By observing the microstructure evolution of Mg-Ga alloy during tensile deformation, it is found that the prismatic slip and the pyramidal <c+a> slip occur during the tensile process at room temperature, which ...By observing the microstructure evolution of Mg-Ga alloy during tensile deformation, it is found that the prismatic slip and the pyramidal <c+a> slip occur during the tensile process at room temperature, which finally leads to the plenty of dislocation accumulation. After 8% tensile deformation,the {1012} extension twin is the main way to coordinate the strain in the c-axis direction for the alloy with the Ga content lower than 2 wt.%, but the pyramidal <c+a> slip is the main way to coordinate the strain along the c-axis direction for the alloy with the Ga content higher than 2 wt.%. The Ga addition can promote the activation of the non-basal slip, which is beneficial to the work-hardening of the alloy to achieve better plasticity. Dynamic precipitation can slightly reduce the increment of dislocations.The preparation method of high strain rate rolling(HSRR) is another important reason for the plasticity of magnesium alloy sheets, and it is an important embodiment of the application of the dislocation engineering concept in magnesium alloy. The non-basal dislocations derived from the HSRR deformation can provide the non-basal dislocation sources when magnesium alloy is deformed at room temperature,resulting in good ductility. This study can be used as a reference for preparing wrought magnesium alloy with high strength and high plasticity by Ga alloying and hot deformation.展开更多
Different application scenarios put forward diverse requirements of mechanical properties for magnesium alloys.In this study,the extruded Mg-Sc-Nd-Zn alloy series with high plasticity and medium strength was developed...Different application scenarios put forward diverse requirements of mechanical properties for magnesium alloys.In this study,the extruded Mg-Sc-Nd-Zn alloy series with high plasticity and medium strength was developed.The uniformly distributed Mg_(3)Nd(β_(1))phase,high-density twins,and the activated non-basal dislocation slips contribute to the high plasticity of Mg-Sc-Nd alloy.With the addition of Zn element,the appearance of coarse ScZn phases,which prevents the activation of{1012}tensile twins,leads to an increase in strength but a simultaneous decrease in the plasticity of the extruded alloys.Adjusting the Zn content in the Mg-Sc-Nd-xZn allows a series of alloys with various strengths and plasticity matching.The results obtained in this work are of great importance for developing a regulatable magnesium alloy series that aims at different application scenarios.展开更多
Cr is the most important element in nickel-based alloys to prevent high temperature oxidation and corrosion. However, high-Cr content will lead to a decline of hot workability which limits the addition of Cr for most ...Cr is the most important element in nickel-based alloys to prevent high temperature oxidation and corrosion. However, high-Cr content will lead to a decline of hot workability which limits the addition of Cr for most nickel-based superalloys. In order to add more Cr into Ni-based alloy for improving high temperature oxidation and corrosion resistance, the poor hot workability of high-Cr alloy must be first solved. Deformation characteristic of a high-Cr nickel-based alloy （40 wt% Cr） under hot compression conditions at 800-1200 ℃ has been investigated by using a Gleeble 3500 machine, and the microstructural evolution during hot working process has been observed by optical microscopy and scanning electron microscopy. The results show that a high-temperature low-plasticity （HTLP） region exists in this high-Cr nickel-based alloy. This phenomenon can be attributed to its non-uniform interdendritic microstructure at high temperatures. These results can explain the poor hot workability of high-Cr nickel-based alloy.展开更多
The surface effect induced transformation texture during vacuum annealing of cold-rolled high manganese transformation-induced plasticity(TRIP)steels was studied.Due to Mn removal occurring at the surface layer,γ→δ...The surface effect induced transformation texture during vacuum annealing of cold-rolled high manganese transformation-induced plasticity(TRIP)steels was studied.Due to Mn removal occurring at the surface layer,γ→δdiffusional phase transformation leads to the formation of hard pancake-shaped ferrite grains due to solution strengthening at the surface and the centre layer remains as austenite+martensite after annealing.In the case of slow heating,{112}/{111}<110>textures for the surface ferrite were strengthened with the increase in temperature and holding time,indicating an inheritance of rolling textures.By increasing the heating rate of annealing,the rotated cube texture was developed in surface ferrite.This kind of multiphase sandwich structure with hard ferrite surface layer and tough austenite dominant centre can increase tensile strength and should also improve deep drawing properties,therefore providing new possibility of controlling properties for the application of high manganese TRIP steel.展开更多
The text determines the hot plasticity of CC blank for heavy rail between BNbRE and BNbRE(V) under 1300～850 ℃ by using Gleeble 1500D. It also makes comparative analysis of the microstructure and fracture of the tens...The text determines the hot plasticity of CC blank for heavy rail between BNbRE and BNbRE(V) under 1300～850 ℃ by using Gleeble 1500D. It also makes comparative analysis of the microstructure and fracture of the tensile specimens by scanning electronic microscope. The result indicates that hot plasticity is almost zero when temperature is between 1200～1300 ℃. While hot plasticity of BNbRE(V) is better than BNbRE between 975～1200 ℃. Plasticity decreases with the reducing temperature from 975 ℃. Hot plasticity of BNbRE(V) reaches the minimum because of the precipitation of vanadium in the specimens reaches the maximum at 850 ℃.Vanadium largely affects the plasticity of steel in brittle temperature region Ⅲ and the embrittlement extends to lower temperature.展开更多
The hot deformation behavior and microstructure evolution of high manganese transformation induced plasticity steel(Fe - 20Mn - 3Si - 3Al) were investigated by using hot compression test in a temperature range from 80...The hot deformation behavior and microstructure evolution of high manganese transformation induced plasticity steel(Fe - 20Mn - 3Si - 3Al) were investigated by using hot compression test in a temperature range from 800℃to 1 050℃and strain rate ranging from 0.01 s^(-1) to 5.0 s^(-1).The effects of temperature,strain rate,and true strain on the flow behavior and microstructures of high manganese transformation induced plasticity steel were discussed.The results show that the dynamic recrystallization occurs only at higher temperature and lower strain rate.Hot deformation behaviors of high manganese transformation induced plasticity steel were sensitive to temperature and strain rate.The apparent stress exponent and the apparent activation energy of the investigated steel were about 4.280 and 463.791 kJ/mol, respectively.The apparent activation energy of the high manganese transformation induced plasticity steel was approached to the austenitic stainless steel(400 -500 kJ/mol).The hot working equation is obtained. Hot deformation peak stress increased with increasing of the value of lnZ.Peak stress and InZ exhibits a linear variation,the linear correlation coefficient was 0.988 9.The results show that the dynamic recrystallization was prone to occur when lnZ≤43.842 26 and Z≤1.098×10^(19),and better hot deformation properties would be obtained under this condition.展开更多
For successfully forming multi-sheet cylinder sandwich structure of Inconel 718 superalloy, high temperature tensile properties of laser butt-welded plate of Inconel 718 superalloy were studied. The experiment results...For successfully forming multi-sheet cylinder sandwich structure of Inconel 718 superalloy, high temperature tensile properties of laser butt-welded plate of Inconel 718 superalloy were studied. The experiment results show that tensile direction has great effect on elongation of the laser butt-welded plate. Under conditions of transverse direction tension, the maximum elongation reaches 458.56% at 950 °C with strain rate of 3.1-10-4 s-1, in which the strain rate sensitivity value m is 0.352 and the welding seam is not deformed. Under conditions of longitudinal direction tension, the maximum elongation is 178.96% at 965 °C with strain rate of 6.2-10-4 s-1, in which m-value is 0.261, and the welding seam contributes to the deformation with the matrix. The microstructure in as-welded fusion zone is constituted of austenite dendrites and Laves phase precipitated in interdendrites. After longitudinal direction tension, a mixed microstructure with dendrite and equiaxed crystal appears in the welding seam due to dynamic recrystallization. After high temperature deforming, many δ-phase grains are transformed from Laves phase grains but a small part of residual Laves phase grains still exist in the welding seam. The deformation result of multi-sheet cylinder sandwich structure verifies that high temperature plasticity of the laser butt-welded plate can meet the requirement of superplastic forming.展开更多
Low-alloyed magnesium(Mg)alloys have emerged as one of the most promising candidates for lightweight materials.However,their further application potential has been hampered by limitations such as low strength,poor pla...Low-alloyed magnesium(Mg)alloys have emerged as one of the most promising candidates for lightweight materials.However,their further application potential has been hampered by limitations such as low strength,poor plasticity at room temperature,and unsatisfactory formability.To address these challenges,grain refinement and grain structure control have been identified as crucial factors to achieving high performance in low-alloyed Mg alloys.An effective way for regulating grain structure is through grain boundary(GB)segregation.This review presents a comprehensive summary of the distribution criteria of segregated atoms and the effects of solute segregation on grain size and growth in Mg alloys.The analysis encompasses both single element segregation and multi-element co-segregation behavior,considering coherent interfaces and incoherent interfaces.Furthermore,we introduce the high mechanical performance low-alloyed wrought Mg alloys that utilize GB segregation and analyze the potential impact mechanisms through which GB segregation influences materials properties.Drawing upon these studies,we propose strategies for the design of high mechanical performance Mg alloys with desirable properties,including high strength,excellent ductility,and good formability,achieved through the implementation of GB segregation.The findings of this review contribute to advancing the understanding of grain boundary engineering in Mg alloys and provide valuable insights for future alloy design and optimization.展开更多
The different chemical composition of silicon and manganese as well as different retained austenite fraction ranged from 4% to 10% of the high strength and high elongation steels were studied in the paper. The disloca...The different chemical composition of silicon and manganese as well as different retained austenite fraction ranged from 4% to 10% of the high strength and high elongation steels were studied in the paper. The dislocations and carbon concentration in retained austenite were observed by a transmission electron microscope and an electric probe analyzer, respectively. The experimental results showed that silicon and manganese are two fundamental alloying elements to stabilize austenite effectively but retaining austenite in different mechanisms. Meanwhile, the cooling processing played an important role in controlling the fraction of retained austenite of the hot-rolled high strength and high plasticity steels.展开更多
Leakage of oil and its derivatives into the soil can change the engineering behavior of soil as well as cause environmental disasters.Also,recovering the contaminated sites into their natural condition and making cont...Leakage of oil and its derivatives into the soil can change the engineering behavior of soil as well as cause environmental disasters.Also,recovering the contaminated sites into their natural condition and making contaminated materials as both environmentally and geotechnically suitable construction materials need the employment of remediation techniques.Bioremediation,as an efficient,low cost and environmentalfriendly approach,was used in the case of highly plastic clayey soils.To better understand the change in geotechnical properties of highly plastic fine-grained soil due to crude oil contamination and bioremediation,Atterberg limits,compaction,unconfined compression,direct shear,and consolidation tests were conducted on natural,contaminated,and bioremediated soil samples to investigate the effects of contamination and remediation on fine-grained soil properties.Oil contamination reduced maximum dry density(MDD),optimum moisture content(OMC),unconfined compressive strength(UCS),shear strength,swelling pressure,and coefficient of consolidation of soil.In addition,contamination increased the compression and swelling indices and compressibility of soil.Bioremediation reduced soil contamination by about 50%.Moreover,in comparison with contaminated soil,bioremediation reduced the MDD,UCS,swelling index,free swelling and swelling pressure of soil,and also increased OMC,shear strength,cohesion,internal friction angle,failure strain,porosity,compression index,and settlement.Microstructural analyses showed that oil contamination does not alter the soil structure in terms of chemical compounds,elements,and constituent minerals.While it decreased the specific surface area of the soil,and the bioremediation significantly increased the mentioned parameters.Bioremediation resulted in the formation of quasi-fibrous textures and porous and agglomerated structures.As a result,oil contamination affected the mechanical properties of soil negatively,but bioremediation improved these properties.展开更多
Recrystallized grains, less than 200 nm in diameter were observed in heavily shear zones of a high strength low alloy steel and a Ni-based alloy, and Also grain refinement, less than 3 μm in diameter was made in high...Recrystallized grains, less than 200 nm in diameter were observed in heavily shear zones of a high strength low alloy steel and a Ni-based alloy, and Also grain refinement, less than 3 μm in diameter was made in high purity aluminum by ECAE at ambient temperature. The experimental results showed that high strain rate and large deformation could induce dynamic recrystallization.Based on dislocation dynamics and grain orientation change enhanced by plastic deformation,a model for the recrystallization process is developed. The model is used to explain the ultra fine grains which are formed at a temperature still much lower than that for the conventional recrystallization展开更多
For the very soft clay with high water content, its void ratio, compressibility coefficient and permeability varied with stress during consolidation. It is necessary to use large strain consolidation based on the perm...For the very soft clay with high water content, its void ratio, compressibility coefficient and permeability varied with stress during consolidation. It is necessary to use large strain consolidation based on the permeability-void ratio relationship and effective stress-void ratio relationship to analyze these properties. To overcome the disadvantages of conventional oedometer test, and determine the effective stress-void relations of this kind of soil, osmotic pressure consolidation test for highly plastic clay study and the expression of permeability-void ratio are performed. Therefore, the decided properties will be reasonably used for solving the large strain consolidation equation.展开更多
On the basis of the data obtained on Gleeble 1500 Thermal Simulator, the predicting models for the relation between stable flow stress during high temperature plastic deformation and deformation strain, strain rate an...On the basis of the data obtained on Gleeble 1500 Thermal Simulator, the predicting models for the relation between stable flow stress during high temperature plastic deformation and deformation strain, strain rate and temperature for 1420 Al Li alloy have been developed with BP artificial neural networks method. The results show that the model on basis of BPNN is practical and it reflects the actual feature of the deforming process. It states that the difference between the actual value and the output of the model is in order of 5%. [展开更多
The effects of plastic deformation and H2 S on fracture toughness of high strength casing steel（C110 steel） were investigated. The studied casing specimens are as follows： original casing, plastic deformation（PD）...The effects of plastic deformation and H2 S on fracture toughness of high strength casing steel（C110 steel） were investigated. The studied casing specimens are as follows： original casing, plastic deformation（PD） casing and PD casing after being immersed in NACE A solution saturated with H2S（PD＋H2S）. Instrumented impact method was employed to evaluate the impact behaviors of the specimens, meanwhile, dynamic fracture toughness（JId） was calculated by using Rice model and Schindler model. The experimental results show that dynamic fracture toughness of the casing decreases after plastic deformation. Compared with that of the original casing and PD casing, the dynamic fracture toughness decreases further when the PD casing immersed in H2 S, moreover, there are ridge-shaped feature and many secondary cracks present on the fracture surface of the specimens. Impact fracture mechanism of the casing is proposed as follows： the plastic deformation results in the increase of defect density of materials where the atomic hydrogen can accumulate in reversible or irreversible traps and even recombine to form molecular hydrogen, subsequently, the casing material toughness decreases greatly.展开更多
A novel plastic/multi-walled carbon nanotube（MWNTs）-nickel（Ni）-platinum（Pt） electrode（PMNP） is prepared by chemical-reducing Pt onto the surface of Ni film covered plastic/MWNTs（PM） substrate. The MWNTs are ...A novel plastic/multi-walled carbon nanotube（MWNTs）-nickel（Ni）-platinum（Pt） electrode（PMNP） is prepared by chemical-reducing Pt onto the surface of Ni film covered plastic/MWNTs（PM） substrate. The MWNTs are adhered by a piece of commercial double faced adhesive tape on the surface of plastic paper and the Ni film is prepared by a simple electrodeposition method. The morphology and phase structure of the PMNP electrode are characterized by scanning electron microscopy,transmission electron microscope and X-ray diffractometer. The catalytic activity of the PMNP electrode for Na BH4 electrooxidation is investigated by means of cyclic voltammetry and chronoamperometry. The catalyst combines tightly with the plastic paper and exhibits a good stability. MWNTs serve as both conductive material and hydrogen storage material and the Ni film and Pt are employed as electrochemical catalysts. The PMNP electrode exhibits a high electrocatalytic performance and the oxidation current density reaches to 10.76 A/（mg·cm） in 0.1 mol/dm3 Na BH4at0 V,which is much higher than those in the previous reports. The using of waste plastic reduces the discarding of white pollution and consumption of metal resources.展开更多
The security of use for Al-Li alloy will be greatly influenced by the damage degree of plastic deformation within i t at high temperature . Based on continuum damage mechanics theory, the damage e volution of Al-5.4...The security of use for Al-Li alloy will be greatly influenced by the damage degree of plastic deformation within i t at high temperature . Based on continuum damage mechanics theory, the damage e volution of Al-5.44Mg-2.15Li-0.12Zr alloy during plastic deforming at high te mperature is simulated by using the damage evolution model of high temperature p lastic deformation. The changing rule of its inner damage with deformation tempe rature, strain rate and strain is gained in this paper. The equation of damage e volution for high temperature plastic deformation is developed, providing an aca demic basis for the technology of plastic process of Al-Li alloys.展开更多
The computer simulation of Al three-dimensional crystallite containing grain boundary of special type was carried out and its behaviour under high rate loading was investigated. The molecular dynamics method was used ...The computer simulation of Al three-dimensional crystallite containing grain boundary of special type was carried out and its behaviour under high rate loading was investigated. The molecular dynamics method was used and interaction betwen atoms was described based on pseudopotential method. Vortical character of the atom movements in the grain boundary region is realized under shear loading in certain directions. Back and forth movements of atoms in the direction which is perpendicular to the shear also arise. Amplitude of such movements is approximately equal to an interplanar distance in this direction.展开更多
This study investigates the efficacy of sodium alginate(SA),xanthan gum(XG),guar gum(GG)and chitosan(CS)d each applied at five different solid biopolymer-to-water mass ratios(or dosages)and cured for 7 d and 28 d d on...This study investigates the efficacy of sodium alginate(SA),xanthan gum(XG),guar gum(GG)and chitosan(CS)d each applied at five different solid biopolymer-to-water mass ratios(or dosages)and cured for 7 d and 28 d d on the unconfined compressive strength(UCS)performance of a high plasticity clayey soil.Moreover,on identifying the optimum biopolymer-treatment scenarios,their performance was compared against conventional stabilization using hydrated lime.For a given curing time,the UCS for all biopolymers followed a riseefall trend with increasing biopolymer dosage,peaking at an optimum dosage and then subsequently decreasing,such that all biopolymer-stabilized samples mobilized higher UCS values compared to the unamended soil.The optimum dosage was found to be 1.5%for SA,XG and CS,while a notably lower dosage of 0.5%was deemed optimum for GG.Similarly,for a given biopolymer type and dosage,increasing the curing time from 7 d to 28 d further enhanced the UCS,with the achieved improvements being generally more pronounced for XG-and CS-treated cases.None of the investigated biopolymers was able to produce UCS improvements equivalent to those obtained by the 28-d soilelime samples;however,the optimum XG,GG and CS dosages,particularly after 28 d of curing,were easily able to replicate 7-d lime stabilization outcomes achieved with as high as twice the soil’s lime demand.Finally,the fundamental principles of clay chemistry,in conjunction with the soil mechanics framework,were employed to identify and discuss the clayebiopolymer stabilization mechanisms.展开更多
China has been developed into one of the most active regions in terms of both fundamental and applied research on magnesium （Mg） and its alloys in the world from a solid base laid by its prominent metallurgist and m...China has been developed into one of the most active regions in terms of both fundamental and applied research on magnesium （Mg） and its alloys in the world from a solid base laid by its prominent metallurgist and materials scientists over the past decades. Nowadays, a large number of young-generation researchers have been inspired by their predecessors and become the key participants in the fields of Mg alloys, which consequently led to the establishment of China Youth Scholar Society for Magnesium Alloys Research in 2015. Since then, the first two China Youth Scholars Symposiums on Mg Alloys Research had been held at Harbin （2015） and Chongqing （2016） China, respectively. A number of crucial research inter- ests related to fundamental and applied Mg research were discussed at the conferences and summarized in this short perspective, aiming to boost far-reaching initiatives for development of new Mg-based materials to satisfy the requirements for a broad range of industrial employments. Herein, four main aspects are included as follows： i） Plastic deformation mechanism and strengthening strategy, ii） Design and development of new Mg-based materials, iii） Key service properties, and iv） New processing technologies.展开更多
Al_(18)B_(4)O_(33) whisker was coated by SnO_(2) particles using a chemical precipitation method,and an aluminum matrix composite reinforced by the coated whisker was fabricated by squeeze casting technique.It is foun...Al_(18)B_(4)O_(33) whisker was coated by SnO_(2) particles using a chemical precipitation method,and an aluminum matrix composite reinforced by the coated whisker was fabricated by squeeze casting technique.It is found that the SnO_(2) coating can react with aluminum matrix during squeeze casting process,and Sn particles are induced near the interface between Al_(18)B_(4)O_(33) whisker and matrix.The tensile test at room temperature indicated that the tensile strength of Al_(18)B_(4)O_(33) whisker reinforced aluminum matrix composite can be enhanced by suitable content of SnO_(2) coating.The composites with various whisker coating contents exhibit maximum tensile plasticity at about 300℃,and the composite with a suitable whisker coating content could enhance its tensile plasticity evidently,which suggest that an Al_(18)B_(4)O_(33) whisker-Al composite with both high strength at room temperature and high formability at elevated temperature can be designed.展开更多
基金financially supported by the National Natural Science Foundation of China (no. 51871093)the Natural Science Foundation of Hunan Province, China (no. 2019JJ40044)。
文摘By observing the microstructure evolution of Mg-Ga alloy during tensile deformation, it is found that the prismatic slip and the pyramidal <c+a> slip occur during the tensile process at room temperature, which finally leads to the plenty of dislocation accumulation. After 8% tensile deformation,the {1012} extension twin is the main way to coordinate the strain in the c-axis direction for the alloy with the Ga content lower than 2 wt.%, but the pyramidal <c+a> slip is the main way to coordinate the strain along the c-axis direction for the alloy with the Ga content higher than 2 wt.%. The Ga addition can promote the activation of the non-basal slip, which is beneficial to the work-hardening of the alloy to achieve better plasticity. Dynamic precipitation can slightly reduce the increment of dislocations.The preparation method of high strain rate rolling(HSRR) is another important reason for the plasticity of magnesium alloy sheets, and it is an important embodiment of the application of the dislocation engineering concept in magnesium alloy. The non-basal dislocations derived from the HSRR deformation can provide the non-basal dislocation sources when magnesium alloy is deformed at room temperature,resulting in good ductility. This study can be used as a reference for preparing wrought magnesium alloy with high strength and high plasticity by Ga alloying and hot deformation.
基金Project supported by the National Natural Science Foundation of China(52301107)the National Key Research and Development Program of China(2021YFC2400703)。
文摘Different application scenarios put forward diverse requirements of mechanical properties for magnesium alloys.In this study,the extruded Mg-Sc-Nd-Zn alloy series with high plasticity and medium strength was developed.The uniformly distributed Mg_(3)Nd(β_(1))phase,high-density twins,and the activated non-basal dislocation slips contribute to the high plasticity of Mg-Sc-Nd alloy.With the addition of Zn element,the appearance of coarse ScZn phases,which prevents the activation of{1012}tensile twins,leads to an increase in strength but a simultaneous decrease in the plasticity of the extruded alloys.Adjusting the Zn content in the Mg-Sc-Nd-xZn allows a series of alloys with various strengths and plasticity matching.The results obtained in this work are of great importance for developing a regulatable magnesium alloy series that aims at different application scenarios.
基金support from the National Natural Science Foundation of China, No.50771011
文摘Cr is the most important element in nickel-based alloys to prevent high temperature oxidation and corrosion. However, high-Cr content will lead to a decline of hot workability which limits the addition of Cr for most nickel-based superalloys. In order to add more Cr into Ni-based alloy for improving high temperature oxidation and corrosion resistance, the poor hot workability of high-Cr alloy must be first solved. Deformation characteristic of a high-Cr nickel-based alloy （40 wt% Cr） under hot compression conditions at 800-1200 ℃ has been investigated by using a Gleeble 3500 machine, and the microstructural evolution during hot working process has been observed by optical microscopy and scanning electron microscopy. The results show that a high-temperature low-plasticity （HTLP） region exists in this high-Cr nickel-based alloy. This phenomenon can be attributed to its non-uniform interdendritic microstructure at high temperatures. These results can explain the poor hot workability of high-Cr nickel-based alloy.
基金supported by the National Natural Science Foundation of China(Grant No.51771024).
文摘The surface effect induced transformation texture during vacuum annealing of cold-rolled high manganese transformation-induced plasticity(TRIP)steels was studied.Due to Mn removal occurring at the surface layer,γ→δdiffusional phase transformation leads to the formation of hard pancake-shaped ferrite grains due to solution strengthening at the surface and the centre layer remains as austenite+martensite after annealing.In the case of slow heating,{112}/{111}<110>textures for the surface ferrite were strengthened with the increase in temperature and holding time,indicating an inheritance of rolling textures.By increasing the heating rate of annealing,the rotated cube texture was developed in surface ferrite.This kind of multiphase sandwich structure with hard ferrite surface layer and tough austenite dominant centre can increase tensile strength and should also improve deep drawing properties,therefore providing new possibility of controlling properties for the application of high manganese TRIP steel.
文摘The text determines the hot plasticity of CC blank for heavy rail between BNbRE and BNbRE(V) under 1300～850 ℃ by using Gleeble 1500D. It also makes comparative analysis of the microstructure and fracture of the tensile specimens by scanning electronic microscope. The result indicates that hot plasticity is almost zero when temperature is between 1200～1300 ℃. While hot plasticity of BNbRE(V) is better than BNbRE between 975～1200 ℃. Plasticity decreases with the reducing temperature from 975 ℃. Hot plasticity of BNbRE(V) reaches the minimum because of the precipitation of vanadium in the specimens reaches the maximum at 850 ℃.Vanadium largely affects the plasticity of steel in brittle temperature region Ⅲ and the embrittlement extends to lower temperature.
文摘The hot deformation behavior and microstructure evolution of high manganese transformation induced plasticity steel(Fe - 20Mn - 3Si - 3Al) were investigated by using hot compression test in a temperature range from 800℃to 1 050℃and strain rate ranging from 0.01 s^(-1) to 5.0 s^(-1).The effects of temperature,strain rate,and true strain on the flow behavior and microstructures of high manganese transformation induced plasticity steel were discussed.The results show that the dynamic recrystallization occurs only at higher temperature and lower strain rate.Hot deformation behaviors of high manganese transformation induced plasticity steel were sensitive to temperature and strain rate.The apparent stress exponent and the apparent activation energy of the investigated steel were about 4.280 and 463.791 kJ/mol, respectively.The apparent activation energy of the high manganese transformation induced plasticity steel was approached to the austenitic stainless steel(400 -500 kJ/mol).The hot working equation is obtained. Hot deformation peak stress increased with increasing of the value of lnZ.Peak stress and InZ exhibits a linear variation,the linear correlation coefficient was 0.988 9.The results show that the dynamic recrystallization was prone to occur when lnZ≤43.842 26 and Z≤1.098×10^(19),and better hot deformation properties would be obtained under this condition.
基金Project(20102302120002)supported by the Research Fund for the Doctoral Program of Higher Education of China
文摘For successfully forming multi-sheet cylinder sandwich structure of Inconel 718 superalloy, high temperature tensile properties of laser butt-welded plate of Inconel 718 superalloy were studied. The experiment results show that tensile direction has great effect on elongation of the laser butt-welded plate. Under conditions of transverse direction tension, the maximum elongation reaches 458.56% at 950 °C with strain rate of 3.1-10-4 s-1, in which the strain rate sensitivity value m is 0.352 and the welding seam is not deformed. Under conditions of longitudinal direction tension, the maximum elongation is 178.96% at 965 °C with strain rate of 6.2-10-4 s-1, in which m-value is 0.261, and the welding seam contributes to the deformation with the matrix. The microstructure in as-welded fusion zone is constituted of austenite dendrites and Laves phase precipitated in interdendrites. After longitudinal direction tension, a mixed microstructure with dendrite and equiaxed crystal appears in the welding seam due to dynamic recrystallization. After high temperature deforming, many δ-phase grains are transformed from Laves phase grains but a small part of residual Laves phase grains still exist in the welding seam. The deformation result of multi-sheet cylinder sandwich structure verifies that high temperature plasticity of the laser butt-welded plate can meet the requirement of superplastic forming.
基金the support of the National Natural Science Foundation of China(52071093 and 51871069)the Natural Science Foundation of Heilongjiang Province of China(LH2023E059)+1 种基金the Fundamental Research Program of Shenzhen Science and Technology Innovation Commission(JCYJ20210324131405015)PolyU Grant(1-BBR1)。
文摘Low-alloyed magnesium(Mg)alloys have emerged as one of the most promising candidates for lightweight materials.However,their further application potential has been hampered by limitations such as low strength,poor plasticity at room temperature,and unsatisfactory formability.To address these challenges,grain refinement and grain structure control have been identified as crucial factors to achieving high performance in low-alloyed Mg alloys.An effective way for regulating grain structure is through grain boundary(GB)segregation.This review presents a comprehensive summary of the distribution criteria of segregated atoms and the effects of solute segregation on grain size and growth in Mg alloys.The analysis encompasses both single element segregation and multi-element co-segregation behavior,considering coherent interfaces and incoherent interfaces.Furthermore,we introduce the high mechanical performance low-alloyed wrought Mg alloys that utilize GB segregation and analyze the potential impact mechanisms through which GB segregation influences materials properties.Drawing upon these studies,we propose strategies for the design of high mechanical performance Mg alloys with desirable properties,including high strength,excellent ductility,and good formability,achieved through the implementation of GB segregation.The findings of this review contribute to advancing the understanding of grain boundary engineering in Mg alloys and provide valuable insights for future alloy design and optimization.
文摘The different chemical composition of silicon and manganese as well as different retained austenite fraction ranged from 4% to 10% of the high strength and high elongation steels were studied in the paper. The dislocations and carbon concentration in retained austenite were observed by a transmission electron microscope and an electric probe analyzer, respectively. The experimental results showed that silicon and manganese are two fundamental alloying elements to stabilize austenite effectively but retaining austenite in different mechanisms. Meanwhile, the cooling processing played an important role in controlling the fraction of retained austenite of the hot-rolled high strength and high plasticity steels.
文摘Leakage of oil and its derivatives into the soil can change the engineering behavior of soil as well as cause environmental disasters.Also,recovering the contaminated sites into their natural condition and making contaminated materials as both environmentally and geotechnically suitable construction materials need the employment of remediation techniques.Bioremediation,as an efficient,low cost and environmentalfriendly approach,was used in the case of highly plastic clayey soils.To better understand the change in geotechnical properties of highly plastic fine-grained soil due to crude oil contamination and bioremediation,Atterberg limits,compaction,unconfined compression,direct shear,and consolidation tests were conducted on natural,contaminated,and bioremediated soil samples to investigate the effects of contamination and remediation on fine-grained soil properties.Oil contamination reduced maximum dry density(MDD),optimum moisture content(OMC),unconfined compressive strength(UCS),shear strength,swelling pressure,and coefficient of consolidation of soil.In addition,contamination increased the compression and swelling indices and compressibility of soil.Bioremediation reduced soil contamination by about 50%.Moreover,in comparison with contaminated soil,bioremediation reduced the MDD,UCS,swelling index,free swelling and swelling pressure of soil,and also increased OMC,shear strength,cohesion,internal friction angle,failure strain,porosity,compression index,and settlement.Microstructural analyses showed that oil contamination does not alter the soil structure in terms of chemical compounds,elements,and constituent minerals.While it decreased the specific surface area of the soil,and the bioremediation significantly increased the mentioned parameters.Bioremediation resulted in the formation of quasi-fibrous textures and porous and agglomerated structures.As a result,oil contamination affected the mechanical properties of soil negatively,but bioremediation improved these properties.
文摘Recrystallized grains, less than 200 nm in diameter were observed in heavily shear zones of a high strength low alloy steel and a Ni-based alloy, and Also grain refinement, less than 3 μm in diameter was made in high purity aluminum by ECAE at ambient temperature. The experimental results showed that high strain rate and large deformation could induce dynamic recrystallization.Based on dislocation dynamics and grain orientation change enhanced by plastic deformation,a model for the recrystallization process is developed. The model is used to explain the ultra fine grains which are formed at a temperature still much lower than that for the conventional recrystallization
文摘For the very soft clay with high water content, its void ratio, compressibility coefficient and permeability varied with stress during consolidation. It is necessary to use large strain consolidation based on the permeability-void ratio relationship and effective stress-void ratio relationship to analyze these properties. To overcome the disadvantages of conventional oedometer test, and determine the effective stress-void relations of this kind of soil, osmotic pressure consolidation test for highly plastic clay study and the expression of permeability-void ratio are performed. Therefore, the decided properties will be reasonably used for solving the large strain consolidation equation.
文摘On the basis of the data obtained on Gleeble 1500 Thermal Simulator, the predicting models for the relation between stable flow stress during high temperature plastic deformation and deformation strain, strain rate and temperature for 1420 Al Li alloy have been developed with BP artificial neural networks method. The results show that the model on basis of BPNN is practical and it reflects the actual feature of the deforming process. It states that the difference between the actual value and the output of the model is in order of 5%. [
基金Funded by the Construction of Key Disciplines for Young Teacher Science Foundation of the Southwest Petroleum University(No.P209)the Research Fund for the Doctoral Program of Higher Education(No.20105121120002)the National Natural Science Foundation of China(Nos.51004084 and 51374177)
文摘The effects of plastic deformation and H2 S on fracture toughness of high strength casing steel（C110 steel） were investigated. The studied casing specimens are as follows： original casing, plastic deformation（PD） casing and PD casing after being immersed in NACE A solution saturated with H2S（PD＋H2S）. Instrumented impact method was employed to evaluate the impact behaviors of the specimens, meanwhile, dynamic fracture toughness（JId） was calculated by using Rice model and Schindler model. The experimental results show that dynamic fracture toughness of the casing decreases after plastic deformation. Compared with that of the original casing and PD casing, the dynamic fracture toughness decreases further when the PD casing immersed in H2 S, moreover, there are ridge-shaped feature and many secondary cracks present on the fracture surface of the specimens. Impact fracture mechanism of the casing is proposed as follows： the plastic deformation results in the increase of defect density of materials where the atomic hydrogen can accumulate in reversible or irreversible traps and even recombine to form molecular hydrogen, subsequently, the casing material toughness decreases greatly.
基金supported by the Fundamental Research Funds for the Central Universities (HEUCF201403018)the Heilongjiang Postdoctoral Fund (LBHZ13059)+1 种基金the China Postdoctoral Science Foundation (2014M561332)the National Natural Science Foundation of China (21403044)
文摘A novel plastic/multi-walled carbon nanotube（MWNTs）-nickel（Ni）-platinum（Pt） electrode（PMNP） is prepared by chemical-reducing Pt onto the surface of Ni film covered plastic/MWNTs（PM） substrate. The MWNTs are adhered by a piece of commercial double faced adhesive tape on the surface of plastic paper and the Ni film is prepared by a simple electrodeposition method. The morphology and phase structure of the PMNP electrode are characterized by scanning electron microscopy,transmission electron microscope and X-ray diffractometer. The catalytic activity of the PMNP electrode for Na BH4 electrooxidation is investigated by means of cyclic voltammetry and chronoamperometry. The catalyst combines tightly with the plastic paper and exhibits a good stability. MWNTs serve as both conductive material and hydrogen storage material and the Ni film and Pt are employed as electrochemical catalysts. The PMNP electrode exhibits a high electrocatalytic performance and the oxidation current density reaches to 10.76 A/（mg·cm） in 0.1 mol/dm3 Na BH4at0 V,which is much higher than those in the previous reports. The using of waste plastic reduces the discarding of white pollution and consumption of metal resources.
文摘The security of use for Al-Li alloy will be greatly influenced by the damage degree of plastic deformation within i t at high temperature . Based on continuum damage mechanics theory, the damage e volution of Al-5.44Mg-2.15Li-0.12Zr alloy during plastic deforming at high te mperature is simulated by using the damage evolution model of high temperature p lastic deformation. The changing rule of its inner damage with deformation tempe rature, strain rate and strain is gained in this paper. The equation of damage e volution for high temperature plastic deformation is developed, providing an aca demic basis for the technology of plastic process of Al-Li alloys.
文摘The computer simulation of Al three-dimensional crystallite containing grain boundary of special type was carried out and its behaviour under high rate loading was investigated. The molecular dynamics method was used and interaction betwen atoms was described based on pseudopotential method. Vortical character of the atom movements in the grain boundary region is realized under shear loading in certain directions. Back and forth movements of atoms in the direction which is perpendicular to the shear also arise. Amplitude of such movements is approximately equal to an interplanar distance in this direction.
基金supported by an Australian Government Research Training Program(RTP)scholarship.
文摘This study investigates the efficacy of sodium alginate(SA),xanthan gum(XG),guar gum(GG)and chitosan(CS)d each applied at five different solid biopolymer-to-water mass ratios(or dosages)and cured for 7 d and 28 d d on the unconfined compressive strength(UCS)performance of a high plasticity clayey soil.Moreover,on identifying the optimum biopolymer-treatment scenarios,their performance was compared against conventional stabilization using hydrated lime.For a given curing time,the UCS for all biopolymers followed a riseefall trend with increasing biopolymer dosage,peaking at an optimum dosage and then subsequently decreasing,such that all biopolymer-stabilized samples mobilized higher UCS values compared to the unamended soil.The optimum dosage was found to be 1.5%for SA,XG and CS,while a notably lower dosage of 0.5%was deemed optimum for GG.Similarly,for a given biopolymer type and dosage,increasing the curing time from 7 d to 28 d further enhanced the UCS,with the achieved improvements being generally more pronounced for XG-and CS-treated cases.None of the investigated biopolymers was able to produce UCS improvements equivalent to those obtained by the 28-d soilelime samples;however,the optimum XG,GG and CS dosages,particularly after 28 d of curing,were easily able to replicate 7-d lime stabilization outcomes achieved with as high as twice the soil’s lime demand.Finally,the fundamental principles of clay chemistry,in conjunction with the soil mechanics framework,were employed to identify and discuss the clayebiopolymer stabilization mechanisms.
基金support from Chinese Committee for Magnesium and its Application
文摘China has been developed into one of the most active regions in terms of both fundamental and applied research on magnesium （Mg） and its alloys in the world from a solid base laid by its prominent metallurgist and materials scientists over the past decades. Nowadays, a large number of young-generation researchers have been inspired by their predecessors and become the key participants in the fields of Mg alloys, which consequently led to the establishment of China Youth Scholar Society for Magnesium Alloys Research in 2015. Since then, the first two China Youth Scholars Symposiums on Mg Alloys Research had been held at Harbin （2015） and Chongqing （2016） China, respectively. A number of crucial research inter- ests related to fundamental and applied Mg research were discussed at the conferences and summarized in this short perspective, aiming to boost far-reaching initiatives for development of new Mg-based materials to satisfy the requirements for a broad range of industrial employments. Herein, four main aspects are included as follows： i） Plastic deformation mechanism and strengthening strategy, ii） Design and development of new Mg-based materials, iii） Key service properties, and iv） New processing technologies.
基金Funded by the Specialized Research Fund for the Doctoral Program of Higher Education(No.20070213042)
文摘Al_(18)B_(4)O_(33) whisker was coated by SnO_(2) particles using a chemical precipitation method,and an aluminum matrix composite reinforced by the coated whisker was fabricated by squeeze casting technique.It is found that the SnO_(2) coating can react with aluminum matrix during squeeze casting process,and Sn particles are induced near the interface between Al_(18)B_(4)O_(33) whisker and matrix.The tensile test at room temperature indicated that the tensile strength of Al_(18)B_(4)O_(33) whisker reinforced aluminum matrix composite can be enhanced by suitable content of SnO_(2) coating.The composites with various whisker coating contents exhibit maximum tensile plasticity at about 300℃,and the composite with a suitable whisker coating content could enhance its tensile plasticity evidently,which suggest that an Al_(18)B_(4)O_(33) whisker-Al composite with both high strength at room temperature and high formability at elevated temperature can be designed.
