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Micro-cantilever bending tests are performed to quantify the fracture toughness and reveal the deformation mechanism of a Ti-based metallic glass. Plastic deformation is localized in shear bands initiating from the roots of the notches of the cantilevers. Although the load-displacement curves show considerable ductile failure characteristics, the notch fracture toughness values that obtained from the bending tests are extremely low (∼4.7 MPa m). Size dependent fracture is thought to be observed, where the fracture toughness increases with decreasing the uncracked ligament size of the cantilevers. TEM bright field images show that the shear bands with the width of 4–7 nm present brighter contrast. The regions in vicinity of the shear bands show dark zones (ranging from 3 to 5 nm in size) surrounded by continues bright zones. Cu nanocrystals are found not only inside the shear bands, but also around them. The free volume theory together with the simulation results is applied to explain the formation of shear bands in this Ti-based metallic glass during the bending deformation. The observed Cu nanocrystals are thought to be formed as a consequence of plastic-deformation-assisted crystallization. It is suggested that local atomic rearrangements lead to shifting of Cu nanocrystals towards more stable positions and cause the formation of Cu nanocrystals in regions subjected to high shear stress field.

Tailoring nanostructures is nowadays a common approach for enhancing the performance of thermoelectric Heusler compounds by decreasing the thermal conductivity without significantly affecting the electrical conductivity. However, the most widely reported method for obtaining nanostructured thermoelectrics, an approach based on crushing as-cast alloy ingots followed by sintering of the debris, only gives limited control of the final nanostructure due to residual elemental segregation after casting. Here, a novel approach for fabricating nanostructured Heusler compounds is presented, which is based on crystallizing an amorphous precursor of NbCo1.1Sn composition. This method yields two distinct nanostructures, namely one comprising only half-Heusler grains and another one comprising half-Heusler grains and full-Heusler nano-precipitates. The latter sample exhibits enhanced negative Seebeck coefficients as compared to the former over a wide temperature range. Using advanced characterization techniques, such as high-resolution transmission electron microscopy and atom probe tomography, in conjunction with ab initio density functional theory, detailed insights into the nanostructure and electrical properties of the specimens are provided. Filtering of low energy and mobility electrons at the half-Heusler and full-Heusler interface along with the formation of Co interstitial defects in the half-Heusler matrix are proposed to be the possible causes for the enhanced Seebeck coefficient of the nano-precipitate containing specimen., Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Team Marcel Sluiter, Team Poulumi Dey

This study demonstrates how multi-alloying the Fe-Si–B–P–Cu (Nanomet®) can avoid the strict requirements on the annealing scheme in terms of high heating rate and narrow annealing temperature range in order to grow a homogeneous ultrafine nanocrystalline structure. The rather restricted amorphization capability sets a low limit of the maximum thickness of the amorphous precursor. These shortcomings have their origin in the existence of detrimental pre-existing nuclei in the amorphous precursors, which in turn potentially lead to a heterogeneous crystallization. Here, we have multialloyed Nanomet with CoCNi- and CoCMo- to avoid the creation of these pre-existing nuclei. This leads to improved amorphization capability and changes a potentially heterogeneous crystallization to a homogeneous nanocrystallization over a much broader temperature range than for unalloyed Nanomet. Thus, the requirements for the annealing are much relaxed. This work encompasses quenching the amorphous precursors using melt-spinning, investigating the crystallization temperatures by calorimetry, showing the depletion of pre-existing nuclei by magneto-thermo-gravimetry, conceptualizing the crystallization dynamics using isothermal calorimetry, and finally revealing the excellent soft magnetic properties over a broad annealing temperature interval (390–490 °C for the substituted alloys compared to 410–470 °C for unalloyed Nanomet). The multi-elemental substitution of Fe with CoCMo and CoCNi in Nanomet alloy nearly maintains the saturation magnetization and the coercivity. We believe the substituted alloys provide a better alternative to Nanomet with improved amorphization capability and homogeneous nanocrystallization without any special heat treatment scheme. Graphical abstract: [Figure not available: see fulltext.], QC 20211215

Surface severe plastic deformation (S²PD) of additively manufactured/three-dimensional (3D) printed metallic parts is gaining increased attention as a post-manufacturing operation to enhance the material performance in a wide variety of applications. Surface mechanical attrition treatment (SMAT) is an S²PD technique that can yield a nanostructured surface layer induced by compressive stresses and work hardening. In the present study, SMAT was performed on 316L (austenitic) stainless steel (SS) processed by selective laser melting (SLM), and the consequent effects on mechanical response were investigated. The underlying mechanisms of microstructural evolution leading to the formation of nanocrystalline grains resulting from SMAT in SLM 316L SS are elucidated. The interactions between twins and deformation bands act as potential sites for impeding the movement of dislocations, which in turn leads to the formation of stacking faults, twinning, and occasionally transform to a different crystal structure. Twin-twin and/or twin-deformation band intersections sub-divide the matrix grains into smaller cells or low-angle disoriented blocks, which result in the formation of low-angle grain boundaries and finally in nanocrystallization at the surface. The size of nanocrystalline grains increases progressively with depth from the surface to micrometer size grains in bulk. The gradient nanostructure in the additively manufactured alloy after SMAT imparts an unusual combination of strength and ductility that markedly exceeds that of conventional, bulk nanostructured, or even high-performance 316L SS (containing nanoscale deformation twins embedded in submicron-sized austenitic grains obtained by dynamic plastic deformation processes). Analytical models revealed that strengthening results from a combination of grain boundaries and dislocations. The results of the present investigation pave the way for engineering high-performance SS for a variety of engineering applicatio

Tailoring nanostructures is nowadays a common approach for enhancing the performance of thermoelectric Heusler compounds by decreasing the thermal conductivity without significantly affecting the electrical conductivity. However, the most widely reported method for obtaining nanostructured thermoelectrics, an approach based on crushing as-cast alloy ingots followed by sintering of the debris, only gives limited control of the final nanostructure due to residual elemental segregation after casting. Here, a novel approach for fabricating nanostructured Heusler compounds is presented, which is based on crystallizing an amorphous precursor of NbCo1.1Sn composition. This method yields two distinct nanostructures, namely one comprising only half-Heusler grains and another one comprising half-Heusler grains and full-Heusler nano-precipitates. The latter sample exhibits enhanced negative Seebeck coefficients as compared to the former over a wide temperature range. Using advanced characterization techniques, such as high-resolution transmission electron microscopy and atom probe tomography, in conjunction with ab initio density functional theory, detailed insights into the nanostructure and electrical properties of the specimens are provided. Filtering of low energy and mobility electrons at the half-Heusler and full-Heusler interface along with the formation of Co interstitial defects in the half-Heusler matrix are proposed to be the possible causes for the enhanced Seebeck coefficient of the nano-precipitate containing specimen., Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Team Marcel Sluiter, Team Poulumi Dey

©2020 American Chemical Society The authors acknowledge the financial support from the Spanish Ministry of Science, Innovation and Universities under the projects RTI2018-095856-B-C21, MAT2017-86540-C4-1R, and RTI2018-095303-A-C52 and from Comunidad de Madrid NANOFRONTMAG S2013/MIT-2850 and NANOMAGCOST S2018/NMT-4321. A.S. acknowledges the financial support from the Comunidad de Madrid for an "Atracción de Talento Investigador" contract (no. 2017-t2/IND5395)., A combination of high-energy ball milling, vacuum filtering, and sedimentation processes has been demonstrated to be a useful approach to reduce, in a controlled way, the length of as-cast Fe_(73.5)Si_(13.5)Nb_3Cu_1B_9 amorphous magnetic microwires (MWs) and annealed material at 550 degrees C in nitrogen conditions. Homogeneous compositional microstructures with fairly narrow size distributions between 1300 and 11.7 mu m are achieved, exhibiting tunable response as a soft magnetic material and as a microwave absorber. From the magnetic perspective, the soft magnetic character is increased with smaller length of the MWs, whereas the remanence has the opposite behavior mainly due to the structural defects and the loss of the shape anisotropy. From the microwave absorption perspective, a novel potential applicability is tested in these refined microstructures. This innovation consists of coatings based on commercial paints with a filling percentage of 0.55% of MWs with different lengths deposited on metallic sheets. Large attenuation values around -40 dB are obtained in narrow spectral windows located in the GHz range, and their position can be varied by combining different optimized lengths of MW. As an example of this powerful mechanism for absorbing microwaves at specific frequencies, MW lengths of 2 mm and 50 mu m are chosen, where precise tailoring of the minimum reflection loss (R_L)is obtained in a range between 8.85 and 13.25 GHz. To confirm these experimental results, an effective medium standard model proposed for electrical permittivity is used. Experimental and theoretical results are consistent and these novel composites are also proposed as a feasible candidate for designing frequency-selective microwave absorbers on demand, with low filling percentages and high absorption intensity values., Ministerio de Ciencia e Innovación (MICINN), Comunidad de Madrid, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

Among metamagnetic materials, FeRh alloys are technologically appealing due to their uncommon antiferromagnetic-to-ferromagnetic metamagnetic transition which occurs at a temperature T* just above room temperature. Here, a controlled increase of T* (DT* B 20 8C) is induced in pre-selected regions of FeRh films via mechanical strain nanopatterning. Compressive stresses generated at the vicinity of predefined nanoindentation imprints cause a local reduction of the FeRh crystallographic unit cell parameter, which leads to an increase of T* in these confined micro-/nanometric areas. This enhances the stability of the antiferromagnetic phase in these localized regions. Remarkably, generation of periodic arrays of nanopatterned features also allows modifying the overall magnetic and electric transport properties across large areas of the FeRh films. This approach is highly appealing for the design of new memory architectures or other AFM-spintronic devices.

The material for investigation was a ribbon with an amorphous structure obtained by the melt spinning technique from a melt of molybdenum-modified Finemet-type high-permeability Fe72.5Cu1Nb2Mo1.5Si14B9 alloy. Using the methods of non-ambient X-ray diffraction, calorimetry, and dilatometry, temperature intervals of transformations during the transition of material from the amorphous state to the nanocrystalline one with subsequent recrystallization were determined. Each method was characterized by its own heating rate: 1 K / min for the non-ambient X-ray diffraction, 30 K / min for calorimetry, and 20 K / min for dilatometry. Regardless of the heating rate, phase and structure transformations (crystallization and recrystallization, respectively) were observed sequentially. With decreasing heating rate, the crystallization temperature significantly decreased and the recrystallization temperature slightly decreased. Specific heats of crystallization (386 kJ / mol) and recrystallization (88 kJ / mol) were calculated from calorimetry data. Basing on the results of X-ray diffraction and calorimetric studies, the possibility of using the structural unit model was analyzed to describe the amorphous state. It was supposed that any condensed state of the material (amorphous, nanocrystalline and recrystallized) were distinguished by different sizes of coherent scattering regions (CSRs). The lower estimate of coherent scattering regions size was made from the X-ray diffraction halo width for the amorphous state and (110) diffraction line broadening for polycrystals. The Wigner-Seitz cell (truncated octahedron) containing one atom has been adopted as a structural unit. Specific heats of transformations were compared to the values of energies related to the transitions of atoms from CSR borders to lattice sites. Satisfactory applicability of the structural unit model for the description of the amorphous state was demonstrated. © 2019, Institute for Metals Superplasticity Problems

Critical points of amorphous alloy of Fe-Si-Nb-Cu-Mo-B system was determined using the non-ambient x-ray diffraction method. The sample with amorphous structure was produced by planar flow casting process. Temperature range of alloy nanocrystalline state was established. © 2019, National University of Science and Technology MISIS. All rights reserved.

Metallic amorphous Finemet-type material, made in the ribbon form by the melt spinning technique, with thickness 20 μm, temperature transformations intervals were determining, using methods non-ambient x‑ray diffraction and calorimetry. The possibility of applying structural units model was analyzed to describe amorphous state based on matching x‑ray diffraction data with heating values., Методами терморентгеновского фазового и калориметрического анализов определялись температурные интервалы превращений металлического аморфного материала типа Finemet, изготовленного в форме ленты толщиной 20 мкм методом спиннингования. На основе сопоставления рентгенографических данных и величин тепловых эффектов проанализирована возможность применения модели структурных единиц к описанию аморфного состояния.

В настоящей работе объектом исследования является магнитомягкий аморфный сплав системы Fe-Si-Nb-Cu-Mo-B из группы материалов Finemet. Образец выполнен в виде ленты толщиной 20…30 мкм методом быстрой закалки (спиннингованием). Для определения температурных интервалов фазовых и структурных превращений в исходно аморфном сплаве были использованы методы калориметрии, дилатометрии, терморентгеновского фазового анализа. При скоростях нагрева 0,3…0,5 o/сек установлен температурный диапазон существования данного сплава в нанокристаллическом состоянии., The research object in that work is magnetically soft amorphous Fe-Si-Nb-Cu-Mo-B alloy. That and same alloy systems was named as Finemet material. The sample is an amorphous ribbon, which has thickness of 20…30 μm, it was producing by melt spinning method. The samples were studied using methods of calorimetry, dilatometry and non-ambient x-ray diffraction analysis. The alloy was heat treated. Data about thermal effects, changes in geometric dimensions, changes in the phase composition, and about critical points are obtained. Interval of nanocrystallic state existence for heating rate 0.3…0.5 o/sec was determined.

In this work, we present a complete study of the influence of Nb and Cu addition on the crystallization behavior of Nd-lean Nd-Fe-B melt-spun alloys. Alloys with compositions Nd10-x-yFe84B6NbxCuy (x = 1, y = 0 and x = 0.5, y = 0.5) were melt-spun at different wheel speeds (15-40 m s(-1)) to obtain samples in amorphous, highly disordered and nanocrystalline structures. The crystallization process, induced by different heat treatments, was studied by means of differential thermal analysis and x-ray powder thermodiffraction. Magnetic properties of as-made and heat-treated ribbons were measured by magnetometry. The as-made amorphous samples showed a crystallization to the 2: 14: 1 hard magnetic phase at T-1 similar to 350 degrees C. Doping with Nb results in an increase of T1, and addition of Cu lowers T1. This behavior is explained in terms of an inhibition of grain growth by Nb and a nucleation enhancement by Cu additions. During the crystallization process, a secondary phase (identified as a bcc-Fe-rich phase) is formed. The amount of such a phase increases with the annealing temperature. Coercivity increases upon annealing reaching maxima at 700-750 degrees C. This can be explained in terms of competition between the two phases formed: the 2: 14: 1 hard phase and the soft bcc-Fe-rich phase. The highest coercivity of the Nd-lean samples is observed when the microstructure is appropriate and both phases are exchange-coupled.

In this work, we present a complete study of the influence of Nb and Cu addition on the crystallization behavior of Nd-lean Nd-Fe-B melt-spun alloys. Alloys with compositions Nd10-x-yFe84B6NbxCuy (x = 1, y = 0 and x = 0.5, y = 0.5) were melt-spun at different wheel speeds (15-40 m s(-1)) to obtain samples in amorphous, highly disordered and nanocrystalline structures. The crystallization process, induced by different heat treatments, was studied by means of differential thermal analysis and x-ray powder thermodiffraction. Magnetic properties of as-made and heat-treated ribbons were measured by magnetometry. The as-made amorphous samples showed a crystallization to the 2: 14: 1 hard magnetic phase at T-1 similar to 350 degrees C. Doping with Nb results in an increase of T1, and addition of Cu lowers T1. This behavior is explained in terms of an inhibition of grain growth by Nb and a nucleation enhancement by Cu additions. During the crystallization process, a secondary phase (identified as a bcc-Fe-rich phase) is formed. The amount of such a phase increases with the annealing temperature. Coercivity increases upon annealing reaching maxima at 700-750 degrees C. This can be explained in terms of competition between the two phases formed: the 2: 14: 1 hard phase and the soft bcc-Fe-rich phase. The highest coercivity of the Nd-lean samples is observed when the microstructure is appropriate and both phases are exchange-coupled.

In this work, we present a complete study of the influence of Nb and Cu addition on the crystallization behavior of Nd-lean Nd-Fe-B melt-spun alloys. Alloys with compositions Nd10-x-yFe84B6NbxCuy (x = 1, y = 0 and x = 0.5, y = 0.5) were melt-spun at different wheel speeds (15-40 m s(-1)) to obtain samples in amorphous, highly disordered and nanocrystalline structures. The crystallization process, induced by different heat treatments, was studied by means of differential thermal analysis and x-ray powder thermodiffraction. Magnetic properties of as-made and heat-treated ribbons were measured by magnetometry. The as-made amorphous samples showed a crystallization to the 2: 14: 1 hard magnetic phase at T-1 similar to 350 degrees C. Doping with Nb results in an increase of T1, and addition of Cu lowers T1. This behavior is explained in terms of an inhibition of grain growth by Nb and a nucleation enhancement by Cu additions. During the crystallization process, a secondary phase (identified as a bcc-Fe-rich phase) is formed. The amount of such a phase increases with the annealing temperature. Coercivity increases upon annealing reaching maxima at 700-750 degrees C. This can be explained in terms of competition between the two phases formed: the 2: 14: 1 hard phase and the soft bcc-Fe-rich phase. The highest coercivity of the Nd-lean samples is observed when the microstructure is appropriate and both phases are exchange-coupled.

Vanadium pentoxide glassy-crystalline nanostructured materials were prepared by solidification of the molten V 2O 5, using the twin rollers technique. The studied materials were characterized by: X-ray diffractometry (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and impedance spectroscopy (IS). It was found that the morphology, the relative content of the glassy and crystalline phases, and the average dimensions of the V 2O 5 nanocrystallites in the glassy matrix depended on the synthesis parameters (temperature and duration of melting, twin rollers speed, additional grinding). The pelletized samples exhibited considerable electrical conductivity of ca. 10 - 3 Scm - 1 at room temperature. Preliminary charge-discharge tests of laboratory lithium metal batteries with cathodes based on the materials under study have been carried out. © 2011 Elsevier B.V.

The magnetoresistance (MR) was measured at 200, 250 and 300 K in magnetic fields up to B=12 T for a nanocrystallized Fe63.5Cr 10Nb3Cu1Si13.5B9 alloy. Both the longitudinal (LMR) and transverse (TMR) component of the magnetoresistance decreased from B=0 to about 0.1 T. This could be ascribed to a giant MR (GMR) effect due to spin-dependent scattering of conduction electrons along their path between two FeSi nanograins via the non-magnetic matrix. Such a scattering may occur if the nanograin moments are not or only weakly coupled in the absence of a strong exchange coupling (due to the high Cr content in the matrix) and/or only weak dipoledipole coupling is present (due to sufficiently large separations between the nanograins). For larger fields, the GMR saturated and a slightly nonlinear increase in MR with B was observed due to a contribution by the residual amorphous matrix. The anisotropic MR effect (AMR≡LMR-TMR) was negative for all fields and temperatures investigated. By measuring the MR of melt-quenched Fe100-xSix solid solutions with x=15, 18, 20, 25 and 28, the observed AMR could be identified as originating from the FeSi nanograins having a D03 structure.

The magnetoresistance (MR) was measured at 200, 250 and 300 K in magnetic fields up to B=12 T for a nanocrystallized Fe63.5Cr 10Nb3Cu1Si13.5B9 alloy. Both the longitudinal (LMR) and transverse (TMR) component of the magnetoresistance decreased from B=0 to about 0.1 T. This could be ascribed to a giant MR (GMR) effect due to spin-dependent scattering of conduction electrons along their path between two FeSi nanograins via the non-magnetic matrix. Such a scattering may occur if the nanograin moments are not or only weakly coupled in the absence of a strong exchange coupling (due to the high Cr content in the matrix) and/or only weak dipoledipole coupling is present (due to sufficiently large separations between the nanograins). For larger fields, the GMR saturated and a slightly nonlinear increase in MR with B was observed due to a contribution by the residual amorphous matrix. The anisotropic MR effect (AMR≡LMR-TMR) was negative for all fields and temperatures investigated. By measuring the MR of melt-quenched Fe100-xSix solid solutions with x=15, 18, 20, 25 and 28, the observed AMR could be identified as originating from the FeSi nanograins having a D03 structure.

The magnetoresistance (MR) was measured at 200, 250 and 300 K in magnetic fields up to B=12 T for a nanocrystallized Fe63.5Cr 10Nb3Cu1Si13.5B9 alloy. Both the longitudinal (LMR) and transverse (TMR) component of the magnetoresistance decreased from B=0 to about 0.1 T. This could be ascribed to a giant MR (GMR) effect due to spin-dependent scattering of conduction electrons along their path between two FeSi nanograins via the non-magnetic matrix. Such a scattering may occur if the nanograin moments are not or only weakly coupled in the absence of a strong exchange coupling (due to the high Cr content in the matrix) and/or only weak dipoledipole coupling is present (due to sufficiently large separations between the nanograins). For larger fields, the GMR saturated and a slightly nonlinear increase in MR with B was observed due to a contribution by the residual amorphous matrix. The anisotropic MR effect (AMR≡LMR-TMR) was negative for all fields and temperatures investigated. By measuring the MR of melt-quenched Fe100-xSix solid solutions with x=15, 18, 20, 25 and 28, the observed AMR could be identified as originating from the FeSi nanograins having a D03 structure.

The magnetoresistance (MR) was measured at 200, 250 and 300 K in magnetic fields up to B=12 T for a nanocrystallized Fe63.5Cr 10Nb3Cu1Si13.5B9 alloy. Both the longitudinal (LMR) and transverse (TMR) component of the magnetoresistance decreased from B=0 to about 0.1 T. This could be ascribed to a giant MR (GMR) effect due to spin-dependent scattering of conduction electrons along their path between two FeSi nanograins via the non-magnetic matrix. Such a scattering may occur if the nanograin moments are not or only weakly coupled in the absence of a strong exchange coupling (due to the high Cr content in the matrix) and/or only weak dipoledipole coupling is present (due to sufficiently large separations between the nanograins). For larger fields, the GMR saturated and a slightly nonlinear increase in MR with B was observed due to a contribution by the residual amorphous matrix. The anisotropic MR effect (AMR≡LMR-TMR) was negative for all fields and temperatures investigated. By measuring the MR of melt-quenched Fe100-xSix solid solutions with x=15, 18, 20, 25 and 28, the observed AMR could be identified as originating from the FeSi nanograins having a D03 structure.

The magnetoresistance (MR) was measured at 200, 250 and 300 K in magnetic fields up to B=12 T for a nanocrystallized Fe63.5Cr 10Nb3Cu1Si13.5B9 alloy. Both the longitudinal (LMR) and transverse (TMR) component of the magnetoresistance decreased from B=0 to about 0.1 T. This could be ascribed to a giant MR (GMR) effect due to spin-dependent scattering of conduction electrons along their path between two FeSi nanograins via the non-magnetic matrix. Such a scattering may occur if the nanograin moments are not or only weakly coupled in the absence of a strong exchange coupling (due to the high Cr content in the matrix) and/or only weak dipoledipole coupling is present (due to sufficiently large separations between the nanograins). For larger fields, the GMR saturated and a slightly nonlinear increase in MR with B was observed due to a contribution by the residual amorphous matrix. The anisotropic MR effect (AMR≡LMR-TMR) was negative for all fields and temperatures investigated. By measuring the MR of melt-quenched Fe100-xSix solid solutions with x=15, 18, 20, 25 and 28, the observed AMR could be identified as originating from the FeSi nanograins having a D03 structure.

Temperature dependence, from room temperature up to 1000 K, of the initial permeability of Fe83−xCoxGe5Zr6B5Cu1 x=5 and 20 alloys at different stages of devitrification is reported. As nanocrystallization progresses, room temperature decreases but high temperature one increases, leading to an improvement of its thermal stability extended from room temperature up to 915 K, characterized by a temperature coefficient of permeability 0.1%/K 4000 and 0.04%/K 800 for 5 and 20 at. % Co containing alloys, respectively.

Temperature dependence, from room temperature up to 1000 K, of the initial permeability of Fe83−xCoxGe5Zr6B5Cu1 x=5 and 20 alloys at different stages of devitrification is reported. As nanocrystallization progresses, room temperature decreases but high temperature one increases, leading to an improvement of its thermal stability extended from room temperature up to 915 K, characterized by a temperature coefficient of permeability 0.1%/K 4000 and 0.04%/K 800 for 5 and 20 at. % Co containing alloys, respectively.

Temperature dependence, from room temperature up to 1000 K, of the initial permeability of Fe83−xCoxGe5Zr6B5Cu1 x=5 and 20 alloys at different stages of devitrification is reported. As nanocrystallization progresses, room temperature decreases but high temperature one increases, leading to an improvement of its thermal stability extended from room temperature up to 915 K, characterized by a temperature coefficient of permeability 0.1%/K 4000 and 0.04%/K 800 for 5 and 20 at. % Co containing alloys, respectively.

Temperature dependence, from room temperature up to 1000 K, of the initial permeability of Fe83−xCoxGe5Zr6B5Cu1 x=5 and 20 alloys at different stages of devitrification is reported. As nanocrystallization progresses, room temperature decreases but high temperature one increases, leading to an improvement of its thermal stability extended from room temperature up to 915 K, characterized by a temperature coefficient of permeability 0.1%/K 4000 and 0.04%/K 800 for 5 and 20 at. % Co containing alloys, respectively.

General topical areas and categories included: 1. Theoretical modeling and computer simulations of nanostructures and properties 2. Synthesis and processing thin films and layers 3. Synthesis and processing solidification technique 4. Synthesis and processing-mechanical methods 5. Synthesis and processing-nanocrystallization of amorphous alloys 6. Synthesis and processing-electrodeposition, other physical, chemical, and biological methods 7. Nanocomposite (metal-metal, metal-ceramic, biocomposites) 8. Structure and characterization 9. Crystallography of nanocrystalline and nanoquasicrystalline material 10. Clusters and cluster assembled material 11. Mechanical properties and deformation behavior 12. Magnetic properties 13. Electrical and optical properties 14. Designing properties by microstructural control 15. Thermal stability and phase transformations in nanomaterials 16. Performance and applications 17. MEMS, sensors, and other microengineered structures 18. Bulk nanostructured materials.

A multidisciplinary team of Carnegie Mellon University (CMU) researchers with substantial support from the public and private sectors was assembled to develop new materials with improved magnetic and mechanical properties at high temperature. The group worked on the refinement of existing soft bulk materials while conducting research on novel nanocrystalline magnets in parallel. The team also studied existing and new high temperature permanent magnetic materials for use in aircraft engine applications. A vigorous search for new magnetic materials, both hard and soft, was conducted. Prototypes for bulk soft magnets were Fe-Co alloys. The effects of alloy grain size, structural order, orientation, and texture were studied to maximize induction and permeability, and minimize hysteretic and eddy current losses at elevated temperatures. Investigation of nanocrystalline materials for soft magnetic applications proceeded on two fronts: plasma synthesis of magnetic nanoparticles followed by the use of compaction techniques to form dense magnets, and the nanocrystallization of amorphous precursors to produce exchange coupled magnetic nanocrystals. The first effort has led to the synthesis of metallic nanoparticles, of new core shell structures, and nanocrystalline ferrites. The second effort has led to the discovery of a new nanocrystalline soft magnetic material called HITPERM on which work continues to explore its use in power electronic applications. For hard magnetic materials capable of operating at up to 400 degrees, the team investigated Co-containing 2:17, 1:12, and 3:29-based permanent magnet materials. They investigated the fundamental properties of these alloy systems as well as processing protocols for engineering optimal microstructures for hard magnetic properties. Co-containing 3:29 phase magnets have extended the temperature range of these materials. Rapid solidification was used to tailor microstructure and harness anisotropy.