1,314 research outputs found
On the origin of extremely high strength of ultrafine-grained Al alloys produced by severe plastic deformation
Ultrafine-grained Al alloys produced by high pressure torsion are found to
exhibit a very high strength, considerably exceeding the Hall-Petch predictions
for the ultrafine grains. The phenomena can be attributed to the unique
combination of ultrafine structure and deformation-induced segregations of
solute elements along grain boundaries, which may affect the emission and
mobility of intragranular dislocations
Relations between the aromaticity and magnetic dipole transitions in the electronic spectra of hetero[8]circulenes
Magnetically induced current densities have been calculated at the second-order MOller-Plesset perturbation theory (MP2) level for seven hetero[8]circulenes and their dicationic and dianionic forms. Calculations of the magnetic dipole transition moments have also been carried out at the algebraic diagrammatic construction (ADC(2)) and the second-order approximate coupled-cluster (CC2) levels. The calculations show that the degree of aromaticity and the size of the magnetic dipole transition moment of the lowest magnetic-dipole allowed excited state are related. We show that neutral hetero[8]circulenes are weakly antiaromatic when the first excited state with a large magnetic dipole transition moment of 10-16 a.u. lies at high energies (approximate to 2.8-3.5 eV). For the dications, this transition often lies at much lower energies. Hetero[8]circulene dications with large magnetic dipole transition moments are strongly antiaromatic. The lowest excited states of the hetero[8]circulene dianions have very small magnetic dipole transition moments implying that they are aromatic.Peer reviewe
ΠΡΠ΅Π΄ΠΏΠΎΡΡΠ»ΠΊΠΈ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΡ ΠΏΡΠΎΡΠ²Π΅ΡΠΈΠ²Π°ΡΡΠ΅ΠΉ ΡΠ»Π΅ΠΊΡΡΠΎΠ½Π½ΠΎΠΉ ΠΌΠΈΠΊΡΠΎΡΠΊΠΎΠΏΠΈΠΈ ΠΊΠ°ΠΊ Π³Π΅ΠΎΡ ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΌΠ΅ΡΠΎΠ΄ΠΈΠΊΠΈ Π²ΡΡΠ²Π»Π΅Π½ΠΈΡ ΠΌΠΈΠ³ΡΠ°ΡΠΈΠΎΠ½Π½ΡΡ ΠΌΠΈΠ½Π΅ΡΠ°Π»ΡΠ½ΡΡ ΡΠΎΡΠΌ Π½Π°Π΄ ΡΠ³Π»Π΅Π²ΠΎΠ΄ΠΎΡΠΎΠ΄Π½ΡΠΌΠΈ Π·Π°Π»Π΅ΠΆΠ°ΠΌΠΈ
ΠΠΊΡΡΠ°Π»ΡΠ½ΠΎΡΡΡ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ ΠΎΠ±ΡΡΠ»ΠΎΠ²Π»Π΅Π½Π° Π½Π΅ΠΎΠ±Ρ
ΠΎΠ΄ΠΈΠΌΠΎΡΡΡΡ ΡΠ°Π·ΡΠ°Π±ΠΎΡΠΊΠΈ ΠΌΠ΅ΡΠΎΠ΄ΠΈΠΊΠΈ Π½Π°Ρ
ΠΎΠΆΠ΄Π΅Π½ΠΈΡ ΠΈ ΠΎΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΡ ΠΌΠΈΠ³ΡΠ°ΡΠΈΠΎΠ½Π½ΡΡ
ΡΠΎΡΠΌ ΠΌΠ΅ΡΠ°Π»Π»ΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΠΎΠ΅Π΄ΠΈΠ½Π΅Π½ΠΈΠΉ Π½Π°Π΄ ΠΊΠΎΠ½ΡΡΡΠ°ΠΌΠΈ ΡΠ³Π»Π΅Π²ΠΎΠ΄ΠΎΡΠΎΠ΄Π½ΡΡ
Π·Π°Π»Π΅ΠΆΠ΅ΠΉ Π½Π° ΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠΈ ΠΠ΅ΠΌΠ»ΠΈ, ΡΠ°ΠΊ ΠΊΠ°ΠΊ ΡΡΡΠ΅ΡΡΠ²ΡΡΡΠ°Ρ Π² Π½Π°ΡΡΠΎΡΡΠ΅Π΅ Π²ΡΠ΅ΠΌΡ ΠΈΠ½ΡΠΎΡΠΌΠ°ΡΠΈΡ ΠΎ Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΡΡΠΈ ΠΏΠ΅ΡΠ΅Π½ΠΎΡΠ° ΠΌΠ΅ΡΠ°Π»Π»ΠΎΠ² Ρ ΡΡΠΎΠ²Π½Ρ Π·Π°Π»Π΅ΠΆΠΈ Π·Π°ΡΠ°ΡΡΡΡ ΠΏΡΠΎΡΠΈΠ²ΠΎΡΠ΅ΡΠΈΠ²Π°, ΡΡΠΎ ΡΡΠ°Π²ΠΈΡ ΠΏΠΎΠ΄ ΡΠΎΠΌΠ½Π΅Π½ΠΈΠ΅ ΡΠ°ΠΌΡ Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΡΡΡ Π³Π΅ΠΎΡ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΏΠΎΠΈΡΠΊΠΎΠ² ΡΠ³Π»Π΅Π²ΠΎΠ΄ΠΎΡΠΎΠ΄Π½ΡΡ
Π·Π°Π»Π΅ΠΆΠ΅ΠΉ Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ ΠΈΠ½ΡΠΎΡΠΌΠ°ΡΠΈΠΈ ΠΎ ΡΠΎΠ΄Π΅ΡΠΆΠ°Π½ΠΈΠΈ ΠΌΠ΅ΡΠ°Π»Π»ΠΎΠ² Π² ΠΏΡΠΈΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠ½ΡΡ
Π³ΠΎΡΠΈΠ·ΠΎΠ½ΡΠ°Ρ
. ΠΠ±ΡΡΠΆΠ΄Π°Π΅ΠΌΠ°Ρ ΠΌΠ΅ΡΠΎΠ΄ΠΈΠΊΠ° ΡΠ±ΠΎΡΠ° ΠΈ Π°Π½Π°Π»ΠΈΠ·Π° ΠΏΠΎΠ·Π²ΠΎΠ»ΡΠ΅Ρ ΠΈΠ·ΡΡΠ°ΡΡ Π½Π°Π½ΠΎΡΠ°Π·ΠΌΠ΅ΡΠ½ΡΠ΅ ΡΠΎΠ΅Π΄ΠΈΠ½Π΅Π½ΠΈΡ ΠΌΠ΅ΡΠ°Π»Π»ΠΎΠ², ΠΌΠΈΠ³ΡΠΈΡΡΡΡΠΈΡ
Π² ΡΠΎΡΡΠ°Π²Π΅ Π³Π°Π·ΠΎΠ²ΠΎΠ³ΠΎ ΠΏΠΎΡΠΎΠΊΠ° Π΄ΠΎ ΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠΈ ΠΠ΅ΠΌΠ»ΠΈ. ΠΠΎΡΠ²Π»ΡΠ΅ΡΡΡ Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΡΡΡ ΡΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½ΠΈΡ ΠΏΡΠΎΠΈΡΡ
ΠΎΠΆΠ΄Π΅Π½ΠΈΡ Π½Π°ΠΉΠ΄Π΅Π½Π½ΠΎΠ³ΠΎ Π½Π°Π½ΠΎΡΠ°Π·ΠΌΠ΅ΡΠ½ΠΎΠ³ΠΎ ΠΌΠ΅ΡΠ°Π»Π»ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠΎΠ΅Π΄ΠΈΠ½Π΅Π½ΠΈΡ Ρ Π΄ΠΎΠΏΡΡΡΠΈΠΌΠΎΡΡΡΡ Π΄ΠΎΠΊΠ°Π·Π°ΡΡ Π³Π»ΡΠ±ΠΈΠ½Π½ΡΡ ΠΏΡΠΈΡΠΎΠ΄Ρ ΠΏΡΠΎΠΈΡΡ
ΠΎΠΆΠ΄Π΅Π½ΠΈΡ Π²Π΅ΡΠ΅ΡΡΠ²Π°, Π½Π°ΠΉΠ΄Π΅Π½Π½ΠΎΠ³ΠΎ Π½Π° Π΄Π½Π΅Π²Π½ΠΎΠΉ ΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠΈ. Π¦Π΅Π»Ρ ΡΠ°Π±ΠΎΡΡ: ΠΎΠ±Π·ΠΎΡ ΠΈ Π°Π½Π°Π»ΠΈΠ· ΡΡΡΠ΅ΡΡΠ²ΡΡΡΠΈΡ
Π·Π½Π°Π½ΠΈΠΉ ΠΎ Π³Π΅ΠΎΡ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΌΠ΅ΡΠΎΠ΄Π°Ρ
ΠΏΠΎΠΈΡΠΊΠΎΠ² ΠΌΠ΅ΡΡΠΎΡΠΎΠΆΠ΄Π΅Π½ΠΈΠΉ Π½Π΅ΡΡΠΈ ΠΈ Π³Π°Π·Π°; ΠΌΠΎΠ΄Π΅Π»ΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ Π½ΠΎΠ²ΠΎΠΉ Π³Π΅ΠΎΡ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΌΠ΅ΡΠΎΠ΄ΠΈΠΊΠΈ, ΡΠ²ΡΠ·Π°Π½Π½ΠΎΠΉ Ρ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠ΅ΠΌ ΠΎΠ±ΡΠ°Π·ΡΠΎΠ² Π½Π° ΠΏΡΠΎΡΠ²Π΅ΡΠΈΠ²Π°ΡΡΠ΅ΠΌ ΡΠ»Π΅ΠΊΡΡΠΎΠ½Π½ΠΎΠΌ ΠΌΠΈΠΊΡΠΎΡΠΊΠΎΠΏΠ΅, Ρ Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΡΡΡΡ ΡΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½ΠΈΡ ΡΠ°ΡΡΠΈΡ Π² Π½Π°Π½ΠΎΡΠ°Π·ΠΌΠ΅ΡΠ½ΠΎΠΌ ΡΠΎΡΡΠΎΡΠ½ΠΈΠΈ. ΠΠ΅ΡΠΎΠ΄Ρ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ: Π³Π΅ΠΎΡ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΠΌΠ΅ΡΠΎΠ΄Ρ ΠΏΠΎΠΈΡΠΊΠ° ΠΈ ΡΠ°Π·Π²Π΅Π΄ΠΊΠΈ ΠΌΠ΅ΡΡΠΎΡΠΎΠΆΠ΄Π΅Π½ΠΈΠΉ Π½Π΅ΡΡΠΈ ΠΈ Π³Π°Π·Π°, ΠΏΡΠΎΡΠ²Π΅ΡΠΈΠ²Π°ΡΡΠ°Ρ ΡΠ»Π΅ΠΊΡΡΠΎΠ½Π½Π°Ρ ΠΌΠΈΠΊΡΠΎΡΠΊΠΎΠΏΠΈΡ. Π Π΅Π·ΡΠ»ΡΡΠ°ΡΡ. ΠΡΠΎΠ²Π΅Π΄Π΅Π½ ΠΎΠ±Π·ΠΎΡ ΠΈ Π°Π½Π°Π»ΠΈΠ· Π»ΠΈΡΠ΅ΡΠ°ΡΡΡΡ Π½Π° ΡΠ΅ΠΌΡ Π³Π΅ΠΎΡ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΌΠ΅ΡΠΎΠ΄ΠΎΠ² ΠΏΠΎΠΈΡΠΊΠΎΠ² Π·Π°Π»Π΅ΠΆΠ΅ΠΉ Π½Π΅ΡΡΠΈ ΠΈ Π³Π°Π·Π°, ΠΏΡΠΎΠ°Π½Π°Π»ΠΈΠ·ΠΈΡΠΎΠ²Π°Π½Ρ Π·Π°ΠΊΠΎΠ½ΠΎΠΌΠ΅ΡΠ½ΠΎΡΡΠΈ ΠΎΡΠΎΠ±Π΅Π½Π½ΠΎΡΡΠ΅ΠΉ Π³Π΅ΠΎΡ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΏΠΎΠ»Π΅ΠΉ Π½Π°Π΄ ΠΌΠ΅ΡΡΠΎΡΠΎΠΆΠ΄Π΅Π½ΠΈΡΠΌΠΈ Π½Π΅ΡΡΠΈ ΠΈ Π³Π°Π·Π° ΠΠ°ΠΏΠ°Π΄Π½ΠΎ-Π‘ΠΈΠ±ΠΈΡΡΠΊΠΎΠΉ Π½Π΅ΡΡΠ΅Π³Π°Π·ΠΎΠ½ΠΎΡΠ½ΠΎΠΉ ΠΏΡΠΎΠ²ΠΈΠ½ΡΠΈΠΈ. ΠΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½Π° Π½ΠΎΠ²Π°Ρ Π³Π΅ΠΎΡ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠ°Ρ ΠΌΠ΅ΡΠΎΠ΄ΠΈΠΊΠ° ΠΏΠΎΠΈΡΠΊΠΎΠ² ΠΈ ΡΠ°Π·Π²Π΅Π΄ΠΊΠΈ, ΠΊΠΎΡΠΎΡΠ°Ρ ΡΠΏΠΎΡΠΎΠ±Π½Π° Π²ΡΡΠ²Π»ΡΡΡ ΠΌΠΈΠ½Π΅ΡΠ°Π»ΡΠ½ΡΠ΅ ΡΠΎΡΠΌΡ Π½Π°Ρ
ΠΎΠΆΠ΄Π΅Π½ΠΈΡ Ρ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΠ»Π΅ΠΌΠ΅Π½ΡΠΎΠ² Π² Π½Π°Π½ΠΎΡΠ°Π·ΠΌΠ΅ΡΠ½ΠΎΠΌ ΡΠΎΡΡΠΎΡΠ½ΠΈΠΈ Π½Π° ΠΏΡΠΎΡΠ²Π΅ΡΠΈΠ²Π°ΡΡΠ΅ΠΌ ΡΠ»Π΅ΠΊΡΡΠΎΠ½Π½ΠΎΠΌ ΠΌΠΈΠΊΡΠΎΡΠΊΠΎΠΏΠ΅, Π² ΡΠ°ΡΡΠ½ΠΎΡΡΠΈ Π½Π°Ρ
ΠΎΠ΄ΠΈΡΡ ΠΈ ΠΈΠ΄Π΅Π½ΡΠΈΡΠΈΡΠΈΡΠΎΠ²Π°ΡΡ ΠΌΠΈΠ³ΡΠ°ΡΠΈΠΎΠ½Π½ΡΠ΅ ΠΌΠ΅ΡΠ°Π»Π»ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΡΠΎΠ΅Π΄ΠΈΠ½Π΅Π½ΠΈΡ.The relevance of the discussed issue is caused by the necessity to develop the technique for finding and identifying metal compounds migration forms over the boundaries of hydrocarbon deposits on the Earth surface. The existing information on possibility of metal transfer from the level of deposits is often contradictory and it can cast doubt on the possibility of geochemical prospecting of hydrocarbon deposits on the basis of information on metal content in the subsurface horizons. The technique of collection and analysis allows us to study nanoscale metal compounds migrating as a part of gas flow to the Earth surface. It becomes possible to determine the origin of nanoscale metal compounds with the ability to prove the genesis of the deep nature of the substance found on the surface. The main aim of the research is to review and to analyze the existing knowledge on geochemical methods of prospecting for oil and gas; to model a new geochemical method associated with the study of samples on a transmission electron microscope for identifying nanoscale particles. The methods used in the study: geochemistry methods of prospecting and exploration of oil and gas fields, transmission electron microscopy. The results of the research. The authors have reviewed and analyzed the literature on geochemical methods to search for oil and gas deposits and analyzed the patterns of geochemical features and magnetic fields on deposits of the West Siberian oil and gas province. The paper introduces a new prospecting and exploration geochemical and magnetic technique which can help identify nanoscale mineral forms of chemical elements with a transmission electron microscope, in particular find and identify migration metal compounds
First-principles method for calculating the rate constants of internal-conversion and intersystem-crossing transitions
A method for calculating the rate constants for internal-conversion (k(IC)) and intersystem-crossing (k(ISC)) processes within the adiabatic and Franck-Condon (FC) approximations is proposed. The applicability of the method is demonstrated by calculation of k(IC) and k(ISC) for a set of organic and organometallic compounds with experimentally known spectroscopic properties. The studied molecules were pyrromethene-567 dye, psoralene, hetero[8]circulenes, free-base porphyrin, naphthalene, and larger polyacenes. We also studied fac-Alq(3) and fac-Ir(ppy)(3), which are important molecules in organic light emitting diodes (OLEDs). The excitation energies were calculated at the multi-configuration quasi-degenerate second-order perturbation theory (XMC-QDPT2) level, which is found to yield excitation energies in good agreement with experimental data. Spin-orbit coupling matrix elements, non-adiabatic coupling matrix elements, Huang-Rhys factors, and vibrational energies were calculated at the time-dependent density functional theory (TDDFT) and complete active space self-consistent field (CASSCF) levels. The computed fluorescence quantum yields for the pyrromethene-567 dye, psoralene, hetero[8]circulenes, fac-Alq(3) and fac-Ir(ppy)(3) agree well with experimental data, whereas for the free-base porphyrin, naphthalene, and the polyacenes, the obtained quantum yields significantly differ from the experimental values, because the FC and adiabatic approximations are not accurate for these molecules.Peer reviewe
Fast electrochemical doping due to front instability in organic semiconductors
The electrochemical doping transformation in organic semiconductor devices is
studied in application to light-emitting cells. It is shown that the device
performance can be significantly improved by utilizing new fundamental
properties of the doping process. We obtain an instability, which distorts the
doping fronts and increases the doping rate considerably. We explain the
physical mechanism of the instability, develop theory, provide experimental
evidence, and perform numerical simulations. We further show how improved
device design can amplify the instability thus leading to a much faster doping
process and device kinetics.Comment: 4 pages, 4 figure
Effect of surface friction on ultrafast flame acceleration in obstructed cylindrical pipes
The Bychkov model of ultrafast flame acceleration in obstructed tubes [Valiev et al., βFlame Acceleration in Channels with Obstacles in the Deflagration-to-Detonation Transition,β Combust. Flame 157, 1012 (2010)] employed a number of simplifying assumptions, including those of free-slip and adiabatic surfaces of the obstacles and of the tube wall. In the present work, the influence of free-slip/non-slip surface conditions on the flame dynamics in a cylindrical tube of radius R, involving an array of parallel, tightly-spaced obstacles of size Ξ±R, is scrutinized by means of the computational simulations of the axisymmetric fully-compressible gasdynamics and combustion equations with an Arrhenius chemical kinetics. Specifically, non-slip and free-slip surfaces are compared for the blockage ratio, Ξ±, and the spacing between the obstacles, ΞZ, in the ranges 1/3 β€ Ξ± β€ 2/3 and 0.25 β€ ΞZ/R β€ 2.0, respectively. For these parameters, an impact of surface friction on flame acceleration is shown to be minor, only 1βΌ4%, slightly facilitating acceleration in a tube with ΞZ/R = 0.5 and moderating acceleration in the case of ΞZ/R = 0.25. Given the fact that the physical boundary conditions are non-slip as far as the continuum assumption is valid, the present work thereby justifies the Bychkov model, employing the free-slip conditions, and makes its wider applicable to the practical reality. While this result can be anticipated and explained by a fact that flame propagation is mainly driven by its spreading in the unobstructed portion of an obstructed tube (i.e. far from the tube wall), the situation is, however, qualitatively different from that in the unobstructed tubes, where surface friction modifies the flame dynamics conceptually
Quasi-steady stages in the process of premixed flame acceleration in narrow channels
The present paper addresses the phenomenon of spontaneous acceleration of a pre-mixed flame front propagating in micro-channels, with subsequent deflagration-to-detonation transition. It has recently been shown experimentally [M. Wu, M. Burke, S. Son, and R. Yetter, Proc. Combust. Inst. 31, 2429 (2007)], computationally [D. Valiev, V. Bychkov, V. Akkerman, and L.-E. Eriksson, Phys. Rev. E 80, 036317 (2009)], and analytically [V. Bychkov, V. Akkerman, D. Valiev, and C. K. Law, Phys. Rev. E 81, 026309 (2010)] that the flame acceleration undergoes different stages, from an initial exponential regime to quasi-steady fast deflagration with saturated velocity. The present work focuses on the final saturation stages in the process of flame acceleration, when the flame propagates with supersonic velocity with respect to the channel walls. It is shown that an intermediate stage may occur during acceleration with quasi-steady velocity, noticeably below the Chapman-Jouguet deflagration speed. The intermediate stage is followed by additional flame acceleration and subsequent saturation to the Chapman-Jouguet deflagration regime. We elucidate the intermediate stage by the joint effect of gas pre-compression ahead of the flame front and the hydraulic resistance. The additional acceleration is related to viscous heating at the channel walls, being of key importance at the final stages. The possibility of explosion triggering is also demonstrated
Single-layer polymeric tetraoxa[8]circulene modified by s-block metals : toward stable spin qubits and novel superconductors
Tunable electronic properties of low-dimensional materials have been the object of extensive research, as such properties are highly desirable in order to provide flexibility in the design and optimization of functional devices. In this study, we account for the fact that such properties can be tuned by embedding diverse metal atoms and theoretically study a series of new organometallic porous sheets based on two-dimensional tetraoxa[8]circulene (TOC) polymers doped with alkali or alkaline-earth metals. The results reveal that the metal-decorated sheets change their electronic structure from semiconducting to metallic behaviour due to n-doping. Complete active space self-consistent field (CASSCF) calculations reveal a unique open-shell singlet ground state in the TOC-Ca complex, which is formed by two closed-shell species. Moreover, Ca becomes a doublet state, which is promising for magnetic quantum bit applications due to the long spin coherence time. Ca-doped TOC also demonstrates a high density of states in the vicinity of the Fermi level and induced superconductivity. Using the ab initio Eliashberg formalism, we find that the TOC-Ca polymers are phonon-mediated superconductors with a critical temperature T-C = 14.5 K, which is within the range of typical carbon based superconducting materials. Therefore, combining the proved superconductivity and the long spin lifetime in doublet Ca, such materials could be an ideal platform for the realization of quantum bits.Peer reviewe
Decomposition process in a FeAuPd alloy nanostructured by severe plastic deformation
The decomposition process mechanisms have been investigated in a Fe50Au25Pd25
(at.%) alloy processed by severe plastic deformation. Phases were characterized
by X-ray diffraction and microstructures were observed using transmission
electron microscopy. In the coarse grain alloy homogenized and aged at , the bcc \alpha-Fe and fcc AuPd phases nucleate in the fcc
supersaturated solid solution and grow by a discontinuous precipitation process
resulting in a typical lamellar structure. The grain size of the homogenized
FeAuPd alloy was reduced in a range of 50 to 100nm by high pressure torsion.
Aging at this nanostructure leads to the decomposition
of the solid solution into an equi-axed microstructure. The grain growth is
very limited during aging and the grain size remains under 100nm. The
combination of two phases with different crystallographic structures (bcc
\alpha-Fe and fcc AuPd) and of the nanoscaled grain size gives rise to a
significant hardening of the allo
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