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RE-containing magnesium alloys were prepared via molten-salt-mediated magnesiothermic reduction by using RE2O3 (RE=Y, Nd and Gd) and Mg metal as raw materials. The thermomechanical analysis of the magnesiothermic reduction reactions in molten salt was investigated. Then the molten-salt-mediated magnesiothermic reduction process was studied from three different perspectives. After that, the RE-containing magnesium alloy was characterized by using chemical analysis, XRD analysis and SEM analysis. The magnesiothermic reduction was a liquid-liquid reaction with relatively weak driving force. During the melting process and the magnesiothermic reduction process, magnesium metal and the obtained alloy went up and down as a whole in molten salt, which improved the process safety without introducing chloride inclusions. Meanwhile, the hydrolysis of the RECl3-containing molten salt occurred at elevated temperature, which severely impeded the magnesiothermic reduction process. After the magnesiothermic reduction at 750 °C for 2.0 h, the content of RE and the common impurity elements in the obtained RE-containing alloy met the both requirements of the commercial WE43A and WE43B.

Based on the deforming technique of severe plastic deformation (SPD), the grain refinement of a Mg-9Gd-3Y-2Zn-0.5Zr alloy treated with decreasing temperature reciprocating upsetting-extrusion (RUE) and its influence on the mechanical properties and wear behavior of the alloy were studied. The RUE process was carried out for 4 passes in total, starting at 0 °C and decreasing by 10 °C for each pass. The results showed that as the number of RUE passes increased, the grain refinement effect was obvious, and the second phase in the alloy was evenly distributed. Room temperature tensile properties of the alloy and the deepening of the RUE degree showed a positive correlation trend, which was due to the grain refinement, uniform distribution of the second phase and texture weakening. And the microhardness of the alloy showed that the microhardness of RUE is the largest in 2 passes. The change in microhardness was the result of dynamic competition between the softening effect of DRX and the work hardening effect. In addition, the wear resistance of the alloy showed a positive correlation with the degree of RUE under low load conditions. When the applied load was higher, the wear resistance of the alloy treated with RUE decreased compared to the initial state alloy. This phenomenon was mainly due to the presence of oxidative wear on the surface of the alloy, which could balance the positive contribution of severe plastic deformation to wear resistance to a certain extent.

High-purity anhydrous magnesium chloride was prepared from magnesia and ammonium chloride. The chlorination process was analyzed and then the critical stages affecting the purity of anhydrous magnesium chloride were pinpointed. The effect of sample dimension on the above critical stages was investigated respectively. The purity guarantee mechanism of anhydrous magnesium chloride was proposed. After that, magnesium metal was obtained via electrolyzing the anhydrous magnesium chloride-containing molten salt. The new process for the continuous production of magnesium metal from magnesia was proposed and discussed. The incomplete chlorination reaction and the hydrolysis of anhydrous magnesium chloride are the two critical stages affecting the purity of the anhydrous magnesium chloride. The dimension of the sample can influence reaction process and reaction mechanism, and thus the problems of incomplete chlorination reaction and hydrolysis can be solved together. The magnesia content in anhydrous magnesium chloride was below 0.1 wt.% when the ratio of height to diameter of the sample was over 2.43. The content of impurities in the magnesium metal obtained met the specifications of the product Mg9980. The current efficiency was (94.7±1.8)% and the electricity consumption was (9107±97) kW h/t.

Regarding the as-cast Mg-9.5Gd-4Y-2.2Zn-0.5Zr alloy, the effect of heat treatment on its properties at room temperature (RT), as well as the mechanical properties and microstructure evolution of various peak-aging samples at different tensile temperatures were discussed in this article. The results indicated that the optimal heat treatment process of the alloy was: 520 °C × 24 h + 200 °C × 112 h. Under this condition, the yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) at RT were: 238 MPa, 327 MPa and 2.5 %, respectively. As the tensile temperature increases, the strength increases firstly and then decreases, but the ductility increases monotonously. The microstructures evolution of 200 °C peak-aging (200PA) and 250 °C peak-aging (250PA) samples were different with the increasing tensile tenperature. When tensile test processed at 150°C, the dense β' phase and rod-shaped basal γ' phase will be formed in the 200PA sample. However, at 300 °C, the β' phases disappeared. The β' and LPSO phases in the 250PA sample coarsened gradually as the tensile temperature increased, and 14H-LPSO phases were formed during tensile at 300 °C. The 200PA sample reached the highest strength when tensile at 150 °C, which was attributed to the hindrance of the basal dislocation and non-basal dislocation slip by the prismatic β' phases and the newly formed basal γ' precipitates.

The effects of deep cryogenic treatment (DCT) on the tensile property and microstructure of Mg-9Gd-4Y–2Zn-0.5Zr(wt.%) alloy were investigated by comparing the alloy treated by solution treatment, deep cryogenic treatment and aging treatment (ST + DCT + AT) and that treated by solution treatment and aging treatment (ST + AT). The lamellar 14H-type long-period stacking ordered (14H-LPSO) in grain was precipitated in the alloy treated by ST + AT. However, the particle and needle-like Mg5RE (RE = Gd, Y) phases instead of the lamellar 14H-LPSO were precipitated, and a high-density dislocation existed in the alloy treated by ST + DCT. The greater ultimate tensile strength (UTS) and yield strength (YS) of the alloy treated by ST + DCT + AT were obtained because of the precipitation of the Mg5RE phases. The trend, the UTS and YS firstly increased then decreased with the increasing of soaking time, is corresponding to the volume fraction increasing and size-coarsening of Mg5RE precipitates, respectively. The greater elongation (EL) was obtained after the short-time DCT for 0–2 h (DCT0h-DCT2h) and the smaller EL was obtained for the long soaking time (>DCT2h). The fracture mode of the samples is all quasi-cleavage fracture.

Photothermal materials with broadband optical absorption and high conversion efficiency are intensively pursued to date. Here, proposing by the d-d interband transitions, we report an unprecedented high-entropy alloy FeCoNiTiVCrCu nanoparticles that the energy regions below and above the Fermi level (±4 eV) have been fully filled by the 3 d transition metals, which realizes an average absorbance greater than 96% in the entire solar spectrum (wavelength of 250 to 2500 nm). Furthermore, we also calculated the photothermal conversion efficiency and the evaporation rate towards the steam generation. Due to its pronounced full light capture and ultrafast local heating, our high-entropy-alloy nanoparticle-based solar steam generator has over 98% efficiency under one sun irradiation, meanwhile enabling a high evaporation rate of 2.26 kg m -2 h -1 .

The isothermal repetitive upsetting extrusion (RUE) was implemented to process ZK60 magnesium alloy at 380 °C. Then, the relationship between the microstructural characters, including grain refinement and texture evolution, and the mechanical performance of the alloy was investigated. Results showed that after 3 passes of RUE, the average grain size was refined from 115.0 to 26.5 μm, which was mainly caused by the continuous dynamic recrystallization and discontinuous dynamic recrystallization. Meanwhile, the elongation of the alloy increased from 13.8 to 21.6%, and the superplasticity (142%) of the alloy has been achieved in the following high temperature tensile test, which is very beneficial for the further processing of the alloy into components. In particular, the alloy formed a distinctive texture distributed between and , which was greatly related to the Schmid factor of extrusion direction (ED) and transverse direction (TD). This texture changed the initiation ability of basal and prismatic slip in both directions and inhibited the initiation of partial tensile twinning in TD; thus, the anisotropy in both directions was weakened. As expected, the tensile yield strength difference decreased from 25.9 to 3.4 MPa, but it was used as the cost of tensile yield strength in ED.

The spark plasma-sintered Ti-6Al-4V alloy was used as experimental specimens to perform the multi-pass hot compression. The deformation temperature was 950, 900, 850 °C, and the compressed amount was 20, 30, 20% corresponding to one pass, two passes and three passes, respectively. The flow behaviors revealed that the curve with the strain rate of 5 s−1 appeared obvious oscillatory phenomenon after peak. Additionally, the curve with strain rate of 0.1 and 1 s−1 almost kept constant after peak stress during the process of two-pass compression. The microstructures showed that the sintered voids with the average diameter of 7.53 μm could be observed in initial Widmanstatten structures with the aspect ratio of 11.49 ± 0.5. The deformed inhomogeneity had prominent influence on the microstructures. For three-pass deformation with the strain rate of 0.1 s−1, the microstructures of severe plastic deformation area were equiaxial microstructures with the grain diameter of 3.82 μm, while the microstructures for medial and small plastic deformation area were dual and Widmanstatten, respectively. With the strain rate of 0.1 s−1, the fraction of dynamic recrystallization (fDRX) increased from 0.034 through 0.112 to 0.440 with the passes increased, and the variation tendency toward average diameter of grain size versus compressed passes shifted reversely. The β→α phase transformation was the main reason for the misorientation angle nearby 60° for one pass with the strain rate of 0.1 s−1. The fDRX declined from 0.440 through 0.225 to 0.297 with raising the strain rate for three-pass deformation, but the grain size changed oppositely. The CDRX and DDRX were both appeared during multi-pass hot deformation.

The compression behavior and mechanical properties of the Mg-13Gd-4Y-2Zn-0.5Zr (wt.%) alloy filled with intragranular long-period stacking ordered (LPSO) phases at different temperatures were investigated. The results showed that the higher the compression temperature, the smaller the plastic strain that the grains withstand. The grains changed from equiaxed to flat strips when compressed at 350°C, and the morphology of the grains did not change at 450°C. Due to the existence of DRX grains, compression at 450 °C didn’t cause large-angle kink, but the kink angle at 350°C was very large. DRX grains only appeared at the grain boundaries and around the intergranular LPSO phase at the beginning of compression, and only appear at the kink bands (KBs) after the lamellar LPSO phases begin to kink. DRX grains gradually increased with the KBs increasing.

The homogenized Mg-10.37Gd-3.66Y-2.27Zn-0.52Zr alloy was subjected to multi-passes reciprocating upsetting extrusion (RUE) deformation with variable temperature. The microstructure evolution and mechanical properties of as-homogenized and RUEed samples were investigated. The results showed that the area fraction of DRX grains gradually increased via the continuous consumption of coarse grains containing lamellar LPSO, and the content of the bulk LPSO phases gradually decreased due to continuous fragmentation. After three passes deformation, the microstructure was almost composed of completely DRXed grains. The LPSO phases with different morphologies were coordinated deformation by kinking, tearing, etc during RUE process. It is worth noting that after four passes, the lamellar LPSO phase did not disappear, but mixed with the fine DRXed grains together. In addition, a mass of particles were produced after each low temperature deformation, indicating that reducing the deformation temperature is beneficial to the dynamic precipitation. The yield tensile strength (TYS), Ultimate tensile strength (UTS) and fracture elongation (FE) of four passes deformed alloy reached 372.6 MPa, 320.8 MPa, 8.1%, respectively. The improvement of mechanical properties is attributed to the two main strengthening mechanisms: grain refinement and LPSO strengthening.

In order to determine the deformation temperature of next pass, the hot compression tests were performed by Gleeble-3800 at different temperature form 380 to 420 °C. The microstructure and texture evolution of repetitive upsetting-extruded (RUEed) Mg-Gd-Y-Zn-Zr alloy during hot compression were studied by electron backscattering diffraction (EBSD) analysis. The results showed that the dynamic recrystallization (DRX) occured during the hot compression processing from the strain-stress flow curves. When the temperature increased to 420 °C, the average grain size reduced to 6.64 μm, and the volume fraction of DRXed grains increased to 81.5%. All the compressed alloys exhibited a typical compression texture, the maximum texture intensity of {0001} plane gradually decreased with increasing temperature. When the compression temperature was up to 420°C, the the maximum texture intensity of {0001} plane was 3.207 due to the effect of DRXed grains. Finally, 420°C is chosen as the next deformation of next pass because of the more precipitation and DRXed grains.

The multi-directional forging process can achieve large plastic deformation, and has great application prospects in industrial production. The Mg-9.55Gd-3.28Y-1.77Zn-0.34Zr (wt%) alloy containing LPSO phase was deformed in different passes and then quenched immediately by the multi-directional forging process with decreasing temperature, and the microstructure and mechanical properties of the alloy were analyzed. It is found that as the number of deformation passes increases, the coarse grains decrease, and the dynamic recrystallization fraction increases. The dynamic recrystallization grains swallow the original grains, promote the continuous refinement of the grains, and greatly improve the uniformity of the microstructure. At the same time, the maximum texture intensity of the (0001) basal plane is significantly reduced, and the pole figure distribution is more dispersed, which is attributed to the random orientation of dynamic recrystallization. Due to the refinement of the microstructure and the weakening of the texture, the tensile strength and yield strength at room temperature increase significantly. After 3 passes of deformation, the alloy has the highest mechanical properties, with tensile strength, yield strength, and elongation reaching 317 MPa, 233 MPa, and 15%, respectively.

In the present work, two processing routes (A and B) with 3 CEE-AEC passes are performed on Mg–13Gd–4Y–2Zn–0.4Zr alloys, and the resultant microstructure evolution, texture analysis and mechanical properties are investigated systematically. The core difference between the two processing routes is the orientation between the expansion and extrusion steps, i.e., they are parallel to each other for on route A and perpendicular to each other for route B. The results show that a remarkable grain refinement is achieved via both processing routes due to dynamic recrystallization (DRX). Fine equiaxed grains are observed in the samples processed with route B with a final size of 3.6 ± 0.4 µm compared to the grain size of 4.5 ± 0.5 µm with route A. With an increasing number of CEE-AEC passes, the overall texture intensity decreases, and the basal texture gradually changes to the mixed texture components. The shear deformation introduced by the asymmetrical extrusion cavity promotes a broad angular distribution of the basal planes on routes A and B, leading to an obvious increase in the Schmid factor for the activation of the basal 〈a〉 slip system. The tensile test at ambient temperature reveals that the comprehensive mechanical properties are improved, and the conventional mechanical anisotropy of as-received alloys is alleviated by successive CEE-AEC processing, which is mainly derived from the competitive balance relation between the grain refinement and texture modification.

Brittle fracture of the composite insulator is a malignant accident. There is a lack of means to monitor the formation and expansion of stress corrosion cracking in rods, resulting in little understanding of the process of brittle fracture development. First, this article proposes a mechanical model for identifying cracks in rods by the wavelength shift trends of fiber Bragg gratings (FBGs). Second, several FBGs and FBG temperature compensation sensors are pasted on the 10-kV composite insulator rod’s surface. Then an optical fiber monitoring system for the brittle fracture process of the rod is established. Finally, the model and system were validated by conducting stress corrosion testing with different tensions. The results show that the surface quasi-distributed FBGs can monitor the temperature and stress in the complete brittle fracture process of a glass-fiber-reinforced polymer (GFRP) rod, which verified the correctness of the mechanical model for wavelength shift identification of cracks in axial cross sections. A temperature difference of 1 °C and the wavelength shift of the FBG on two or more fibers reach $1.1~\lambda _{s\mathrm {min}}$ and $0.9~\lambda _{s\mathrm {min}}$ can be used as warning thresholds for corrosive heat release, crack initiation, and rapid development of cracks to fracture, respectively. This article provides a quasi-distributed FBGs’ monitoring system and method to study brittle fracture of composite insulators in stress corrosion testing. It provides a technical means to evaluate and warn the mechanical properties of composite insulators.

A large density difference of a basin-type insulator in gas-insulated metal-enclosed switchgear (GIS) weakens its mechanical strength, which will threaten the safe and stable operation of GIS. In this article, an ultrasonic nondestructive testing method for density uniformity of GIS basin-type insulators was proposed. First, seven standard samples with different Al2O3 content were tested by an ultrasonic testing system, and then a mapping relationship between density and ultrasonic velocity was established. Second, the uncertainty of the testing system was obtained, and the ultrasonic velocities of 192 positions in a 126 kV three-phase basin-type insulator were measured. Finally, the density distribution of the insulator was obtained based on the mapping equation of velocity-density, and a contour plot of density was established by the cubic spline interpolation. The results show that there was a positive linear correlation between the density of standard samples and the ultrasonic velocity, and the determination coefficient was 0.992. Notably, the expanded uncertainty of ultrasonic propagation time for detecting 45 mm-thick EP/Al2O3 composites was only $0.0112~\mu \text{s}$ . The ultrasonic propagation time of detection positions in the insulator was from 31.0634 to $31.4708~\mu \text{s}$ and the difference was greater than $0.0112~\mu \text{s}$ , which illustrated that the testing system meets the requirements for detecting the density of the insulator. According to the contour plot of density, the density distribution of the insulator was shown clearly and efficiently. The density was higher at the bottom edge of the insulator and the upper part of the insert, whereas the density was smaller at the lateral upper part of the insulator and the lower part of the insert. Specifically, the maximum density of the insulator was 2.36 g/cm3 and the minimum density was 2.25 g/cm3. The feasibility of nondestructive testing density by the ultrasonic method is verified, which provides a new method for density evaluation of GIS insulators.

Raman spectroscopy can provide structural fingerprints to identify molecules by means of spectral library searching. However, it is difficult to share the spectral library between different Raman spectrometers because of the nonlinear displacement in Raman shift. In this study, we propose a Raman spectra Standardization method using Variable Penalty dynamic time warping (RS-VPdtw), which can synchronize the nonlinear displacement between spectra acquired with different spectrometers. We have compared the standardization performance of RS-VPdtw and MWFFT on the spectra of 13 real samples acquired with 6 different spectrometers. The mean spectral similarity of RS-VPdtw and MWFFT increased from 0.79 to 0.97 and 0.91 respectively. Results show that RS-VPdtw is significantly better than MWFFT in Raman spectra standardization. The Raman spectra acquired with different spectrometers can be standardized by RS-VPdtw to search the same spectral library, which can avoid the time-consuming and labor-intensive reestablishment of spectral libraries for different spectrometers. This means that RS-VPdtw is a promising and valuable method to solve the spectra standardization problem in large-scale applications of Raman spectroscopy.

The multifactor accelerated aging test is an important means to predict the lifetime of gas-insulated switchgear (GIS) O-ring seals, while the leakage rate (LR) is a potential index for failure evaluation. This article proposed a three-factor accelerated aging test platform and a leakage test system (LTS) for GIS seal rings. The aging factors are thermal, mechanical compression, and pressured SF6 gas. The pressure aging vessel (PAV) can be filled with various gases to simulate the operating conditions of the GIS and age multiple samples simultaneously. During the aging process, leakage tests are conducted on flange pairs without disassembling and separating the seal rings. After the test, the aging can be continued so as to study the evolution of LR with aging time. In order to analyze the properties of leakage test and validate the platform, a three-factor accelerated aging and a traditional two-factor accelerated aging (thermal and compression) were conducted on GIS O-ring seals of EPDM material. Compression set (CS) and LR were tested. The result showed that a steady inherent LR $F_{0}$ exists for the LTS. The LR rose linearly with accumulating time, allowing simplified calculation of LR. The three-factor aged samples had significantly smaller CS than those of the two-factor aged samples, indicating that the working condition of GIS with SF6 atmosphere significantly slows the aging rate of GIS seal rings. The findings proved that the three-factor accelerated aging test platform and LTS effectively simulate the operating conditions of GIS seal rings and evaluate their properties.

Neotame is an artificial sweetener with increasing consumption in recent years, excessive intake of it may bring potential health risk. In this work, a rapid method was developed to detect neotame in instant grain beverages, which was based on surface-enhanced Raman scattering (SERS) technique and filter paper-based silver nanoparticles (AgNPs@FP) substrates. The designed substrate exhibits good SERS activity with an enhancement factor of 105 because of the synergistic effect of the concentrated silver nanoparticles and filter paper. Meanwhile, the stability and repeatability of this fabricated substrate have been investigated with the relative standard deviation of 6.1%. In addition, it shows an excellent linear relationship (R 2 = 0.997) between the SERS signal and the logarithm concentration of neotame with a wide concentration range (0.05–5 g/kg) in the quantitative analysis. The limit of detection of neotame can be as low as 0.01 g/kg in instant grain beverages, which is below the maximum allowable addition level for neotame in instant grain beverages set in China (GB2760-2014, 0.16 g/kg). The proposed method has great potential for the identification and quantification of neotame in food safety applications with high sensitivity.

The cylindrical samples of TC4 titanium alloy prepared by spark plasma sintering (SPS) were compressed with hot deformation of 70% on the thermosimulation machine of Gleeble-1500. The temperature of the processes ranged from 850°C to 1,050°C, and the strain rates varied between 0.001 and 5 s−1. The relative density of the sintered and compressed samples was measured by the Archimedes principle. During hot deformation, the microstructure of the sample was observed. The results show that the average relative density of the samples was 90.2% after SPS. And the relative density was about 98% after the hot deformation of 70%. Under high temperature (>950°C), the sensitivity of flow stress to temperature was reduced. At low strain rate (0.001 s−1), the increase in the deformation temperature promoted the growth of dynamic recrystallization (DRX). At the same temperature, the increase in strain rate slowed down the growth of DRX grains. And the variation tendency was shown from the basket-weave structure to the Widmanstätten structure at a low strain rate (−1), with increase in the strain rate.

This paper provided an efficient single pass severe plastic deformation (SPD) method, annular channel angular extrusion (ACAE), for fabricating AZ80 magnesium alloy shell part. The effect of ACAE process on the microstructure homogeneity, texture, and mechanical properties of extruded part was experimentally investigated. For comparison, conventional backward extrusion (BE) was also conducted on processing AZ80 part with same specification. The results showed that ACAE process has a better capacity to refine the microstructure and dramatic improve the deformation homogeneity of the extruded part than BE process. Due to two strong shear deformations were implemented, ACAE process could also concurrently modify the basal texture more notably than BE process. In particular, a bimodal texture was found in ACAE extruded part, which was greatly related to the enhanced synergetic action of basal slip and secondary slip caused by the effective shear stress. More uniform and superior hardness along the thickness and height of part were achieved via ACAE process. Further surveying of tensile tests also showed that the part fabricated by ACAE process exhibited significantly higher and far more homogeneous tensile properties with an excellent balance of strength and ductility. The remarkable enhanced tensile properties of ACAE extruded part could be primarily attributed to the significant grain refinement, which provided a powerful grain boundary strengthening effect and meaningfully suppressed the development of twin-sized cracks during tensile deformation. It was established that ACAE process seemed to be a very promising single pass SPD method for manufacturing Mg-based alloy shell parts with more homogeneous microstructure and superior performance.

This study describes a sensitive and rapid method for the quantification of Cimetidine (Cim) based on surface-enhanced Raman scattering (SERS), using silver nanoparticles as an SERS substrate. Ag nanoparticle was fabricated by hydrothermal method. The experiment includes the selection of solvent types and optimisation of volume radio. Results suggested that the intensity and logarithmic Cim concentration in the range from 1.0 × 10−8 to 1.0 × 10−4 M has a linear relationship with the coefficient of determination (R 2) of 0.989, the limit of detection (LOD) of 2.9 × 10−9 M, by targeting the characteristic peak at 2150 cm−1. The LOD of Cim in plasma using this method was as low as 1 ng/ml. This indicates that the method has a potential for detection of Cim in biological samples.

The TC4 titanium alloy powder test piece was prepared by spark plasma sintering. The multi-pass hot deformation of the TC4 titanium alloy was tested by using the Gleeble-1500 experiment machine. Measurement of relative density, X-ray diffraction, optical microscopy, scanning electron microscopy and electron backscatter diffraction were carried out for the TC4 titanium alloy. In order to reveal the evolution of the microstructure, describing its changes systematically is necessary, which has become the focus of this article. The results show that after multi-pass hot deformation, the relative density of the TC4 titanium alloy could reach 99.93%. With the increase in deformation and decrease in temperature, the β-transformed phase was retained, and many fine β-transformed phases were formed between two adjacent lamellar α. During the one-pass hot deformation, the rapid increase in relative density was the main reason for the instability of the flow stress in the stress–strain curve. For two-pass and three-pass hot deformations, more features of dynamic recrystallization and the characteristics of dynamic recovery at high strain rates (5 s−1) could be found. The size of the grains was about 15 µm after the three-pass hot deformation.

By means of annular channel angular extrusion technology and solution treatment, the AZ80 supersaturated solid solution was prepared. The β-Mg17Al12 precipitate morphologies analysis along with its sizes and area fraction measurement was performed to investigate mechanical properties variation of alloy at various aging temperature. The results indicated that after solution treatment, the intergranular precipitate of as-extruded alloy was re-dissolved into the matrix, effectively decreasing the stress concentration, which was beneficial to the enhancement of elongation. At aging temperatures of 300 °C, Widmanstatten structure, lath-shaped precipitate, and intergranular precipitate were observed, while at 175–200 °C, cellular structure and oval-shaped particle were also identified. The morphology, area fraction, size of the precipitates, and PFZs (precipitate free zones) width worked together to affect the age-hardening behavior of the alloy. The strength and hardness of the peak-aged samples decreased with the increase in aging temperature, which is primarily attributed to the reduction in cellular structure area fraction and the corresponding increase in the interlamellar spacing, and the coarsening of the rhombus precipitate.

Super-resolution optical microscopy is a useful tool to investigate physical and biological characteristics on the sub-100-nanometer scale. Here, we develop pulsed saturated absorption competition ...

Severe plastic deformation can be produced by repetitive upsetting-extrusion process. Using the repetitive upsetting-extrusion (RUE) process at decreasing temperature, the Mg-12.0Gd-4.5Y-2.0Zn-0.4Zr (wt %) alloy was deformed by different RUE passes and then heat treated. The microstructure, texture and mechanical properties of the alloy were compared and analyzed. The results demonstrate that with the increase of deformation passes, the coarse grains of the alloy decreased, the dynamic recrystallization fraction increased, and the dynamic recrystallized grains phagocytized the original grains. This can promote the continuous refinement of the grains and the microstructure uniformity. The maximum texture intensity of the (0001) basal plane decreased significantly with the increase of processing passes and the dispersion degree of pole figure increased. The orientation of dynamic recrystallized grains was randomly distributed to weaken texture. Due to the refinement of microstructure and the weakening of texture, the tensile strength and yield strength of the alloy obviously increased at room temperature. The mechanical properties of the alloy reached the highest after 3 passes and heat treatment.

The high temperature tensile behavior of Mg-13Gd-4Y-2Zn-0.5Zr alloy was investigated at deformation temperature of 400-520 °C and strain rate of 0.001-0.5 s-1, and the stress-strain curves were obtained by using INSTRON 3382. The high temperature tensile constitutive model and hot processing map of the alloy were established, and the reliability of the hot processing map was further verified by analyzing the microstructure of the deformed alloy. The results showed that the dynamic recrystallization (DRX) occurred of Mg-13Gd-4Y-2Zn-0.5Zr alloy during the tensile tests under high temperature conditions, and its peak stress decreased with the increase of deformation temperature or strain rate. The Arrhenius equation can be used to fit the rheological behavior of the alloy. The thermal deformation activation energy Q was 259.13kJ/mol, and the maximum error between the model and the experimental data was less than 9%. It can be concluded that the optimum deformation parameters of the alloy were temperature of 500-520 °C and strain rate of 0.01-0.001 s-1 based on the dynamic material model and hot processing map.

TC4 titanium alloy powder was made into the test piece by spark plasma sintering. The hot deformation of TC4 titanium alloy was performed on the Gleeble-1500 experiment machine. The effects of microstructure were studied. The results show that the number of passes increased with the increasing of the relative density at the same amount of deformation. The relative density have an important influence in one-pass deformation. At the deformation temperature of 950°C and a strain rate of 0.1s-1, the microstructure of TC4 titanium alloy was the weave-basket structure, and the widmanstatten structure existed. The increase in the number of passes could promote the growth of dynamic recrystallization grains under the same amount of deformation.

In this paper, the compression-torsion composite deformation of homogenized Mg-13Gd-4Y-2Zn-0.5Zr alloy with strain rate of 0.001 s-1-0.5 s-1 during the temperature interval of 350 °C-480 °C was studied by the torsional test using the equipment of Gleeble3500 unique to North University of Chain. The effects of temperature and strain rate on the flow behavior of the alloy during compression-torsion deformation were investigated. And the compression-torsion constitutive equation of the high temperature flow stress of the alloy was constructed by introducing the temperature compensation factor Z, providing a theoretical basis for subsequent finite element analysis. The results showed that the flow stress increased with the increase of strain when the flow curves of the alloy were 350 °C and 400 °C. When the deformation temperatures were 450 °C and 480 °C, the flow stress was a typical recrystallization type. The influence of temperature and strain rate on dynamic recrystallization behavior was investigated by OM observation. The results showed that the number and size of recrystallized grains increased with the increase of temperature at the same strain rate, and the number and size of recrystallized grains increased with the decrease of strain rate at the same temperature.

AZ80+0.4%Ce alloy ultra-thin-walled tube with a wall thickness of 0.6 mm was fabricated by multi-pass variable wall thickness extrusion (VWTE) at 693 K. Microsturcture and texture evolution were investigated. The results indicate that the average grain size decreases from ~47 μm of extruded alloy to ~8.9 μm after 5 passes VWTE. The total area reduction of Mg alloy tube is 91 %. Homogeneity of microstructure is improved obviously and the morphology of Mg17Al12 phases in coarse grains and fine DRXed grains exhibit lamellar and granular shapes, respectively. In addition to the microstructure evolution, the VWTEed tubes showed a strong texture of (0001) planes, and the intensity decreased with deformation increasing to 4 passes. After 5p-VWTE, a strong texture characterized by (0001) pole tilting 20 degrees rotated from extrusion direction (ED) towards normal direction (ND).

This aim of this study was to identify the genomic mutations present in fluoride-resistant Streptococcus mutans (strain UA159-FR) using next generation sequencing, and to establish the role of these mutations by comparing fluoride-sensitive (UA159) and UA159-FR strains. In this paper, the genome of UA159-FR strains was sequenced by PacBio RS and IIIumina sequencing platform using silica-based nanopore. The genomic alignment to the reference S. mutans strain UA159 (NC_004350) was conducted using MUMmer 3.22 to list all the structural variations (SVs), single nucleotide polymorphisms (SNPs) and indels. A second round of Sanger sequencing of all regions in which the relevant mutations (SVs, indels, and SNPs) were identified was conducted to confirm these findings. In addition, blast comparison of virulence factor sequence was carried out. In order to explore the effect of the mutant gene against S. mutans, the KEGG pathway, COG function and go enrichment of the annotated gene were analyzed. Expressions of these variants were compared between S. mutans UA159 and UA159-FR through RT-qPCR. Genome sequencing revealed the presence of a single 2,031,692 bp circular chromosome, including 1940 ORFs, of which the G+C content was 37.46%. In addition, 35 genomic SNPs and 5 SVs type in UA159-FR were identified through an extensive bioinformatics analysis. The results of indel analysis showed that there was no insertion or deletion of genes in UA159 and UA159- FR; Synteny analysis showed that the gene of UA159 was collinear with UA159-FR, which further indicated that the main type of gene mutation was single base mutation. By comparing the amino acid sequences of UA159-FR samples with virulence factors, blast obtained 92 virulence factors, among which, ciaH, eno and pykF had gene mutations. The mutations of ciaH, eno and pykF may be responsible for the functional changes of Streptococcus. At the same time, enrichment analysis showed that the expression genes of S. mutans were mainly enriched in KEGG pathway such as glycolysis/gluconeogenesis, citric acid cycle (TCA cycle), pentose phosphate pathway, involved in DNA replication, and related to biological processes such as cell development and cell metabolism. ciaH, eno and pykF were involved in these processes. In summary, this study highlights new mutations in fluoride-resistant bacteria that may enhance our current understanding of fluoride-resistant pathways in microorganisms. It has been proved that silicon based nanopores and nanopores arrays can detect gene sequences sensitively and can be used as the main means of gene sequencing in the next generation.

In this study, a new damage mode for the explosive reactive armour (ERA) of a shaped charge jet was proposed. The response characteristics of polytetrafluoroethylene (PTFE) and polyamide (PA) polymer jet impact on the ERA were analysed. The expansion degree and the diameter of the PTFE jet are larger than those of the PA jet, but the compactness of the PTFE jet head is lower than that of the PA jet, resulting in different impact pressures of the different polymer expansive jets on the target. The PTFE jet achieved the penetration without initiation of the ERA at different standoffs, while the PA jet directly detonated the sandwich charge when impacting the ERA vertically and failed to penetrate the front plate when impacting the ERA at 68°. With the increase of standoff, the reaction degree of the PTFE jet to the ERA decreased gradually, and the aperture of the front plate did not change.

The spark plasma sintered (SPS) TC4 titanium alloy was deformed at deformation temperature of 900℃ and 1000℃ on Gleeble-1500D thermal simulator, and then the microstructure and α/ β phases evolution at different heat treatment parameters were investigated. The results showed that the effect of heat treatment on the microstructure of TC4 titanium alloy was not obvious when the deformation temperature lower than β-transus temperature. On the contrary, when the heat deformation temperature was above the β-transus temperature, the content of equiaxed α-phase increased and the lamellar α-phase coarsened with the decrease of solution temperature. When the solution temperature was lower than β-transus temperature 10℃-30℃ and the aging time was up to 20h, a tri-modal structure( equiaxed α-phase+lamellar α-phase+β-transformed matrix) was formed. Controlling the increase of the primary α-phase and the coarsening of the lamellar α-phase is the key to the formation of the tri-modal structure. Subsequent microhardness tests showed that the microhardness of TC4 titanium alloy with the basket-weavestructure and widmanstatten structuren was the highest, which reached 438HV. In addition, the microhardness of the equiaxed structure and tri-modal structure were 348HV and 373HV,respectively.

The Mg-Gd-Y-Zr alloy was subjected to the variable temperature repetitive upsetting-extrusion process, a kind of severe plastic deformation. The evolution of microstructure, texture and deformation mechanism under different passes was analysed. It is found that when the deformation temperature was relatively high at 420℃, the morphology of the grains was approximately equiaxed. Some precipitated phases were distributed at the grain boundaries and the fraction of them was relatively low. When the deformation temperature was decreased, the precipitation phases increased remarkably, playing the pinning effect and stimulate the particle stimulated nucleation (PSN) mechanism to significantly refine the grain. As the number of deformation passes increased, The grains were remarkably refined from the 80.45 μm of initial billet to 4.08 μm of 4-pass sample, gaining the more uniform microstructure. With the increase of deformation amount, the coarse grains decreased with the fraction of dynamic recrystallization increased and secondary dynamic recrystallization occurred inside the grown dynamic recrystallized grains. The (1010) fiber texture disappeared and the texture was weakened. The random of the high-temperature deformation texture was obvious due to the non-basal slip of alloy which was easier to activate.

The application of optical microscopy in four-dimensional (spatial and temporal) super-resolution imaging poses challenges because of the requirement of a long acquisition time or high illumination intensity. In this paper, we introduce simultaneous two-angle axial ratiometry (STARII) for

We report a widefield super-resolution (SR) fluorescence microscopy technique termed total internal reflection fluorescence pattern-illuminated Fourier ptychographic microscopy (TIRF-piFPM). It employs pattern-illuminated Fourier ptychography (piFP) under the total internal reflection fluorescence (TIRF) mode, providing a lateral resolution of ∼100 nm, reducing the background level, and correcting unknown optical aberrations. Like the total internal reflection fluorescence structure illuminated microscopy (TIRF-SIM), the illumination field of TIRF-piFPM is modulated by sinusoidal patterns generated by evanescent wave interference. It differs from TIRF-SIM in that TIRF-piFPM reconstructs the SR image by FP iteration. To demonstrate the performance of TIRF-piFPM, we compare it with TIRF-SIM by conducting simulations and experiments and prove that TIRF-piFPM can provide a better result than TIRF-SIM in terms of its robustness to noise and aberration correction ability. In addition, dynamic changes of mitochondria in U2OS cells are captured with a temporal resolution of 2 s, demonstrating its live-cell imaging capability. The addvantages may enable TIRF-piFPM to serve as an alternative to SR fluorescence microscopes in the TIRF family, with promising applications in biological and biomedical imaging.

The quasi-static and low cycle fatigue tests of extruded 7075 Al alloy (Φ200 mm) were investigated in three directions: the extrusion direction (ED), the radial direction (RD), and 45° with ED (45°). Grain morphology analysis, texture measurement, and fatigue fracture characterization were conducted to discuss the relationship between microstructure and mechanical properties. The experimental results showed that the ED specimen had higher ultimate tensile strength (UTS) and low cycle fatigue (LCF) properties, which were mainly attributed to the following three causes. First, the grain boundaries (GBs) had an obvious effect on the crack growth. The number of GBs in the three directions was different due to the shape of the grains elongated along the ED. Second, the sharp &lt, 111&gt, texture and the small Schmidt factor along the ED explained the higher ultimate tensile strength (UTS) of the ED specimens. Third, fatigue fracture observation showed that the ED specimen had a narrow fatigue striation spacing, which indicated that the plastic deformation of the ED specimen was the smallest in each cycle. In addition, two fatigue prediction models were established to predict the LCF life of extruded 7075 Al alloy, based on the life response behavior of the three directions under different strains.

There is a new long-period stacking ordered structure in Mg–RE–Zn magnesium alloys, namely the LPSO phase, which can effectively improve the yield strength, elongation, and corrosion resistance of Mg alloys. According to different types of Mg–RE–Zn alloy systems, two transformation modes are involved in the heat treatment transformation process. The first is the alloy without LPSO phase in the as-cast alloy, and the MgxRE phase changes to 14H-LPSO phase. The second is the alloy containing LPSO phase in the as-cast state, and the 14H-LPSO phase is obtained by the transformations of 6H, 18R, and 24R. The effects of different solution parameters on the second phase of Mg–9Gd–2Y–2Zn–0.5Zr alloy were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The precipitation mechanism of 14H-LPSO phase during solution treatment was further clarified. At a solution time of 13 h, the grain size increased rapidly initially and then decreased slightly with increasing solution temperature. The analysis of the volume fraction of the second phase and lattice constant showed that Gd and Y elements in the alloy precipitated from the matrix and formed 14H-LPSO phase after solution treatment at 490 °C for 13 h. At this time, the hardness of the alloy reached the maximum of 74.6 HV. After solution treatment at 500 °C for 13 h, the solid solution degree of the alloy increases, and the grain size and hardness of the alloy remain basically unchanged.

Depletion beams with long pulse durations ( ∼ 600 p s ) have recently been applied in stimulated emission depletion (STED) microscopy to reduce photobleaching and phototoxicity. Therefore, improving the resolution of pulse STED at lower depletion power for the super-resolution imaging of live biological specimens has attracted increasing interest. Herein, we present a simple method termed ratiometric photon reassignment based on the fluorescence lifetime, in which highly spatially resolved long-lifetime fluorophore components in the center are extracted, and short-lifetime fluorophore components in the periphery are discarded to improve resolution without increasing the depletion power. The experimental results demonstrate improved resolution and signal-to-noise ratio compared with traditional time-gated STED. Our proposed method requires lower budget and data processing because, in contrast to the separation of photons by lifetime tuning, lifetime measurements are not required.

Here, we propose a novel imaging method, which is called image scanning difference microscopy (ISDM), for superresolution imaging. In ISDM, we implement a detector array composed of 19 avalanche photodiodes (APD) rather than single-point detector in standard confocal microscopy for reconstructing superresolved images with higher signal-to-noise ratio (SNR). Combining with our former proposed fluorescence emission difference (FED) method, we have achieved a lateral resolution of 111 nm (∼λ/6) without the damage of image quality, the highest FED resolution to the best of our knowledge. With its simple setup and remarkable performance, we believe that ISDM can become a versatile observation tool in biology and other fundamental studies. LAY DESCRIPTION: Fluorescence emission difference (FED) microscopy is a really simple and generalisable superresolved fluorescence microscopy method based on PSF engineering and difference algorithm recently. Compared to stimulated-emission-depletion fluorescence microscopy (STED), FED don't need complicated system or precise alignment and polarisation, available for wide variety of dyes and has low photobleaching and phototoxicity for living cells. However, the distortion caused by negative value is one of the biggest obstacles to the further development of FED. In light of this, we propose a novel superresolution imaging method based on the FED method with parallel detection system, which is called image scanning difference microscopy (ISDM). Our method has achieved a significant breakthrough in FED, increasing the resolution further while reducing artefacts generated by negative values, which cannot be accomplished through combining other methods. In addition, ISDM does not require complex setup and optical alignment, long time imaging and imposing no constraint on dyes. Importantly, we realised a transverse resolution of ∼λ/6 (triple diffraction limit) with single wavelength, single incident path and low light intensity, which has never been achieved in any other far-field superresolution microscopy.

Repetitive upsetting-extrusion (RUE), a severe plastic deformation, was performed on the Mg-12.0Gd-4.5Y-2.0Zn-0.4Zr (wt %) alloy at different deformation temperatures in the range of 693–773 K for 1, 2 and 3 passes. The study was aimed to determine the effects of deformation temperatures and processing passes of RUE on the microstructure and texture evolution of the RUEed alloy. It is found that dynamic recrystallization (DRX) occurred in the alloy and β- Mg5(Gd,Y,Zn) phase particles precipitated at grain boundaries during the RUE processing. The microstructure was refined remarkably during RUE, the microstructure distribution became more homogeneous and the degree of DRX was increased with the number of the processing passes increasing. The grain refinement was mainly caused by DRX, and the LPSO phases stimulated the DRX around the grain boundaries via particle stimulation nucleation mechanism. The microstructure and texture evolution were mainly depended on the RUE processing parameters, such as processing passes and deformation temperatures. The basal texture was gradually weakened during more processing passes and higher deformation temperatures of RUE processing. The microstructure and texture evolution of the alloy were affected more by processing passes than deformation temperatures during RUE. After 3 RUE passes, some (0001) basal planes were perpendicular to the ED and that also were parallel to the ED in some grains, which is different from that observed in both extruded alloys and other plastically deformed counterparts. The number fraction of low angle grain boundaries tended to decrease while the average misorientation angles tended to increase with the processing passes and deformation temperatures of the RUE increasing.

The thermal deformation behavior of Mg-11.95Gd-4.5Y-2Zn-0.37Zr alloy was investigated by torsion tests under different deformation conditions. Electron backscattered diffraction (EBSD) technique was used to study the effect of deformation temperature and strain rate on the dynamic recrystallization grain (DRX) and texture evolution during torsion deformation. The results indicate that the equivalent stress-strain curve of the alloy under hot torsion is similar to the curve under thermal compression. A predictive model for the critical strain ( e c ) and the Z parameter of the investigated Mg-alloy during torsion deformation has been established. The influence of deformation temperature on the DRX and grain size distribution is significantly different in different temperature regimes. We have observed that the grain size distribution is significantly wider at higher temperatures. Moreover, the distribution of pole density is relatively uniform under different torsion deformation conditions. The torsion has significantly declined the texture and the maximum texture intensity decreased with the decrease in grain size under different deformation conditions.

Hot deformation behavior of Al–0.2Sc–0.04Zr (wt.%) aluminum alloy was investigated via conducting hot compression tests at temperatures of 440–600 °C and at strain rates, ranging from 0.001 to 5 s−1, at an interval of an order of magnitude. The characteristics of the true stress–strains acquired in the hot compression tests were investigated, and the influence of processing parameters on the microstructure of the deformed samples was observed by using optical microscope and electron back-scattered diffraction (EBSD). Two types of processing maps for Al–0.2Sc–0.04Zr alloy were developed using the Kumar–Prasad (K–P) and Murty–Rao (M–R) instability/stability criteria, respectively. The prediction results of two types of processing maps were examined. Based on the analysis of the M–R processing map and EBSD, a deformation mechanism map covering a wide range of temperature and strain rate was developed. The result shows that the flow stress had a rapid increase to the maximum stress, and subsequently, the flow stress decreases continually to be of steady-state type when the deformation continues on. The M–R criterion can more accurately predict the unstable region than the K–P criterion. The optimum temperature T and strain rate $$ \dot{\varepsilon } $$ combination conditions for Al–0.2Sc–0.04Zr alloy are T = 520–560 °C, $$ \dot{\varepsilon } $$ = 10−3 s−1 or $$ \dot{\varepsilon } $$ = 0.1–5 s−1. The microstructure evolution dominated by the predominant or complete dynamic recrystallization can be acquired by deformation at the combination conditions. However, it is dominated mainly by dynamic recovery at lower temperatures (T 520 °C). In addition, the microstructure of specimen deformed at 600 °C shows a growing and coarse trend. Moreover, the nano-dimension precipitate particles of Al3(Sc,Zr) are uniformly distributed throughout Al matrix. The efficiency parameter η value of Al–0.2Sc–0.04Zr alloy in processing maps is smaller in comparison with that in pure aluminum, and it could be attributed to these nano-dimension particles.

High-purity anhydrous MgCl2-containing molten salt was directly synthesized from MgCl2 · 6H2O via complex salts dehydration and protection. After that, Mg-Al and Mg-Zn alloys were prepared by elect...

An ultrasensitive and highly reproducible novel surface-enhanced Raman scattering (SERS)-enabled capillary platform was developed for on-site detection of methotrexate (MTA) in serum. By employing a facile mirror reaction and a self-assembly procedure, glass capillaries were compactly coated with core-shell-satellite microspheres (CSSM) via a batch-fabrication process without using any pre-surface modifications or specialized equipment. The quality of the prepared capillaries was facilely evaluated and controlled by detecting SERS signals of 4-mercaptobenzoic acid (4-MBA) that were specifically anchored in the middle gap of CSSM. The CSSM-modified glass capillaries exhibit strong enrichment of MTA due to electrostatic interaction, high SERS performance ascribed to the interparticle plasmonic coupling, and the stimulation of strong signal of 4-MBA, enabling the detection of MTA molecules at low concentrations. The fabricated capillaries allow rapid detection of MTA via a facile “aspiration-measure” detection mode. Based on the inherent SERS spectra of MTA and 4-MBA, the intensity ratio of MTA and 4-MBA versus the concentration of MTA shows a correlation coefficient of 0.990 in the range of 0.1 nM–110 nM. Given electrostatic force and capillary action, this developed portable SERS-enabled device holds great potential for practical applications in point-of-care (POC) diagnosis.

This paper reports a new candidate material λ-Ti3O5 for microwave absorption. λ-Ti3O5 has been proposed to be metastable and has emerged at room temperature only in the form of nanocrystals. To prepare high purity λ-Ti3O5, the formation energies of 27 different elements doped into λ-Ti3O5 were calculated by first-principles from the energy point of view. It was found that Li has the strongest stabilizing effect on λ-Ti3O5. The prepared λ-Ti3O5 and Li/λ-Ti3O5 show good microwave absorption properties: the efficient absorption bandwidth of λ-Ti3O5 can reach 7.9 GHz at 1.7 mm thickness, and the efficient absorption bandwidth of Li/λ-Ti3O5 can reach 7.4 GHz at 1.2 mm thickness. In addition, we propose a strategy of using the number of states of the micro-electric field to predict the microwave absorption properties of materials, which is helpful to the understanding of the origin and development of microwave absorption.

As a kind of extrusion process, the forward–backward–radial extrusion (FBRE) process can be used to produce complex-shaped parts with hoop protrusions or flanges. The control of metal flow is the key to affect forming, strain distribution, and forming load during the FBRE process. On the basis of summarizing the research of the FBRE process, this paper presents the numerical and experimental results of aluminum alloy hub production using this method. Material flow behavior and strain distribution within the final product were investigated by finite element methods. The parameters such as billet size, die corner radius, and friction conditions are optimized and determined to control the material flow in different sections. While the uniformity of extrusion deformation is greatly improved, the extrusion forming load is reduced, and the aluminum alloy hub was manufactured by the FBRE process. The comparison between the theoretical and the experimental results shows good agreement.

Reciprocating Upsetting-Extrusion (RUE) deformation process can significantly refine the grains size and weaken the basal plane texture by applying a large cumulative strain to the alloy, which is of great significance to weaken the anisotropy of magnesium (Mg) alloys and increase the application range. In this paper, the Mg-8.27Gd-3.18Y-0.43Zr (wt %) alloy was subjected to isothermal multi-passes RUE. The microstructure and texture evolution, crystal orientation-dependent deformation mechanism of the alloy after deformation were investigated. The results clearly show that with the increase of RUE process, the grains are significantly refined through continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) mechanisms, the uniformity of the microstructure is improved, and the texture intensity is reduced. At the same time, a large number of particle phases are dynamically precipitated during the deformation process, promoting grain refinement by the particle-stimulated nucleation (PSN) mechanism. The typical [10-10] fiber texture is produced after one pass due to the basal plane of the deformed grains with a relatively high proportion is gradually parallel to the ED during extrusion process. However, the texture concentration is reduced compared with the traditional extrusion deformation, indicating that the upsetting deformation has a certain delay effect on the subsequent extrusion texture generation. After three or four passes deformation, the grain orientation is randomized due to the continuous progress of the dynamic recrystallization process.

The condition assessment and lifetime estimation methods of rubber O-ring seal used in gas-insulated metal-enclosed switchgear (GIS) has prospective significance. Previous research had built nonlinear models for the degradation of mechanical properties for O-rings, but this conflicted to the common-known linearity of oxygen consumption rate (OCR) which characterized the chemical aging rate. Perhaps this might be explained by the gradually losing of compressive stress, and the effort of this paper was to verify this explanation. In this paper, the thermal-compressive two-factor accelerated aging were conducted on GIS O-ring seals of two EPDM formulations. Determination methods of compression set (CS) and residual compression ratio (RCR) were proposed for GIS O-rings. The compression set at unit residual compression ratio (CSU) and its derivation (ARU) was derived. The results showed that CSU had good linearity with aging time and the trends of ARU was consistent with OCR, which verified the explanation.