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In this paper, the Mg-9.32Gd-3.72Y-1.68Zn-0.72Zr (wt%) alloy has undergone three times of repetitive upsetting extrusion deformation. Alloys with different morphologies and distribution patterns of the second phase have been prepared by varying the deformation temperature in each pass. The effects of the second phase on microstructure, texture and mechanical properties are investigated. The results show that (i) the second phase, including Mg _5 Gd and LPSO phase, has an important effect on the dynamic recrystallization (DRX) behavior of the alloy. (ii) Appropriate lamella distance and block phase size can promote the activation of the slip system and effectively weaken the texture strength. (iii) The DT sample has an effective combination of fine grain strengthening and second phase strengthening due to the reasonable second phase distribution and size, which greatly improves the UTS and YS of the alloy.

For an extrusion process of 7075 Al alloy, the extrusion direction of the initial blank is changed to study the mechanical properties of the formed plates and characterize their microstructure. The as-received bar is extruded 7075 Al alloy. The secondary extrusion deformation is along and perpendicular to the initial extrusion direction. The results show that the anisotropy of mechanical properties of the two samples decreases obviously after secondary deformation. The anisotropy of yield strength and ultimate tensile strength of ED90 sample is lower than that of ED0 sample, but the plastic anisotropy is slightly higher than that of ED0 sample. In addition, the recrystallized grain proportion of ED90 sample is high and the texture strength is low, so the Schmid factor in the three directions is similar. The tensile fracture mode of the two samples belongs to ductile fracture, but the morphology of dimple and the size of cleavage plane are slightly different.

Using torsion and compression experiments, the kink behavior of the long period stacking ordered (LPSO) phase under different stress deformation of the Mg-13Gd-4Y-2Zn-0.5Zr alloy were studied. The results show that different stress states have different effects on the kink of LPSO phase. The grain deformation of the shear stress deformed (SSD) alloy is relatively weak, where LPSO phases are mostly C-shaped or S-shaped kinks. The kink forms can be divided into parallel kinks and angular kinks. The grains of compressive stress deformed (CSD) alloy are significantly elongated and perpendicular to the compression direction, in which occur more Z-shaped zigzag kinks. The kink angle and kink times of the shear stress deformed alloy are small, while the relative kink width is larger. There are large number kink bands during compressive stress deformation, almost all of which are distributed in perpendicular to the compression direction. The difference in the kink behavior is due to the non-basal slip of SSD is easy to active, while in the CSD alloy, the non-basal slip is relatively difficult to active, resulting in more dislocation pile-up. Different forms of kinks can release stress concentration, and all of kinks make the grains deflect in the direction with higher non-basal slip schmid factor.

Cyclic expansion extrusion with an asymmetrical extrusion cavity (CEE-AEC) was carried out on pure magnesium up to 3 passes at different deformation temperatures of 250 °C and 350 °C. The microstructure and texture evolution of its edge and center regions are studied respectively, and their mechanical properties are correlated. The results show that there is an incomplete dynamic recrystallization (DRX) region in pure magnesium deformed at 250 °C. Therefore, pure magnesium processing at 250 °C has a larger grain size and higher texture strength than that processing at 350 °C. According to the tensile test, the ultimate tensile strength (UTS) of different positions of different temperatures is very close because the DRXed grains grow at 350 °C. But the value of tensile yield strength (TYS) is nearly doubled, the main reasons are that the effect of (0001) basal slip and texture softening is greater than that of grain refinement.

Ti-6Al-4V titanium alloy specimens fabricated through hot isostatic pressing (HIP) were made by multi-pass thermal deformation. The temperature was 950 °C, 850 °C and 900 °C for one pass, two passes and three passes, respectively, and each pass corresponded to three strain rate (i.e. 0.01 s ^−1 , 0.1 s ^−1 and 1 s ^−1 ), in addition, the total reduction in height was 70%. When the true strain was greater than 0.51 and the strain rate was 1 s ^−1 , the stress-strain curves showed the phenomenon of flow softening. X-ray diffraction (XRD) patterns indicated that the diffraction peak of α lattice plane of (0002) increased first and then declined with the strain under the strain rate of 0.1 s ^−1 . Besides, the Vickers hardness increased with the strain at the same strain rate and was not sensitive to strain rate. Moreover, when the strain rate was 0.1 s ^−1 , the fraction of LAGBs decreased from two passes to three passes and the microstructure results showed that the fraction of equiaxed α phases increased with the passes increasing. This is due to the strain energy increased as the increasing passes which could provide driving force for dynamic recrystallization (DRX). At the same amount of deformation, increasing the strain rate, the slender lamellar α bended and the equiaxed α grains gradually took place of the discontinuous lamellar α . Additionally, the spheroidization mechanism of lamellar α phase was mainly through grain boundaries bulging. After completing three passes deformation, the average grain size was approximately 12 μ m.

Energy absorption for AZ31 magnesium Alloy was investigated with Split Hopkinson Pressure Bar using single stress wave so as to avoid multiple stress wave loading. The stress wave amplitude, which was in elastic stress range and propagated along the AZ31 magnesium bar, was reduced with increasing propagating distance, and with increasing stress wave amplitude, the stress wave amplitude reduction along the magnesium bar was increased losing more energy as compared with that of the stress wave with lower amplitude. The drastically decreased stress wave amplitude could be explained based on dislocations movements, which was similar to the established theory of damping for the explanation of the energy loss during cyclic loading. However, it was not the case for LY12 aluminum alloy: the stress wave amplitude changed slightly without drastic energy loss regardless of the variation of stress wave amplitude.

This study investigates the effects of long-period stacking order (LPSO) phases on the dynamic recrystallization (DRX) process. By comparing Mg-Gd-Y-Zn-Zr (GWZ) alloy and Mg-Gd-Y-Zr (GW) alloy deformed by 4 passes of Isothermal Reciprocating Upsetting-Extrusion (RUE), the initial alloy grain sizes are 113.4 μ m and 88.2 μ m, respectively, after 4 passes, the grain size becomes 3.5 μ m and 4.8 μ m, and the grain refinement of GWZ is greater. After 1 pass, the DRX volume fraction of GWZ alloy is 83% and 15%, which is related to the LPSO phases contained in the GWZ alloy. The texture strength of the GWZ alloy ranges from 8.5 of 1 pass to 2.2 of 4 passes, while the GW alloy is from 5.9 of 1 pass to 2.8 of 4 passes, mainly due to the DRX grain volume fraction. The tensile test results at room temperature (RT) showed that the ultimate tensile strength (UTS) and tensile yield strength (TYS) of GWZ alloy are higher than that of GW alloy, and the elongation is lower than that of GW alloy.

In this paper, the effect of annealing treatment on the microstructure and hardness of extruded Mg-9Gd-4Y-2Zn-0.5Zr alloy (wt. %) was discussed. The microstructure evolution of the alloy under different annealing conditions was studied by optical microscope (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD), and the variation of hardness was analyzed. With the increase of annealing temperature, the large deformed grains first break into small recrystallized grains. When the temperature continues to increase, the recrystallized grains grow abnormally with the precipitation of chain phase and the fragmentation of lamellar long-period stacking ordered (LPSO) phase. The alloy does not recrystallize at low temperature, and the recrystallize grains grow abnormally at high temperature. The increase of annealing time will also lead to abnormal growth of recrystallized grains. The texture gradually diffuses from the classical extrusion texture to the extrusion direction (ED). The results show that under the condition of 430 °C × 5 h, the recrystallization volume of the alloy is the largest, the recrystallization grain distribution is uniform, and the hardness value is the highest.

In this article, a new type of severe plastic deformation process named cyclic expansion extrusion with an asymmetric extrusion cavity (CEE-AEC), was used to prepare pure magnesium with three passes repetitive deformation at 250 °C. This article mainly studies the microstructure evolution, texture analysis and mechanical properties of pure magnesium. The results display that the grain size is refined, from 74 um to 19 um, which is attributed to continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). With the increasing CEE-AEC passes, the texture is weakened, and the (0001) plane of a large number of grins are inclined from the ED direction. The Schmid factor that activates the basal slip system gradually increases from 0.29 to 0.3 after three passes. After three passes of CEE-AEC, from the tensile tests of the deformed samples at room temperature, it can be seen the samples have excellent comprehensive mechanical properties, the tensile yield strength (TYS) is 54 MPa, ultimate tensile strength (UTS) is 110 MPa, and fracture elongation is 19%.

The microstructure, tensile properties and fatigue properties of Mg- 8.8Gd- 3.5Y- 1.5Zn- 0.5Zr alloy under T4 and T6 heat treatment have been studied. The as-cast alloy was homogenized to eliminate the inhomogeneous structure and the strength of the alloy was increased by aging treatment. The microstructure evolution and mechanical properties of the alloy were investigated by optical microscope, scanning electron microscope, energy dispersive spectrometer and universal mechanical testing machine. The as-cast alloy is composed of dendritic α -Mg matrix, metastable lamellar stacking fault, eutectic Mg _24 (Gd, Y, Zn) _5 , massive long-period stacking ordered (LPSO) phase Mg _12 (Gd, Y)Zn and a few rare earth rich phases. In the process of homogenization, the lamellar phase and Mg _24 (Gd, Y, Zn) _5 eutectic phase dissolved in the α -Mg matrix gradually, and the massive LPSO phase disappeared gradually, while the lamellar LPSO phase steadily grew into grains and formed some precipitate particles near the grain boundary. As the tensile temperature increases, the ductility of solid solution alloy increases, but decreases at 250 °C, which is related to the melting reaction of γ phase at high temperature and the cracking caused by grain boundary sliding. Intergranular fracture occurs at 250 °C. When the tensile temperature rises to 150 °C, the ultimate tensile strength of the alloy increases first before 150 °C and decreases after 150 °C, which is related to two strengthening mechanisms, namely, dissolution of Gd and Y elements into α -Mg matrix results in solid solution strengthening and the co-lattice strengthening between petal β ′ and α -Mg matrix. Compared with the fatigue properties of the alloy after solution treatment and aging treatment, the fatigue life of the alloy after aging treatment is longer.

In this paper, a relatively novel severe plastic deformation method cyclic expansion extrusionwith an asymmetrical extrusioncavity (CEE-AEC) was carried out to prepare large-sized pure magnesium (Mg) with high comprehensive performance. Finite element analysis (FEM) was used to study the plastic deformation process and Electron Back-Scattered Diffraction (EBSD) was aimed to research the microstructural evolution. Three passes and isothermal deformation at 250 °C were chosen to satisfy the research. The central part of the billet was cut as the research area, and the resultant microstructure and mechanical properties were analyzed systematically. The results showed that the grain size was remarkably refined due to continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). Twins participated in the progress of deformation. The shear strain introduced by the asymmetrical extrusion cavity determined the formation of inclined basal texture, leading to the increasing value of basal 〈a〉 slip system Schmid factor. The best comprehensive tensile properties were obtained after three passes of deformation, and the contributions came from grain refinement strengthening and texture modification, respectively.

n -Alkanes and fatty acids are important molecular markers for the source apportionment of organic matter in the atmosphere. Traditional approaches to date have mostly relied upon the source-specific differences in their molecular distributions and carbon preference index. Alternatively, we demonstrate here the use of stable carbon and radiocarbon isotopic composition ( δ ^13 C and Δ ^14 C, respectively) of n -alkanes and n -fatty acids in aerosols from two urban receptor sites (Beijing and Tianjin) in Northeast China to assess their sources in autumn. The Δ ^14 C _n _-alkanes of C _19 –C _24 and C _26 –C _32 even-carbon homologs (−851 to −708‰) indicate their dominance from fossil fuel combustion. In contrast, the Δ ^14 C of most abundant palmitic acid (C _16:0 ) and stearic acid (C _18:0 ) suggest a larger contribution from nonfossil sources (∼91%–94%), mainly due to inputs from cooking, biomass burning and microorganisms. Compared with lower Δ ^14 C of C _27 and C _31 n -alkanes (−449‰), C _29 n -alkane (−241‰) and C _20 –C _30 n -fatty acids (−263‰) showed more contemporary likely due to significant contribution from plant litter and biomass burning that contain more fresh biogenic material. Fossil character of C _27 –C _31 n -alkanes (40%) and C _20 –C _30 n -fatty acids (30%) could be from soil resuspension and/or loess deposits in upwind regions through long-range atmospheric transport.

Mg-8.3Gd-3.2Y-0.4Zr alloy underwent severe plastic deformation at 420 °C using 4-pass isothermal repetitive upsetting-extrusion (RUE) process. The deformation uniformity in different regions of the same sample after 4 passes of RUE was studied. The results showed that though there was slightly uneven deformation, the isothermal RUE process can improve uniformity. The strain in the central area is relatively small, and there are more deformed large grains. The dynamic recrystallization fraction at different positions is above 0.5, forming a more uniform microstructure, with the minimum average grain size being 10.66 μ m. Discontinuous dynamic recrystallization and continuous dynamic recrystallization occur at the same time, which promotes grain refinement and improvement of microstructure uniformity. Dynamic recrystallization weakens the texture, resulting the similar texture intensity of different positions of the sample. The bottom edge position with the most uniform microstructure obtained the best tensile properties, UTS reached 323 MPa.

In this paper, WC-10Co4Cr coating was prepared on the surface of LC9 aluminum alloy by high velocity air-fule (HVAF) process. And a thermal deformation method was developed to enhance the coating properties. Experimental results show that, during the process of thermal deformation, the increase of temperature and deformation amount could improve the microhardness of coating surface. With temperature of 480 °C and deformation amount of 16% (0.8 mm), the microhardness reached the maximum value of 1349 HV0.3, which increased nearly 20% compared with that of specimen (1137 HV0.3) without compressive deformation. Besides, the strengthening effects of thermal deformation temperature and deformation amount on the bonding strength of coating were obvious. With deformation temperature of 450 °C and deformation amount of 8% (4 mm), the bonding strength reached the maximum critical load of 188 N, which was 17.5% higher than that of initial state.

A hollow billet Expanding-Reducing Extrusion (ERE) wheel hub forming process was carried out with AZ80 magnesium alloy. The effects of ageing on Low-cycle fatigue (LCF) properties were investigated, and the microstructure was characterized with scanning electronic microscopy (SEM). The LCF testing results exhibited that the stress amplitude increased with increasing ageing time, while the plastic strain decreased with increasing ageing time. Cyclic softening followed by hardening was observed for 0 h and 16 h aged samples; however, there was no obvious cyclic softening or hardening for 36 h aged sample. The tension-compression asymmetry were not obvious due to the low strain, precipitation and the non typical basal texture. Fracture observations indicated that the fatigue cracks were initiated on the surface, and the crack propagation area decreased with increasing ageing time. Thus, it can be concluded that ageing has strong effects on the fatigue life for the studied magnesium alloy.

Objective: Sleep quality helps to reflect on the physical and mental condition, and efficient sleep stage scoring promises considerable advantages to health care. The aim of this study is to propose a simple and efficient sleep classification method based on entropy features and a support vector machine classifier, named SC-En&SVM. Approach: Entropy features, including fuzzy measure entropy (FuzzMEn), fuzzy entropy, and sample entropy are applied for the analysis and classification of sleep stages. FuzzyMEn has been used for heart rate variability analysis since it was proposed, while this is the first time it has been used for sleep scoring. The three features are extracted from 6 376 730 s epochs from Fpz-Cz electroencephalogram (EEG), Pz-Oz EEG and horizontal electrooculogram (EOG) signals in the sleep-EDF database. The independent samples t-test shows that the entropy values have significant differences among six sleep stages. The multi-class support vector machine (SVM) with a one-against-all class approach is utilized in this specific application for the first time. We perform 10-fold cross-validation as well as leave-one-subject-out cross-validation for 61 subjects to test the effectiveness and reliability of SC-En&SVM. Main results: The 10-fold cross-validation shows an effective performance with high stability of SC-En&SVM. The average accuracy and standard deviation for 2–6 states are 97.02  ±  0.58, 92.74  ±  1.32, 89.08  ±  0.90, 86.02  ±  1.06 and 83.94  ±  1.61, respectively. While for a more practical evaluation, the independent scheme is further performed, and the results show that our method achieved similar or slightly better average accuracies for 2–6 states of 94.15%, 85.06%, 80.96%, 78.68% and 75.98% compared with state-of-the-art methods. The corresponding kappa coefficients (0.81, 0.74, 0.72, 0.71, 0.67) guarantee substantial agreement of the classification. Significance: We propose a novel sleep stage scoring method, SC-En&SVM, with easily accessible features and a simple classification algorithm, without reducing the classification performance compared with other approaches. [ABSTRACT FROM AUTHOR]