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The peculiarities and modes of material modification with high-intensity, high-power density ion beams on the irradiated surface are studied for the first time. Chromium ions are implanted into a zirconium alloy using a 25 kW/cm2, 450 μs beam at the pulse repetition rates within 8–35 pps. Every high-energy ion pulse impact is followed by ultrafast cooling of the surface due to heat removal into the target material. Three modes are studied at the temperatures of 580, 700, and 900 °C with an additional pulsed heating. An increase in the average target temperature from 580 to 700 °C within 1 h at the same pulse power density allows increasing the depth of chromium ion alloying from 1.5 to more than 7 μm. The use of ultrafast cooling of the Zr1%Nb alloy surface offers a grain size reduction from a few μm to approximately 50–250 nm, without any microstructural changes throughout the sample volume. An inhomogeneous chromium ion distribution over the target surface and depth is observed. [ABSTRACT FROM AUTHOR]

The surface properties of nickel-based alloys with different alloying compositions against aggressively corrosive species were systematically evaluated by using the segregated and non-segregated models designed through first-principles calculations. The presence of typical VIB alloying elements such as chromium (Cr), molybdenum (Mo), and tungsten (W) elements near the nickel surface was identified to significantly enhance the surface adsorption of water molecules (H2O) and their decomposed products (OH, O, and H). The doping patterns and surface electronic structures were found to determine the adsorption diversity of these substances. Consequently, adsorbates containing oxygen were likely to induce the segregation tendencies of these selected alloying elements from the deep area of nickel toward the top-most surface layer (TSL). The electrode potential shifts of the surface Ni atom in the designed alloying systems, compared to the bare Ni (111) surface, were further calculated to identify the beneficial electrochemical performance of alloy surfaces in the absence/presence of various adsorbates. In vacuum, the locations of these alloying elements in the near-surface layers would more increase the electrode potential shifts, thereby delaying the dissolution of Ni atoms from metal substrates. Nevertheless, the presence of adsorbates led to notably negative electrode potential shifts for the Ni (111) surface, among which the decomposed products (hydroxyl and oxygen) were of the most passive effects on corrosion behavior of nickel. The detrimental effects of these adsorbates on surface stability would be effectively alleviated with the aid of atomic VIB alloying elements of nickel-based alloys, especially W segregation to the TSL regardless of the pH in aqueous environments. [ABSTRACT FROM AUTHOR]

This study investigated the effects on the magnetocaloric properties and corrosion resistance of Cr substitution for Fe in (Mn,Fe)2(P,Si) alloys. The characteristics of the first-order phase transition and the crystal structure were maintained, even after Cr substitution. In particular, a discontinuous change in the lattice parameters was exhibited during the transition from the ferromagnetic to paramagnetic phase at the Curie temperature. Increasing the Cr content reduced the Curie temperature and isothermal entropy change. The thermal hysteresis gradually increased by increasing the Cr content. Meanwhile, the small Cr content maintained the adiabatic temperature change and improved the corrosion resistance. Therefore, the tuning of the Cr content in (Mn,Fe)2(P,Si) alloys can provide possible applications due to their notable magnetocaloric properties and improved corrosion resistance. [ABSTRACT FROM AUTHOR]

Monolayer CrI3 is a rare ferromagnetic semiconductor with intrinsic long-range magnetic order, which makes it a great potential material in spintronic devices [Song et al., Science 360, 1214 (2018)]. To extend the applications of monolayer CrI3 in flexible devices, the modulation of its electronic and magnetic properties is important. Here, we investigated the combined effect of strain and alloy on the properties of monolayer CrI3 by first-principles calculations. Br is chosen as the alloyed element due to the similar atomic configuration and property of CrX3 (X = Br, I), and the strain is applied by simultaneously changing the in-plane lattice constants (a and b). We find that the bandgap of monolayer Cr2I6−xBrx can be tuned greatly, while the magnetic moment of monolayer Cr2I6−xBrx is regulated very little under different strain and Br concentration. This unique property of monolayer Cr2I6−xBrx under strain makes it a good candidate for the flexible spintronic devices. [ABSTRACT FROM AUTHOR]

Synergistic effects in the evolution of He bubbles and dislocation loops in Hastelloy N alloy were investigated using transmission electron microscopy and nanoindentation. Results show that the sizes of both He bubbles and dislocation loops induced by the He and Xe irradiation were larger than those in the individual irradiation cases. The corresponding hardening degree of irradiated sample was also measured to be higher than the combined hardening value of two individual irradiation cases. The underlying physics controlling the synergistic effects have revealed that the vacancies are preferentially captured by pre-existed He bubbles as compared to their annihilation with the interstitial atoms during the subsequent Xe irradiation. [ABSTRACT FROM AUTHOR]

High entropy alloys (HEAs) provide superior mechanical and functional properties. However, these advantages may disappear when a metastable single-phase solid solution decomposes at low temperatures upon long-term annealing. Therefore, understanding the underlying phase separation mechanisms is important for the design of new HEAs with controlled properties. In the current work, the thermal stability of a nanocrystalline CrMnFeCoNi HEA was investigated at different annealing conditions using a combinatorial processing platform, involving fast and parallel synthesis of nanocrystalline thin films, short annealing time for a rapid phase evolution, and direct characterization by atom probe tomography. The microstructural features of the decomposed CrMnFeCoNi alloy as well as its decomposition process were analyzed in terms of elemental distributions at the near-atomic scale. The results show that the segregation of Ni and Mn to grain boundaries in the initial single-phase alloy is a prerequisite and is observed to be the only occurring physical process at the early stage of phase decomposition. When the concentrations of Ni and Mn reach a certain value, phase decomposition starts and a MnNi-rich phase forms at grain boundaries. Next, two Cr-rich phases form at the interface between the MnNi-rich phase and the matrix. Meanwhile, a FeCo-rich phase forms in the grain interior. Based on these observations, the underlying mechanisms involving nucleation, diffusivity as well as thermodynamic considerations were discussed. [ABSTRACT FROM AUTHOR]

Numerous alloying elements can improve the mechanical properties of NbMoTaW refractory high-entropy alloys (RHEAs), but the relationship between the alloying of different elements and the changes in the microstructure and mechanical properties of RHEAs is ambiguous. The first principles based on density functional theory are used to calculate the lattice parameters, electronic properties, and elastic properties of NbMoTaW-based RHEAs to reveal the microstructure and mechanical properties of NbMoTaW RHEAs with alloying elements of the same period or subgroup. The melting point, lattice constant, and mass density of NbMoTaW-based RHEAs are controlled by the alloying elements such as Cr, V, Ti, Zr, and Hf. Valence electron concentration (VEC) is a key factor affecting the electronic structure and mechanical properties of NbMoTaW-based RHEAs. High VEC can improve the mechanical properties of RHEAs but reduce the ductility. Cr-alloying has a significant effect on mechanical properties of NbMoTaW RHEAs, and Ti has a significant effect on ductility. The orbital electronic interactions between the alloying elements and Nb, Mo, Ta, and W atoms shown by the density of states and electron density difference may explain the relationship between VEC and the mechanical properties of RHEAs. Our results provide the underlying insights needed to guide the design of NbMoTaW RHEAs with excellent mechanical properties. [ABSTRACT FROM AUTHOR]

Employing the first-principles exact muffin-tin orbital method in combination with the coherent potential approximation, we calculated the total energy and local magnetic moments of paramagnetic Fe-Cr-M (M = Cr, Mn, Fe, Co, Ni) alloys along the tetragonal distortion (Bain) path connecting the body centered cubic (bcc) and the face centered cubic (fcc) structures. The paramagnetic phase is modeled by the disordered local magnetic moment scheme. For all alloys, the local magnetic moments on Fe atoms decrease from the maximum value corresponding to the bcc phase toward the minimum value realized for the fcc phase. Cobalt atoms have non-vanishing local magnetic moments only for tetragonal lattices with c/a < 1.30, whereas the local magnetic moments of Mn show weak crystal structure dependence. We find that Cr stabilizes the bcc lattice and increases the energy barrier as going from the bcc toward the fcc phase. Both Co and Ni favor the fcc lattice and decrease the energy barrier relative to the bcc phase. On the other hand, the tetragonal distortion around the fcc phase is facilitated by Cr and to a somewhat lesser extent also by Ni, but strongly impeded by Co. Manganese has negligible effect on the structural energy difference as well as on the energy barrier along the Bain path. Our findings on the alloying induced softening or hardening of Fe-Cr based alloys against tetragonal distortions are important for understanding the interstitial driven martensitic transformations in alloy steels. [ABSTRACT FROM AUTHOR]

In this paper we take a few steps further in the development of an approach based on the use of an artificial neural network (ANN) to introduce long-range chemical effects and zero temperature relaxation (elastic strain) effects in a rigid lattice atomistic kinetic Monte Carlo (AKMC) model. The ANN is trained to predict the vacancy migration energies as calculated given an interatomic potential with the nudged elastic band method, as functions of the local atomic environment. The kinetics of a single-vacancy migration is thus predicted as accurately as possible, within the limits of the given interatomic potential. The detailed procedure to apply this method is described and analyzed in detail. A novel ANN training algorithm is proposed to deal with the necessarily large number of input variables to be taken into account in the mathematical regression of the migration energies. The application of the ANN-based AKMC method to the simulation of a thermal annealing experiment in Fe–20%Cr alloy is reported. The results obtained are found to be in better agreement with experiments, as compared to already published simulations, where no atomic relaxation was taken into account and chemical effects were only heuristically allowed for. [ABSTRACT FROM AUTHOR]

Using state-of-the-art first-principles calculations, we study the properties of the ferromagnetic Heusler compounds NiYSi, where Y stands for V, Cr, or Mn. NiCrSi and NiMnSi contrary to NiVSi are half-metallic at their equilibrium lattice constant exhibiting integer values of the total spin magnetic moment, and thus we concentrate on these two alloys. The minority-spin gap has the same characteristics as for the well-known NiMnSb alloy being around ∼1 eV. Upon tetragonalization, the gap is present in the density of states even for expansion or contraction of the out-of-plane lattice parameter by 5%. The Cr–Cr and Mn–Mn interactions make ferromagnetism extremely stable and the Curie temperature exceeds 1000 K for NiMnSi. Surface and interfaces with GaP, ZnS, and Si semiconductors are not half-metallic but, in the case of NiCrSi, the Ni-based contacts present spin polarization at the Fermi level around 90%. Finally, we show that there are two cases of defects and atomic-swaps. The first ones, which involve the Cr(Mn) and Si atoms, induce states at the edges of the gap, which persists for a moderate concentration of defects. Defects involving Ni atoms induce states localized within the gap completely destroying the half-metallicity. Based on single-impurity calculations, we associate these states to the symmetry of the crystal. [ABSTRACT FROM AUTHOR]

The effect of Cr addition on the glass-forming ability (GFA), the magnetic properties, and corrosion resistance in Fe–Mo–Ga–P–C–B–Si glassy alloys was investigated. In addition to a slight increase of supercooled liquid region from 50 to 55 K, the substitution of a small amount of Fe with Cr was found to be effective for approaching alloy to a eutectic point, resulting in an increase in GFA. By copper mold casting, bulk glassy alloy rods with diameters up to 3 mm were produced. These glassy alloys exhibit a rather high saturation magnetization of 0.84–1.11 T with good soft-magnetic properties, i.e., low coercive force of 2.3–2.9 A/m, and high effective permeability of 13 360–15 960 at 1 kHz under a field of 1 A/m. The passive current density of the glassy alloy rod in 3 mass % NaCl solution decreased significantly from 1×102 to 3×10-1 A/m2 with an increase in Cr content, indicating that the addition of Cr is effective in enhancing the corrosion resistance. [ABSTRACT FROM AUTHOR]

Iron-9% chromium alloy of controlled purity and microstructure was helium implanted and studied using transmission electron microscopy and electron holography (EH). Fresnel imaging is compared with electron holography for a set of identical helium bubbles of size 2–4 nm. Electron holography reveals that the bubbles are, in fact, faceted and the lateral and projected dimensions of the cavities are measured. Current measurements allow the detection of 1 nm diameter bubbles using EH. The merits of conventional and holographic techniques are discussed and future improvements anticipated. Electron holography seems to be the ideal technique for investigating the morphology of helium bubbles and cavities in general. [ABSTRACT FROM AUTHOR]

Magnetization reversal phenomena (MRP) along magnetic order-order transitions have recently been reported on impurity-doped magnetic systems. Because imperfect long-range magnetic order exists in these systems, it is expected that a systematic investigation of MRP will give physical information on thermomagnetic processes of magnetic systems in the range from the micro- to nanoscales. As a typical order-order transition (a state doubly modulated by helical and canting orders to a collinear ferrimagnetic state) has been known to occur on Cr5S6 at a transition temperature Tt, we investigate the magnetizations of (Cr0.70Ti0.30)5S6 on heating and cooling runs in various magnetic fields. At 20 Oe, the field-cooled magnetization just below the Curie temperature has a positive sign; the sign turns negative below the compensation temperature TCM (first step) and finally returns to positive below Tt (second step). The first-step MRP observed in this system is explained by the potential barriers resulting from anisotropy energy when the preferred direction of collinear ferrimagnetic moment reverses. The proposed mechanism for second-step MRP is the pinning effect caused by the impurity atoms (Ti) in the helical long-range-order chains. Comparing other examples of MRPs, we discuss the roles of local impurity centers in the thermomagnetic process in magnetic order-order transitions. [ABSTRACT FROM AUTHOR]

Magnetization reversal phenomena (MRP) along magnetic order-order transitions have recently been reported on impurity-doped magnetic systems. Because imperfect long-range magnetic order exists in these systems, it is expected that a systematic investigation of MRP will give physical information on thermomagnetic processes of magnetic systems in the range from the micro- to nanoscales. As a typical order-order transition (a state doubly modulated by helical and canting orders to a collinear ferrimagnetic state) has been known to occur on Cr5S6 at a transition temperature Tt, we investigate the magnetizations of (Cr0.70Ti0.30)5S6 on heating and cooling runs in various magnetic fields. At 20 Oe, the field-cooled magnetization just below the Curie temperature has a positive sign; the sign turns negative below the compensation temperature TCM (first step) and finally returns to positive below Tt (second step). The first-step MRP observed in this system is explained by the potential barriers resulting from anisotropy energy when the preferred direction of collinear ferrimagnetic moment reverses. The proposed mechanism for second-step MRP is the pinning effect caused by the impurity atoms (Ti) in the helical long-range-order chains. Comparing other examples of MRPs, we discuss the roles of local impurity centers in the thermomagnetic process in magnetic order-order transitions. [ABSTRACT FROM AUTHOR]

A study by transmission electron microscopy of the influence of the In and N contents in the ranges of 20%–35% and 1.1%–3%, respectively, on the microstructure of Ga1-xInxNyAs1-y quantum wells is presented. Frank dislocation loops characterized as extrinsic have been found in the samples with x>=0.25. In these structures, threading dislocations appear as a consequence of the unfaulting of the loops for y>=0.014. An analysis of the density and size of the dislocation loops has provided an estimation of the critical radius for the unfaulting process. A model for this critical radius of the unfaulting process of extrinsic Frank loops is proposed. From this model and experimental values of critical radius, an estimation of the stacking fault energy of the GaInNAs alloy has been made. We have found a reduction in the stacking fault energy of the GaInNAs alloys when increasing the N content from 1.4% to 2.3% in good agreement with the theoretical estimation of the stacking fault energies of zinc-blende GaN and InN. [ABSTRACT FROM AUTHOR]

The electrochemical characteristics of single bcc phase Ti-30V-15Cr-15Mn alloy were investigated. It was demonstrated that the single bcc phase alloy has high electrochemical discharge performance at high temperature. Its discharge capacity is closely related with temperature and discharge current. The first discharge capacities of 580–814 mAh g-1 of the alloy powder were obtained at discharge current of 45–10 mA g-1 in 6 M KOH solution at 353 K. Although the electrochemical cycle life of the alloy is unsatisfactory at present, it opens up prospects for developing a new hydrogen storage alloy with high hydrogen capacity for use as high performance metal hydride electrodes in rechargeable Ni-MH battery. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Unusual metastable paramagnetic phases have been observed in Fe-Cr thin films (thickness about 40 nm) fabricated by pulsed laser deposition. In the present article, x-ray diffraction and Mössbauer spectroscopy have been applied to follow the structural and magnetic phase transformation in these alloys induced by ion irradiation with a projected range positioned in the center of the films. It has been found that the critical dose for the transformation to the more stable body-centered cubic (bcc) structure depends on the initial phase of the film and the ion mass. The initial body-centered tetragonal phase, which forms in the alloys with low Cr content (∼30 at. %), can be completely transformed to the bcc phase already by a dose of 5 × 10[sup 15] Cr/cm², whereas the primitive orthorhombic phase of roughly equiatomic Fe-Cr alloys is about four times more resistant against ion bombardment. A five times higher Ne ion dose is required to induce the same transformation as by the Cr bombardment. The observed effects are discussed in view of radiation damage caused by the different ions and the grade of affinity of the initial phase to the bcc one. [ABSTRACT FROM AUTHOR]

Examines the temperature dependence of semiconducting and structural properties of coevaporated chromium-silicon (Cr-Si) thin alloy films. Kinetics of amorphous-to-crystalline transformation of Cr-Si alloy film; Measurements of the thermoelectric properties of Cr-Si; Conduction mechanism of thin Cr-Si polycrystalline layers.

Presents information on a study which measured the rate at which recorded signals decay in perpendicular cobalt (Co) [sub78] chromium (Cr) [sub17] tantalum (Ta) [sub5] alloys, Co[sub70] Cr[sub15] Ta[sub5] platinum[sub10] alloys and palladium/cobalt multilayers. Importance of time relaxation in information storage; Experimental procedure; Results.

Deals with a study which investigated the damping capacity of thermally sprayed iron-chromium-X alloy coatings using a cantilever method. Experimental procedures; Discussion; Conclusions.

Studies the interface structure and reactions of nickel-chromium alloy and aluminum thin film bilayers using glancing-angle x-ray reflectivity and extended x-ray-absorption fine structure techniques. Sample preparation and x-ray measurements; Results; Discussion.

Presents a study that investigated the properties of cobalt-chromium alloy double-layered thin films. Analysis of the magnetic properties of the thin films; Examination of the structural properties of the thin films; Evaluation of the recording properties of the thin films.

L10 ordered FePt thin films with face-centered-tetragonal (001) texture have been prepared by magnetron sputtering on Cr100-xWx underlayer. The dependence of Cr100-xWx microstructure and FePt texture on the W content in the Cr underlayer was investigated. The addition of W element in Cr underlayer enhances the Cr (200) texture and increases the lattice constant of Cr, which is favorable for lowering the transformation temperature from fcc to fct phase because of the increase of the tensile stress along the FePt a axis. A good FePt (001) texture is obtained on the Cr85W15 underlayer with a substrate temperature of 400 °C. The coercivity of FePt thin films on CrW underlayer is higher than on Cr underlayer and increases with increasing W content in the Cr underlayer because the formation of the CrW alloy inhibits the diffusion between FePt and CrW layer. A 5 nm Pt intermediate layer was employed to suppress the diffusion between FePt and CrW underlayer further. [ABSTRACT FROM AUTHOR]

The alloy doping effects of the CrMo underlayer were investigated on the texture, grain size, and magnetic properties of CoCrPt longitudinal media. 5% Mn dissolving into CrMo lattices enhanced the texture of the recording layer and significantly raised the coercivity from 2200 (on the CrMo underlayer) to 3200 Oe. Further increases in the Mn content resulted in the grain growth of the recording layer, and less enhanced coercivity. The doped Zr, Ag, and Nb atoms into CrMo underlayers were segregated and led to reduction of grain size. Among them, Zr doping exhibited the most pronounced effects. [ABSTRACT FROM AUTHOR]

Studies the recording of beyond 10 gigabit/square inch with cobalt-chromium based perpendicular recording media and ring heads. Disk samples used; Experimental details; Results and discussion.

Investigates the relationship between the remanent magnetization and the film microstructure for various types of CoCr-alloy single-layer perpendicular media. Experimental procedure; Results and discussions.

Demonstrates the deposition of magnetic perpendicular recording cobalt-chromium layers with nano-size domains using a plasma enhanced type of sputtering apparatus. Experimental procedure; Results.

Provides information on a study which investigated the effects of chromium...titanium.../cobalt-titanium bilayer on the magnetic and crystallographic properties in cobalt-chromium-platinum longitudinal recording media. Experimental method; Results and discussion.

Reports on electrical resistivity studies on single-crystal samples of dilute chromium-aluminum (Cr-Al) alloys to resolve the complex features reported for the magnetic phase diagram of Cr-Al system. Infrared reflectivity data; Disappearance of antiferromagnetism.

Focuses on a study which determined magnetic phase diagrams for dilute tin and antimony alloys of chromium using neutron diffraction techniques. Antiferromagnetism ni chromium metal dilute alloys; Results and discussion.

Provides some anomalous aspects of resistivity behavior in dilute chromium alloy systems. Features of resistivity in relation to the spin density wave antiferromagnetism of chromium; Effect of the addition of vanadium on the electron-hole pairs; Characteristics of the CrPd dilute alloys.

Studies the Kondo effect in the paramagnetic phase of CrFe alloy with the spin-density-wave suppressed by pressure or V doping. Manifestation of impurity resonance scattering.

Presents the results for the dynamics of the charge-density-wave (CDW) within the random phase approximation. Formation of CDW with wavevector 2Q in chromium alloys; Near linear dispersion of charge phasons.