Mg and its alloys have been extensively used in many fields given their low density and extensive resources. However, their strength and plasticity cannot satisfy the requirements of large-scale application. This investigation aims to provide a deep understanding of the influence of Mn on microstructure evolution to develop high strength and ductility of Mg–Ca–Mn extruded alloys. Results revealed that the mechanical properties containing tensile, compress strengths, and yield asymmetry of as-extruded alloys were significantly enhanced with the increase in Mn. The grains of Mg–Ca alloy were significantly refined because a mass of Mn particles efficaciously blocked newborn grain growth during extrusion. The enhanced strengths were mainly ascribed to the fine dynamic recrystallized grains and abundant fine Mn particles. Furthermore, the microstructure evolution and strengthening mechanism were discussed.

The effect of nonmetallic solutes on the ductility of Zr-X (X=H, N, O and C) by calculating the generalized stacking-fault energies (GSFEs) of {0001} <10-10> and {11-22} <11-23> and (0001) surface energies of Zr-X binary systems using first-principles calculations. Calculation results show that all nonmetallic solutes considered here reduce both the basal and pyramidal SFEs. However, based on values of ductility parameter D, all nonmetallic alloying elements herein have not exhibited the ductility. This work provides a basis for investigating the effect of nonmetallic alloying elements on mechanical properties of zirconium alloys.

This study presented a novel intense plastic straining process called on-line twist extrusion (OLTE). An on-line torsional strain was applied on magnesium extruded rod during extrusion. After OLTE, the grains are refined from the periphery to the center of the bar, and the refined extent can be promoted with increased torsion speed. A fully recrystallized ultrafine grained structures and spiral shaped basal texture with the average grain size of 1.2 mu m are successfully achieved with increased torsion speed. The microstructure evolution and strengthening mechanism were also discussed. (C) 2019 The Authors. Published by Elsevier Ltd.

Mg-Zn-Mn alloys have drawing crucial attention because of the high strength, high ductility and excellent age harden ability. In the current work, we have systematically investigated the influence of Mn on the microstructure evolution and mechanical properties of as-extruded Mg-2Zn-Mn alloy. Results revealed that the mechanical properties that containing tensile and compressive strengths remarkably increased with high Mn content (2 wt%) addition. The dynamic recrystallized grains of Mg-2Zn alloy were significantly refined from 20 gm to 2 gm because of a mass of fine Mn precipitates effectively blocked newborn grain growth during extrusion process. The enhanced strengths were mainly ascribed to the high volume fraction of fine grains and the numerous fine precipitates. The strengthening mechanism and strain hardening behaviors of the alloys were also discussed.

The narrow genetic variation present in common wheat (Triticum aestivum) varieties has greatly restricted the improvement of crop yield in modern breeding systems. Alien addition lines have proven to be an effective means to broaden the genetic diversity of common wheat. Wheat-rye addition lines, which are the direct bridge materials for wheat improvement, have been wildly used to produce new wheat cultivars carrying alien rye germplasm. In this study, we investigated the genetic and epigenetic alterations in two sets of wheat-rye disomic addition lines (1R-7R) and the corresponding triticales. We used expressed sequence tag-simple sequence repeat, amplified fragment length polymorphism, and methylation-sensitive amplification polymorphism analyses to analyze the effects of the introduction of alien chromosomes (either the entire genome or sub-genome) to wheat genetic background. We found obvious and diversiform variations in the genomic primary structure, as well as alterations in the extent and pattern of the genomic DNA methylation of the recipient. Meanwhile, these results also showed that introduction of different rye chromosomes could induce different genetic and epigenetic alterations in its recipient, and the genetic background of the parents is an important factor for genomic and epigenetic variation induced by alien chromosome addition.

It is well demonstrated that wheat-rye 1BL/1RS translocated chromosome leads to some valuable novel traits such as disease resistance, high yield and functional stay-green after anthesis. To understand the physiological mechanism of 1BL/1RS translocation responsible for osmotic stress, two wheat cultivars, CN12 and CN17, carrying the translocated chromosome and MY11 without the translocated chromosome were employed in the study. During 5-day osmotic stress, fresh weight inhibition, chlorophyll content, soluble protein content, MDA concentration, antioxidant enzymes activity and free polyamines content were examined. CN12 and CN17, especially cultivar CN17, registered greater biomass and minor oxidative damage compared with their wheat parent. Meanwhile, the concentration of Spd and Spm in CN17 was significantly higher than the others. In addition, we found a positive correlation of fresh weight inhibition (FWI) and Put concentration, and a negative one with the parameters (Spd + Spm): Put ratio, indicating the importance of higher polyamine (Spd and Spm) accumulation on the adaptation to osmotic stress. Therefore, we proposed that the accumulation of higher polyamines (Spd and Spm) should play an important role on the adaptation of 1BL/1RS translocation lines to osmotic stress and might be important factors for the origin of novel traits introduced by 1BL/1RS.

High Mn content added to Mg–6Zn–0.3Ca extruded alloy remarkably refined dynamically recrystallized (DRXed) grains, and enhanced tensile and compressive strengths without sacrificing ductility. The large amount of fine Mn precipitates of homogenized alloy that formed effectively restricted new grain growth during the subsequent extrusion and generated ultra-fine DRXed grains. The ultra-fine DRXed grains and large amount of precipitates essentially enhanced the strength and improved the anisotropy of alloy. The Mg–Mn–x ternary systems that potentially formed ultra-fine grains were also discussed.

The influence of alloying elements on the stacking fault energy (SFE) of magnesium alloys containing long period stacking ordered (LPSO) structure was studied systematically by means of first-principles calculation. The element features and criterion of formation of LPSO in Mg-RE-X system was discussed, when X=Zn, Cu, Ag and Cu, and RE=Gd, Dy, Ho, Er and La. It was found that stacking faults played a crucial role in formation of LPSO structure. The influence of SFE should be considered into the element features and criterion of the formation of LPSO. The element features and criterion of formation of LPSO in Mg-RE-X system were suggested to be modified as follows: the element RE and X can decrease the SFE of magnesium alloys and the algebraic expression for the sum of chemical misfit of RE and chemical misfit of X was negative with a bigger numerical value. The present results were helpful for further investigation on strengthening-toughening of magnesium alloys for LPSO was found to increase the strength and toughness of magnesium alloys effectively.

Wrought magnesium alloys commonly exhibit strong texture, which significantly affects the properties of alloys. The effect of texture on the electromagnetic shielding property of these alloys as promising shielding materials is rarely reported. In the present study, the electromagnetic interference shielding effectiveness (SE) of AZ31 sheets with different texture intensities was investigated by coaxial cable method within the testing frequency range of 30–1500MHz. Results indicated that the SE of the sheets gradually increased with the strengthening of the basal texture intensity. The SE increment was mainly attributed to the improvement in the reflection attenuation of the incident electromagnetic wave, which was induced by the expansion of the impedance mismatch between the air and sheet surface. Furthermore, the relationship among texture, conductivity, and impedance was also discussed.

In the present work, in order to investigate the grain refinement mechanism of AM containing Sn alloys, the as-cast AM60, AM90 alloys, and the alloys with addition of 1 wt.% Sn were fabricated by traditional casting, respectively. During the solidification of AM + Sn alloys, the morphology of divorced eutectic Mg17Al12 was refined by Mg2Sn intermetallic that served as the heterogeneous nucleation cores. The modified Mg17Al12 effectively restricted the grain growth and resulted in a grain refinement. As a result, the yield strength of as-cast AM alloys was significantly enhanced by addition of Sn, while the ductility also improved. Moreover, the edge-to-edge model was employed to predict the orientation relationship between Mg17Al12 and Mg2Sn.

This work examined the effects of Sc addition of 0.7-1.3 wt.% on the microstructure and tensile properties of ZK60 alloy. The investigation showed that the Sc3Zn17 intermetallic compound was present in the as cast ZK60 alloy with the addition of Sc. After the hot extrusion, the degree of recrystallisation was decreased with the increasing of Sc content and the recrystallised grains were effectively refined due to the presence of Sc solute and particles in the grain boundaries which led to the significant improvement of the ultimate and yield strength of ZK60 alloy with Sc addition at room temperature. Furthermore, the addition of Sc to ZK60 alloy sharpened the extrusion texture.

The ferroelectric capacitance is usually nonlinear against increasing/decreasing voltage in sweeping time longer than 1 s and achieves a maximum value at around a coercive voltage within each loop. With the improved short-pulse measurements, we estimated the differential capacitance of ferroelectric Au/BiFeO3/LaNiO3/SrTiO3 thin-film capacitors from a nanosecond discharging current induced by a delta voltage after a stressing voltage pulse with widths of 500 ns–50 ms. With the shortening of the voltage sweeping time, we clearly observed two capacitance maxima from each branch of a capacitance-voltage (C-V) loop, reminiscent of an antiferroelectric behavior. After transformation of nanosecond domain switching current transients under pulses into polarization–voltage hysteresis loops, we further measured time dependent polarization retention as well as imprint in the range of 100 ns–1 s. Both positive and negative polarizations decay exponentially at characteristic times of 2.25 and 198 μs, suggesting the coexistence of preferred domains pointing to top and bottom electrodes in most epitaxial films. This exponential time dependence is similar to the dielectric degradation under a dc voltage, and the polarization retention can be improved through long-time opposite voltage stressing. With this improvement, the additional antiferroelectric-like dielectric maximum within each branch of a C-V loop disappears. This experiment provides the strong evidence of the effect of time-dependent charge injection on polarization retention and dielectric degradation.

Nonvolatile memories on the basis of tunneling junctions of ferroelectric ultrathin-film barriers make use of resistance switching between high and low conductance states upon polarization reversal, which facilitates the nondestructive readout of the binary information within a tiny memory cell. The apparent electroresistance effect for the generation of a large on/off current ratio depends on the modulation of the tunneling barrier height in two opposite polarization orientations due to asymmetric finite screening lengths of top and bottom electrodes, where the direct tunneling current attenuates quickly with enhanced film thickness. To break through the atomistic thickness requirement of the tunneling junction, we separately observed the same electroresistance effect in a semiconducting BiFeO3 film with the thickness of 120 nm. Its working mechanism depends on the formation of a ferroelectric diode for the film in contacts with top and bottom electrodes, where the polarity of diode junction can be switched by polarization reversal.

The phase diagrams of the Ho-Sb and Sb-Yb binary systems have been evaluated by using the CALPHAD (CALculation of PHAse Diagram) method with experimental data including the phase equilibria and thermodynamic properties. The Gibbs free energies of the liquid, bcc_A2, fcc_A1, hcp_A3, and rhombohedral_A7 phases were modeled by the subregular solution model with the Redlich-Kister formula, and those of the intermetallic compounds (Ho5Sb3, alpha Ho4Sb3, beta Ho4Sb3, alpha HoSb, beta HoSb, HoSb2, Sb2Yb, SbYb, Sb10Yb11, Sb3Yb4, alpha Sb3Yb5, and beta Sb3Yb5) in these two binary systems were described by the two-sublattice model. An agreement between the present calculated results and experimental data was obtained. (C) 2012 Elsevier Ltd. All rights reserved.

Generally, the organic ferroelectric P(VDF-TrFE) thin film is partially crystallized with a mixture of ferroelectric crystallites, non-crystalline molecules, and additional non-ferroelectric crystallites, e.g., Trifluoroethylene, in the copolymers. Therefore, it is almost impossible for the domains to switch under a normal field without incurring of charge injection across these non-ferroelectric phases. In this paper, we use an equivalent-circuit description of the film consisting of a non-ferroelectric layer in series with a ferroelectric layer. Based on the polynomial fitting of polarization switching/non-switching results, we extract the intrinsic coercive field across the ferroelectric layer in the films with different thicknesses.

The Bi–U and Bi–Mn binary systems have been critically assessed by using the CALPHAD (Calculation of Phase Diagrams) technique on the basis of the experimental data including thermodynamic properties and phase equilibria. The Gibbs free energies of the solution phases (liquid, bcc, fcc, αU, βU, αMn, (Bi), and βMn) were modeled by a sub-regular solution model with the Redlich–Kister equation, and those of the intermetallic compounds (UBi, U3Bi4, UBi2, αBiMn and βBiMn) in these two binary systems were described by a two-sublattice model. A proper set of thermodynamic parameters has been derived for describing the Gibbs free energies of each phase in the Bi–U and Bi–Mn systems. An agreement between the calculated results and experimental data is obtained.

We developed a ferroelectric assisted current-voltage characterization technique for continuous/semicontinuous high-k ultrathin films under the field as high as 17 MV/cm without invoking of dielectric breakdown. The leakage current of the ultrathin films equals domain switching current with breakdown paths blocked efficiently by underneath ferroelectric thick layer. The extracted field dependences of current density for a 1-6 nm thick Al2O3 layer deposited on top of a 300 nm thick Pb(Zr,Ti)O-3 layer obey the equation of Schottky mission. This technique is helpful for investigations of high-field charge emission and quantum physics for ultrathin films in loss of the atomic-layer flatness.

ABSTRACT The effect of Pb excess on the crystallization and ferroelectric properties in Pb(Zr0.3Ti0.7)O3 (PZT) thin films has been investigated. Owning to atomic interdiffusion and volatilization during heat treatment, the Pb loss has an impact on PZT stoichiometric composition, perovskite structure, and ferroelectric properties. The electrical characterization shows that the polarization-voltage (P-V) hysteresis loop is closely correlated with the appropriate Pb content and frequency. With the aid of the Ishibashi's power law model, we extract the frequency coefficient of the model dependence of the Pb excess.

In this work, the advances in the resistance switching characteristics of stoichiometric ZrO2 thin films were studied. The Al/ZrO2/Al structure exhibits reliable and reproducible switching behaviours. The thickness dependence and electrode size effect was demonstrated and understood in terms of a combined model of conductive filament/carriers trapping. Analyses of current–voltage characteristics were performed and it is suggested that the resistive switching characteristics of the ZrO2 film are governed by both the electrode/interface effect and the formation of conductive multi-filaments.