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1.
Microalloying experiments on amorphous Al84La4Er2Ni8TM2 alloys were performed with the substitution of all 3d TM (transition metal) elements and one 4d TM element. The critical thickness of the amorphous alloys was used as a criterion for glass formability in this system. The results show that, other than atomic size differences and the negative heats of mixing among the solvent and solute atoms, the atomic interactions among the solute atoms play an important role on glass formation. When the solute–solute interaction becomes repulsive (positive heat of mixing), glass formability suffers. Similarly, when the solute–solute interaction becomes highly attractive, exceeding that between the solvent and solute atoms, glass formability is also degraded. Evaluation of a large number of known multicomponent bulk metallic glasses provides additional support to these conjectures. This study shows that the solute–solute interaction plays an important role in glass formation, which has not been recognized previously. 相似文献
2.
《中国物理 B》2020,(6)
The interactions of solute atoms with vacancies play a key role in diffusion and precipitation of alloying elements,ultimately influencing the mechanical properties of aluminum alloys. In this study, first-principles calculations are systematically performed to quantify the solute–vacancy interactions for the 3 d–4 p series and the 4 d–5 p series. The solute–vacancy interaction gradually transforms from repulsion to attraction from left to right. The solute–vacancy binding energy is sensitive to the supercell size for elements at the beginning. These behaviors of the solute–vacancy binding energy can be understood in terms of the combination and competition between the elastic and electronic interactions. Overall, the electronic binding energy follows a similar trend to the total binding energy and plays a major role in the solute–vacancy interactions. 相似文献
3.
The vacancy–solute interactions during artificial ageing at 250○C of cold worked samples of a commercial magnesium alloy WE54 (Mg–RE based) were studied by coincidence Doppler broadening of positron annihilation radiation and positron annihilation lifetime spectroscopy. The results show that, in the as-cold-worked state, the vacancies are associated with dislocations that are generated by the cold work and that, after artificial ageing at 250○C, the vacancies are associated with solute elements and help the formation of precipitate precursors. This mechanism accelerates the formation of hardening precipitates without any apparent changes in the precipitation sequence and in the products of the decomposition of the supersaturated solid solution. The present study demonstrates that the stronger hardening response achieved in the cold-worked samples originates from the presence of a higher concentration of vacancies that is introduced by the cold work and is retained in the first few minutes of ageing. 相似文献
4.
Three kinds of Al–Ti nanoparticles (7.7, 27.8, and 42.6 at.% Ti) have been prepared from Al–65, Al–85, and Al–88 at.% Ti master
alloys by hydrogen plasma-metal reaction, with average particle sizes of 30, 25, and 80 nm, respectively. The higher evaporation
rate of Al than Ti resulted in the low Ti contents in the nanoparticles than those in the master alloys. Microscopy observation
revealed that the primary nanoparticles are spherical in shape, and occur as chain aggregates of several individual nanoparticles
due to the faster collision rate than the coalescence rate. All the Al–Ti nanoparticles contain amorphous alumina layers of
about 2–3 nm in thickness surrounding the crystalline core. AlTi intermetallic nanoparticles were successfully produced for
Al–27.8 at.% Ti, with a single crystal of AlTi in one chain aggregate. The composite nanoparticles of Al together with some
Al3Ti phases are prepared for Al–7.7 at.% Ti, with each phase in the individual particle of one chain aggregate. The composite
nanoparticles of AlTi with some AlTi3 were produced for Al–42.6 at.% Ti, with each phase in the individual particle of one chain aggregate. The formation mechanism
of Al–Ti nanoparticles was interpreted in terms of phase transition and the effect of hydrogen. 相似文献
5.
The two-,four-,five-and fourteen-state approximations of the inpact parameter method have been applied to the excitation of hydrogen atoms by proton(p)and antiproton(p) impact.The effect of both channel and back couplings on the 2s and 2p excitations are investigated.The total cross sections are calculated for incident energies ranging from 1 to 2500keV.it is found that the effect of both channel and back couplings on the antiproton-induced reactions is greater than on that induced by protons.We compare the results with those of other theoretical and experimental works. 相似文献
6.
J.L. Bocquet 《哲学杂志》2013,93(31):3603-3631
Using a double Laplace and Fourier transform of the transport equation for the vacancy, we obtain the exact values of the return probabilities of the vacancy in the close vicinity of the tracer atom in the presence of a solute-vacancy interaction of arbitrary range. The study of model cases shows that taking into account the interaction up to the third neighbour shell is mandatory to obtain the solute diffusivity in BCC and FCC structures with a good precision. A thorough ab initio evaluation of all the migration barriers is rarely available in the literature; it is shown that the approximations often used to overcome this lack of data must be chosen with care in order to avoid puzzling conclusions. An examination of dilute systems studied in the recent literature is presented. 相似文献
7.
Available data on the temperature and concentration dependence of critical resolved shear stress (CRSS) of KCl–KBr solid-solution crystals containing 9, 17, 27 and 45?mol% KBr in the temperature range 77–230?K have been analyzed within the framework of the kink-pair nucleation model of plastic flow in solid- solution crystals. It is found that CRSS τ decreases with increasing temperature T in accordance with the model relation lnτ?=?A???BT, where A and B are positive constants. The CRSS τ at a given temperature depends on solute concentration c as τ?∝?cp , where exponent p has a value between 0.33 and 0.57 as temperature T rises from 0 to 230?K. The model parameter W o, i.e. binding energy between the edge-dislocation segment L o involved in the unit activation process and the solute atoms close to it (T?→?0?K), which is inversely proportional to B, increases with solute concentration c monotonically as W o?∝?c 0.33 up to a critical value c m?=?35?mol% KBr, which is in reasonable agreement with the model prediction W o?∝?c 0.25. However, W o decreases with an increase in c beyond c m, which indicates somewhat ordered distribution of solute in the host lattice of concentrated KCl–KBr solid solutions with c?>?c m. 相似文献
8.
V.N. Voyevodin G.D. Tolstolutskaya M.A. Tikhonovsky A.N. Velikodnyi I.E. Kopanets 《哲学杂志》2020,100(7):822-836
ABSTRACTA single-phase fcc high-entropy alloy (HEA) of 20%Cr–40%Fe–20%Mn–20%Ni composition and its strength with yttrium and zirconium oxides version was irradiated with 1.4?MeV Ar ions at room temperature and mid-range doses from 0.1 to 10 displacements per atom (dpa). Transmission electron microscopy (TEM), scanning transmission electron microscopy with energy dispersive X-ray spectrometry (STEM/EDS) and X-ray diffraction (XRD) were used to characterise the radiation defects and microstructural changes. Nanoindentation was used to measure the ion irradiation effect on hardening. In order to understand the irradiation effects in HEAs and to demonstrate their potential advantages, a comparison was performed with hardening behaviour of 316 austenitic stainless steel irradiated under an identical condition. It was shown that hardness increases with irradiation dose for all the materials studied, but this increase is lower in high-entropy alloys than in stainless steel. 相似文献
9.
Diamagnetism of condensed microcavity polaritons in a vertically applied magnetic field is theoretically studied by using the density of free energy of polaritons. The magnetic dependence of polariton–polariton interactions and spin polarization degree of polaritons are derived, and are used to show the diamagnetic behavior of the polariton spin polarization, which is discussed for GaAs-based microcavities. We show that for strong magnetic field the spin polarization of the polaritons is paramagnetic as usual, while around positive exciton–photon detuning and special Rabi splitting, the spin polarization of the polaritons could be diamagnetic. In addition, weak magnetic field and high polariton density are beneficial to observe the polariton diamagnetism. 相似文献
10.
Takanori Iino Po-Lin Li Wen-Zhe Wang Jia-Huei Deng Yun-Chang Lu Fu-Jen Kao Yoichiroh Hosokawa 《Applied Physics A: Materials Science & Processing》2014,116(1):389-393
When an intense femtosecond laser is focused in a cell culture medium, shock wave, stress wave, and cavitation bubble are generated at the laser focal point. Cell–cell adhesion can be broken at the cellular level by the impacts of these factors. We have applied this breaking of the adhesion to an estimation of the cell–cell adhesion strength. In this application, it is important to identify which of these factors is the dominant factor that breaks the adhesion. Here we investigated this issue using streptavidin-coated microbeads adhering to a biotin-coated substrate as a mimic of the cell–cell adhesion. The results indicated that the break was induced mainly by the stress wave, not by the impact of the cavitation bubble. 相似文献
11.
A. Bertoluzza S. Bonora G. Fini M. A. Morelli 《Journal of Raman spectroscopy : JRS》1988,19(5):369-373
The effect of polyamines (putrescine, spermine and spermidine) on the physical properties of liposomes of phospholipids with different amount of charge on the bilayer was studied. The measured effect depends both on the charge of the lipid and on the charge of the polyamine, which under physiological conditions can be considered as a polycation. No interaction was observed with a neutral phospholipid for all the polyamines considered. With charged phospholipids, polyamines modify the surface charge and, as a consequence, the inner structure of the core of the bilayer also changes. The polyamine with the highest positive charge and the phospholipid with the highest content of negative groups showed the strongest interaction. 相似文献
12.
Secondary electron yield suppression using millimeter-scale pillar array and explanation of the abnormal yield–energy curve
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《中国物理 B》2019,(7)
The phenomenon of secondary electron emission is of considerable interest in areas such as particle accelerators and on-board radio frequency(RF) components.Total secondary electron yield(TSEY) is a parameter that is frequently used to describe the secondary electron emission capability of a material.It has been widely recognized that the TSEY vs.primary electron energy curve has a single-hump shape.However, the TSEY–energy curve with a double-hump shape was also observed experimentally—this anomaly still lacks explanation.In this work, we explain this anomaly with the help of a millimetre-scale(mm-scale) silver pillar array fabricated by three-dimensional(3 D) printing technology.The TSEY–energy curve of this pillar array as well as its flat counterpart is obtained using sample current method.The measurement results show that for the considered primary electron energy(40–1500 eV), the pillar array can obviously suppress TSEY,and its TSEY–energy curve has an obvious double-hump shape.Through Monte Carlo simulations and electron beam spot size measurements, we successfully attribute the double-hump effect to the dependence of electron beam spot size on the primary electron energy.The observations of this work may be of help in determining the TSEY of roughened surface with characteristic surface structures comparable to electron beam spot size.It also experimentally confirms the TSEY suppression effect of pillar arrays. 相似文献
13.
The main properties of the interaction of ultra low‐energy antiprotons (E⩽10-6 a.u.) and antihydrogen with atomic hydrogen are established. Elastic and inelastic cross‐sections and Protonium formation
spectrum are calculated within quantum mechanical coupled channels approach. The results of calculations differ strongly from
predictions made by extrapolation of semiclassical models to the energy domain of interest. It is shown that the main feature
of the observables behaviour is determined by existence of a family of
H,
H near‐threshold metastable states.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
S. Nayek A. Ghoshal 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,64(2-3):257-268
We have made an investigation on H(ns) → H(n′ s) transition processes by positron impact with screened Coulomb potentials (SCP) by employing a distorted-wave formalism in the momentum space. Making use of simple variational wave functions of the hydrogen atom interacting with SCP we have been able to obtain the partial-wave scattering amplitudes in closed analytical forms. We have then used these distorted-wave scattering amplitudes to make a detailed study on differential and total cross sections in the energy range 20–300 eV. This study reveals some hitherto unknown features of the differential and total cross section. To the best of our knowledge such a study on the differential and total cross sections for inelastic positron-hydrogen collisions with SCP is reported for the first time in the literature. 相似文献
15.
A method for study of charge-transfer interactions between solute molecules and solvent based on the comparison of the ratios of spectral shifts of different electronic transitions in solute molecules in chemically inert solvent is proposed. The method is applicable to molecules that do not change their dipole moment on excitation. As an example, a presence of charge transfer interactions in higher electronic states of aromatic hydrocarbons (benzene, phenanthrene, and naphthalene) dissolved in water and alcohols was demonstrated. 相似文献
16.
17.
Influence of annealing on the microstructure and mechanical properties has been studied for Al–Zr (0.4 wt.%) alloy with the ultrafine-grained (UFG) structure formed by high-pressure torsion (HPT) at room temperature. A drastic hardening effect by short-term annealing in the temperature range of 90–280°С was observed for the HPT-processed Al–Zr alloy. The effect of hardening by annealing for the HPT-processed Al–Zr alloy is compared with that for the HPT-processed commercial purity (CP) Al. It was shown that addition of 0.4 wt.% Zr in Al does not cause a significant impact on the magnitude of hardening by annealing up to 150°С, however it leads to a shift of its maximum to higher annealing temperatures and expansion of the thermal stability range of strength up to 280°С. The kinetics of hardening by annealing for CP Al and Al–Zr alloys in the UFG state has been studied for the first time. It was shown that in both materials the strength first increases linearly with the duration of annealing and then reaches saturation. The temperature dependence of the rate of hardening by annealing was analysed through an Arrhenius law, and apparent activation energy was extracted for both systems. The addition of Zr results in the reduction of the activation energy of annealing-induced hardening by ~2 times. Possible physical mechanisms controlling the kinetics of hardening by annealing are discussed for the ultrafine-grained CP Al and Al–Zr alloy. 相似文献
18.
Yu. A. Abzaev A. M. Lider V. A. Klimenov R. S. Laptev Yu. S. Bordulev G. D. Sadritdinova M. A. Zakharova A. A. Mikhailov 《Physics of the Solid State》2016,58(10):1939-1944
The VT1-0 titanium alloy (phase α-Ti) with various hydrogen and hydrogen-vacancy concentrations has been studied. The stability of the 32-atom Ti–nV–mH supercell (n is the number of the V vacancies, and m is the number of hydrogen atoms H) with varying numbers of vacancies and hydrogen atoms has been calculated from the first principles. The structural state of the α-Ti phase has been identified by the Rietveld method based on the calculations of the supercell stability and the data on the defect concentration obtained using positron spectroscopy. The complete structural information on the considered states of the α-Ti phase (the lattice parameters, spatial distribution of titanium and hydrogen atoms and vacancies) has been obtained. 相似文献
19.
Spin inverter and polarizer curved nanowire driven by Rashba and Dresselhaus spin–orbit interactions
We propose in theory a curved nanowire structure that can both serve as a spin inverter and a spin polarizer driven by a periodic Rashba spin–orbit coupling (SOC) and a uniform Dresselhaus SOC. The curved section of the U-shaped quasi-one dimensional nanowire with an arc of radius R and circumferential length is divided into segments of equal length initially having only its inherent homogeneous Dresselhaus SOC. Then a Rashba-type SOC is applied at every alternating segment. By tuning the Rashba SOC strength and the incident electron energy, this device can flip the spin at the output of an incoming spin-polarized electron. On the other hand, this same device acts as a spin filter for an unpolarized input for which an outgoing electron with a non-zero polarization can be achieved without the application of an external magnetic field. Moreover, the potential modulation caused by the periodic Rashba SOC enables this device to function as an attenuator for a certain range of incident electron energies that can make the probability current density drop to 10−4 of its otherwise magnitude in other regimes. 相似文献
20.
Results of investigations of the structure-phase state and dislocation substructure formation during thermomechanical hardening
of Fe–0.09C–2Mn–1Si steel in different regimes are presented. Methods of transmission electron microscopy reveal the formation
of gradient states characterized by regular changes of the structure, phase composition, types, and parameters of the dislocation
substructures over the structure cross section. 相似文献