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The pathogen SARS-CoV-2 binds to the receptor angiotensin-converting enzyme 2 (ACE2) of the target cells and then replicates itself through the host, eventually releasing free virus particles. After infection, the CD8 T-cell response is triggered and appears to play a critical role in the defense against virus infections. Infected cells and their activated CD8 T-cells can cause tissue damage. Here, we established a mathematical model of within-host SARS-CoV-2 infection that incorporates the receptor ACE2, the CD8 T-cell response, and the damaged tissues. According to this model, we can get the basic reproduction number R 0 and the immune reproduction number R 1. We provide the theoretical proof for the stability of the disease-free equilibrium, immune-inactivated equilibrium, and immune-activated equilibrium. Finally, our numerical simulations show that the time delay in CD8 T-cell production can induce complex dynamics such as stability switching. These results provide insights into the mechanisms of SARS-CoV-2 infection and may help in the development of effective drugs against COVID-19. [ABSTRACT FROM AUTHOR]

COVID-19, which broke out globally in 2019, is an infectious disease caused by a novel strain of coronavirus, and its spread is highly contagious and concealed. Environmental vectors play an important role in viral infection and transmission, which brings new difficulties and challenges to disease prevention and control. In this paper, a type of differential equation model is constructed according to the spreading functions and characteristics of exposed individuals and environmental vectors during the virus infection process. In the proposed model, five compartments were considered, namely, susceptible individuals, exposed individuals, infected individuals, recovered individuals, and environmental vectors (contaminated with free virus particles). In particular, the re-positive factor was taken into account (i.e., recovered individuals who have lost sufficient immune protection may still return to the exposed class). With the basic reproduction number R 0 of the model, the global stability of the disease-free equilibrium and uniform persistence of the model were completely analyzed. Furthermore, sufficient conditions for the global stability of the endemic equilibrium of the model were also given. Finally, the effective predictability of the model was tested by fitting COVID-19 data from Japan and Italy. [ABSTRACT FROM AUTHOR]

• Annealing induced hardening was due to dislocation wall locked with nano-particles. • Dislocation walls and columnar crystals coordinated plastic deformation. • Dislocation motion controlled the main deformation mechanism. Annealing softening is commonly observed in traditional coarse–grained materials. Herein, an annealing–induced hardening mechanism in selective laser melted 316L stainless steel (SLM–ed 316L SS) was investigated. The SLM–ed 316L SS, without prior cold–working history, displayed evident hardening behaviour as the annealing temperature increased from 400 °C to 500 °C. Several dedicated scanning transmission electron microscope and quasi–in–situ/electron backscatter diffraction techniques were employed to investigate the intrinsic characteristics evolution of the samples, including cellular/wall dislocation structure, nano–particles/segregation, dislocation density, crystallographic orientations, and low–angle grain boundaries (LAGBs).This phenomenon primarily arises from unique guardrail–like dislocation walls decorated with nano–particles (O, Cr, Mo, and Si) and a high proportion of LAGBs, hindering movement of dislocations and leading to their accumulation. Furthermore, this structure and the stable configuration of columnar crystals can synergistically affect the 500 °C annealed sample, resulting in a high yield stress of 628 MPa. On the other hand, complex deformation substructures, such as stacking faults, Lomer–Cottrell locks, and forest dislocations, also proliferated during deformation. These substructures enabled multiscale plastic strain partitioning, intensifying strain hardening and realizing a strength–ductility combination of a comparable yield/ultimate tensile strength of 628 MPa/789 MPa and tensile ductility of 32%. Dislocation motion was the dominant deformation mechanism based on the strengthening mechanism model in this study. [Display omitted] [ABSTRACT FROM AUTHOR]

• Strain induced grain growth quickly consumes high-strain regions through grain boundaries. • Fine grains form from the uniform activation and growth of strain induced grain growth grains by grain boundaries. • Pre–existing twins facilitate GBs low-mobility GBs in tuning their configuration and local plasticity strain. A strain induced grain growth behaviour in laser powder bed fusion 316L austenitic stainless steel was investigated in this work. The intrinsic characteristics of the samples, such as crystallographic orientations, dislocation density, low angle grain boundaries and twins, were investigated via quasi–in–situ electron backscatter diffraction. Additionally, grain growth during plastic deformation in samples annealed at 800 °C was attributed to the combined influence of pre–existing twins and strain–induced grain boundary migration. [ABSTRACT FROM AUTHOR]

This paper succeeds to fabricate the micro-channel structure efficiently and accurately with our self-made small hot embossing system. Furthermore, a new evaluation method is proposed to obtain the optimal embossing condition parameters such as hot embossing temperature, embossing force, and force holding time, for fabricating the high-performance micro-channel for flexible proton exchange membrane fuel cell (PEMFC). With the optimal fabrication parameters, the fabricated micro-channel filling ratio can be realized by more than 95%. The results show that micro-pattern arrays can be directly fabricated on commercially available polymer substrate by metal master mold in hot embossing technology with self-made equipment. The fabricated micro-channel-based polymer substrate is capable of the application of PEMFC with a pillar structure to improve the power density of fuel cells. [ABSTRACT FROM AUTHOR]

In order to investigate the influence of carbonation treatment on the rebound strength measurement curve of machine-made sand concrete, this study conducted research on the carbonation mechanism sand concrete rebound strength measurement curve through rebound and compressive strength tests using carbonation degree and concrete strength grade as control variables. The results showed that in the short aging period, carbonation treatment had little effect on the compressive strength of manufactured sand concrete but could cause an increase in the rebound value measured by the high-strength and heavy rebound hammers. As the strength grade of the manufactured sand concrete increased, the rebound value measured by both the high-strength and heavy rebound hammers increased accordingly. Compared with the high-strength rebound hammer, the heavy rebound hammer had higher accuracy in detecting the rebound of the carbonated manufactured sand concrete. This study established measurement curves for uncorrected and corrected carbonation depths, among which the accuracy of the corrected carbonation depth measurement curve was higher. At the same time, this measurement curve has been applied to the rebound test of the Pinglu Canal Extra-Large Bridge Project in Guangxi, China, and its practicality and reliability have been verified. [ABSTRACT FROM AUTHOR]

Hierarchically porous P substituted HZSM‐5 (H[P, Al]‐ZSM‐5‐AT‐0.05 M) was successfully synthesized by isomorphous substitution method with introduced P atoms into ZSM‐5 zeolite frameworks followed by alkali treatment. H[P, Al]‐ZSM‐5‐AT‐0.05 M was characterized by XRD, ICP‐OES, SEM, FT‐IR, N2 adsorption‐desorption, NH3‐TPD, XPS, Py‐IR, and TG‐DTA, respectively. The surface area, pore volume, particle size and P/Al (molar ratio) are 328 m2.g−1, 0.23 cm3.g−1, 563 nm and 0.027, respectively. The catalytic performance of H[P, Al]‐ZSM‐5‐AT‐0.05 M in coupling reaction of methanol with 1‐butene was investigated in the fixed‐bed reactor. On the condition of reaction temperature at 500°C under atmosphere pressure, the main product is propylene with the selectivity and yield of 33.7% and 31.0%, respectively. Hydrogen transfer index was calculated to 0.24. Moreover, its diffusion limitation was investigated with the self‐etherification of benzyl alcohol reaction. The value of Thiele modulus (η) and effectiveness factor (ϕ) are 0.08 and 16.9, respectively. The scheme of isomorphously substituted method of introducing P into ZSM‐5 framework and catalytic performance over H[P, Al]‐ZSM‐5 and H[P, Al]‐ZSM‐5‐AT‐0.05 M in coupling methanol with 1‐butene. P substituted HZSM‐5 is treated with NaOH solution to form mesoporous zeolites. The result shows that H[P, Al]‐ZSM‐5‐AT‐0.05 M exhibited higher catalytic stability, higher apparent reaction rate, effectiveness factor and lower content of diffusion limitation in coupling of methanol with 1‐butene to propylene reaction. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic has brought a serious threat to human life safety worldwide. SARS-CoV-2 virus mainly binds to the target cell surface receptor ACE2 (Angiotensin-converting enzyme 2) through the S protein expressed on the surface of the virus, resulting in infection of target cells. During this infection process, the target cell ACE2 receptor plays a very important mediating role. In this paper, a delay differential equation model containing the mediated effect of target cell receptor is established according to the mechanism of SARS-CoV-2 virus invasion of target cells, and the global stability of the infection-free equilibrium and the infected equilibrium of the model is obtained by using the basic reproduction number ℛ 0 and constructing the appropriate Lyapunov functional. The expression of the basic reproduction number ℛ 0 intuitively gives the dependence on the expression ratio of the target cell surface ACE2 receptor, which is helpful for the understanding of the mechanism of SARS-CoV-2 virus infection. [ABSTRACT FROM AUTHOR]

Many NiO platelets were formed on Ni foam after hydrothermal process, while flower-like NiO with many small mesoporous nanoflakes was obtained on the surface of graphene foam. Electrochemical results showed that the NiO/graphene composites exhibited very high specific capacitance 1062 F g −1 at 1 A g −1 and excellent cycling stability (90.6% capacitance retention after 5000 cycles at 1 A g −1 ). The promising NiO/graphene composites exhibited higher supercapacitor performance than NiO platelets on Ni foam. The excellent supercapacitor performance of the former should be attributed to the 3D graphene conductive network and the mesoporous NiO nanoflakes which promoted efficient charge transport and electrolyte diffusion. [ABSTRACT FROM AUTHOR]

This study showed that the increasing of ball milling time caused a beneficial surface chromium enrichment of AISI 304 stainless steel. In addition, grain size decreased with the increasing of ball milling time. The electrochemical results showed that oxidation reaction transition of Cr 2 O 3 to CrO 3 was significantly inhibited by surface enriched chromium, which improved corrosion resistance of AISI 304 stainless steel. Moreover, higher surface enriched chromium reduced acceptor concentration in passive film, which also improved corrosion resistance of AISI 304 stainless steel. Moreover, more chromium oxides improved corrosion resistance of AISI 304 stainless steel in borate buffer solution. [ABSTRACT FROM AUTHOR]

The pure MoS 2 and MoS 2 @reduced graphene oxide were synthesized on commercially available Ti plate by one-step hydrothermal method. The hole microspheres were successfully synthesized. The resulting MoS 2 @reduced graphene oxide electrode on Ti plate exhibited higher catalytic activity than pure MoS 2 electrode on Ti plate for hydrogen evolution reaction. In addition, the excellent cycling stability was also obtained in MoS 2 @reduced graphene oxide electrode on Ti plate. Such enhanced catalytic activity and excellent cycling stability occurred due to the abundance of catalytic edge sites, high specific surface area and the unique synergic effects between the MoS 2 and reduced graphene oxide. [ABSTRACT FROM AUTHOR]

The effects of pre-deformation on sensitization of AISI 304 stainless steel were investigated by the double loop electrochemical potentiokinetic reactivation test. The effects of pre-deformation and sensitization on high temperature oxidized film formed in high temperature water were analyzed by a XRD and SEM. The electrochemical impedance spectroscopy at room temperature was used to study corrosion resistance of oxidized film. The point defect density of oxidized film was calculated by Mott–Schottky plots. The results showed that the value of the degree of sensitization first decreased and then slight increased with the increasing of engineering strain. Moreover, low temperature promoted to form sensitization induced “secondary” α′-martensite. The sample with 20% engineering strain had higher impedance value than other samples. The result was supported by further Mott–Schottky experiments. Considering increased α′-martensite with the increasing of strain, the results of the impedance were more consistent with values of the degree of sensitization. [ABSTRACT FROM AUTHOR]

Effect of pre-deformation on the corrosion resistance of 2205 duplex stainless steel was investigated by microstructure observations, electronic work function measurement and electrochemical experiments. Transmission electron microscope observations showed that the dislocation density in ferritic and austenitic phases increased with the increasing of strain. Moreover, the strain induced α′ -martensite was observed in sample with large strain based on XRD analysis and Transmission electron microscope observations. The electron work function of ferrite was higher than that of austenite. In addition, the surface electron work function of ferritic and austenitic phases decreased with the increasing of strain. More dislocations and chloride ions promoted to form more oxygen vacancies and cation vacancies in the passive film based on point defect model and autocatalytic reaction. Therefore, the corrosion resistance of the passive film formed on 2205 duplex stainless steel decreased with the increasing of strain in borate buffer solution with chloride ions. These results were proven by further immersion test. [ABSTRACT FROM AUTHOR]

Nanohole graphene oxide (NHGO) was obtained in a homogeneous aqueous mixture of graphene oxide (GO) and H 2 O 2 at 120 °C. Supercapacitors were fabricated as the electrode material by using NHGO. A specific capacitance of 240.1 F g −1 was obtained at a current density of 1 A g −1 in 6 m KOH electrolyte and specific capacitance remained 193.6 F g −1 at the current density of 20 A g −1 . This was attributed to reducing the inner space between the double-layers, enhanced ion diffusion and large specific surface area. Supercapacitor prepared with NHGO electrodes also exhibited an excellent cycle stability. [ABSTRACT FROM AUTHOR]

The effects of reduced graphene oxide and molybdenum in amorphous nickel–phosphorus as bipolar plates on corrosion resistance in proton exchange membrane fuel cell environment were investigated. The amorphous nickel–phosphorus, amorphous nickel–phosphorus with molybdenum and amorphous nickel–phosphorus with reduced graphene oxide were obtained by the electrodeposition technique from a nickel sulfate bath. The electrochemical studies showed that the molybdenum in amorphous nickel–phosphorus improved corrosion resistance in typical proton exchange membrane fuel cell environment. In addition, the amorphous nickel–phosphorus with reduced graphene oxide exhibited the best corrosion resistance in typical proton exchange membrane fuel cell environment. The synergistic combination of amorphous nickel–phosphorus and reduced graphene oxide could improve corrosion resistance, which was supported further by Mott–Schottky analysis. [ABSTRACT FROM AUTHOR]

The effect of sensitization at 600 °C on passive films on the surface of 2205 duplex stainless steel was investigated by the double loop electrochemical potentiokinetic reactivation technique, potentiodynamic polarization curves, electrochemical impedance spectroscopy and X-ray Photoelectron Spectroscopy. With the increasing of the passivation potential, the passivation property of the solid solution annealed sample decreased. Moreover, the corrosion resistance of the passive film on sensitized sample was lower than that on solid solution annealed sample, especially at 0.6 V SCE . These results were supported by X-ray Photoelectron Spectroscopy and Mott–Schottky analyses. [ABSTRACT FROM AUTHOR]

The fluoride ion in artificial saliva significantly changed semiconductor characteristic of the passive film formed on the surface of 316L stainless steels. The electrochemical results showed that nanocrystalline α′-martensite improved corrosion resistance of the stainless steel in a typical artificial saliva compared with coarse grained stainless steel. Moreover, comparing with nitrided coarse grained stainless steel, corrosion resistance of the nitrided nanocrystalline stainless steel was also improved significantly, even in artificial saliva solution containing fluoride ion. The present study showed that the cryogenic cold rolling and electrochemical nitridation improved corrosion resistance of 316L stainless steel for the dental application. [ABSTRACT FROM AUTHOR]

The electron work function in coarse grained stainless steel was higher than that in nano/ultrafine grained one. More M2O3 types oxides and thicker passive film were observed in nano/ultrafine grained 304 stainless steel. The electrochemical impedance spectroscopy results showed that grain refinement improved corrosion resistance of 304 stainless steel. The results obtained indicated that the impedance increase was attributed to decreased electron work function. Lower electron work function facilitated to form thicker passive films. The same characteristics were observed with the increasing of chloride ion concentration. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the effects of strain and heat treatment on strain-induced α′-martensite of AISI 304 stainless steel tubes were measured by X-ray diffraction. Moreover, the effects of strain and content of α′-martensite on passivated property on the surface of the material in borate buffer solution were evaluated by electrochemical technique. The results showed that the volume fraction of α′-martensite increased gradually with the increase of tensile strain for as-received and solid solution samples. However, α′-martensite in as-received sample was more than that in the solid solution sample. The electrochemical impedance spectroscopy results showed that the solid solution treatment improved corrosion resistance of the steel, especially for samples with small strain. Moreover, acceptor densities were always higher than donor densities for as-received and solid solution samples. With the increase of strain, the increase tendency of acceptor density was more significant than that of donor density. We also found that the total density of the acceptor and donor almost increased linearly with the increase of α′-martensite. The present results indicated that the increased acceptor density might lead to the decreased corrosion resistance of the steel. [Copyright &y& Elsevier]

A large number of pitting pits were formed on the surface of Ni foam by immersion corrosion in NaCl solution. The graphene was deposited on Ni foam templates, then 3D graphene foams were obtained by removing Ni foam in the mixed solution of ferric chloride and hydrochloric acid. It was found that pitting pits on Ni foam facilitated to form fewer-layers graphene, however, pitting pits on Ni foam induced more defects on 3D graphene foam. The graphene with fewer-layers exhibited better electrical and mechanical properties for strain sensor devices. Moreover, fewer-layers graphene effectively inhibited degradation of resistance during cycling stability tests. [ABSTRACT FROM AUTHOR]

The supercapacitor performances of MnO 2 , Co 3 O 4 nanowire and Co 3 O 4 @MnO 2 core-shell structure are compared, and optimized Co 3 O 4 @MnO 2 core-shell nanowire arrays present the highest specific capacitance of 1646 F g −1  at a current density of 1 A g −1 and lowest interfacial charge transfer resistance. The impedance spectroscopy clearly shows the MnO 2 nanosheets surrounding Co 3 O 4 nanowire play an important role in reducing the resistance. During the hydrothermal process, the concentration of KMnO 4 solution has a significant effect on the final morphology of Co 3 O 4 @MnO 2 core-shell structure which is controllable and shows quite different electrochemical property. The relationship between morphology and supercapacitor behavior is studied, and the optimal concentration of KMnO 4 solution is approximately 0.015 M. The pore size distribution shows that the sample synthesized in 0.015 M KMnO 4 solution has the highest percentage of relatively larger poles, which facilitate the electrolyte ion transfer. [ABSTRACT FROM AUTHOR]

Microstructure evolution of Ti-Mo microalloyed ferritic steel was studied via warm rolling process. Results revealed that rolling at 500 °C (R3) mainly facilitated the formation of superdense microbands (∼200 nm in spacing), especially in the γ textured region. Average spacing of microbands (MBs) increased with temperature and it turned to be about 850 nm when rolling at 650 °C (R2). As rolling temperature further increased to 700 °C (R1), average ferritic grain size was refined to near 1.9 μm whereas no MBs appeared. Additionally, due to the preexisting superdense MBs, ultimate tensile stress of R3 increased to 1041 MPa and the elongation kept high at 22.9% simultaneously. MBs are characterized by high density dislocation walls and formed through the activation of {112}<111> slip systems, which is induced by the pile up of dislocations during grain boundary sliding. In that process steps appear in the grain boundary and gradually heighten with the extension of MBs. Large dynamic recovery rate could slack the dislocation pile up rate and increase the spacing of MBs. Moreover, preexisting of superdense MBs sheds new insights on the development of high strength ferritic steels with excellent combination of strength and ductility. [ABSTRACT FROM AUTHOR]

Mesoporous zirconia microspheres, with a diameter of 900 μm, were prepared as an inert accelerator driven system (ADS) transmutation element matrix by the sol-gel method. The purpose of mesopores is to improve the adsorption capacity of inert matrix fuel (IMF) for minor actinides. The study indicated that the mesoporous zirconia performance was improved after the microspheres were hydrothermally treated at 150 °C, the specific surface area increased from 28.29 m 2 /g to 61.28 m 2 /g, and hydrothermal treatment avoided the cracking of the microspheres. Pre-decomposition of the organics during the hydrothermal process stabilized the mesoporous structure. The average pore diameter of mesoporous microsphere was 14.3 nm. [ABSTRACT FROM AUTHOR]

The feasibility of polyaniline emeraldine base (EB) for enhancing long-term corrosion resistance of magnesium alloy (AZ91D Mg alloy) was confirmed, since the complex impedance of Mg alloy protected by EB/epoxy resin (ER) composite coating with 10 wt% EB loading maintained around 2 GΩ cm 2 even after 80 day exposure in 0.5 M NaCl solution, while that of pure ER coated analogue decreased to 0.17 MΩ cm 2 only after 31 days. The improvement in corrosion resistance was attributed to the transition of interface layer from porous Mg(OH) 2 dominated one underneath pure ER coating to dense MgO dominated one underneath EB/ER coating, induced by the redox interaction of EB with Mg alloy. When the EB loading in EB/ER coating increased from 0 to 10 wt%, the relative XPS peak area ratio of MgO to Mg(OH) 2 increased from 0.78 to 1.18, indicating that EB behaved as effective corrosion inhibitor causing the transformation of oxide layer from porous Mg(OH) 2 to dense MgO. [ABSTRACT FROM AUTHOR]

In order to explore the influence of water dilution on performance of Cr3+ polymer weak gel in porous medium, the performances of pure polymer solution and Cr3+ polymer weak gel were studied according to the laboratory testing of viscosity, micro-structure performances (polymer molecule aggregate dimension, polymer molecule aggregate configuration and Zeta potential), seepage characteristics and oil displacement effect under the condition of water dilution. The results indicated that, after diluting by water, pure polymer solution and Cr3+ polymer weak gel had an almost same viscosity, but there were obvious differences in micro-structure performance and seepage characteristics. Different with pure polymer solution, with the decrease of polymer concentration, on the one hand, the influence of free Cr3+ on electric double layer and shielding effect on electrostatic exclusion got weaker, on the other hand, water molecules were attracted by hydrophilic groups on the Cr3+ polymer weak gel molecular chains and then entered into the three-dimensional spatial structure of Cr3+ polymer weak gel, producing hydration and expansion. Therefore, the polymer molecule aggregate dimension of Cr3+ polymer weak gel presented a trend of continuous increasing. This characteristic was good for keeping the injection pressure at a higher value during diluting in the porous medium, which could be used to improve oil recovery in offshore oilfield through conducting injection of water-alternating- Cr3+ polymer weak gel. [ABSTRACT FROM AUTHOR]

Abstract In order to quantitatively study the matching between hydrophobically associating polymers (HAPs) and reservoir pore-throat size in offshore oilfields, the geological characteristics and fluid properties of the S area reservoir in the Bohai Oilfield were used as a research platform. After determining the matching of HAP solutions with different association degrees and core permeabilities using a seepage experiment at a constant flow rate, the matching between the diameter of the HAP aggregates (D h) and the median pore-throat radius was quantified by combining the relationship between core permeability and median pore-throat radius. Finally, the importance of matching on the oil displacement effect of the HAP solution was demonstrated using homogeneous cores and heterogeneous cores with separate injection and production interlayers. The results showed that the diameter of the HAP aggregates, as well as their morphology and ability to increase viscosity, were highly related to the association degree of HAP. As the association degree of HAP was varied, the matching between cores with different permeabilities and the beta-cyclodextrin (β-CD)/HAP compound systems also changed. Under the experimental conditions used in this study, the ratio between the median pore-throat radius and D h ranged from 4 to 7. During the process of HAP flooding, suitably increasing the D h , i.e., increasing the association degree between HAP molecules, could allow control of the mobility of the HAP solution. The oil displacement effect of HAP was closely related to the matching between the HAP and reservoir pore-throat, rather than the viscosity of the HAP solution. Good matching between the HAP and reservoir pore-throat not only achieves fluid diversion but can also expand the swept volume in the low-permeability layer to ensure good oil displacement ability. Highlights • As for HAP, the diameter of aggregates, morphology and ability to increase viscosity were highly related to the association degree of HAP. • The oil displacement effect of HAP was closely related to the compatibility between the HAP and reservoir pore-throat instead of the viscosity. • Well compatibility not only achieves fluid diversion but can also expand the swept volume in the low-permeability layer. [ABSTRACT FROM AUTHOR]

Based on 170 references, this study summarizes the processes, materials, improvement mechanisms, and factors affecting the improvement for two methods of recycled aggregate concrete (RAC): pretreatment of recycled concrete aggregate (RCA) and RAC modification. The improvement effects were analyzed according to the improvement methods and research directions were proposed. The results indicated that RCA pretreatment could improve its physical properties by removing or strengthening the RCA surface of the old mortar. RAC modification optimizes the internal structure of concrete by modifying its materials. Both can optimize the interface transition zone of the RAC and compact the concrete. However, to remove old mortar, appropriate conditions must be maintained to avoid secondary damage to the original aggregate. Future research should emphasize establishing a multifactor RCA grading system, forming optimal parameter selection criteria for pretreatments, improving the RAC theoretical system, exploring the combined effects of multiple methods, and verifying the long-term performance. [ABSTRACT FROM AUTHOR]

Present research reports the effect of nano-scale martensite (αʺ) and β phase on the passive film formation and electrochemical corrosion behaviour of Ti-10V-2Fe-3Al alloy in the 3.5% NaCl solution. Nanocrystals with different αʺ/β phase proportion were obtained by room temperature (RT) and Low temperature (LT) burnishing processing. The results show that nano-scale martensite and β phase could promote the growth of passive film and the diffusion of element V, respectively. Corrosion resistance of Ti-10V-2Fe-3Al alloy was enhanced due to the presence of passive film with large thickness and stability, resulting from nano-scale martensite and more β phase in the alloy. Combined with the results of passive film and electrochemical corrosion, a probable mechanism is proposed to interpret the influence of nano-scale martensite (αʺ) and β phase on the passive film formation and corrosion behaviour of Ti-10V-2Al-3Fe titanium alloy. [ABSTRACT FROM AUTHOR]

Samples with different prior microstructures, quasi-polygonal ferritic (QPF) matrix and polygonal ferritic (PF) matrix, were compressed at 500 ℃ with different strain rates. As for the QPF matrix, its microstructure more tend to be compressed and refined under small strain rate, while it is opposite for the PF matrix. Increase of deformation temperature to 600 ℃ and 700 ℃ illustrates that during cDRX process, extending of geometric necessary boundaries (GNBs) increases the flow stress whereas the rearrangement of geometric necessary dislocations (GNDs) mainly causes the softening phenomenon. Additionally, extending of GNBs in prior grains firstly facilitates the increase of texture intensity on certain orientations, then the texture intensity decreases with further conduct of continuous dynamic recrystallization (cDRX) process, during which the subgrains mainly rotate along < 001 > //SD or < 111 > //SD and make orientations distributed more randomly within fiber textures. Deformation at 600 ℃ shows better refining effect and the average grain size can be refined to submicron scale, however, deformation at 700 ℃ presents better ultra-refining uniformity that the area fraction of ultra-refined regions can reach 94.8% with an average grain size of 1.1 µm. TEM observation clarifies that with the increase of deformation temperature, low angle boundaries (LABs) will replace dislocation walls dividing the prior grains and show better extending ability. Activation energy of the cDRX process also been estimated and it is about 768 KJ/mol. [ABSTRACT FROM AUTHOR]

Coarsening of nanoscale (Ti,Mo)C precipitates within quasi-polygonal ferritic (QPF) matrix and polygonal ferritic (PF) matrix is studied via HRTEM and In-situ heating TEM. Influenced by different nucleation processes, inverse coarsening process showing dissolution of large clustered precipitates and growth of small interphase precipitates is directly observed in the PF matrix. However, due to the evolution of high-density subboundaries, coarsening of precipitates in QPF matrix is mainly characterized by the subboundary migration assisted coarsening process, during which arch-like coarsened precipitates form after the sweeping of subboundaries. Analysis of atomic structure clarify that “imposts” of the arch-like coarsened precipitates are established by the re-precipitation of solute atoms from movable subboundary to the close packed planes {111} of (Ti,Mo)C precipitates, and that the “key stones” are constructed due to the change of re-precipitation planes to {200}. Geometric phase analysis (GPA) illustrates that not only the change of re-precipitation direction during the formation of arch-like precipitates, but also the selective coarsening of clustered precipitates in PF matrix, is caused by the highly anisotropic strain field around (Ti,Mo)C precipitates. [ABSTRACT FROM AUTHOR]