A Nickel Titanium (NiTi) shape memory alloy band plate (strip) of less than 0.8 mm thickness was strained by four-point bending at various temperatures. When the bending stress was beyond the elastic ...range, the inelastic strain on the top surface deviated from that on the bottom surface, which resulted in two different bending curves. The bending strain in tension under a given load was always larger than that in compression in both cubic and martensite phases. The crystallographic theory of martensite was applied to calculate the strains of a variant (Bain correspondence variant), a variant pair (correspondent variant pair), and the reorientation of martensite variants (detwinning). It is concluded that the asymmetry observed in the band plate may due to 111 texture in the rolling direction, as has been pointed out in former studies of bulk alloys.
Although the atomic structure of amorphous alloys, which lacks long-range translational symmetry, may appear homogeneous at the macroscopic scale, their local dynamic and/or static properties however ...vary significantly according to the recent experimental and simulation results. In the literature of amorphous alloys, the nature of such local heterogeneities is currently an issue under debate. More importantly, since amorphous alloys are in a thermodynamically nonequilibrium state, their local structures constantly evolve during structural relaxation, physical aging and mechanical deformation. As such, local structural heterogeneities, which vary with the thermal and mechanical history of amorphous alloys, could provide a key to understand the structural origin of their mechanical behavior, such as anelasticity, viscoelasticity, plasticity and fracture. In this review article, we first review mechanical spectroscopy or dynamic mechanical analyses as an important tool to study the relaxation dynamics in amorphous alloys, with a focus on the possible correlation between the secondary (also called β) relaxation and the local structural heterogeneities of amorphous alloys. After that, we discuss the recent advances on the understanding of structural heterogeneities in metallic supercooled liquids and the influence of the structural heterogeneities on the overall mechanical properties of the corresponding amorphous alloys. Finally, we briefly discuss the further development of research on this subject.
Solid-state single spins are promising resources for quantum sensing, quantum-information processing and quantum networks, because they are compatible with scalable quantum-device engineering. ...However, the extension of their coherence times proves challenging. Although enrichment of the spin-zero
C and
Si isotopes drastically reduces spin-bath decoherence in diamond and silicon, the solid-state environment provides deleterious interactions between the electron spin and the remaining spins of its surrounding. Here we demonstrate, contrary to widespread belief, that an impurity-doped (phosphorus) n-type single-crystal diamond realises remarkably long spin-coherence times. Single electron spins show the longest inhomogeneous spin-dephasing time (Formula: see text ms) and Hahn-echo spin-coherence time (T
≈ 2.4 ms) ever observed in room-temperature solid-state systems, leading to the best sensitivities. The extension of coherence times in diamond semiconductor may allow for new applications in quantum technology.
FeCo alloys are important soft magnetic materials with the highest saturation magnetizations, high Curie temperature, high permeability, and low losses. In this study, 3D interconnected nanoporous ...(3DNP) FeCo soft magnetic materials were produced by liquid metal dealloying (LMD). Ni atoms were selectively dissolved from (FeCo)xNi100−x precursor alloys into Mg metallic melt, and Fe and Co atoms self-organized 3DNP structures. Morphology and grain boundary characteristics depended on the LMD processing temperature and Ni concentration in precursor alloy. Developed 3DNP FeCo materials demonstrated soft magnetic properties with high saturation magnetization over 220 emu/g. Although 3DNP structure increases hysteresis loss due to its porosity, it leads to lower eddy current loss than bulk FeCo at high frequencies. The LMD process has advantages for synthesizing nanostructured FeCo with high magnetization and low coercivity.
•Liquid metal dealloying was applied to synthesize 3D interconnected FeCo materials.•Microstructural evolution and magnetic properties were investigated.•3D interconnected FeCo demonstrated high saturation magnetization over 220 emu/g.•The LMD process has advantages on low coercivity.•3D interconnected FeCo showed low core losses at high frequencies.
The glass-forming ability of Zr–Cu-based metallic glass with high entropy is investigated. Samples are prepared by adding elements, such as Ag, Hf, and Ni, to ternary Zr48Al7Cu45 to systematically ...evaluate the multicomponent effect. The glass structures are fabricated by tilt casting. In quaternary and senary alloys with increased glass-forming ability, new competitive liquid crystalline phases are generated with the addition of elements. Compared with the quaternary alloy, the quinary alloy does not form a new crystalline phase, and the added Hf is highly soluble in the base crystalline phase. The driving force for crystallization, which is evaluated based on specific heat measurements, is the largest for the quinary alloys. This suggests that stabilization of the competitive phase by the high-entropy effect leads to a decrease in the glass-forming ability. From the kinetics point of view, the relationship between the liquid-phase fragility and glass-forming ability is clarified, and the addition of Ag and Ni, which strengthens the liquid properties, is found to improve the glass-forming ability. Based on the high-entropy strategy, a new high-entropy metallic glass Zr35Hf13Al11Ag8Ni8Cu25, with a maximum vitrification diameter of 20 mm, is fabricated.
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•The glass-forming ability of metallic glasses did not increase monotonically with increase configuration entropy.•When the high-entropy effect occurs in the crystalline phase, the glass-forming ability is reduced.•The driving force of the crystallization and the fragility index of alloys were correlated with the glass-forming ability.•The largest Be-free high-entropy bulk metallic glass with a maximum vitrification diameter of 20 mm, was newly fabricated.
CoCrFeMnNi high-entropy alloy (HEA) materials were fabricated using mechanical alloying (MA) and spark plasma sintering (SPS). The MA time, SPS temperature, and contaminations strongly affected the ...final microstructure and mechanical properties. Nanocrystal face-centered cubic (FCC) solid solution was made during MA, and the FCC phase maintained as the matrix after SPS at 900 °C and 1100 °C. However, Cr carbides were transformed near the surface due to the carbon contamination. When MA time increased, phase stability of the FCC phase was improved, and the contaminant (ZrO2) from the MA balls was also increased. Ultrafine-grained microstructure was obtained at 60 min MA and 900 °C SPS. On the other hand, the higher SPS temperature and lower levels of contamination were required to achieve tensile ductility. Irregularly distributed ZrO2 particles developed bimodal microstructures.
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•CoCrFeMnNi high-entropy alloys were fabricated using powder metallurgy.•Contaminations highly affected microstructural evolution and mechanical properties.•Phase stability was improved with increasing ball milling time.•UFG microstructure was obtained under a certain condition.
The present study is the first to show that the supply of nanometer-sized particles of Fe
2O
3, SnO
2, CuO, or Bi
2O
3 oxide on rubbing steel surfaces induces transition to mild wear with sliding ...distance, and that the wear transition behavior depends on the type of supplied oxide. The mild wear is due to formation of the wear-protective tribofilm on the rubbing surfaces, and observations confirm that the tribofilms are produced by tribo-sintering of the supplied oxide particles. The mild wear transition behavior is explained by the sintering rate of the supplied oxide particles, which is related to the oxygen diffusion coefficient in the oxide and the particle diameter. When the supplied oxide is of high diffusivity, the tribofilm formation rate is high, owing to the high sintering rate of the oxide particles, and the mild wear transition occurs at a short sliding distance. In the case of Fe
2O
3 oxide, the sliding distance of the transition from severe to mild wear is decreased when finer particles are supplied, suggesting that fine particles are easily sintered on the wear surface.
Integral cross sections for optically allowed electronic-state excitations of atoms and molecules by electron impact, by applying scaled plane-wave Born models, are reviewed. Over 40 years ago, ...Inokuti presented an influential review of charged-particle scattering, based on the theory pioneered by Bethe forty years earlier, which emphasized the importance of reliable cross-section data from low eV energies to high keV energies that are needed in many areas of radiation science with applications to astronomy, plasmas, and medicine. Yet, with a couple of possible exceptions, most computational methods in electron-atom scattering do not, in general, overlap each other's validity range in the region from threshold up to 300 eV and, in particular, in the intermediate region from 30 to 300 eV. This is even more so for electron-molecule scattering. In fact this entire energy range is of great importance and, to bridge the gap between the two regions of low and high energy, scaled plane-wave Born models were developed to provide reliable, comprehensive, and absolute integral cross sections, first for ionization by Kim and Rudd and then extended to optically allowed electronic-state excitation by Kim. These and other scaling models in a broad, general application to electron scattering from atoms and molecules, their theoretical basis, and their results for cross sections along with comparison to experimental measurements are reviewed. Where possible, these data are also compared to results from other computational approaches.
This study is the first to show a quantitative condition required for the establishment of severe–mild wear transition with sliding distance, by studying the effects of supply of Fe
2O
3 particles ...onto rubbing steel surfaces on the transition and oxide film formation process. The supply of fine Fe
2O
3 particles was found to accelerate the wear transition, and the sliding distance at which the transition occurs was found to increase with particle diameter and applied load. Oxide films are produced on the rubbing surfaces by sintering of the supplied Fe
2O
3 oxide particles. At the severe–mild wear transition, the relative area of oxide films is the same for all diameters of supplied Fe
2O
3 particles. This finding suggests that the transition occurs when the relative area of oxide films reaches a specific value, which is proportional to the area of real contact.
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