elements and by referring to their crystallographic structures in the periodic chart. The initial component and composition of these alloys were determined by considering exact and near equiatomic sub binary phase diagrams, followed by optimizing the composition by Thermo-Calc with the TCHEA3 database for HEAs as well as the SSOL5 database for solid solutions. The X-ray diffraction analysis, scanning electron microscopy observation, and energy-dispersive X-ray spectroscopy analysis revealed that the Ir26Mo20Rh22.5Ru20W11.5 and Ir25.5Mo20Rh20Ru25W9.5 alloys annealed at 2373 K for 1 h were formed in an hcp single phase. The formation of the hcp structure was principally evaluated by the VEC values of 7.855 and 7.865 for Ir26Mo20Rh22.5Ru20W11.5 and Ir25.5Mo20Rh20Ru25W9.5 alloys, respectively, such that these values were close to VEC = 8 for pure elements Ru and Os with an hcp structure. It is considered that Ru is a strong hcp-forming element under this strategy because the other pure constituent elements have different crystallographic structures. The formation of Ir26Mo20Rh22.5Ru20W11.5 and Ir25.5Mo20Rh20Ru25W9.5 HEAs with an hcp structure is unique because these alloys, which consist of only transition metals, can be produced without applying high pressure, similar to a CrMnFeCoNi HEA with an hcp structure.

©2018 The Japan Institute of Metals and Materials. The formation of site-percolated states of exact equiatomic high-entropy alloys (HEAs) with body-centered-cubic (bcc) and face-centered-cubic (fcc) structures was investigated where their critical concentrations (p csite ) are given as 0.245 and 0.198, respectively, from conventional percolation theory. Molecular dynamics simulations were performed for WNbMoTa and WNbMoTaV HEAs with a bcc structure and AuCuNiPt and AuCuNiPdPt HEAs with an fcc structure. The simulation conditions included a generalized embedded atom method potential under NTp ensemble where the number of elements (N), absolute temperature (T), and pressure (p) were maintained constant. N-element alloys (N = 4 and 5) with a fraction of constituent elements (x = 1/N) were initially prepared in 10 © 10 © 10 supercells randomly in terms of chemical species and were simulated under atmospheric pressure at T = 1000 K. The total pair-distribution functions of the alloys revealed that the nearest neighbor distance (d n ) for fcc ranged from 0.20 to 0.33 nm, whereas d n and the second neighbor distance (d nn ) for bcc ranged from 0.235 to 0.305 nm and 0.305 to 0.370 nm, respectively. A 3-dimensional topological analysis for atomic correlations revealed that the alloys were in percolated and isolated states, respectively, when x 2 p csite and x < p csite and that the values of 1/p csite correspond to the ideal values of N for exact equi-atomic HEAs. Furthermore, it was observed that exact equi-atomic quaternary alloys (N = 4) with a bcc structure and quinary alloys (N = 5) with an fcc structure are in the critically percolated states.

The phase stability of high entropy alloy (HEA), Al0.5TiZrPdCuNi, under fast electron irradiation was studied by in-situ high voltage electron microscopy (HVEM). The initial phase of this alloy quenched from the melt was dependent on cooling rate. At high cooling rates an amorphous phase was obtained, whereas a body-centered cubic (b.c.c.) phase were obtained at low cooling rates. By thermal crystallization of the amorphous phase b.c.c. phase nano-crystals were formed. Upon fast electron irradiation solid state amorphization (SSA) was observed in b.c.c. phase regardless of the initial microstructure (i.e., “coarse crystalline structure” or “nano-crystalline structure with grain boundaries as a sink for point defects”). SSA behavior in the Al0.5TiZrPdCuNi HEAs was investigated by in-situ transmission electron microscopy observations. Because the amorphization is very rarely achieved in a solid solution phase under fast electron irradiation in common metallic materials, this result suggests that the Al0.5TiZrPdCuNi HEA from other common alloys and the other HEAs. The differences in phase stability against the irradiation between the Al0.5TiZrPdCuNi HEA and the other HEAs were discussed. This is the first experimental evidence of SSA in HEAs stimulated by fast electron irradiation.

Ti33.33Zr33.33Hf13.33Ni20 and Zr30Hf30Ni15Cu10Ti15 alloys were investigated for their possibility to be formed into a high-entropy alloy (HEA) with a quasicrystalline (QC) structure that contains an icosahedral- (I-) phase. The melt-spun alloys quenched at a circumference speed of 39 m/s were formed into an amorphous single phase. The amorphous alloys annealed up to a temperature between the first and second crystallization temperatures exhibited mixed phases of I- and remaining amorphous phases. Observation of the Zr30Hf30Ni15Cu10Ti15 amorphous alloy heated up to 745 K with transmission electron microscope revealed the presence of precipitates with diameters ranging 10–20 nm. Nano-beam diffraction demonstrated that the precipitates were identified to be the I-phase with the five-, three- and two-fold symmetries. The Ti33.33Zr33.33Hf13.33Ni20 and Zr30Hf30Ni15Cu10Ti15 alloys were not formed into a single quasicrystalline phase as HEAs, but the discussions of the current and early experimental data led to provide the way to approach high-entropy quasicrystalline alloys (HE-QCs).

Quinary exact equi-atomic MnFeNiCuPt and MnFeNiCuCo alloys were investigated to examine their formation of high-entropy alloys (HEAs) by focusing on an L1(0) structure from Pettifor map for binary compounds with 1: 1 stoichiometry. The MnFeNiCuPt alloy was practically selected through computer-assisted alloy design under conditions of &lt;= 20 at% noble metals, and the condition that the L1(0) structure appears as frequently as possible in the constituent binary equi-atomic compositions comprised of 78 elements. MnFeNiCuCo was selected by substituting Pt with Co from the MnFeNiCuPt alloy as the second candidate. X-ray diffraction and observations by scanning electron microscopy (by energy dispersive spectroscopy for composition analysis) revealed that as-prepared MnFeNiCuPt and MnFeNiCuCo alloys were formed into HEAs with dual fcc structures containing dendrites of similar to 10 mu m in width. The MnFeNiCuPt and MnFeNiCuCo alloys annealed at 1373 K for 43.2 ks and subsequently quenched in water formed single fcc phases and dual fcc phases, respectively. The annealed MnFeNiCuPt and MnFeNiCuCo alloys were subsequently cooled in a furnace and formed single L1(2) ordered phases and dual fcc phases, respectively. These phases, experimentally observed in the annealed samples, could be partially explained by thermodynamic calculations using Thermo-Calc with SSOL4 and SSOL5 databases for solid solutions. The MnFeNiCuPt and MnFeNiCuCo alloys exhibit soft magnetism with saturation magnetization of 0.23 and 0.43 T, respectively, with coercivity values of similar to 1 kA m(-1). An alloy design for HEAs based on digitalized crystallographic data of these samples could lead to the discovery of new HEAs. (C) 2016 Elsevier Ltd. All rights reserved.

Molecular dynamics (MD) simulations were performed for an Fe50Ni50 (at.%) alloy with NTp ensemble to keep the number of atoms (N), temperature (T=673 K), and pressure (p similar to 101.325 kPa) constant under a GrujicicZhou-type MD potential from an Embedded Atom Method scheme with a cut-off distance of 1 nm. An Fe50Ni50 alloy was initially created as a hypothetical chemically-ordered B2 structure with a 12x 12x12 supercell comprising 3456 atoms. Subsequently, it was annealed at 673 K, without the application of stress, and then under a uniaxial tension of similar to 290 MPa, and shear stresses of similar to 570 and similar to 2940 MPa. The results revealed that stress contributed to a change in the transformation scheme to the L10 phase from partially to fully of the system with a reduction of time. On the other hand, an as-quenched amorphous phase under a shear stress of similar to 680 MPa, transformed to a disordered fcc-derivative phase. Therefore it is clear that stresses in MD simulations play a crucial role in enhancing the atomic motion during a transformation.

Effect of substitution of Cu by the same group element (Ag, Au) on the soft magnetic properties of Fe83.3Si4B8P4Cu0.7 alloy was investigated. Ag-/Au-substituted alloys have a similar hetero-amorphous structure with Fe-Si-B-P-Cu alloy, and consists of large alpha-Fe grains with a high distribution ratio and residual amorphous phase. The large coercivity, low permeability and unsatisfied saturation magnetization of Fe84.32Si3.87B7.59P4.16Ag0.05 and Fe83.47Si3.89B7.88P4.04Au0.71 alloys are attributed to their large alpha-Fe grain size in comparison to Fe83.3Si4B8P4Cu0.7 alloy according to Herzer's random anisotropy model. Cu atoms supersaturated in hetero-amorphous Fe-Si-B-P-Cu matrix results in the formation of alpha-Fe grains with smaller grain size around large numbers of pre-existing nuclei during annealing than those of Ag-/Au-substituted Fe-Si-B-P-Cu alloys. The competition driven nanocrystallization mechanism governs the balance between the nucleation and growth of alpha-Fe grains, and the saturation degrees, surface diffusivities and competition abilities of seed elements Ag, Au and Cu finally determine the dependency between their microstructure and soft magnetic performances. The Cu seed element plays an optimal role in controlling the microstructure and soft magnetic properties of NANOMET (R) alloys. (C) 2016 Elsevier B.V. All rights reserved.

A senary ScYLaTiZrHf alloy was investigated for its ability to form a solid solution with an hcp structure, also known as a high-entropy alloy (HEA). X-ray diffraction analysis of the ScYLaTiZrHf alloy produced by arc-melting method confirmed this hcp structure. The microstructure of the ScYLaTiZrHf was composed of dual phases that were enriched in (Y, La) or (Ti, Zr, Hf), with Sc distributed evenly across both phases. The positive mixing enthalpy of 11.4 kJ mol(-1) derived from Miedema's model, and the immiscible tendencies of its constituent binary phase diagrams help to explain the presence of dual phases in the ScYLaTiZrHf alloy. When formed into dual hcp solid solutions, the ScYLaTiZrHf alloy can be more accurately described as a multi-principal-element alloy (MPEA) rather than as a HEA, since the ScYLaTiZrHf alloy is a solid solution that is enthalpy-driven instead of entropy driven. The results also disclosed another procedure to stabilize solid solutions excepting for high-entropy scheme. (c) 2015 Elsevier Ltd. All rights reserved.

This chapter applies the concept of high entropy to metallic glasses (MGs), in particular, to those in a bulk shape: bulk metallic glasses (BMGs). The resultant target materials in this chapter are mainly high-entropy bulk metallic glasses (HE-BMGs), which have recently been developed as alloys with characteristics of both high-entropy alloys (HEAs) and BMGs. The contents in this chapter start by introducing historic background of HE-BMGs and by summarizing the differences between HEAs and BMGs. Then, the fundamental properties of representative HE-BMGs found to date are described mainly in terms of thermodynamic and mechanical behaviors. Besides the experiments, the latest computational approach for clarifying the features of HE-BMGs is described based on the results using ab initio molecular dynamics simulations for the atomic structure, chemical interaction, and diffusivity in this unique class of materials. The current status and future prospects of the HE-BMGs by utilizing their unique features are outlined for their future applications.

Exact equi-atomic senary alloys including three elements from 3d, 4d and 5d transition metals (TMs) were investigated for their ability to form solid solutions as high-entropy alloys (HEAs). Three alloys of CoCuPdTiZrIIf, CoCuFeTiZrIIf and AgAuCuNiPdPt were selected by focusing on (Ti, Zr, lift from Early-TMs, and (Cu, Ag, Au) and/or (Ni, Pd, Pt) from Late-TMs based on an alloy design with a help of Pettifor map for binary compounds with several stoichiometries and binary phase diagrams, together with a marginal Al(4)CoNiPdPi alloy. the XRD analysis revealed that the CoCuPdTiZrHf alloy was formed into a bcc, whereas both the CoCuFeTiZrElf and AL(4)CoNiPLIPt alloys were a (and the AgAuCuNiPdPt alloy was dual fcc structures. The observations with optical and scanning-electron microscopes and analysis with energy dispersive X-ray for chemical composition revealed the homogeneous morphologies of these alloys in micrometer scale. The types of crystalloeraphic structures of the CoCuPdTiZrIIf, CoCuFeTiZrIIf and AgAuCuNiPdPt HEAs and the Al4CoNiPdPt alloy can be principally explained by valence electron concentration. Three constituent elements from TMs in the same group enhance the increase in the number of complete solid solutions in the constituent binary systems, leading to forming these HEAs.

Pettifor map for binary compounds with 1:1 stoichiometry was utilized as an alloy design for highentropy alloys (HEAs) with exact or near equi-atomicity in multicomponent systems. Experiments started with selecting GuGd binary compound with CsCI structure from Pettifor map, followed by its extensions by selecting the binary compounds with the same CsCI structure to CuDyGdTbY equi-atomic quinary alloy and to Cu4GdTbDyY and Ag4GdTbDyY quinary alloys and Cu2Ag2GdTbDyY senary alloy in sequence. X-ray diffraction revealed that CuDyGdTbY alloy was formed into a HEA with mixture of bcc, fcc and hcp structures, whereas the Cu2Ag2GdTbDyY HEA was a single CsCI phase. The results suggest a potential of Pettifor map for the development of HEAs by utilizing its information of crystallographic structures. The further analysis was performed for composition diagrams of multicomponent systems corresponding to simplices in a high dimensional space. The present results revealed that a strategy of equi-mole of compounds instead of conventional equi-atomicity also works for the development of HEAs. (C) 2015 Elsevier Ltd. All rights reserved.

New Fe25CO25Ni25(E, Si)(25) high entropy bulk metallic glasses (HE-BMGs) with superior soft magnetic and mechanical properties are developed. The HE-BMGs show high glass transition temperature and wide supercooled liquid region WO. Fully glassy rods with diameters up to 1.5 mm were fabricated for the Fe25Co25Ni25(BoiSio(3))(25) alloy by copper mold casting method. The HE-BMGs exhibit high yield strength of -3624 MPa with large plastic strain of -3.1%, which is superior to the pre-developed HE-BMGs. The alloys also possess good soft magnetic properties, i.e., rather high saturation magnetization of -0.87 T, low coercive force of -1.1 A/m, and high effective permeability at 1 kHz of -19,800. This combination of these excellent properties gives the new HE-BMGs good promise for both scientific and engineering applications. (C) 2015 Elsevier Ltd. All rights reserved.

The magnetic influence of silicon, boron, phosphorous, niobium, as well as Cu in Fe-rich amorphous was studied through ab initio molecular dynamics simulations. The small concentration of metalloids with large electronegativity is beneficial to the saturation magnetization of Fe-rich amorphous alloys, but may reduce the magnetization by p-d orbital hybridization with a large amount of inclusion. On the other hand, owing to their low electronegativity, early transition metals may bring excess electrons to the alloys system and reduce the effect of Fe electron absorption by boron or phosphorous; therefore, the inclusion of them will significantly reduce the magnetization of the alloy. The minor inclusion of Cu slightly exhibits negatively charged in Fe-rich amorphous alloys, which indicates that the transition metals with low electron losing tendency are acceptable in the alloy to maintain excellent soft magnetic properties with high magnetization.

Chemically ordered hard magnetic L1(0)-FeNi phase of higher grade than cosmic meteorites is produced artificially. Present alloy design shortens the formation time from hundreds of millions of years for natural meteorites to less than 300 hours. Electron diffraction detects four-fold 110 superlattice reflections and a high chemical order parameter (S >= 0.8) for the developed L1(0)-FeNi phase. The magnetic field of more than 3.5 kOe is required for the switching of magnetization. Experimental results along with computer simulation suggest that the ordered phase is formed due to three factors related to the amorphous state: high diffusion rates of the constituent elements at lower temperatures when crystallizing, a large driving force for precipitation of the L1(0) phase, and the possible presence of L1(0) clusters. Present results can resolve mineral exhaustion issues in the development of next-generation hard magnetic materials because the alloys are free from rare-earth elements, and the technique is well suited for mass production.

It is known that Cu plays an essential role in reducing the grain size of precipitated bcc Fe(Si) nanocrystallites in a nanocrystalline soft-magnetic Fe85.2Si1B9P4Cu0.8 (NANOMET (R)) alloys like as an Fe73.5Si13.5B9Nb3Cu1 (FINEMET (R)). However, significant differences are there between two alloys; NANOMET has much higher iron content (similar to 85%) than FINEMET (73.5%) and the former contains P instead of Nb for the latter. In the present work, the local structure around Cu in FINEMET was measured by X-ray absorption fine structure (XAFS) at 20K and compared with those of NANOMET during nanocrystallization. Definite differences between NANOMET and FINEMET are found in the way of the evolution of Cu clusters during nanocrystallization. In FINEMET, an fcc structure of Cu is recognized in an as-quenched ribbon indicating existence of a small number of Cu clusters or a very small size of Cu clusters which is stable up to 450 degrees C, while the fcc Cu clusters are developed rapidly above 450 degrees C. An fcc structure of the Cu clusters in FINEMET is retained all the way to the end of the nanocrystallization. On the contrary, for NANOMET the local structure around Cu changes in a sequence as "amorphous &gt; fcc &gt; bcc &gt; fcc" by annealing. The reasons of such different behaviors of the local structure around Cu during nanocrystallization are discussed in terms of different contributions of Cu clusters in bcc Fe precipitation between FINEMET and NANOMET. A significantly fast crystallization process with an extraordinary large heat release can be another reason for the transition of the local structure around Cu from fcc to bcc for NANOMET. (C) 2015 AIP Publishing LLC.

In the work reported in this paper, ab initio molecular dynamics simulation was performed on Fe85Si2B9P4 amorphous alloy. Preferred atomic environment of the elements was analyzed with Voronoi polyhedrons. It showed that B and P atoms prefer less neighbors compared with Fe and Si, making them structurally incompatible with Fe rich structure and repulsive to the formation of alpha-Fe. However, due to the low bonding energy of B and P caused by low coordination number, the diffusion rates of them were considerably large, resulting in the requirement of fast annealing for achieving optimum nano-crystallization for its soft magnetic property. The simulation work also indicates that diffusion rate in amorphous alloy is largely determined by bonding energy rather than atomic size. (c) 2015 AIP Publishing LLC.

Fe-based Fe85B15, Fe84B15Cu1, Fe82Si2B15Cu1, Fe85Si2B12Cu1, and Fe85Si2B8P4Cu1 (NANOMET (R)) alloys were experimental and computational analyzed to clarify the features of NANOMET that exhibits high saturation magnetic flux density (B-s) nearly 1.9 T and low core loss than conventional nanocrystalline soft magnetic alloys. The X-ray diffraction analysis for ribbon specimens produced experimentally by melt spinning from melts revealed that the samples were almost formed into an amorphous single phase. Then, the as-quenched samples were analyzed with differential scanning calorimeter (DSC) experimentally for exothermic enthalpies of the primary and secondary crystallizations (Delta H-x1 and Delta H-x2) and their crystallization temperatures (T-x1 and T-x2), respectively. The ratio Delta H-x1/Delta H-x2 measured by DSC experimentally tended to be extremely high for the Fe85Si2B8P4Cu1 alloy, and this tendency was reproduced by the analysis with commercial software, Thermo-Calc, with database for Fe-based alloys, TCFE7 for Gibbs free energy (G) assessments. The calculations exhibit that a volume fraction (V-f) of alpha-Fe tends to increase from 0.56 for the Fe85B15 to 0.75 for the Fe85Si2B8P4Cu1 alloy. The computational analysis of the alloys for G of alpha-Fe and amorphous phases (G(alpha-Fe) and G(amor)) shows that a relationship G alpha-Fe similar to G(amor) holds for the Fe85Si2B12Cu1, whereas G(alpha-Fe)&lt; G(amor) for the Fe85Si2B8P4Cu1 alloy at T-x1 and that an extremely high V-f = 0.75 was achieved for the Fe85Si2B8P4Cu1 alloy by including 2.8 at.% Si and 4.5 at.% P into alpha-Fe. These computational results indicate that the Fe85Si2B8P4Cu1 alloy barely forms amorphous phase, which, in turn, leads to high Vf and resultant high B-s. (C) 2015 AIP Publishing LLC.

Iron-based amorphous alloys have attracted a growing interest due to their potential in the application of magnetic coil production. However, the magnetization of this kind of material is usually low due to the lack of long range ordering and high alloying element content. In this paper, an Fe76B19P5 amorphous alloy was simulated with ab initio molecular dynamics based on a previous simulation work on an Fe76Si9B10P5 amorphous alloy exhibiting that electron absorbers such as B and P can help enhance the magnetization of nearby Fe atoms. The present simulation results show that replacing Si with B can destabilize the amorphous structure, making it easier to crystallize, but no separate alpha-Fe participation can be observed in experiments during annealing due to its high B/P content. The results also show an increase in saturation magnetization by 8% can be expected due to the intensified electron transfer from Fe to B/P, and the glass forming ability decreases correspondingly. The idea of enhancing electron transfer can be applied to the development of other Fe-based amorphous alloys for the purpose of larger saturation magnetization.

The crystallization processes of Fe83.3+xB7-x,P9Cu0.7 (x = 0 to 2.5 at%) amorphous alloys were thermodynamically assessed using Thermo-Calc software with TCFE7 database for Fe-based alloys. The analysis of the alloys for a primary crystallization precipitating bcc-Fe revealed metastability among four phases comprising bcc-Fe, two kinds of Fe-based amorphous phases that are rich in Fe-B and Fe-P and crystalline Cu-rich phase. The roles of P and Cu additions to the Fe-based amorphous alloys are thermodynamically interpreted as stabilizing the remaining amorphous phase at the primary crystallization. The dual Fe-rich amorphous phases due to the inclusion of P characterize a heterogeneous amorphous structure of NANOMET family alloys comprising Fe and metalloids mainly and without early-transition metals.

The glass-forming ability (GFA) of an Fe26Si9B10P5 bulk metallic glass (BMG) was evaluated thermodynamically with commercial software, Thermo-Calc, with Fe-base database, TCFE7 by utilizing its best ability to deal with equilibrium phases. The Fe26Si9B10P3 BMG was selected because it is the simplest Fe-rich BMG belonging to Fe-metalloid type with the greatest sample dimensions. A possible reason for the presence of intermediate equilibrium phases to degrade GFA of the Fe26Si9B10P3 was discussed. The results revealed that the Fe26Si9B10P5 BMG is characterized by near eutectic composition in the Fe-rich Fe-Si-B-P quaternary system and by the simultaneous presence of Fe3P and absence of Fe2B phases in equilibrium at a range below the solidus- to the glass-transition temperatures. The analysis of Fe-26(Si,B,P)(24) alloys for equilibrium phases revealed that the Fe2P phase can degrade GFA of the Fe26Si9B10P5 BMG.

Effects of an addition of Si and P into amorphous Fe85.2B14Cu0.8 based soft magnetic alloys were investigated in boric-borate buffer solution. The addition of P decreased the passive current density effectively. Substituting Si for Pin Fe85.2SixB9P5 - xCu0.8 (x = 0, 1, 2 at.%) alloys further improved corrosion resistance. After the removal of the oxide films, the passive current density was higher than those covered by the oxide films. The lowest passive current density was observed at 5 x 10(-6) A/cm(2) on the Fe85.2Si1B9P4Cu0.8 alloy. On the other hand, the pitting potential of the alloys before and after removal of the oxide films was as high as about 0.96 V and was independent of chemical composition of the alloys. The addition of Si and P could enhance the corrosion resistance of Fe85.2SixB9P5 - xCu0.8 alloys via modification of the chemical composition of the oxide films. Cyclic voltammetric results indicated that the addition of Si suppressed the formation rate of bivalent Fe species, which slows down reaction rates of this rate-determining step. (C) 2014 Elsevier B.V. All rights reserved.

High-entropy alloys (HEAs) with an atomic arrangement of a hexagonal close-packed (hcp) structure were found in YGdTbDyLu and GdTbDyTmLu alloys as a nearly single hcp phase. The equi-atomic alloy design for HEAs assisted by binary phase diagrams started with selecting constituent elements with the hcp structure at room temperature by permitting allotropic transformation at a high temperature. The binary phase diagrams comprising the elements thus selected were carefully examined for the characteristics of miscibility in both liquid and solid phases as well as in both solids due to allotropic transformation. The miscibility in interest was considerably narrow enough to prevent segregation from taking place during casting around the equi-atomic composition. The alloy design eventually gave candidates of quinary equi-atomic alloys comprising heavy lanthanides principally. The XRD analysis revealed that YGdTbDyLu and GdTbDyTmLu alloys thus designed are formed into the hcp structure in a nearly single phase. It was found that these YGdTbDyLu and GdTbDyTmLu HEAs with an hcp structure have delta parameter (delta) values of 1.4 and 1.6, respectively, and mixing enthalpy (Delta H-mix) = 0 kJ/mol for both alloys. These alloys were consistently plotted in zone S for disordered HEAs in a delta-Delta H-mix diagram reported by Zhang et al. (Adv Eng Mater 10:534, 2008). The value of valence electron concentration of the alloys was evaluated to be 3 as the first report for HEAs with an hcp structure. The finding of HEAs with the hcp structure is significant in that HEAs have been extended to covering all three simple metallic crystalline structures ultimately followed by the body- and face-centered cubic (bcc and fcc) phases and to all four simple solid solutions that contain the glassy phase from high-entropy bulk metallic glasses.

Iron-based amorphous and nano-crystalline alloys have attracted a growing interest due to their potential in the application of magnetic coil production. However, fundamental understanding of the nano-crystallization mechanisms and magnetic features in the amorphous structure are still lack of knowledge. In the present work, we performed ab initio molecular dynamics simulation to clarify the ionic and electronic structure in atomic scale, and to derive the origin of the good magnetic property of Fe85Si2B8P4Cu1 amorphous alloy. The simulation gave a direct evidence of the Cu-P bonding preference in the amorphous alloy, which may promote nucleation in nano-crystallization process. On the other hand, the electron transfer and the band/orbital features in the amorphous alloy suggests that alloying elements with large electronegativity and the potential to expand Fe disordered matrix are preferred for enhancing the magnetization. (C) 2014 AIP Publishing LLC.

A role of Cu on the nanocrystallization of an Fe85.2Si1B9P4Cu0.8 alloy was investigated by X-ray absorption fine structure (XAFS) and transmission electron microscopy (TEM). The Cu K-edge XAFS results show that local structure around Cu is disordered for the as-quenched sample whereas it changes to fcc-like structure at 613 K. The fcc Cu-clusters are, however, thermodynamically unstable and begin to transform into bcc structure at 638 K. An explicit bcc structure is observed for the sample annealed at 693 K for 600 s in which TEM observation shows that precipitated bcc-Fe crystallites with similar to 12 nm are homogeneously distributed. The bcc structure of the Cu-clusters transforms into the fcc-type again at 973 K, which can be explained by the TEM observations; Cu segregates at grain boundaries between bcc-Fe crystallites and Fe-3(B, P) compounds. Combining the XAFS results with the TEM observations, the structure transition of the Cu-clusters from fcc to bcc is highly correlated with the preliminary precipitation of the bcc-Fe which takes place prior to the onset of the first crystallization temperature, T-x1 = 707 K. Thermodynamic analysis suggests that an interfacial energy density gamma between an fcc-Cu cluster and bcc-Fe matrix dominates at a certain case over the structural energy between fcc and bcc Cu, Delta G(fcc-bcc), which causes phase transition of the Cu clusters from fcc to bcc structure. (C) 2014 Author( s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

The values of mixing enthalpy (Delta H-mix) and Delta parameter (delta) were calculated with 73 elements from Miedema's model for multicomponent equi-atomic alloys to investigate the possibilities of the alloys to be formed into high-entropy (H-E) alloys or high-entropy bulk metallic glasses (HE-BMGs). The equi-atomic alloys from about 15 million (C-73(5)) quinary to 621 billion (C-73(10)) decimal systems were evaluated by referring to a Delta H-mix-delta diagram for zones S and B's for H-E alloys with disordered solid solutions and BMGs, respectively, reported by Zhang et al. The results revealed that the number of quinary equi-atomic alloys plotted in zone S is 28405 (similar to 0.19% in C-73(5)), whereas those in zones B-1 and B-2 for conventional and Cu- and Mg-based BMGs, respectively, were 1036385 and 21518 (similar to 6.90 and similar to 0.14%), respectively. This kind of statistical approach using Delta H-mix-delta diagram will lead to finding out unprecedented H-E alloys and HE-BMGs.

High-entropy (H-E) alloys, bulk metallic glasses (BMGs) and high-entropy BMGs (HE-BMGs) were statistically analyzed with the help of a database of ternary amorphous alloys. Thermodynamic quantities corresponding to heat of mixing and atomic size differences were calculated as a function of composition of the multicomponent alloys. Actual calculations were performed for configurational entropy (S-config.) in defining the H-E alloys and mismatch entropy (S-sigma) normalized with Boltzmann constant (k(B)), together with mixing enthalpy (Delta H-mix) based on Miedema's empirical model and Delta parameter (delta) as a corresponding parameter to S-sigma/k(B). The comparison between Delta H-mix-delta and Delta H-mix-root S-sigma/k(B) diagrams for the ternary amorphous alloys revealed S-sigma/k(B) similar to (delta/22)(2). The zones S, S' and B's where H-E alloys with disordered solid solutions, ordered alloys and BMGs are plotted in the Delta H-mix-delta diagram are correlated with the areas in the Delta H-mix - S-sigma/k(B) diagram. The results provide mutual understandings among H-E alloys, BMGs and HE-BMGs.

Owing to recent progress in nanotechnology, the ability to tune the surface properties of metals has opened an avenue for creating a new generation of biomaterials. Here we demonstrate the successful development of a novel Ti-based nanoglass composite with submicron-nanometer-sized hierarchical glassy structures. A first exploratory study was performed on the application of the unique nanostructure to modulate osteoblast behaviors. Our results show that this Ti-based nanoglass composite, relative to conventional metallic glasses, exhibits significantly improved biocompatibility. In fact, a 10 times enhancement in cell proliferation has been achieved. To a great extent, this superior bioactivity (such as enhanced cell proliferation and osteogenic phenotype) is promoted by its unique hierarchical structures combining nanoglobules and submicron button-like clusters from collective packing of these nanoglobules. This nanoglass composite could be widely applicable for surface modifications by means of coating on various materials including BMGs, crystalline metals or ceramics. Therefore, our successful experimental testing of this nanostructured metallic glass may open the way to new applications in novel biomaterial design for the purpose of bone replacement. © 2013 The Royal Society of Chemistry.

An Al0.5TiZrPdCuNi high-entropy (H-E) alloy with a bcc single phase was found through a Ti20Zr20Pd20Cu20Ni20 H-E glassy alloy designed based on equi-atomicity inherent to H-E alloys. The constituent elements and the composition of the Ti20Zr20Pd20Cu20Ni20 alloy were determined by regarding a binary Cu64Zr36 bulk metallic glass as Cu60Zr40 alloy and subsequent replacements of the Cu and Zr atoms with other late- and early-transition metals, respectively. The Ti20Zr20Pd20Cu20Ni20 alloy in a ribbon shape forms into a glassy single phase. The addition of 0.5Al to the Ti20Zr20Pd20Cu20Ni20 H-E glassy alloy resulted in forming a bcc single phase for a rod specimen with a diameter of 1.5 mm. The analysis revealed that the Al0.5TiZrPdCuNi H-E alloy is characterized by mixing enthalpy of -46.7 kJ.mol(-1) and Delta parameter of 8.8, which are considerably larger and negative for the former and larger for the latter against the conventional H-E alloys.

We produce nanostructured metallic glasses in different metal-based glass-forming systems by using magnetron sputtering with powder targets. This new class of materials: nanograined metallic glasses (NGMGs) show unique mechanical, physical and chemical properties. Attributed to the surface nanostructural topography, Ti-based NGMGs exhibit enhanced cell proliferation, comparable to or even higher than the well known biocompatible Ti metals.

In order to stabilize the supercooled liquid and enhance the glass forming ability of Al-based glass forming alloy, the alloying design based on minor Ca substitution for Al was examined to retard the precipitation of face-centered-cubic (FCC) Al. Calcium was selected as the alloying element, because it has a large negative mixing heating with Al but a positive value with the other components. This is anticipated to facilitate formation of Al-Ca clusters and then inhibit the diffusion of Al atoms which is thought to be the dominant reason that limits the glass forming ability (GFA) of Al-based alloys. The proposed strategy was confirmed in experiments by the observation of a greatly increased reduced glass transition temperature, T-rg = T-g/T-l (T-g the glass transition temperature and T-l the liquidus temperature), the increased the activation energy for crystallization, and the increased activation energy for diffusion. The Al85-xY8Ni5Co2Cax (x = 0.5-5) system is found to possess extraordinarily high T-rg = 0.613 far exceeding that for any known Al-based glass forming alloys. (C) 2012 Elsevier Ltd. All rights reserved.

The compositional features of bulk metallic glasses were statistically analyzed with an s-d(E)f-d(L)p(M)-p(MLD) tetrahedral composition diagram comprising s-, p-, d- and f-blocks in the periodic table, early- and late-transition metals and Metal Metalloid. The s-d(E)f-d(L)p(M)-p(MLD) diagram was filled with 25 BMGs with critical diameter over half-inch (similar to 12.7 cm), 264 BMGs with the critical diameter ranging 0.2 - 12 mm, 6 150 amorphous alloys from 351 ternary systems and 35 400 compounds. The analysis revealed that BMGs as well as the ternary amorphous alloys are principally plotted on s-d(E)f-d(L)p(M) and d(E)f-d(L)p(M)-p(MLD) faces and their edges and vertices, whereas no plots are seen in s-p(MLD) edge and deep inside the diagram of each component of s, d(E)f, d(L)p(M) or p(MLD) &gt;= 10 at. %. The s-d(E)f-d(L)p(M)-p(MLD) tetrahedral composition diagram is a useful tool for alloy design of bulk metallic glasses.

Molecular dynamics (MD) simulations based on a plastic crystal model (PCM) were performed for a Cu0.618Zr0.382 binary bulk metallic glass (BMG). The local atomic arrangements of the Cu0.618Zr0.382 BMG were demonstrated with MD-PCM under an assumption that the BMG is composed of randomly-rotated as well as distorted hypothetical clusters. The Cu-rich Cu0.618Zr0.382 alloy was computationally created from a tentatively-created Zr-rich Zr0.73Cu0.27 alloy through two steps. The first step includes the Zr0.73Cu0.27 alloy quenched from a liquid through conventional MD simulation, whereas the second step has a replacement of the Zr and Cu atoms in the Zr0.73Cu0.27 alloy with randomly-rotated icosahedral and tetrahedral clusters, respectively, and subsequent structural relaxation. The Cu0.618Zr0.382 alloy, thus created with MD-PCM, was formed in a noncrystalline state as a critically-percolated cluster-packed structure. The analyses with total pair-distribution and interference functions revealed that the calculation results tend to reproduce the experimental data in an as-quenched state. The results explain that the glass-forming ability of the Cu0.618Zr0.382 BMG is due to (1) a critically-percolated and distorted tetrahedral clusters forming a network and (2) atomistic-level inhomogeneity for the local atomic arrangements with keeping macroscopic homogeneity in terms of the chemical composition and dense random atomic arrangements. [doi:10.2320/matertrans.M2012025]

Molecular dynamics (MD) simulations were performed for a Zr2Ni alloy by referring to crystallographic features of a metastable Zr2Ni phase. Simulation method was identical to our previous studies named plastic crystal model (PCM), which includes crystallographic operations for an intermetallic compound in terms of the random rotations of hypothetical clusters around their center of gravity and subsequent annealing at a low temperature. On the basis of MD-PCM, the present study considers an additional refinement named united atom scheme (UAS) on the motions of atoms in the hypothetical clusters. In MD-PCM-UAS, Dreiding potential was assigned for atomic bonds in a cluster whereas Generalized Embedded Atom Method potential for the other atomic pairs. The simulation results by MD-PCM-UAS yield a liquid-like structure. However, annealing did not cause subsequent structural relaxation, which differs from the results by MD-PCM and conventional MD simulations. Further simulations based on MD-PCM-UAS were performed for a nanostructure comprising clusters and glue atoms, leading to the best fit with the experimental data.

An efficient alloy design for bulk metallic glasses (BMGs) assisted by a composition-configurational entropy (C-CE) diagram has been proposed by introducing a feature of high-entropy (HE) alloys that are defined by an equi-atomic alloy with five or more elements. The proposed alloy design compensated for a shortcoming in determining the compositions of BMGs and led to success in forming a Pd20Pt20Cu20Ni20P20 HE-BMG with a maximum diameter of 10 mm. The C-CE diagram demonstrates the equi-atomicity of alloys, providing candidates for HE-BMGs. The alloy design for HE-BMG will promise opening up the new cutting-edge in both HE alloys and BMGs. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of MRS-Taiwan

A Pd20Pt20Cu20Ni20P20 bulk metallic glass (BMG) with a high-entropy (HE) alloy composition and a maximum diameter of 10 mm was fabricated by fluxed water quenching. The system and composition of the Pd20Pt20Cu20Ni20P20 alloy were determined from a prototype ternary Pd40Ni40P20 BMG in accordance with two strategic alloy designs of (1) HE alloy defined by an equi-atomic alloy with five or more elements and (2) exchangeability of the constituent elements with a similar chemical nature in the periodic table. Pd20Pt20Cu20Ni20P20 HE-BMG had a supercooled liquid range of 65 K and a reduced glass transition temperature of 0.71. Successful formation of Pd20Pt20Cu20Ni20P20 HE-BMG is significant to develop new alloys for HE alloys and BMGs. (C) 2011 Elsevier Ltd. All rights reserved.