A hot-rolled medium Mn(0.2C5Mn)steel is annealed at 650℃ to produce an ultrafine-grained duplex microstructure with different austenite volume fractions by austenite reverted transformation(ART)annealing,and the orie...A hot-rolled medium Mn(0.2C5Mn)steel is annealed at 650℃ to produce an ultrafine-grained duplex microstructure with different austenite volume fractions by austenite reverted transformation(ART)annealing,and the orientation relationship strictly obeys K-S orientation relationship before deformation.Tensile tests are carried out in a temperature range from-196 to 400℃ to examine the effects of the austenite volume fraction and the deformation temperature on the tensile properties and the austenite stability.Microstructural observations reveal that the metastable austenite gradually transformed into a-martensite,which is controlled by the deformation strain,the temperature and the austenite volume fraction.Both strain hardening behavior and ductility of the studied steel are dependent on austenite volume fraction and deformation temperature significantly.The stress-strain curves of ART-annealed 0.2C5Mn steel assume an S shape and a very large work hardening rate of about 10 GPa is obtained at liquid nitrogen deformation temperature.Based on the experimental data,a quantitative relation is proposed to describe the ductility dependence on both the austenite volume fraction and its mechanical stability.展开更多
The ultrafine grained ferritic steels possess shortage of work hardening. Fine grained high strength but low ductility due to the ferrite-martensite dual phase microstruc- ture was obtained in a microalloyed steel and...The ultrafine grained ferritic steels possess shortage of work hardening. Fine grained high strength but low ductility due to the ferrite-martensite dual phase microstruc- ture was obtained in a microalloyed steel and low carbon steels through intercritical annealing of the cold rolled martensite. The dual phase microstructure was uniform and the ferrite grain size was smaller in the microalloyed steel resulted from the pin- ning effect of microalloyed precipitates. But ferrite grown apparently and the volume fraction of the martensite was much higher without the addition of microalloying el- ements. By introducing martensite into the fine grained ferrite, the work hardening was effectively improved, leading to better mechanical stability. As a result of the fine ferrite grain size as well as uniform distribution of the martensite, the work harden- ing was enhanced, showing better strength-ductility balance in the microalloyed dual phase steel.展开更多
Spherical roller bearings in railway car wheels are critical components whose failure may have catastrophic consequences. The present study aims to analyse the mechanical stability of greases and temperature of bearin...Spherical roller bearings in railway car wheels are critical components whose failure may have catastrophic consequences. The present study aims to analyse the mechanical stability of greases and temperature of bearings as indicators for condition-based bearing maintenance. The performed case study includes nine fully-formulated commercial greases examined in the wheel bearings of five ore cars operated in northern Scandinavia. The studied ore cars travelled a distance of about 300 000 km during a period of three years. Small samples of the greases were taken on eight occasions to test their mechanical stability. In addition, the temperatures of the bearings were continuously recorded. After the test period, the wear, electrical damage, and corrosion of the bearings were examined. One of the findings is that the shear stress of the grease at a certain shear velocity （the certain yieldstress （CEY） value） is a good maintenance indicator and is highly dependent on the grease type. The bearing＇s wear, electrical damage and corrosion also depend on the grease type. However, no oxidation of the greases was identified. The paper also outlines a systematic methodology to determine an overall maintenance indicator for railway roller bearings which is based on the field measurements.展开更多
This paper concentrates on investigating the mechanical stability of a Beam Position Monitor (BMP)support prototype of the Shanghai Synchrotron Radiation Facility(SSRF)project.Both finite element analysis and vibratio...This paper concentrates on investigating the mechanical stability of a Beam Position Monitor (BMP)support prototype of the Shanghai Synchrotron Radiation Facility(SSRF)project.Both finite element analysis and vibration measurements have been performed.Inconsistent results between the simulations and experiments motivate us to study three connections between the support and the ground:ground bolt(used in the initial design),part grout and full grout(proposed in the later research).After changing the connection, the first eigenfrequency is increased from 20.2Hz to 50.2Hz,and the ratio of the integrated RMS displacement (4—50Hz)is decreased from 4.36 to 1.23 in the lateral direction.The mechanical stability is improved greatly.展开更多
The thermal decomposition synthesis of long copper nanowires （CuNWs） was achieved by controlling the synthesis parameters. A detailed study was performed to determine the effect of the molar ratio of copper chloride...The thermal decomposition synthesis of long copper nanowires （CuNWs） was achieved by controlling the synthesis parameters. A detailed study was performed to determine the effect of the molar ratio of copper chloride to nickel acetylacetonate, temperature, and stirring rate on the final shape of the products. Transparent electrodes （TEs） were fabricated by wet treatment with acetic acid （AA）, without using a sintering process. The low oxidation stability and high surface roughness are the main disadvantages of the CuNW TEs, which limit their applications. In order to overcome these issues, we prepared CuNW/polymer composite TEs by partial embedding of the CuNWs into poly（methyl methacrylate） （PMMA） on poly（ethylene terephthalate） （PET） substrates. The CuNW/PMMA composite TEs exhibit excellent optoelectronic performance （91.3% at 100.7 ff2/sq）, low surface roughness （4.6 nm in height）, and good mechanical and chemical stability as compared with CuNW TEs. On the basis of these properties, we believe that CuNW-based composite TEs could serve as low-cost materials for a wide range of new optoelectronic devices.展开更多
First principles calculations of structural, electronic, mechanical, and thermodynamic properties of different poly- morphs of BiVO4 are performed using Bender-type plane/wave ultrasoft pseudopotentials within the gen...First principles calculations of structural, electronic, mechanical, and thermodynamic properties of different poly- morphs of BiVO4 are performed using Bender-type plane/wave ultrasoft pseudopotentials within the generalized gradient approximation （GGA） in the flame of density functional theory （DFT）. The calculated structural and electronic properties are consistent with the previous theoretical and experimental results. The electronic structures reveal that m-BiVO4, op- BiVO4, and st-BiVO4 have indirect band gaps, on the other hand, zt-BiVO4 has a direct band gap. From the DOS and Mulliken＇s charge analysis, it is observed that only m-BiVO4 has 6s2 Bi lone pair. Bond population analysis indicates that st-BiVO4 shows a more ionic nature and a similar result is obtained from the elastic properties. From the elastic prop- erties, it is observed that st-BiVO4 is more mechanically stable than the others, st-BiVO4 is more ductile and useful for high electro-optical and electro-mechanical coupling devices. Our calculated thermodynamic properties confirm the similar characteristics found from electronic and elastic properties, m-BiVO4 is useful as photocatalysts, solid state electrolyte, and electrode and other polymorphs are applicable in electronic device fabrications.展开更多
The lanthanum ricinoleate（abbreviated as Lari3） of rare earth heat stabilizer was synthesized by the reaction of ricinoleic acid, lanthanum nitrate and sodium hydroxide. The IR and fluorescence spectra methods confi...The lanthanum ricinoleate（abbreviated as Lari3） of rare earth heat stabilizer was synthesized by the reaction of ricinoleic acid, lanthanum nitrate and sodium hydroxide. The IR and fluorescence spectra methods confirmed the structure of the product. The thermal stability of PVC in the presence of Lari3 was studied by the Congo method and using TG analysis. The results showed that Lari3 could be used as a thermal stabilizer for PVC. When the ratio of Lari3/pentaerythritol was 3：1, the complex exhibited better synergistic effect. Incorporation of Lari3 to PVC resulted in a marked increase of maximum and onset degradation temperature as well as elongation and impact strength of PVC. Lari3 might replace the labile chlorine atoms to interrupt the formation of conjugated double bonds in PVC chains and act as HCl scavenger to restrain the self-catalyticdehydrochlorination.展开更多
Epoxy/graphene nanoplatelets（GNPs） powder coatings were fabricated using ultrasonic predispersion of GNPs and melt-blend extrusion method. The isothermal curing kinetics of epoxy/GNPs powder coating were monitored b...Epoxy/graphene nanoplatelets（GNPs） powder coatings were fabricated using ultrasonic predispersion of GNPs and melt-blend extrusion method. The isothermal curing kinetics of epoxy/GNPs powder coating were monitored by means of real-time Fourier transform infrared spectroscopy（FT-IR） with a heating cell. The mechanical properties of the epoxy/GNPs cured coatings had been investigated, by evaluating their fracture surfaces with field-emission scanning electron microscopy（FE-SEM） after three-point-bending tests. The thermal stability of the epoxy/GNPs cured coatings was studied by thermo-gravimetric analysis（TGA）. The isothermal curing kinetics result showed that the GNPs would not affect the autocatalytic reaction mechanism, but the loading of GNPs below 1.0 wt % additive played a prompting role in the curing of the epoxy/GNPs powder coatings. The fracture strain, fracture toughness and impact resistance of the epoxy/GNPs cured coatings increased dramatically at low levels of GNPs loading（1 wt %）, indicating that the GNPs could improve the toughness of the epoxy/GNPs powder coatings. Furthermore, from FE-SEM studies of the fracture surfaces, the possible toughening mechanisms of the epoxy/GNPs cured coatings were proposed. TGA result showed that the incorporation of GNPs improved the thermal stability of the cured coatings. Hence, the GNPs modified epoxy can be an efficient approach to toughen epoxy powder coating along with improving their thermal stability.展开更多
The aim of present work is to investigate the influencing factors on mechanical property stability of Cu-Mo-Ni alloyed austempered ductile iron （ADI）. The results show that after austenitized at 900℃ for 2 h follow...The aim of present work is to investigate the influencing factors on mechanical property stability of Cu-Mo-Ni alloyed austempered ductile iron （ADI）. The results show that after austenitized at 900℃ for 2 h followed by austempered at 370℃for another 2 h, the mechanical property of the alloyed ADI can reach the Germanite GGG-100 standard, i.e. σb≮1000 MPa,δ≮5%, at 95% confidence level. And the satisfactory mechanical properties were obtained when the alloyed ADI was austenitized at 850℃ to 1 000 ℃ for 1-4 h, and austempered at 355℃ to 400℃ for another 1 h to 4 h. The microstructures, including nodule number, white bright zone content （martensite-containing interdendritic segregation zone） and retained austenite content, can significantly influence the mechanical properties of the ADI. In order to obtain the good combinations of strength and ductility, the volume fraction of white bright zone should he less than 5%, and the retained austenite contents maintain hetween 30 % and 40%. The application of inoculation techniques to increase graphite nodule number can effectively reduce the white bright zone content in the structure.展开更多
Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes dev...Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes developed for the bulk niobium(Nb)cavity and the thick copper(Cu)layer’s high thermal conductivity and rigidity,thereby enhancing the operational stability of the bulk Nb cavities.This study conducted a global review of the technical approaches employed for fabricating Cu-Nb composite superconducting cavities.We explored Cu-Nb composite superconducting cavities based on two technologies at the Institute of Modern Physics,Chinese Academy of Sciences(IMP,CAS),including their manufacturing processes,radio-frequency(RF)characteristics,and mechanical performance.These cavities exhibit robust mechanical stability.First,the investigation of several 1.3 GHz single-cell elliptical cavities using the Cu-Nb composite sheets indicated that the wavy structure at the Cu-Nb interface influenced the reliable welding of the Cu-Nb composite parts.We observed the generation and trapping of magnetic flux density during the T_c crossing of Nb in cooldown process.The cooling rates during the T_c crossing of Nb exerted a substantial impact on the performance of the cavities.Furthermore,we measured and analyzed the surface resistance R_(s)attributed to the trapped magnetic flux induced by the Seebeck effect after quenching events.Second,for the first time,a low-beta bulk Nb cavity was plated with Cu on its outer surface using electroplating technology.We achieved a high peak electric field E_(pk)of~88.8 MV/m at 2 K and the unloaded quality factor Q_(0)at the E_(pk)of 88.8 MV/m exceeded 1×10^(10).This demonstrated that the electroplating Cu on the bulk Nb cavity is a practical method of developing the Cu-Nb composite superconducting cavity with superior thermal stability.The results presented here provide valuable insights for applying Cu-Nb composite superconducting cavities in superconducting accelerators with stringent operational stability requirements.展开更多
Transformation-induced plasticity-aided steel was rolled at room temperature to different thickness reductions （0, 4%, 10%, 20%, 40%, and 60%）. The mechanical properties, microstructure and austenite fractions of th...Transformation-induced plasticity-aided steel was rolled at room temperature to different thickness reductions （0, 4%, 10%, 20%, 40%, and 60%）. The mechanical properties, microstructure and austenite fractions of the rolled samples were measured by tensile test, electron back scattered diffraction （EBSD） and X-ray diffraction （XRD） for each rolling. The deformation behavior was studied based on the analysis of the mechanical properties and microstructure of steel after tensile deformation, aiming at understanding the effects of cold rolling reduction on the decay behavior of the austenite and the change of mechanical properties of the TRIP steels. It was found that increasing rolling reduction increases the yield stress gradually but decreases the total elongation significantly. It is very interesting that after 10% rolling reduction the yield stress is about 1 000 MPa but still with 20% total elongation, which gives an excellent combination of yield strength and ductility. Based on the XRD results, it was revealed that in both rolling and tension the austenite volume fraction monotonically decayed with the increase of rolling strain, but the decaying rate is faster in tension than in rolling, which may be ascribed to the higher temperature in rolled specimens than in the tensioned ones during deformation. Experimental results and theoretical reasoning indicate that the decreasing trend of austenite volume fraction with strain can be formulated by a unique equation.展开更多
The mechanical stability of tRNAs contributes to their biological activities.The mitochondrial tRNAArg from Romanomermis culicivorax is the shortest tRNA ever known.This tRNA lacks D-and T-arms,represents a stem-bulge...The mechanical stability of tRNAs contributes to their biological activities.The mitochondrial tRNAArg from Romanomermis culicivorax is the shortest tRNA ever known.This tRNA lacks D-and T-arms,represents a stem-bulge-stem architecture but still folds into a stable tertiary structure.Although its structure had been reported,studies on its mechanical folding and unfolding kinetic characteristics are lacking.Here,we directly measured the single-molecule mechanical folding and unfolding kinetics of the armless mt tRNAArg by using optical tweezers in different solution conditions.We revealed a two-step reversible unfolding pathway:the first and large transition corresponds to the unfolding of acceptor stem and bulge below 11 pN,and the second and small transition corresponds to the unfolding of anticodon arm at 12 pN-14 pN.Moreover,the free energy landscapes of the unfolding pathways were reconstructed.We also demonstrated that amino acid-chelated Mg^(2+)(aaCM),which mimics the intracellular solution condition,stabilizes the bulge of mitochondrial tRNAArg possibly by reducing the topological constraints or stabilizing the possible local non-canonical base pairings within the bulge region.Our study revealed the solution-dependent mechanical stability of an armless mt tRNA,which may shed light on future mt tRNA studies.展开更多
Thermal or thermo-mechanical loading is one of the major causes of wheel surface damage in Australian heavy haul operations.In addition,multi-wear wheels appear to be particularly sensitive to thermo-mechanical damage...Thermal or thermo-mechanical loading is one of the major causes of wheel surface damage in Australian heavy haul operations.In addition,multi-wear wheels appear to be particularly sensitive to thermo-mechanical damage during their first service life.Such damage can incur heavy machining penalties or even premature scrapping of wheels.The combination of high contact stresses as well as substantial thermal loading(such as during prolonged periods of tread braking) can lead to severe plastic deformation,thermal fatigue and microstructural deterioration.For some high-strength wheel grades,the increased sensitivity to thermo-mechanical damage observed during the first service period may be attributed to the presence of a near-surface region in which the microstructure is more sensitive to these loading conditions than the underlying material.The standards applicable to wheels used in Australian heavy haul operations are based on the Association of American Railroads(AAR) specification M-107/M-208,which does not include any requirements for microstructure.The implementation of acceptance criteria for the microstructure,in particular that in the near-surface region of the wheel,may be necessary when new wheels are purchased.The stability of wheel microstructures during thermo-mechanical loading and the effects of alloying elements commonly used in wheel manufacturing are reviewed.A brief guide to improving thermal/mechanical stability of the microstructure is also provided.展开更多
Utilising the density functional theory, the mechanical and electrical characteristics of Cesium Germanium Bromide, CsGeBr<sub>3</sub> and Cesium Silicon Bromide CsSiBr<sub>3</sub> compounds we...Utilising the density functional theory, the mechanical and electrical characteristics of Cesium Germanium Bromide, CsGeBr<sub>3</sub> and Cesium Silicon Bromide CsSiBr<sub>3</sub> compounds were computed. The complicated and unique physical and chemical properties of these materials include the ideal geometric property, a limited electronic band structure, a charge density distribution, and specific van Hove singularities in the electronic density of states. With the use of the quantum espresso code and pseudo-potentials taken from the quantum espresso data repository, we have applied density functional theory. Plane Wave (PW) basis set and Projector Augmented Wave (PAW) pseudo potentials were used to compute the ground state energy. For the exchange correlation, where plane wave basis sets are used to expand the electronic structure wave function, the Generalised Gradient Approximation (GGA) was employed. For the computation of mechanical behaviour, including the bulk modulus and elastic constants with their derivatives, Thermo_pw was used as a post-processing algorithm. The theoretical framework that is being taught gives a thorough understanding of the many qualities and possible uses for solar cells and other opto-electronic devices. Both the cubic (high-temperature) and tetragonal (low-temperature) phases of CsGeBr<sub>3</sub> were discovered to have an appropriate gap for solar cells. The edge-sharing monoclinic phase exhibits a greater distortion of the band structure than the cubic phase, which has a lower total energy and a somewhat bigger electronic gap. Although our estimations are less definite because the matching silicon-based compounds have not yet been created, they nonetheless point to a small gap for cubic CsGeBr<sub>3</sub> of about 0.2 - 0.8 eV.展开更多
The influence of prior austenite deformed at different temperature on the subsequent continuous cooling bainitic transformation has been investigated in an C-Ma-Cr-Ni-Mo plastic die steel. The results show that the pr...The influence of prior austenite deformed at different temperature on the subsequent continuous cooling bainitic transformation has been investigated in an C-Ma-Cr-Ni-Mo plastic die steel. The results show that the prior deformation in low temperature region of austenite retards significantly the bainitic transformation. For the same continuous cooling schedule, as austenite deformed at lower temperature, the quantity of the classical sheaf-like bainite becomes less. The present results show that severe deformation leads to mechanical stabilization of austenite and causes the difficulty of bainitic ferrite propagation into the austenite.展开更多
Traditional techniques for treatment of waste rubber, such as burning, generate some highly non- degradable synthetic materials that cause unrepairable environmental damages by releasing heavy metals, such as arsenic,...Traditional techniques for treatment of waste rubber, such as burning, generate some highly non- degradable synthetic materials that cause unrepairable environmental damages by releasing heavy metals, such as arsenic, chromium, lead, manganese and nickel. For this, scrap tires are used as light- weight alternative materials in many engineering applications, such as retaining wall backfilling. In the present study, 90 laboratory models were prepared to evaluate the stability of mechanically stabilized earth （MSE） walls with plate anchors. Then, the bearing capacity and horizontal displacements of the retaining walls were monitored by exerting a static loading to investigate the effects of adding different contents （5 wt%, 10 wt%, 15 wt% and 20 wt%） of recycled crumb rubber （RCR） to the fill of a mechanically stabilized retaining wall with plate anchors. To visualize the critical slip surface of the wall, the particle image velocimetry （PIV） technique was employed. Results showed that the circular anchor plates almost continually provided a higher bearing capacity and wall stability than the square plates. Moreover, the backfill with 15 wt% RCR provided the maximum bearing capacity of the wall. Increasing the weight percentage of RCR to 20 wt% resulted in a significant reduction in horizontal displacement of the wall, which occurred due to the decrease in lateral earth pressure against the whole walls. An increase in RCR content resulted in the decrease in the formation of failure wedge and the expansion of the wall slip surface, and the failure wedge did not form in the sand mixtures with 15 wt% and 20 wt% RCRs.展开更多
Great attention has been focused on super-hydrophobic surfaces due to their fantastic applications.Fluoride chemicals are widely used to fabricate super-hydrophobic surfaces due to their convenience,simplicity,and hig...Great attention has been focused on super-hydrophobic surfaces due to their fantastic applications.Fluoride chemicals are widely used to fabricate super-hydrophobic surfaces due to their convenience,simplicity,and high efficiency.Previous research has made extensively efforts on corrosion resistance of fluorinated super-hydrophobic surfaces in corrosive media.Nevertheless,rare papers focused on the underlying reasons of anticorrosion property and stability mechanism on the fluorinated super-hydrophobic coatings in alkaline solution.Therefore,this work aims to reveal these mechanisms of fluorinated super-hydrophobic copper samples in strong alkaline solution(pH 13).Through the characterization of surface wettability and surface morphology,the laser-induced super-hydrophobic surface retained excellent stability after soaking in alkaline solution for 4 h.Through measurement of chemical compositions,the anticorrosion mechanism and stability mechanism of the fluorinated super-hydrophobic surface were proposed.Importantly,the hydroxyl ion(OH−)can further promote the hydrolysis reaction to improve the density and bonding strength of the fluoride molecules.Finally,the electrochemical experiments(PDP and EIS tests)were conducted to validate the rationality of our proposed conclusions.展开更多
The Micropile-Mechanically Stabilized Earth(MSE) wall, specially designed for mountain roads, is proposed to improve the MSE wall local stability, global stability and impact resistance of roadside barriers. Model tes...The Micropile-Mechanically Stabilized Earth(MSE) wall, specially designed for mountain roads, is proposed to improve the MSE wall local stability, global stability and impact resistance of roadside barriers. Model tests and the corresponding numerical modeling were conducted to validate the serviceability of the Micropile-MSE wall and the reliability of the numerical method. Then, a parametric study of the stress and deformation of Micropile-MSE wall based on the backfill strength and interfacial friction angle between backfill and backslope is conducted to evaluate its performance.The test results indicate that the surcharge-induced horizontal earth pressure, base pressure and lateral displacement of the wall panel of Micropile-MSE wall decrease. The corresponding numerical results are nearly equal to the measured values. The basic failure mode of MSE wall in steep terrain is the sliding of backfill along the backslope, while A-frame style micropiles are capable of preventing the sliding trend.The maximum resultant displacement can be decreased by 6.25% to 46.9% based on different interfacial friction angles, and the displacement canbe reduced by 6% ~ 56.1% based on different backfill strengths. Furthermore, the reduction increases when the interfacial friction angle and internal friction angle of backfill decrease. In addition, the lateral displacement of wall panel, the deformation of backfill decrease and the tension strain of geogrid obviously, which guarantees the MSE wall functions and provides good conditions for mountain roads.展开更多
In this study, two fluorinated polyurethanes（FPU） containing carborane groups in the main chains were firstly designed and synthesized via the reaction of hexamethylene diisocyanate trimer（HDI trimer） with fluorin...In this study, two fluorinated polyurethanes（FPU） containing carborane groups in the main chains were firstly designed and synthesized via the reaction of hexamethylene diisocyanate trimer（HDI trimer） with fluorinated polyesters（CFPETs） having hydroxyl-terminated carborane groups at room temperature. The structures of carborane fluorinated polyesters（CFPETs） and polyurethanes（CFPUs） were characterized by gel permeation chromatography（GPC）, Fourier transform infrared（FTIR） spectroscopy and nuclear magnetic resonance（NMR） measurements. The thermal stability, mechanical properties, Shore A hardness, solvent resistance and acid-alkali resistance of the carborane fluorinated polyurethane films were also studied. Thermogravimetric analysis（TGA） tests manifested that the introduction of carborane groups into the main chain of fluorinated polyurethane endowed the obtained fluorinated polyurethane with excellent thermal stability. The thermal decomposition temperature of carborane fluorinated polyurethane（CFPU） increased by 190 °C compared with that of the carborane-free fluorinated polyurethane（FPU）. Even at 800 °C, CFPU showed the char yield of 66.5%, which was higher than that of FPU（34.3%）. The carborane-containing fluorinated polyurethanes also showed excellent chemical resistance and prominent mechanical property even after the cured films being immersed into Jet aircraft oil or 37% HCl for 168 h or at high temperature（700 °C）. It is found that the structural characteristics of carborane group and the compacted structure of CFPU effectively improve the thermal stability, mechanical property, solvent resistance and acid-alkali resistance of the carborane-free fluorinated polyurethane. These excellent properties make CFPU as the useful raw materials to prepare the high temperature resistant coatings or adhesives for automotive engines, engine or fuel tank of aircraft and other equipment working in high-temperature or high concentrations of acid-alkali environments.展开更多
Oxide-dispersion-strengthened （ODS） ferritic steels are promising candidates for structural applications in the future nuclear reactors. The higher chromium contents of ODS ferritic steels, the better the corrosion ...Oxide-dispersion-strengthened （ODS） ferritic steels are promising candidates for structural applications in the future nuclear reactors. The higher chromium contents of ODS ferritic steels, the better the corrosion resistance, which can meet the harsh corrosion environment of the advanced reactors. However, increasing the Cr content may also lead to the brittleness of the ODS steels when serving at high temperatures. The ODS ferritic steels with different Cr contents （12, 16 and 18 wt% Cr, respectively） were fabricated by mechanical alloying, hot isostatic pressing and forging. Mechanical properties and microstructure evolution of the ODS ferritic steels after aging at 753 K for 2000 h were investigated. It is found that both Vickers hardness and yield strength of 18%Cr ODS ferritic steel were strongly increased and the impact energy was decreased after aging at 753 K. In order to explore the reasons for changes in the mechanical properties, the fracture surfaces were characterized by scanning electron microscopy, and microstructures after aging were observed by transmission electron microscopy. The impact fracture of 18%Cr ODS ferritic steel belongs to quasi-cleavage facture, which is consistent with its very low impact energy. The grain size and dispersed oxide particles of different ODS steels are very stable. M23C6 carbide and M2C carbide were found in 12%Cr ODS steel and 16%Cr ODS steels, respectively.展开更多
基金This research was supported by both National Natural Science Foundation of China(NSFC,Nos.51871062,51371057 and 11672195)MNSF of Beijing(No.2182088)Chong-xiang Huang acknowledged Sichuan Youth Science and Technology Foundation(No.2016JQ0047).
文摘A hot-rolled medium Mn(0.2C5Mn)steel is annealed at 650℃ to produce an ultrafine-grained duplex microstructure with different austenite volume fractions by austenite reverted transformation(ART)annealing,and the orientation relationship strictly obeys K-S orientation relationship before deformation.Tensile tests are carried out in a temperature range from-196 to 400℃ to examine the effects of the austenite volume fraction and the deformation temperature on the tensile properties and the austenite stability.Microstructural observations reveal that the metastable austenite gradually transformed into a-martensite,which is controlled by the deformation strain,the temperature and the austenite volume fraction.Both strain hardening behavior and ductility of the studied steel are dependent on austenite volume fraction and deformation temperature significantly.The stress-strain curves of ART-annealed 0.2C5Mn steel assume an S shape and a very large work hardening rate of about 10 GPa is obtained at liquid nitrogen deformation temperature.Based on the experimental data,a quantitative relation is proposed to describe the ductility dependence on both the austenite volume fraction and its mechanical stability.
基金supported by the National Natural Science Foundation of China(Nos.51034009 and 51101033)the Fundamental Research Funds for the Central Universities(Nos.N110407002 and N110307002)
文摘The ultrafine grained ferritic steels possess shortage of work hardening. Fine grained high strength but low ductility due to the ferrite-martensite dual phase microstruc- ture was obtained in a microalloyed steel and low carbon steels through intercritical annealing of the cold rolled martensite. The dual phase microstructure was uniform and the ferrite grain size was smaller in the microalloyed steel resulted from the pin- ning effect of microalloyed precipitates. But ferrite grown apparently and the volume fraction of the martensite was much higher without the addition of microalloying el- ements. By introducing martensite into the fine grained ferrite, the work hardening was effectively improved, leading to better mechanical stability. As a result of the fine ferrite grain size as well as uniform distribution of the martensite, the work harden- ing was enhanced, showing better strength-ductility balance in the microalloyed dual phase steel.
文摘Spherical roller bearings in railway car wheels are critical components whose failure may have catastrophic consequences. The present study aims to analyse the mechanical stability of greases and temperature of bearings as indicators for condition-based bearing maintenance. The performed case study includes nine fully-formulated commercial greases examined in the wheel bearings of five ore cars operated in northern Scandinavia. The studied ore cars travelled a distance of about 300 000 km during a period of three years. Small samples of the greases were taken on eight occasions to test their mechanical stability. In addition, the temperatures of the bearings were continuously recorded. After the test period, the wear, electrical damage, and corrosion of the bearings were examined. One of the findings is that the shear stress of the grease at a certain shear velocity （the certain yieldstress （CEY） value） is a good maintenance indicator and is highly dependent on the grease type. The bearing＇s wear, electrical damage and corrosion also depend on the grease type. However, no oxidation of the greases was identified. The paper also outlines a systematic methodology to determine an overall maintenance indicator for railway roller bearings which is based on the field measurements.
文摘This paper concentrates on investigating the mechanical stability of a Beam Position Monitor (BMP)support prototype of the Shanghai Synchrotron Radiation Facility(SSRF)project.Both finite element analysis and vibration measurements have been performed.Inconsistent results between the simulations and experiments motivate us to study three connections between the support and the ground:ground bolt(used in the initial design),part grout and full grout(proposed in the later research).After changing the connection, the first eigenfrequency is increased from 20.2Hz to 50.2Hz,and the ratio of the integrated RMS displacement (4—50Hz)is decreased from 4.36 to 1.23 in the lateral direction.The mechanical stability is improved greatly.
文摘The thermal decomposition synthesis of long copper nanowires （CuNWs） was achieved by controlling the synthesis parameters. A detailed study was performed to determine the effect of the molar ratio of copper chloride to nickel acetylacetonate, temperature, and stirring rate on the final shape of the products. Transparent electrodes （TEs） were fabricated by wet treatment with acetic acid （AA）, without using a sintering process. The low oxidation stability and high surface roughness are the main disadvantages of the CuNW TEs, which limit their applications. In order to overcome these issues, we prepared CuNW/polymer composite TEs by partial embedding of the CuNWs into poly（methyl methacrylate） （PMMA） on poly（ethylene terephthalate） （PET） substrates. The CuNW/PMMA composite TEs exhibit excellent optoelectronic performance （91.3% at 100.7 ff2/sq）, low surface roughness （4.6 nm in height）, and good mechanical and chemical stability as compared with CuNW TEs. On the basis of these properties, we believe that CuNW-based composite TEs could serve as low-cost materials for a wide range of new optoelectronic devices.
文摘First principles calculations of structural, electronic, mechanical, and thermodynamic properties of different poly- morphs of BiVO4 are performed using Bender-type plane/wave ultrasoft pseudopotentials within the generalized gradient approximation （GGA） in the flame of density functional theory （DFT）. The calculated structural and electronic properties are consistent with the previous theoretical and experimental results. The electronic structures reveal that m-BiVO4, op- BiVO4, and st-BiVO4 have indirect band gaps, on the other hand, zt-BiVO4 has a direct band gap. From the DOS and Mulliken＇s charge analysis, it is observed that only m-BiVO4 has 6s2 Bi lone pair. Bond population analysis indicates that st-BiVO4 shows a more ionic nature and a similar result is obtained from the elastic properties. From the elastic prop- erties, it is observed that st-BiVO4 is more mechanically stable than the others, st-BiVO4 is more ductile and useful for high electro-optical and electro-mechanical coupling devices. Our calculated thermodynamic properties confirm the similar characteristics found from electronic and elastic properties, m-BiVO4 is useful as photocatalysts, solid state electrolyte, and electrode and other polymorphs are applicable in electronic device fabrications.
基金Project supported by Bureau of Science and Technology of Xinjiang Production and Construction Corps(2011BC008)
文摘The lanthanum ricinoleate（abbreviated as Lari3） of rare earth heat stabilizer was synthesized by the reaction of ricinoleic acid, lanthanum nitrate and sodium hydroxide. The IR and fluorescence spectra methods confirmed the structure of the product. The thermal stability of PVC in the presence of Lari3 was studied by the Congo method and using TG analysis. The results showed that Lari3 could be used as a thermal stabilizer for PVC. When the ratio of Lari3/pentaerythritol was 3：1, the complex exhibited better synergistic effect. Incorporation of Lari3 to PVC resulted in a marked increase of maximum and onset degradation temperature as well as elongation and impact strength of PVC. Lari3 might replace the labile chlorine atoms to interrupt the formation of conjugated double bonds in PVC chains and act as HCl scavenger to restrain the self-catalyticdehydrochlorination.
基金Funded by the National Natural Science Foundation of China(No.51473104)
文摘Epoxy/graphene nanoplatelets（GNPs） powder coatings were fabricated using ultrasonic predispersion of GNPs and melt-blend extrusion method. The isothermal curing kinetics of epoxy/GNPs powder coating were monitored by means of real-time Fourier transform infrared spectroscopy（FT-IR） with a heating cell. The mechanical properties of the epoxy/GNPs cured coatings had been investigated, by evaluating their fracture surfaces with field-emission scanning electron microscopy（FE-SEM） after three-point-bending tests. The thermal stability of the epoxy/GNPs cured coatings was studied by thermo-gravimetric analysis（TGA）. The isothermal curing kinetics result showed that the GNPs would not affect the autocatalytic reaction mechanism, but the loading of GNPs below 1.0 wt % additive played a prompting role in the curing of the epoxy/GNPs powder coatings. The fracture strain, fracture toughness and impact resistance of the epoxy/GNPs cured coatings increased dramatically at low levels of GNPs loading（1 wt %）, indicating that the GNPs could improve the toughness of the epoxy/GNPs powder coatings. Furthermore, from FE-SEM studies of the fracture surfaces, the possible toughening mechanisms of the epoxy/GNPs cured coatings were proposed. TGA result showed that the incorporation of GNPs improved the thermal stability of the cured coatings. Hence, the GNPs modified epoxy can be an efficient approach to toughen epoxy powder coating along with improving their thermal stability.
文摘The aim of present work is to investigate the influencing factors on mechanical property stability of Cu-Mo-Ni alloyed austempered ductile iron （ADI）. The results show that after austenitized at 900℃ for 2 h followed by austempered at 370℃for another 2 h, the mechanical property of the alloyed ADI can reach the Germanite GGG-100 standard, i.e. σb≮1000 MPa,δ≮5%, at 95% confidence level. And the satisfactory mechanical properties were obtained when the alloyed ADI was austenitized at 850℃ to 1 000 ℃ for 1-4 h, and austempered at 355℃ to 400℃ for another 1 h to 4 h. The microstructures, including nodule number, white bright zone content （martensite-containing interdendritic segregation zone） and retained austenite content, can significantly influence the mechanical properties of the ADI. In order to obtain the good combinations of strength and ductility, the volume fraction of white bright zone should he less than 5%, and the retained austenite contents maintain hetween 30 % and 40%. The application of inoculation techniques to increase graphite nodule number can effectively reduce the white bright zone content in the structure.
基金supported by the Large Research Infrastructures China initiative Accelerator Driven System(No.2017-000052-75-01-000590)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2022422)+1 种基金the Young Scientists of National Natural Science Foundation of China(No.12005275)the Advanced Energy Science and Technology Guangdong Laboratory(No.HND22PTZZYY)。
文摘Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes developed for the bulk niobium(Nb)cavity and the thick copper(Cu)layer’s high thermal conductivity and rigidity,thereby enhancing the operational stability of the bulk Nb cavities.This study conducted a global review of the technical approaches employed for fabricating Cu-Nb composite superconducting cavities.We explored Cu-Nb composite superconducting cavities based on two technologies at the Institute of Modern Physics,Chinese Academy of Sciences(IMP,CAS),including their manufacturing processes,radio-frequency(RF)characteristics,and mechanical performance.These cavities exhibit robust mechanical stability.First,the investigation of several 1.3 GHz single-cell elliptical cavities using the Cu-Nb composite sheets indicated that the wavy structure at the Cu-Nb interface influenced the reliable welding of the Cu-Nb composite parts.We observed the generation and trapping of magnetic flux density during the T_c crossing of Nb in cooldown process.The cooling rates during the T_c crossing of Nb exerted a substantial impact on the performance of the cavities.Furthermore,we measured and analyzed the surface resistance R_(s)attributed to the trapped magnetic flux induced by the Seebeck effect after quenching events.Second,for the first time,a low-beta bulk Nb cavity was plated with Cu on its outer surface using electroplating technology.We achieved a high peak electric field E_(pk)of~88.8 MV/m at 2 K and the unloaded quality factor Q_(0)at the E_(pk)of 88.8 MV/m exceeded 1×10^(10).This demonstrated that the electroplating Cu on the bulk Nb cavity is a practical method of developing the Cu-Nb composite superconducting cavity with superior thermal stability.The results presented here provide valuable insights for applying Cu-Nb composite superconducting cavities in superconducting accelerators with stringent operational stability requirements.
基金Sponsored by National Basic Research Program(973 Program) of China(2010CB630803)
文摘Transformation-induced plasticity-aided steel was rolled at room temperature to different thickness reductions （0, 4%, 10%, 20%, 40%, and 60%）. The mechanical properties, microstructure and austenite fractions of the rolled samples were measured by tensile test, electron back scattered diffraction （EBSD） and X-ray diffraction （XRD） for each rolling. The deformation behavior was studied based on the analysis of the mechanical properties and microstructure of steel after tensile deformation, aiming at understanding the effects of cold rolling reduction on the decay behavior of the austenite and the change of mechanical properties of the TRIP steels. It was found that increasing rolling reduction increases the yield stress gradually but decreases the total elongation significantly. It is very interesting that after 10% rolling reduction the yield stress is about 1 000 MPa but still with 20% total elongation, which gives an excellent combination of yield strength and ductility. Based on the XRD results, it was revealed that in both rolling and tension the austenite volume fraction monotonically decayed with the increase of rolling strain, but the decaying rate is faster in tension than in rolling, which may be ascribed to the higher temperature in rolled specimens than in the tensioned ones during deformation. Experimental results and theoretical reasoning indicate that the decreasing trend of austenite volume fraction with strain can be formulated by a unique equation.
基金supported by the Natural Science Foundation of Guangdong Province,China(Grant No.2017A030310085)the Science and Technology Planning Project of Guangdong Province,China(Grant No.2018A050506034).
文摘The mechanical stability of tRNAs contributes to their biological activities.The mitochondrial tRNAArg from Romanomermis culicivorax is the shortest tRNA ever known.This tRNA lacks D-and T-arms,represents a stem-bulge-stem architecture but still folds into a stable tertiary structure.Although its structure had been reported,studies on its mechanical folding and unfolding kinetic characteristics are lacking.Here,we directly measured the single-molecule mechanical folding and unfolding kinetics of the armless mt tRNAArg by using optical tweezers in different solution conditions.We revealed a two-step reversible unfolding pathway:the first and large transition corresponds to the unfolding of acceptor stem and bulge below 11 pN,and the second and small transition corresponds to the unfolding of anticodon arm at 12 pN-14 pN.Moreover,the free energy landscapes of the unfolding pathways were reconstructed.We also demonstrated that amino acid-chelated Mg^(2+)(aaCM),which mimics the intracellular solution condition,stabilizes the bulge of mitochondrial tRNAArg possibly by reducing the topological constraints or stabilizing the possible local non-canonical base pairings within the bulge region.Our study revealed the solution-dependent mechanical stability of an armless mt tRNA,which may shed light on future mt tRNA studies.
文摘Thermal or thermo-mechanical loading is one of the major causes of wheel surface damage in Australian heavy haul operations.In addition,multi-wear wheels appear to be particularly sensitive to thermo-mechanical damage during their first service life.Such damage can incur heavy machining penalties or even premature scrapping of wheels.The combination of high contact stresses as well as substantial thermal loading(such as during prolonged periods of tread braking) can lead to severe plastic deformation,thermal fatigue and microstructural deterioration.For some high-strength wheel grades,the increased sensitivity to thermo-mechanical damage observed during the first service period may be attributed to the presence of a near-surface region in which the microstructure is more sensitive to these loading conditions than the underlying material.The standards applicable to wheels used in Australian heavy haul operations are based on the Association of American Railroads(AAR) specification M-107/M-208,which does not include any requirements for microstructure.The implementation of acceptance criteria for the microstructure,in particular that in the near-surface region of the wheel,may be necessary when new wheels are purchased.The stability of wheel microstructures during thermo-mechanical loading and the effects of alloying elements commonly used in wheel manufacturing are reviewed.A brief guide to improving thermal/mechanical stability of the microstructure is also provided.
文摘Utilising the density functional theory, the mechanical and electrical characteristics of Cesium Germanium Bromide, CsGeBr<sub>3</sub> and Cesium Silicon Bromide CsSiBr<sub>3</sub> compounds were computed. The complicated and unique physical and chemical properties of these materials include the ideal geometric property, a limited electronic band structure, a charge density distribution, and specific van Hove singularities in the electronic density of states. With the use of the quantum espresso code and pseudo-potentials taken from the quantum espresso data repository, we have applied density functional theory. Plane Wave (PW) basis set and Projector Augmented Wave (PAW) pseudo potentials were used to compute the ground state energy. For the exchange correlation, where plane wave basis sets are used to expand the electronic structure wave function, the Generalised Gradient Approximation (GGA) was employed. For the computation of mechanical behaviour, including the bulk modulus and elastic constants with their derivatives, Thermo_pw was used as a post-processing algorithm. The theoretical framework that is being taught gives a thorough understanding of the many qualities and possible uses for solar cells and other opto-electronic devices. Both the cubic (high-temperature) and tetragonal (low-temperature) phases of CsGeBr<sub>3</sub> were discovered to have an appropriate gap for solar cells. The edge-sharing monoclinic phase exhibits a greater distortion of the band structure than the cubic phase, which has a lower total energy and a somewhat bigger electronic gap. Although our estimations are less definite because the matching silicon-based compounds have not yet been created, they nonetheless point to a small gap for cubic CsGeBr<sub>3</sub> of about 0.2 - 0.8 eV.
文摘The influence of prior austenite deformed at different temperature on the subsequent continuous cooling bainitic transformation has been investigated in an C-Ma-Cr-Ni-Mo plastic die steel. The results show that the prior deformation in low temperature region of austenite retards significantly the bainitic transformation. For the same continuous cooling schedule, as austenite deformed at lower temperature, the quantity of the classical sheaf-like bainite becomes less. The present results show that severe deformation leads to mechanical stabilization of austenite and causes the difficulty of bainitic ferrite propagation into the austenite.
文摘Traditional techniques for treatment of waste rubber, such as burning, generate some highly non- degradable synthetic materials that cause unrepairable environmental damages by releasing heavy metals, such as arsenic, chromium, lead, manganese and nickel. For this, scrap tires are used as light- weight alternative materials in many engineering applications, such as retaining wall backfilling. In the present study, 90 laboratory models were prepared to evaluate the stability of mechanically stabilized earth （MSE） walls with plate anchors. Then, the bearing capacity and horizontal displacements of the retaining walls were monitored by exerting a static loading to investigate the effects of adding different contents （5 wt%, 10 wt%, 15 wt% and 20 wt%） of recycled crumb rubber （RCR） to the fill of a mechanically stabilized retaining wall with plate anchors. To visualize the critical slip surface of the wall, the particle image velocimetry （PIV） technique was employed. Results showed that the circular anchor plates almost continually provided a higher bearing capacity and wall stability than the square plates. Moreover, the backfill with 15 wt% RCR provided the maximum bearing capacity of the wall. Increasing the weight percentage of RCR to 20 wt% resulted in a significant reduction in horizontal displacement of the wall, which occurred due to the decrease in lateral earth pressure against the whole walls. An increase in RCR content resulted in the decrease in the formation of failure wedge and the expansion of the wall slip surface, and the failure wedge did not form in the sand mixtures with 15 wt% and 20 wt% RCRs.
基金supported by the National Key Research and Development Program of China(2017YFB1104700)National Postdoctoral Program for Innovative Talents(BX20190233)+1 种基金Tianjin Natural Science Foundation(19JCQNJC03900)the National Natural Science Foundations of China(51675371,51675376,and 51675367).
文摘Great attention has been focused on super-hydrophobic surfaces due to their fantastic applications.Fluoride chemicals are widely used to fabricate super-hydrophobic surfaces due to their convenience,simplicity,and high efficiency.Previous research has made extensively efforts on corrosion resistance of fluorinated super-hydrophobic surfaces in corrosive media.Nevertheless,rare papers focused on the underlying reasons of anticorrosion property and stability mechanism on the fluorinated super-hydrophobic coatings in alkaline solution.Therefore,this work aims to reveal these mechanisms of fluorinated super-hydrophobic copper samples in strong alkaline solution(pH 13).Through the characterization of surface wettability and surface morphology,the laser-induced super-hydrophobic surface retained excellent stability after soaking in alkaline solution for 4 h.Through measurement of chemical compositions,the anticorrosion mechanism and stability mechanism of the fluorinated super-hydrophobic surface were proposed.Importantly,the hydroxyl ion(OH−)can further promote the hydrolysis reaction to improve the density and bonding strength of the fluoride molecules.Finally,the electrochemical experiments(PDP and EIS tests)were conducted to validate the rationality of our proposed conclusions.
基金sponsored by Colorado Department of Transportation (CDOT Award No. 12 HAA 38229) to R.Y.S.P.partial funding was received by Z.Z. from the National Natural Science Foundation of China (Grant No. 51379067, 51609040, 51420105013)+3 种基金the Natural Science Foundation of Fujian Province (Grant No. 2016J05112)Science and Technology Project of Bureau of Geology and Mineral Resources of Fujian Province (DK2016014)the Natural Science Foundation of Fujian Province (Grant No. 2015J01158)the Fundamental Research Funds for the Central Universities (Grant No. 2015B17314)
文摘The Micropile-Mechanically Stabilized Earth(MSE) wall, specially designed for mountain roads, is proposed to improve the MSE wall local stability, global stability and impact resistance of roadside barriers. Model tests and the corresponding numerical modeling were conducted to validate the serviceability of the Micropile-MSE wall and the reliability of the numerical method. Then, a parametric study of the stress and deformation of Micropile-MSE wall based on the backfill strength and interfacial friction angle between backfill and backslope is conducted to evaluate its performance.The test results indicate that the surcharge-induced horizontal earth pressure, base pressure and lateral displacement of the wall panel of Micropile-MSE wall decrease. The corresponding numerical results are nearly equal to the measured values. The basic failure mode of MSE wall in steep terrain is the sliding of backfill along the backslope, while A-frame style micropiles are capable of preventing the sliding trend.The maximum resultant displacement can be decreased by 6.25% to 46.9% based on different interfacial friction angles, and the displacement canbe reduced by 6% ~ 56.1% based on different backfill strengths. Furthermore, the reduction increases when the interfacial friction angle and internal friction angle of backfill decrease. In addition, the lateral displacement of wall panel, the deformation of backfill decrease and the tension strain of geogrid obviously, which guarantees the MSE wall functions and provides good conditions for mountain roads.
基金financially supported by International Cooperative Project (Harbin Institute of Technology 2014DFR40370)International Cooperative Project (Wuxi HIT Limited Corporation & Research Institute of New Materials BZ2015024)
文摘In this study, two fluorinated polyurethanes（FPU） containing carborane groups in the main chains were firstly designed and synthesized via the reaction of hexamethylene diisocyanate trimer（HDI trimer） with fluorinated polyesters（CFPETs） having hydroxyl-terminated carborane groups at room temperature. The structures of carborane fluorinated polyesters（CFPETs） and polyurethanes（CFPUs） were characterized by gel permeation chromatography（GPC）, Fourier transform infrared（FTIR） spectroscopy and nuclear magnetic resonance（NMR） measurements. The thermal stability, mechanical properties, Shore A hardness, solvent resistance and acid-alkali resistance of the carborane fluorinated polyurethane films were also studied. Thermogravimetric analysis（TGA） tests manifested that the introduction of carborane groups into the main chain of fluorinated polyurethane endowed the obtained fluorinated polyurethane with excellent thermal stability. The thermal decomposition temperature of carborane fluorinated polyurethane（CFPU） increased by 190 °C compared with that of the carborane-free fluorinated polyurethane（FPU）. Even at 800 °C, CFPU showed the char yield of 66.5%, which was higher than that of FPU（34.3%）. The carborane-containing fluorinated polyurethanes also showed excellent chemical resistance and prominent mechanical property even after the cured films being immersed into Jet aircraft oil or 37% HCl for 168 h or at high temperature（700 °C）. It is found that the structural characteristics of carborane group and the compacted structure of CFPU effectively improve the thermal stability, mechanical property, solvent resistance and acid-alkali resistance of the carborane-free fluorinated polyurethane. These excellent properties make CFPU as the useful raw materials to prepare the high temperature resistant coatings or adhesives for automotive engines, engine or fuel tank of aircraft and other equipment working in high-temperature or high concentrations of acid-alkali environments.
文摘Oxide-dispersion-strengthened （ODS） ferritic steels are promising candidates for structural applications in the future nuclear reactors. The higher chromium contents of ODS ferritic steels, the better the corrosion resistance, which can meet the harsh corrosion environment of the advanced reactors. However, increasing the Cr content may also lead to the brittleness of the ODS steels when serving at high temperatures. The ODS ferritic steels with different Cr contents （12, 16 and 18 wt% Cr, respectively） were fabricated by mechanical alloying, hot isostatic pressing and forging. Mechanical properties and microstructure evolution of the ODS ferritic steels after aging at 753 K for 2000 h were investigated. It is found that both Vickers hardness and yield strength of 18%Cr ODS ferritic steel were strongly increased and the impact energy was decreased after aging at 753 K. In order to explore the reasons for changes in the mechanical properties, the fracture surfaces were characterized by scanning electron microscopy, and microstructures after aging were observed by transmission electron microscopy. The impact fracture of 18%Cr ODS ferritic steel belongs to quasi-cleavage facture, which is consistent with its very low impact energy. The grain size and dispersed oxide particles of different ODS steels are very stable. M23C6 carbide and M2C carbide were found in 12%Cr ODS steel and 16%Cr ODS steels, respectively.
