[en] We study the effects of dilute Mg addition on the microstructure formation and mechanical properties of a ZnAl4Cu1 alloy. On the basis of the composition of the commercial alloy Z410 (4 wt% Al, 1 wt% Cu, and 0.04 wt% Mg), three laboratory alloys with different Mg contents (0.04 wt%, 0.21 wt% and 0.31 wt%) are characterised in terms of their mechanical properties and microstructures using ex-situ and in-situ tensile tests in conjunction with scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Increasing Mg content causes the precipitation of Mg_2Zn_1_1 phase precipitates and refined lamellar spacings in the eutectoid phase. The alloy with a medium Mg content (0.21 wt%) exhibits the highest yield strength both at room temperature and at elevated temperatures. Further, we show that dilute Mg alloying causes an improvement of the ductility of ZnAl4Cu1 base-alloys, especially at elevated temperatures. In addition, the alloys reveal two distinct deformation regimes distinguishable close to room temperature and at commonly employed strain rates, with work hardening and brittle fracture exhibited at room temperature and/or elevated strain rate (5×10"−"4 s"−"1), and work softening and ductile fracture at elevated temperature and/or low strain rate (6×10"−"6 s"−"1). The deformation mechanisms and fracture behaviour in both regimes are investigated and the underlying physical mechanisms of the observed phenomena are discussed.

[en] Objective: To explore whether it is possible to distinguish high-grade from low-grade chondrosarcoma in long bones via standard MRI and dynamic enhanced time intensity curve (TIC). Methods: Thirty-eight cases with long bone central chondrosarcoma confirmed by surgery and pathology were retrospectively analyzed, including 10 males and 10 females (age, 48 ± 8 years) in low-grade group, and 8 males and 10 females (age, 61 ± 7 years) in high-grade group. All patients underwent MRI examinations. Imaging protocol included standard MRI and dynamic enhanced MRI (DCE-MRI). Tumor enhancement patterns and TIC types were determined with post-processing software. Comparing the longest diameter of the tumor and TIC type distribution between low and high grade chondrosarcomas respectively by t test and Fisher test. Results: The mean maximum diameter of tumor in the low and high grade groups were 7.3 ± 5.8 cm and 13.1 ± 6.4 cm, respectively, which were statistically significant between the two groups (t = 3.084, P = 0.004). In the low grade group, the enhancement extent of tumor was light and slow, and the edge of chondrosarcoma was enhanced linearly or without obvious enhancement; the distributions of TIC were mainly types I (13, 65.0%) and II (5, 25.0%). In the high grade group, tumors appeared nodular or flower ring-like strong enhancement and slow washout; the distributions of TIC were mainly types II (4, 22.2%) and III (11, 61.1%). The difference in TIC distribution was statistically significant between the two groups (P = 0.02). Conclusion: Conventional MRI and DCE-MRI are important auxiliary means for differentiating high and low grade chondrosarcoma of long bones. (authors)

[en] The effect of vacancy and water adsorption on the electronic structure of semiconducting 2D trichalcogenide material CrPX ₃ (X: S, Se) is studied using state-of-the-art density functional theory (DFT) approach. It is found that chalcogen vacancies play a minor role on the electronic structure of CrPX ₃ in the vicinity of the Fermi level leading to the slightly reduced band gap for these materials, however, inducing strongly localised defect states which are placed in the energy gap formed by the valence band states. Our DFT calculations show that the interaction of water molecules with CrPX ₃, pristine and defective, can be described as physisorption and the adsorption energy for H₂O is insensitive to the difference between pristine and chalcogen-defective surface of trichalcogenide material. These results are the first steps for the theoretical description of the ambient molecules interaction with 2D semiconducting CrPX ₃ material, that is important for its future experimental studies and possible applications. (paper)

[en] Objective: To analyze the radioactive contamination in the process of Thorium-Tungsten electrode production, and to determine the level of radiation contamination in the production site and the production process, which provides a basis for the radiation environment management in the whole production process and the minimization of radioactive contamination damage to workers and the environment. Methods: Firstly, the complete production process of Thorium-Tungsten electrode was analyzed. Then, a typical Thorium-Tungsten electrode manufacturer was taken as an example, the radiation pollution environment in its radiation workplace was detected. The radiation pollution sources, radioactive pollution management key points and radiation pollution prevention and control measures were analyzed. Results: The maximum monitoring value of the air absorbed dose rate of gamma-ray in each workplace was 0.32 μGy/h. The maximum monitoring value of alpha surface contamination level on each work table was 17.75 Bq/cm² and that of beta surface contamination level was 35.55 Bq/cm². The maximum level of surface contamination for the working clothes and gloves of staff in each post was 0.38 Bq/cm², and that of beta contamination level was 4.00 Bq/cm². Conclusion: The radiation pollution of Thorium-Tungsten electrode production site is controllable to the surrounding environment, professional staff and public personnel under the implementation of radiation safety management system and radiation safety protection measures. (authors)

[en] The discharge characteristics of SF₆ dependent on gas pressure under extremely inhomogeneous electric fields are strongly nonlinear and must be carefully considered when optimizing gas-insulated equipment insulation design and defect detection. The main aim of this study was to determine the relationship between nonlinear breakdown characteristics and the pre-breakdown discharge mode transition. The breakdown model established by Niemeyer, as adapted under impulse voltage, was expanded. The images and the phase-resolved patterns of the pre-breakdown discharge as a function of gas pressure and applied voltage were analyzed to observe the relationship between them as per the spatial distribution of the spark paths. A universal model of the nonlinear breakdown phenomenon under steady-state voltage was established accordingly. Experimental results demonstrate the existence of a positive glow corona (PGC) discharge in the interval with the discontinuous breakdown voltage as well as significant interactions between the PGC discharge and leader discharge. The nonlinear characteristics can be attributed to the inception and quenching of the PGC discharge. The shielding effect induced by the PGC discharge is the neglected culprit of the strong nonlinear discharge characteristics under steady-state voltage. The nonmonotonic U–p curve in electronegative gases was also assessed in an effort to build a theoretical basis for the manufacture and condition monitoring of the gas-insulated equipment. (paper)

[en] In this study we investigated the creep behaviour of three eutectic ZnAl4Cu1Mg alloys with different Mg contents, namely ZnAl4Cu1Mg0.04, ZnAl4Cu1Mg0.21 and ZnAl4Cu1Mg0.31 (in wt%), using uniaxial tensile creep tests at temperatures between 25 °C and 105 °C. Furthermore, we studied the creep properties of the individual microstructural constituents of the ZnAl4Cu1Mg0.31 alloy using nanoindentation creep experiments at room temperature (25 °C) and 85 °C. Increasing Mg content causes an acceleration of the creep rate of ZnAl4Cu1 alloys. Zn-Al eutectic and eutectoid structures show a lower creep resistance than the η-Zn matrix phase. Stress exponents of 6.9–8.0 and creep activation energy values of 93–104 kJ/mol are obtained during the uniaxial tests, which suggests dislocation controlled creep.

[en] The evolution of low angle grain boundaries (LAGBs) and Taylor factor (TF) was investigated by EBSD analysis to reveal the micromechanism of ferrite hardening for dual-phase steel during prestraining from 1% to 5%. The results showed plastic deformation was dominated by soft ferrite phases during prestraining from 1% to 3%, and subsequently, transformed to interface deformation during prestraining from 3% to 5%. Due to the evolution of LAGBs, dislocation substructures were generated during prestraining. The fraction of soft grains within the range of TF~2–3 gradually decreased after the hardening, indicating the slip system was more difficult to be activated within ferrite. The hardening of ferrite was attributed to the formation of stable dislocation subgrain structures and the hardening of grain orientation as well. When the prestraining degree went above 3%, the ferrite phases can be completely hardened. After ferrite hardening, the strain hardening ability of the dual-phase steel was reduced, the yield strength was increased and the uniform elongation was decreased at the same time. It was noteworthy that the stress drop (up to 10 MPa) occurred on the stress-strain curve after the completion of strain hardening, and the plastic deformation was initiated directly at interface, exhibiting a mixed mode of failure involving both cleavage brittle and dimple ductile fracture. This work is aiming to provide detailed insights and experimental evidence for ferrite hardening behaviour after prestraining, which is expected to make great contribution for better service protection of the pipeline using dual-phase steel.

[en] Highlights: • At the strain rate of 10⁻² s⁻¹, due to the nearly saturated GNDs and LAGBs density, the completely ferrite hardening occurs. • After pre-straining at higher strain rates, the completely ferrite hardening leads to the early stage of plastic deformation of tensile tests is interface deformation. In this work, the effects of strain rates (10⁻⁴ s⁻¹~10⁻¹ s⁻¹) on ferrite hardening of dual-phase steel were investigated through pre-straining tests. The strain localization was analyzed by the evolution of Kernel average misorientation (KAM). The micromechanism of ferrite hardening was elaborated by the evolution analysis of geometrically necessary dislocations (GNDs), low angle grain boundaries (LAGB) and nano-indentation. The results showed that GNDs and LAGBs in ferrite increased with increasing the strain rate, the average KAM values and nanohardness increased accordingly. Strain localization was observed in the ferrite grains at lower strain rates (10⁻⁴ s⁻¹~10⁻³ s⁻¹), and the considerable strain localization occurred at ferrite/bainite (F/B) interface at higher strain rates. Due to the nearly saturated GNDs and LAGBs density at the strain rate of 10⁻² s⁻¹, the completely ferrite hardening occurred and its nanohardness was close to dual-phase interface. During the tensile deformation after pre-straining, the yield ratio increased while the uniform elongation decreased with strain rates of pre-straining. It was worth noting that the completely ferrite hardening led to the early plastic deformation of tensile tests was interface deformation. This work provides a theoretical basis for the ferrite hardening behavior after pre-straining at different strain rates, and then contributes to the safe service of dual-phase pipeline steel.

[en] Zn-doped α-nickel hydroxide materials with flower-like nanostructures are synthesized by electrochemical deposition method. The samples are characterized by X-ray diffraction (XRD), field emission scanning electron microscope (SEM) and electrochemical measurements. XRD spectra indicate nickel hydroxide doped with Zn is α-Ni(OH)₂ with excellent crystallization. The SEM observation shows that the formation of Zn-doped Ni(OH)₂ includes two steps: a honeycomb-like film forms on the substrate first, then flower-like particles forms on the films. The nickel hydroxide doped with 5% Zn can maintain a maximum specific capacitance of 860 F g^-1, suggesting its potential application in electrochemical capacitors.

[en] Highlights: • Nanoindentation is used to investigate the deformation of individual phases in a complex microstructure. • High resolution strain partitioning in multiphase alloys is obtained by digital image correlation and electron microscopy. • A new non-rigid image registration method to study the local strain partitioning is proposed. In multiphase alloys, the mechanical properties are controlled by both the local properties of individual microstructural constituents, as well as the mutual effect of these constituents as an aggregate. To this end, we systematically studied the local mechanical properties and deformation mechanisms of the microstructural constituents in a ZnAl4Cu1Mg0.31 alloy using nanoindentation tests at room temperature (25 °C) and 85 °C. The obtained strain rate sensitivity and activation volume suggest dislocation-dominated deformation in the primary η-Zn phase and grain/phase boundary sliding in the eutectoid structures. Further, the strain partitioning between individual microstructural constituents and their roles on macroscopic deformation at 85 °C was investigated using quasi in-situ digital image correlation (DIC), supplemented with non-rigid image registration. The DIC measurements showed that eutectic and eutectoid colonies carry higher strain than the primary η-Zn phase grains. The presented approaches and results can therefore be used to design new Zn-Al alloys and also other multiphase alloys with improved mechanical properties.