Commercial wrought high-strength Cu-Cr-Zr alloys face limited high-temperature properties due to the rapid coarsening or dissolution of Cr precipitates.Here,we report a laser powder bed fusion(LPBF)fabricated Cu-0.84C...Commercial wrought high-strength Cu-Cr-Zr alloys face limited high-temperature properties due to the rapid coarsening or dissolution of Cr precipitates.Here,we report a laser powder bed fusion(LPBF)fabricated Cu-0.84Cr-0.42Zr(wt.%)alloy with exceptional heat resistance after aging.Primary Cr@Cu_(5)Zr phase(∼39.8 nm)with core-shell structure and a high density of heat-stable dislocations were intro-duced from the rapid solidification of LPBF and enabled the alloy to gain significant improvement in high-temperature properties.After aging treatment,secondary Cr and Cu_(51)Zr_(14)phases(∼3.4 nm)were precipitated,in which Zr solute was segregated at one side of the Cr phase,enhancing the thermal sta-bility of Cr phase.The excellent combinations of strength and thermal conductivity were achieved at or above 400℃.Particularly at 600℃,the aged sample not only exhibited a high tensile strength of∼196 MPa,which significantly surpassed that of wrought Cu-Cr-Zr alloys,but also possessed a thermal conductivity of∼349 W/(m K)comparable to that of pure copper.展开更多
h-BN rods modified low-carbon alumina-carbon(Al_(2)O_(3)-C)refractories were prepared,and the effect of h-BN rod addition on the high-temperature properties was investigated and compared with commercial h-BN flake,car...h-BN rods modified low-carbon alumina-carbon(Al_(2)O_(3)-C)refractories were prepared,and the effect of h-BN rod addition on the high-temperature properties was investigated and compared with commercial h-BN flake,carbon black,and carbon nanotubes additives.The results demonstrated that Al_(2)O_(3)-C refractories containing h-BN rods exhibited optimal high-temperature service performances,including 25%higher hot modulus of rupture,21.3%higher thermal shock strength residual ratio,20.9%lower in oxidation and 44.3%less in slag corrosion,compared to the counterpart specimens without additives.Moreover,benefiting from the synergistic enhancement of the rod-like h-BN and in-situ generated SiC whiskers,the high-temperature service performances of h-BN rods containing specimens outperformed counterpart specimens containing commercial h-BN flake,carbon black,and carbon nanotubes,respectively.展开更多
This study focuses on finding a solution to the sharp decline in mechanical properties of Al-Si-Cu-Mg alloys due to rapid coarsening of traditional intermediate phases at high temperature.A new type of modified al oy,...This study focuses on finding a solution to the sharp decline in mechanical properties of Al-Si-Cu-Mg alloys due to rapid coarsening of traditional intermediate phases at high temperature.A new type of modified al oy,to be used in automobile engines at high temperatures,was prepared by adding Zr and Mo into Al-Si-Cu-Mg alloy.The synergistic effects of Zr and Mo on the microstructure evolution and high-temperature mechanical properties were studied.Results show that the addition of Zr and Mo generates a series of intermetallic phases dispersed in the alloy.They can improve the strength of the alloy by hindering dislocation movement and crack propagation.In addition,some nano-strengthened phases show coherent interfaces with the matrix and improve grain refinement.The addition of Mo greatly improves the heat resistance of the alloy.The extremely low diffusivity of Mo enables it to improve the thermal stability of the intermetallic phases,inhibit precipitation during aging,reduce the size of the precipitates,and improve the heat resistance of the alloy.展开更多
Fe-based composite coatings were fabricated on 5 CrNiMo die steel by laser beam melting a precursor mixture of ferrotitanium,ferrochromium,ferromolybdenum,B4 C and Y2 O3 powders.Micro structure and properties of the c...Fe-based composite coatings were fabricated on 5 CrNiMo die steel by laser beam melting a precursor mixture of ferrotitanium,ferrochromium,ferromolybdenum,B4 C and Y2 O3 powders.Micro structure and properties of the coatings were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),energy-dispersive spectrometer(EDS),resistance furnace and high-temperature tribometer.The results show that(Ti,Mo)C particles with flower-like and(Ti,Mo)B2 with block-like shapes are in situ formed during laser cladding.Volume faction of multiple ceramic particles increases with the increasing of Y2 O3.The cumulative oxidation mass of the coating with 2 wt% Y2 O3 is decreased by one-third than that of the coating without Y2 O3.The oxidation layer of the coating with Y2 O3 is getting smooth.Meanwhile,high temperature wear volume loss of the coating with 2 wt% Y2 O3 is about 40% that of the coating without Y2 O3.The coating with 2 wt% Y2 O3 shows a smoother wear scar and few flat grooves are observed after high temperature wear test.展开更多
The high-temperature mechanical properties and microstructure of forging billets of C-Si-Mn-Cr and C-Si-Mn-Cr-Mo ultra-high-strength cold-rolled steels（tensile strength≥1000 MPa,elongation≥10%） were studied.Throug...The high-temperature mechanical properties and microstructure of forging billets of C-Si-Mn-Cr and C-Si-Mn-Cr-Mo ultra-high-strength cold-rolled steels（tensile strength≥1000 MPa,elongation≥10%） were studied.Through the comparison of reduction in area and hot deformation resistance at 600-1300°C,the Mo-containing steel was found to possess a higher strength and a better plasticity than the Mo-free one.The equilibrium phase diagram and atom fraction of Mo in different phases at different temperatures were calculated by Thermo-Calc software（TCW）.The results analyzed by using transmission electron microscopy and TCW show that precipitates in the Mo-containing steel are primarily M23C6,which promote pearlite formation.The experimental data also show that a lower ductility point existing in the Mo-free steel at 850°C is eliminated in the Mo-containing one.This is mainly due to the segregation of Mo at grain boundaries investigated by electron probe microanalysis（EPMA）,which improves the strength of grain boundaries.展开更多
The basic high-temperature properties of iron ore play a crucial role in optimizing sintering and ore blending,but the testing process for these properties is complex and has significant lag time,which cannot meet the...The basic high-temperature properties of iron ore play a crucial role in optimizing sintering and ore blending,but the testing process for these properties is complex and has significant lag time,which cannot meet the actual needs of ore blending.A prediction model for the basic high-temperature properties of iron ore fines was thus proposed based on a combination of machine learning algorithms and genetic algorithms.First,the prediction accuracy of different machine learning models for the basic high-temperature properties of iron ore fines was compared.Then,a random forest model optimized by genetic algorithms was built,further improving the prediction accuracy of the model.The test results show that the random forest model optimized by genetic algorithms has the highest prediction accuracy for the lowest assimilation temperature and liquid phase fluidity of iron ore,with a determination coefficient of 0.903 for the lowest assimilation temperature and 0.927 for the liquid phase fluidity after optimization.The trained model meets the fluctuation requirements of on-site testing and has been successfully applied to actual production on site.展开更多
The phase transformation and mechanical behavior of Ti-43Al-9V-0.2Y alloy under varied heat treatments were systematically investigated.The cooling phase sequence is identified as β→β+α→α→γ+α(α_(2))→β+γ+...The phase transformation and mechanical behavior of Ti-43Al-9V-0.2Y alloy under varied heat treatments were systematically investigated.The cooling phase sequence is identified as β→β+α→α→γ+α(α_(2))→β+γ+α(α_(2))→β(β_(0))+γ.Above 1240℃,slow cooling forms lamellar structures via α→γ+α(α_(2))→β+γ+α(α_(2)),while fast cooling follows α→γ+α→β(β_(0))+γ;below 1240℃,α→γ+α(α_(2))dominates.At 800℃ and 1.0×10^(−4)s^(−1),γphase in duplex microstructures restricts dislocation slip due to low stacking fault energy,promoting dynamic recrystallization.Mixed microstructure(γ/β_(0) lamellar and duplex microstructure)achieves a remarkable strength-ductility product of 4907 MPa%through synergistic effects:the duplex enhances plasticity,while the lamellar improves strength.In both microstructures,limited dislocation slip/climb in β_(0) phases creates dislocation density gradients at γ/β_(0) interfaces,inducing micro-void nucleation and microcracks in β_(0).γ phase impedes defect propagation,and micro-voids further suppress crack growth.The crack propagation in α_(2)/γ lamellar microstructure depends on stress direction:parallel stress hinders crack initiation and growth,while perpendicular stress promotes crack nucleation and expansion.展开更多
(TiZrHf)_(50)Ni_(30)Cu_(20-x)Co_(x)(x=2,4,6,at%)high-entropy high-temperature shape memory alloys were fabricated by watercooled copper crucible in a magnetic levitation vacuum melting furnace,and the effects of Co co...(TiZrHf)_(50)Ni_(30)Cu_(20-x)Co_(x)(x=2,4,6,at%)high-entropy high-temperature shape memory alloys were fabricated by watercooled copper crucible in a magnetic levitation vacuum melting furnace,and the effects of Co content on microstructure and mechanical properties were investigated.The results indicate that the grain size of the alloy decreases with increasing the Co content.In the as-cast state,the alloy consists primarily of the B19′phase,with a trace of B2 phase.The fracture morphology is predominantly composed of the B19′phase,whereas the B2 phase is nearly absent.Increasing the Co content or reducing the sample dimensions(d)markedly enhance the compressive strength and ductility of the alloy.When d=2 mm,the(TiZrHf)_(50)Ni_(30)Cu_(14)Co_(6) alloy demonstrates the optimal mechanical properties,achieving a compressive strength of 2142.39±1.8 MPa and a plasticity of 17.31±0.3%.The compressive cyclic test shows that with increasing the compressive strain,the residual strain of the(TiZrHf)_(50)Ni_(30)Cu_(14)Co_(6) alloy increases while the recovery ability declines.The superelastic recovery capability of the alloy is continuously enhanced.The superelastic recovery rate increases from 1.36%to 2.12%,the residual strain rate rises from 1.79%to 5.52%,the elastic recovery rate ascends from 3.86%to 7.36%,while the total recovery rate declines from 74.48%to 63.20%.展开更多
Surface recrystallization(RX) is a typical grain defect observed in directionally solidified(DS) Ni-based superalloys. Most studies have focused on the RX behavior and its impact on the mechanical properties of single...Surface recrystallization(RX) is a typical grain defect observed in directionally solidified(DS) Ni-based superalloys. Most studies have focused on the RX behavior and its impact on the mechanical properties of single-crystal(SC) superalloys, with limited research on its influence on the high-temperature mechanical properties of DS superalloys. This study systematically investigated the effect of RX on the high-temperature tensile properties of a DS DZ409 superalloy. The results show that at 650℃, the yield strength decreases almost linearly with an increase in RX fraction. A significant reduction in elongation is observed as the RX fraction increases from 0% to 4.9%. However, beyond this point, further increase in RX fraction leads to minimal changes in elongation. At 950℃, both yield strength and elongation decrease as the RX fraction increases from 0% to 4.9%. At 650℃, fractures in the RX DS superalloys exhibit a mixed mode of transgranular and intergranular cleavage fracture, while at 950℃, it features a combination of ductile and intergranular dimple fractures. The failure mechanism of the RX DS superalloy is associated with the introduction of transverse grain boundaries(GBs) during RX. In the early stages of tensile testing at intermediate and high temperatures, cracks can easily initiate at these GBs. Subsequently, the cracks propagate along the GBs into the DS matrix, ultimately leading to failure of the DS superalloy.展开更多
Low-to medium-maturity oil shale resources display substantial reserves, offering promising prospects for in-situ conversion inChina. Investigating the evolution of the mechanical properties of the reservoir and capro...Low-to medium-maturity oil shale resources display substantial reserves, offering promising prospects for in-situ conversion inChina. Investigating the evolution of the mechanical properties of the reservoir and caprock under in-situ high-temperature and confine-ment conditions is of considerable importance. Compared to conventional mechanical experiments on rock samples after high-temperat-ure treatment, in-situ high-temperature experiments can more accurately characterize the behavior of rocks in practical engineering,thereby providing a more realistic reflection of their mechanical properties. In this study, an in-situ high-temperature triaxial compressiontesting machine is developed to conduct in-situ compression tests on sandstone at different temperatures(25, 200, 400, 500, and 650℃)and confining pressures(0, 10, and 20 MPa). Based on the experimental results, the temperature-dependent changes in compressivestrength, peak strain, elastic modulus, Poisson's ratio, cohesion, and internal friction angle are thoroughly analyzed and discussed. Resultsindicate that the mass of sandstone gradually decreases as the temperature increases. The thermal conductivity and thermal diffusivity ofsandstone exhibit a linear relationship with temperature. Peak stress decreases as the temperature rises, while it increases with higher con-fining pressures. Notably, the influence of confining pressure on peak stress diminishes at higher temperatures. Additionally, as the tem-perature rises, the Poisson's ratio of sandstone decreases. The internal friction angle also decreases with increasing temperature, with 400℃ acting as the threshold temperature. Interestingly, under uniaxial conditions, the damage stress of sandstone is less affected by tem-perature. However, when the confining pressure is 10 or 20 MPa, the damage stress decreases as the temperature increases. This study en-hances our understanding of the influence of in-situ high-temperature and confinement conditions on the mechanical properties of sand-stone strata. The study also provides valuable references and experimental data that support the development of low-to medium-maturityoil shale resources.展开更多
The high-temperature mechanical properties of Ta-8W-2Hf alloy doped with Re(1wt%)and C(0.01wt%)were investigated at room temperature,1300℃,and 1500℃.Results show that fine and dispersed precipitates Ta2C are detecte...The high-temperature mechanical properties of Ta-8W-2Hf alloy doped with Re(1wt%)and C(0.01wt%)were investigated at room temperature,1300℃,and 1500℃.Results show that fine and dispersed precipitates Ta2C are detected in crystallized TaWHfReC alloy,which significantly enhance mechanical properties of the alloy.The strength of TaWHfReC alloy is much higher than that of TaWHf alloy,especially at 1300 and 1500℃.At 1300℃,the ultimate tensile strength of the TaWHf alloy is 322 MPa,while that of the TaWHfReC alloy reaches 392 MPa.When the temperature rises to 1500℃,precipitated-phase strengthening remains effective in the TaWHfReC alloy,achieving an ultimate tensile strength of 268 MPa.Additionally,at 1300℃,the elongation of the TaWHfReC alloy reaches 23.5%,which is nearly twice of that of the TaWHf alloy.The significant improvement in the mechanical properties of the TaWHfReC alloy at elevated temperatures is primarily attributed to the interaction between dislocations and the fine Ta2C precipitated phase.The fine and uniformly distributed particles effectively inhibit dislocation motion and exhibit a pronounced strengthening effect at high temperatures.展开更多
High-temperature and short-time(HTST)solution heat treatment combined with non-isothermal aging(NIA)was employed to regulate the microstructure and properties of Al−4.5Mg−2.0Zn−0.3Ag alloy.Results indicate that HTST s...High-temperature and short-time(HTST)solution heat treatment combined with non-isothermal aging(NIA)was employed to regulate the microstructure and properties of Al−4.5Mg−2.0Zn−0.3Ag alloy.Results indicate that HTST solution heat treatment can not only retain partial deformation dislocations,but inhibit the recrystallization behavior and increase the proportion of low-angle grain boundaries(LAGBs).In the subsequent NIA process,HTST solution heat treatment combined with NIA is instrumental in restraining the degradation of dislocations and promoting precipitation of nano-scale T'-Mg_(32)(Al,Zn,Ag)49 phase,which improves the strength of the alloy greatly.In addition,a higher fraction of LAGBs and the discontinuous distribution of grain boundary precipitates caused by this novel technology meliorate the corrosion resistance of Al−4.5Mg−2.0Zn−0.3Ag alloy.展开更多
1.Introduction Titanium alloys are widely used in aerospace and weaponry manufacturing due to their high specific strength,low density,heat and corrosion resistance[1,2].However,new titanium alloys with excellent room...1.Introduction Titanium alloys are widely used in aerospace and weaponry manufacturing due to their high specific strength,low density,heat and corrosion resistance[1,2].However,new titanium alloys with excellent room-temperature and high-temperature mechani-cal properties remain rare and hard to obtain in industries such as aerospace,marine engineering and equipment manufacturing[3,4].展开更多
The physical and mechanical properties of metal matrix composites were improved by the addition of reinforcements. The mechanical properties of particulate-reinforced metal-matrix composites based on aluminium alloys ...The physical and mechanical properties of metal matrix composites were improved by the addition of reinforcements. The mechanical properties of particulate-reinforced metal-matrix composites based on aluminium alloys （6061 and 7015） at high temperatures were studied. Titanium diboride （TiB2） particles were used as the reinforcement. All the composites were produced by hot extrusion. The tensile properties and fracture characteristics of these materials were investigated at room temperature and at high temperatures to determine their ultimate strength and strain to failure. The fracture surface was analysed by scanning electron microscopy. TiB2 particles provide high stability of the alumin- ium alloys （6061 and 7015） in the fabrication process. An improvement in the mechanical behaviour was achieved by adding TiB2 particles as reinforcement in both the aluminium alloys. Adding TiB2 particles reduces the ductility of the aluminium alloys but does not change the microscopic mode of failure, and the fracture surface exhibits a ductile appearance with dimples formed by coalescence.展开更多
The well-densified Ni3Al-0.5B-5Cr alloy was fabricated by self-propagation high-temperature synthesis and extrusion technique. Microstructure examination shows that the synthesized alloy has fine microstructure and co...The well-densified Ni3Al-0.5B-5Cr alloy was fabricated by self-propagation high-temperature synthesis and extrusion technique. Microstructure examination shows that the synthesized alloy has fine microstructure and contains Ni3Al, Al2O3, Ni3B and Cr3Ni2 phases. Moreover, the self-propagation high-temperature synthesis and extrusion lead to great deformation and recrystallization in the alloy, which helps to refine the microstructure and weaken the misorientation. In addition, the subsequent extrusion procedure redistributes the Al2O3 particles and eliminates the γ-Ni phase. Compared with the alloy synthesized without extrusion, the Ni3Al-0.5B-5Cr alloy fabricated by self-propagation high-temperature synthesis and extrusion has better room temperature mechanical properties, which should be ascribed to the microstructure evolution.展开更多
The microstructures and properties of the Zn-Cu-Bi-Sn(ZCBS) high-temperature solders with various Sn contents were studied using differential scanning calorimetry(DSC),scanning electron microscopy(SEM) and X-ray diffr...The microstructures and properties of the Zn-Cu-Bi-Sn(ZCBS) high-temperature solders with various Sn contents were studied using differential scanning calorimetry(DSC),scanning electron microscopy(SEM) and X-ray diffraction(XRD).The results indicate that the increase of Sn content can both decrease the melting temperature and melting range of ZCBS solders and it can also effectively improve the wettability on Cu substrate.The shear strength of solder joints reaches a maximum value with the Sn addition of 5%(mass fraction),which is attributed to the formation of refined β-Sn and primary ε-CuZn_5 phases in η-Zn matrix.However,when the content of Sn exceeds 5%,the shear strength decreases due to the formation of coarse β-Sn phase,which is net-shaped presented at the grain boundary.展开更多
Cf/Al composites and TiAl alloys were joined by laser ignited self-propagating high-temperature synthesis（SHS） with Ni-Al-Ti interlayer. The effect of Ti-Al content on interfacial microstructure and mechanical prope...Cf/Al composites and TiAl alloys were joined by laser ignited self-propagating high-temperature synthesis（SHS） with Ni-Al-Ti interlayer. The effect of Ti-Al content on interfacial microstructure and mechanical properties of the joints was investigated. Localized melt of the substrates occurred in the joints. γ-Ni0.35Al0.30Ti0.35, NiA l3 and Ni2Al3 reaction layers formed adjacent to the substrates. Joint flaws, such as pores and cracks, made the joint density decrease and worked as the fracture source, which led to the sharp decline of joint strength. Additive Ti-Al increased joint density and strengthened the interlayer adhesion to Cf/Al. The joint flaws could be controlled by changing the Ti-Al content. When the Ti-Al content was 0.1, the joint was free of cracks with high density and reached the maximum shear strength of 24.12 MPa.展开更多
This study investigates the properties of high-purity starches extracted from Polygonum multiflorum(PMS)and Smilax glabra(SGS).The starches were characterized by scanning electron microscopy,Fouriertransform infrared ...This study investigates the properties of high-purity starches extracted from Polygonum multiflorum(PMS)and Smilax glabra(SGS).The starches were characterized by scanning electron microscopy,Fouriertransform infrared spectroscopy,X-ray diffraction,high-performance anion-exchange chromatography,and differential scanning calorimetry.Significant differences were observed in their morphological,physicochemical,and functional properties.PMS had a smaller particle size(13.68 μm),irregular polygonal shape,A-type,lower water absorption(62.67 %),and higher oil absorption(51.17 %).In contrast,SGS exhibited larger particles(31.75 μm),a nearly spherical shape,B-type,higher crystallinity(50.66 %),and greater amylose content(21.54 %),with superior thermal stability,shear resistance,and gelatinization enthalpy.SGS also contained higher resistant starch(83.28 %) and longer average chain length(20.58 %),but showed lower solubility,swelling power,light transmittance,and freeze-thaw stability.The physicochemical properties differences in crystal pattern and particle morphology between PMS and SGS lead to distinct behaviors during in vitro digestion and fermentation.These findings highlight the potential of medicinal plant starches in functional ingredients and industrial processes.展开更多
To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretre...To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretreatment was employed to construct a Ta_(2)O_(5)ceramic layer on the Ta12W alloy surface.Subsequently,a slurry spraying-vacuum sintering method was used to prepare a Si-Cr-Ti-Zr coating on the pretreated substrate.Comparative studies were conducted on the microstructure,phase composition,and isothermal oxidation resistance(at 1600℃)of the as-prepared coatings with and without the micro-arc oxidation ceramic layer.The results show that the Ta_(2)O_(5)layer prepared at 400 V is more continuous and has smaller pores than that prepared at 350 V.After microarc oxidation pretreatment,the Si-Cr-Ti-Zr coating on Ta12W alloy consists of three distinct layers:an upper layer dominated by Ti_(5)Si_(3),Ta_(5)Si_(3),and ZrSi;a middle layer dominated by TaSi_(2);a coating/substrate interfacial reaction layer dominated by Ta_(5)Si_(3).Both the Si-Cr-Ti-Zr coatings with and without the Ta_(2)O_(5)ceramic layer do not fail after isothermal oxidation at 1600℃for 5 h.Notably,the addition of the Ta2O5 ceramic layer reduces the high-temperature oxidation rate of the coating.展开更多
Herein,antibacterial silver‑doped fluorescent carbon dots(Ag‑CDs)were synthesized through a stepwise hydrothermal method,with polyethyleneimine(PEI),citric acid(CA),and silver nitrate(AgNO3)serving as precursors.The a...Herein,antibacterial silver‑doped fluorescent carbon dots(Ag‑CDs)were synthesized through a stepwise hydrothermal method,with polyethyleneimine(PEI),citric acid(CA),and silver nitrate(AgNO3)serving as precursors.The applicability and antimicrobial efficacy of these nanomaterials were systematically investigated for metal ion sensing.Experimental evidence demonstrated that the Ag‑CDs exhibited a pronounced fluorescence quenching response toward ferric ions(Fe^(3+)),enabling their quantitative determination via a linear concentration‑dependent relationship.These Ag‑CDs exhibited significant inhibitory effects on biofilm growth and disruption for both Escherichia coli and Staphylococcus aureus.Mechanism investigations indicate that Ag‑CDs induced the death of Escherichia coli and Pseudomonas aeruginosa by disrupting their bacterial morphology and structure,triggering the generation of intracellular reactive oxygen species(ROS),and impairing their antioxidant defense system.展开更多
基金supported by the National Natural Science Foun-dation of China(Nos.52127802 and 52431008).
文摘Commercial wrought high-strength Cu-Cr-Zr alloys face limited high-temperature properties due to the rapid coarsening or dissolution of Cr precipitates.Here,we report a laser powder bed fusion(LPBF)fabricated Cu-0.84Cr-0.42Zr(wt.%)alloy with exceptional heat resistance after aging.Primary Cr@Cu_(5)Zr phase(∼39.8 nm)with core-shell structure and a high density of heat-stable dislocations were intro-duced from the rapid solidification of LPBF and enabled the alloy to gain significant improvement in high-temperature properties.After aging treatment,secondary Cr and Cu_(51)Zr_(14)phases(∼3.4 nm)were precipitated,in which Zr solute was segregated at one side of the Cr phase,enhancing the thermal sta-bility of Cr phase.The excellent combinations of strength and thermal conductivity were achieved at or above 400℃.Particularly at 600℃,the aged sample not only exhibited a high tensile strength of∼196 MPa,which significantly surpassed that of wrought Cu-Cr-Zr alloys,but also possessed a thermal conductivity of∼349 W/(m K)comparable to that of pure copper.
基金support from the National Natural Science Foundation of China(Grant Nos.52072274,52272021,U23A20559 and 52232002)the Open Foundation of State Key Laboratory of Advanced Refractories(No.SKLAR202207)+1 种基金the Key Laboratory of Hubei Province for Coal Conversion and New Carbon Materials(Wuhan University of Science and Technology,WKDM202201)the Open/Innovation Foundation of Hubei Three Gorges Laboratory(SK232006).
文摘h-BN rods modified low-carbon alumina-carbon(Al_(2)O_(3)-C)refractories were prepared,and the effect of h-BN rod addition on the high-temperature properties was investigated and compared with commercial h-BN flake,carbon black,and carbon nanotubes additives.The results demonstrated that Al_(2)O_(3)-C refractories containing h-BN rods exhibited optimal high-temperature service performances,including 25%higher hot modulus of rupture,21.3%higher thermal shock strength residual ratio,20.9%lower in oxidation and 44.3%less in slag corrosion,compared to the counterpart specimens without additives.Moreover,benefiting from the synergistic enhancement of the rod-like h-BN and in-situ generated SiC whiskers,the high-temperature service performances of h-BN rods containing specimens outperformed counterpart specimens containing commercial h-BN flake,carbon black,and carbon nanotubes,respectively.
基金supported by the Key R&D Program of Shandong Province of China(Grant number 2019QYTPY057)the Natural Science Foundation of Shandong Province of China(Grant numbers ZR2020ME110,ZR2021ME023)。
文摘This study focuses on finding a solution to the sharp decline in mechanical properties of Al-Si-Cu-Mg alloys due to rapid coarsening of traditional intermediate phases at high temperature.A new type of modified al oy,to be used in automobile engines at high temperatures,was prepared by adding Zr and Mo into Al-Si-Cu-Mg alloy.The synergistic effects of Zr and Mo on the microstructure evolution and high-temperature mechanical properties were studied.Results show that the addition of Zr and Mo generates a series of intermetallic phases dispersed in the alloy.They can improve the strength of the alloy by hindering dislocation movement and crack propagation.In addition,some nano-strengthened phases show coherent interfaces with the matrix and improve grain refinement.The addition of Mo greatly improves the heat resistance of the alloy.The extremely low diffusivity of Mo enables it to improve the thermal stability of the intermetallic phases,inhibit precipitation during aging,reduce the size of the precipitates,and improve the heat resistance of the alloy.
基金the Natural Science Foundation of Shandong Province(ZR2017MEE021),China。
文摘Fe-based composite coatings were fabricated on 5 CrNiMo die steel by laser beam melting a precursor mixture of ferrotitanium,ferrochromium,ferromolybdenum,B4 C and Y2 O3 powders.Micro structure and properties of the coatings were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),energy-dispersive spectrometer(EDS),resistance furnace and high-temperature tribometer.The results show that(Ti,Mo)C particles with flower-like and(Ti,Mo)B2 with block-like shapes are in situ formed during laser cladding.Volume faction of multiple ceramic particles increases with the increasing of Y2 O3.The cumulative oxidation mass of the coating with 2 wt% Y2 O3 is decreased by one-third than that of the coating without Y2 O3.The oxidation layer of the coating with Y2 O3 is getting smooth.Meanwhile,high temperature wear volume loss of the coating with 2 wt% Y2 O3 is about 40% that of the coating without Y2 O3.The coating with 2 wt% Y2 O3 shows a smoother wear scar and few flat grooves are observed after high temperature wear test.
基金supported by the National High-tech Research and Development Program of China (No.2009AA03Z518)
文摘The high-temperature mechanical properties and microstructure of forging billets of C-Si-Mn-Cr and C-Si-Mn-Cr-Mo ultra-high-strength cold-rolled steels（tensile strength≥1000 MPa,elongation≥10%） were studied.Through the comparison of reduction in area and hot deformation resistance at 600-1300°C,the Mo-containing steel was found to possess a higher strength and a better plasticity than the Mo-free one.The equilibrium phase diagram and atom fraction of Mo in different phases at different temperatures were calculated by Thermo-Calc software（TCW）.The results analyzed by using transmission electron microscopy and TCW show that precipitates in the Mo-containing steel are primarily M23C6,which promote pearlite formation.The experimental data also show that a lower ductility point existing in the Mo-free steel at 850°C is eliminated in the Mo-containing one.This is mainly due to the segregation of Mo at grain boundaries investigated by electron probe microanalysis（EPMA）,which improves the strength of grain boundaries.
基金the National Natural Science Foundation of China(52204335)the Cross-disciplinary Research Project for Young Teachers of the University of Science and Technology Beijing(FRF-IDRY-22-004).
文摘The basic high-temperature properties of iron ore play a crucial role in optimizing sintering and ore blending,but the testing process for these properties is complex and has significant lag time,which cannot meet the actual needs of ore blending.A prediction model for the basic high-temperature properties of iron ore fines was thus proposed based on a combination of machine learning algorithms and genetic algorithms.First,the prediction accuracy of different machine learning models for the basic high-temperature properties of iron ore fines was compared.Then,a random forest model optimized by genetic algorithms was built,further improving the prediction accuracy of the model.The test results show that the random forest model optimized by genetic algorithms has the highest prediction accuracy for the lowest assimilation temperature and liquid phase fluidity of iron ore,with a determination coefficient of 0.903 for the lowest assimilation temperature and 0.927 for the liquid phase fluidity after optimization.The trained model meets the fluctuation requirements of on-site testing and has been successfully applied to actual production on site.
基金supported by the National Natural Science Foundation of China(Nos.52201035 and FRF-TP-24-010A).
文摘The phase transformation and mechanical behavior of Ti-43Al-9V-0.2Y alloy under varied heat treatments were systematically investigated.The cooling phase sequence is identified as β→β+α→α→γ+α(α_(2))→β+γ+α(α_(2))→β(β_(0))+γ.Above 1240℃,slow cooling forms lamellar structures via α→γ+α(α_(2))→β+γ+α(α_(2)),while fast cooling follows α→γ+α→β(β_(0))+γ;below 1240℃,α→γ+α(α_(2))dominates.At 800℃ and 1.0×10^(−4)s^(−1),γphase in duplex microstructures restricts dislocation slip due to low stacking fault energy,promoting dynamic recrystallization.Mixed microstructure(γ/β_(0) lamellar and duplex microstructure)achieves a remarkable strength-ductility product of 4907 MPa%through synergistic effects:the duplex enhances plasticity,while the lamellar improves strength.In both microstructures,limited dislocation slip/climb in β_(0) phases creates dislocation density gradients at γ/β_(0) interfaces,inducing micro-void nucleation and microcracks in β_(0).γ phase impedes defect propagation,and micro-voids further suppress crack growth.The crack propagation in α_(2)/γ lamellar microstructure depends on stress direction:parallel stress hinders crack initiation and growth,while perpendicular stress promotes crack nucleation and expansion.
基金National Natural Science Foundation of China(12404230,52061027)Science and Technology Program Project of Gansu Province(22YF7GA155)+1 种基金Lanzhou Youth Science and Technology Talent Innovation Project(2023-QN-91)Zhejiang Provincial Natural Science Foundation of China(LY23E010002)。
文摘(TiZrHf)_(50)Ni_(30)Cu_(20-x)Co_(x)(x=2,4,6,at%)high-entropy high-temperature shape memory alloys were fabricated by watercooled copper crucible in a magnetic levitation vacuum melting furnace,and the effects of Co content on microstructure and mechanical properties were investigated.The results indicate that the grain size of the alloy decreases with increasing the Co content.In the as-cast state,the alloy consists primarily of the B19′phase,with a trace of B2 phase.The fracture morphology is predominantly composed of the B19′phase,whereas the B2 phase is nearly absent.Increasing the Co content or reducing the sample dimensions(d)markedly enhance the compressive strength and ductility of the alloy.When d=2 mm,the(TiZrHf)_(50)Ni_(30)Cu_(14)Co_(6) alloy demonstrates the optimal mechanical properties,achieving a compressive strength of 2142.39±1.8 MPa and a plasticity of 17.31±0.3%.The compressive cyclic test shows that with increasing the compressive strain,the residual strain of the(TiZrHf)_(50)Ni_(30)Cu_(14)Co_(6) alloy increases while the recovery ability declines.The superelastic recovery capability of the alloy is continuously enhanced.The superelastic recovery rate increases from 1.36%to 2.12%,the residual strain rate rises from 1.79%to 5.52%,the elastic recovery rate ascends from 3.86%to 7.36%,while the total recovery rate declines from 74.48%to 63.20%.
基金supported by the National Science and Technology Major Project(No.HT-J2019-VI-0020-0136)the National Youth Talent Support Program,and the Fundamental Research Funds for the Central Universities(No.xtr072024004).
文摘Surface recrystallization(RX) is a typical grain defect observed in directionally solidified(DS) Ni-based superalloys. Most studies have focused on the RX behavior and its impact on the mechanical properties of single-crystal(SC) superalloys, with limited research on its influence on the high-temperature mechanical properties of DS superalloys. This study systematically investigated the effect of RX on the high-temperature tensile properties of a DS DZ409 superalloy. The results show that at 650℃, the yield strength decreases almost linearly with an increase in RX fraction. A significant reduction in elongation is observed as the RX fraction increases from 0% to 4.9%. However, beyond this point, further increase in RX fraction leads to minimal changes in elongation. At 950℃, both yield strength and elongation decrease as the RX fraction increases from 0% to 4.9%. At 650℃, fractures in the RX DS superalloys exhibit a mixed mode of transgranular and intergranular cleavage fracture, while at 950℃, it features a combination of ductile and intergranular dimple fractures. The failure mechanism of the RX DS superalloy is associated with the introduction of transverse grain boundaries(GBs) during RX. In the early stages of tensile testing at intermediate and high temperatures, cracks can easily initiate at these GBs. Subsequently, the cracks propagate along the GBs into the DS matrix, ultimately leading to failure of the DS superalloy.
基金financially supported by the Beijing Natural Science Foundation,China (No.JQ21028)the National Natural Science Foundation of China (Nos.52311530070,52278326,and 52004015)+2 种基金the Major National Science and Technology Project for Deep Earth,China (No.2024ZD1003805)the Project from PetroChina RIPED:the Study on the evolution law of Mineral Structure and Rock Mechanical Properties Under Ultra-High Temperature Conditions (No.2022-KFKT-02)the Fundamental Research Funds for the Central Universities of China (No.FRF-IDRY-20-003,Interdisciplinary Research Project for Young Teachers of USTB)。
文摘Low-to medium-maturity oil shale resources display substantial reserves, offering promising prospects for in-situ conversion inChina. Investigating the evolution of the mechanical properties of the reservoir and caprock under in-situ high-temperature and confine-ment conditions is of considerable importance. Compared to conventional mechanical experiments on rock samples after high-temperat-ure treatment, in-situ high-temperature experiments can more accurately characterize the behavior of rocks in practical engineering,thereby providing a more realistic reflection of their mechanical properties. In this study, an in-situ high-temperature triaxial compressiontesting machine is developed to conduct in-situ compression tests on sandstone at different temperatures(25, 200, 400, 500, and 650℃)and confining pressures(0, 10, and 20 MPa). Based on the experimental results, the temperature-dependent changes in compressivestrength, peak strain, elastic modulus, Poisson's ratio, cohesion, and internal friction angle are thoroughly analyzed and discussed. Resultsindicate that the mass of sandstone gradually decreases as the temperature increases. The thermal conductivity and thermal diffusivity ofsandstone exhibit a linear relationship with temperature. Peak stress decreases as the temperature rises, while it increases with higher con-fining pressures. Notably, the influence of confining pressure on peak stress diminishes at higher temperatures. Additionally, as the tem-perature rises, the Poisson's ratio of sandstone decreases. The internal friction angle also decreases with increasing temperature, with 400℃ acting as the threshold temperature. Interestingly, under uniaxial conditions, the damage stress of sandstone is less affected by tem-perature. However, when the confining pressure is 10 or 20 MPa, the damage stress decreases as the temperature increases. This study en-hances our understanding of the influence of in-situ high-temperature and confinement conditions on the mechanical properties of sand-stone strata. The study also provides valuable references and experimental data that support the development of low-to medium-maturityoil shale resources.
基金Supported by Shaanxi Provincial Department of Science and Technology(2024GX-YBXM-362)Supported by Northwest Institute for Nonferrous Metal Research(070YC2314)+1 种基金Key R&D Plan of Shaanxi Province(2024QCYKXJ-116)Scientific and Technological Innovation Team Project of Shaanxi Innovation Capability Support Plan of China(2022TD-30)。
文摘The high-temperature mechanical properties of Ta-8W-2Hf alloy doped with Re(1wt%)and C(0.01wt%)were investigated at room temperature,1300℃,and 1500℃.Results show that fine and dispersed precipitates Ta2C are detected in crystallized TaWHfReC alloy,which significantly enhance mechanical properties of the alloy.The strength of TaWHfReC alloy is much higher than that of TaWHf alloy,especially at 1300 and 1500℃.At 1300℃,the ultimate tensile strength of the TaWHf alloy is 322 MPa,while that of the TaWHfReC alloy reaches 392 MPa.When the temperature rises to 1500℃,precipitated-phase strengthening remains effective in the TaWHfReC alloy,achieving an ultimate tensile strength of 268 MPa.Additionally,at 1300℃,the elongation of the TaWHfReC alloy reaches 23.5%,which is nearly twice of that of the TaWHf alloy.The significant improvement in the mechanical properties of the TaWHfReC alloy at elevated temperatures is primarily attributed to the interaction between dislocations and the fine Ta2C precipitated phase.The fine and uniformly distributed particles effectively inhibit dislocation motion and exhibit a pronounced strengthening effect at high temperatures.
基金National Natural Science Foundation of China(Nos.52204400,52204401)Natural Science Foundation of Hebei Province,China(No.E2022203033)。
文摘High-temperature and short-time(HTST)solution heat treatment combined with non-isothermal aging(NIA)was employed to regulate the microstructure and properties of Al−4.5Mg−2.0Zn−0.3Ag alloy.Results indicate that HTST solution heat treatment can not only retain partial deformation dislocations,but inhibit the recrystallization behavior and increase the proportion of low-angle grain boundaries(LAGBs).In the subsequent NIA process,HTST solution heat treatment combined with NIA is instrumental in restraining the degradation of dislocations and promoting precipitation of nano-scale T'-Mg_(32)(Al,Zn,Ag)49 phase,which improves the strength of the alloy greatly.In addition,a higher fraction of LAGBs and the discontinuous distribution of grain boundary precipitates caused by this novel technology meliorate the corrosion resistance of Al−4.5Mg−2.0Zn−0.3Ag alloy.
基金supported by the National Natural Science Foundation of China(Nos.52125405,52171122,52371117 and 52271118)the Program for the Innovative Talents of Higher Education Institutions of Shanxi(2024Q005).
文摘1.Introduction Titanium alloys are widely used in aerospace and weaponry manufacturing due to their high specific strength,low density,heat and corrosion resistance[1,2].However,new titanium alloys with excellent room-temperature and high-temperature mechani-cal properties remain rare and hard to obtain in industries such as aerospace,marine engineering and equipment manufacturing[3,4].
文摘The physical and mechanical properties of metal matrix composites were improved by the addition of reinforcements. The mechanical properties of particulate-reinforced metal-matrix composites based on aluminium alloys （6061 and 7015） at high temperatures were studied. Titanium diboride （TiB2） particles were used as the reinforcement. All the composites were produced by hot extrusion. The tensile properties and fracture characteristics of these materials were investigated at room temperature and at high temperatures to determine their ultimate strength and strain to failure. The fracture surface was analysed by scanning electron microscopy. TiB2 particles provide high stability of the alumin- ium alloys （6061 and 7015） in the fabrication process. An improvement in the mechanical behaviour was achieved by adding TiB2 particles as reinforcement in both the aluminium alloys. Adding TiB2 particles reduces the ductility of the aluminium alloys but does not change the microscopic mode of failure, and the fracture surface exhibits a ductile appearance with dimples formed by coalescence.
基金Project (2012CB933600) supported by the National Basic Research Program of ChinaProject (2011AA030104) supported by the National High-tech Research and Development Program of ChinaProject (JC200903170498A) supported by the Science and Technology Research Foundation of Shenzhen Bureau of Science and Technology & Information, China
文摘The well-densified Ni3Al-0.5B-5Cr alloy was fabricated by self-propagation high-temperature synthesis and extrusion technique. Microstructure examination shows that the synthesized alloy has fine microstructure and contains Ni3Al, Al2O3, Ni3B and Cr3Ni2 phases. Moreover, the self-propagation high-temperature synthesis and extrusion lead to great deformation and recrystallization in the alloy, which helps to refine the microstructure and weaken the misorientation. In addition, the subsequent extrusion procedure redistributes the Al2O3 particles and eliminates the γ-Ni phase. Compared with the alloy synthesized without extrusion, the Ni3Al-0.5B-5Cr alloy fabricated by self-propagation high-temperature synthesis and extrusion has better room temperature mechanical properties, which should be ascribed to the microstructure evolution.
基金Project(20115003)supported by the Program for the Development of Science and Technology of Jilin Province,China
文摘The microstructures and properties of the Zn-Cu-Bi-Sn(ZCBS) high-temperature solders with various Sn contents were studied using differential scanning calorimetry(DSC),scanning electron microscopy(SEM) and X-ray diffraction(XRD).The results indicate that the increase of Sn content can both decrease the melting temperature and melting range of ZCBS solders and it can also effectively improve the wettability on Cu substrate.The shear strength of solder joints reaches a maximum value with the Sn addition of 5%(mass fraction),which is attributed to the formation of refined β-Sn and primary ε-CuZn_5 phases in η-Zn matrix.However,when the content of Sn exceeds 5%,the shear strength decreases due to the formation of coarse β-Sn phase,which is net-shaped presented at the grain boundary.
基金Project(51075101)supported by the National Natural Science Foundation of China
文摘Cf/Al composites and TiAl alloys were joined by laser ignited self-propagating high-temperature synthesis（SHS） with Ni-Al-Ti interlayer. The effect of Ti-Al content on interfacial microstructure and mechanical properties of the joints was investigated. Localized melt of the substrates occurred in the joints. γ-Ni0.35Al0.30Ti0.35, NiA l3 and Ni2Al3 reaction layers formed adjacent to the substrates. Joint flaws, such as pores and cracks, made the joint density decrease and worked as the fracture source, which led to the sharp decline of joint strength. Additive Ti-Al increased joint density and strengthened the interlayer adhesion to Cf/Al. The joint flaws could be controlled by changing the Ti-Al content. When the Ti-Al content was 0.1, the joint was free of cracks with high density and reached the maximum shear strength of 24.12 MPa.
基金supported by the National Natural Science Foundation of China (No.82174074)。
文摘This study investigates the properties of high-purity starches extracted from Polygonum multiflorum(PMS)and Smilax glabra(SGS).The starches were characterized by scanning electron microscopy,Fouriertransform infrared spectroscopy,X-ray diffraction,high-performance anion-exchange chromatography,and differential scanning calorimetry.Significant differences were observed in their morphological,physicochemical,and functional properties.PMS had a smaller particle size(13.68 μm),irregular polygonal shape,A-type,lower water absorption(62.67 %),and higher oil absorption(51.17 %).In contrast,SGS exhibited larger particles(31.75 μm),a nearly spherical shape,B-type,higher crystallinity(50.66 %),and greater amylose content(21.54 %),with superior thermal stability,shear resistance,and gelatinization enthalpy.SGS also contained higher resistant starch(83.28 %) and longer average chain length(20.58 %),but showed lower solubility,swelling power,light transmittance,and freeze-thaw stability.The physicochemical properties differences in crystal pattern and particle morphology between PMS and SGS lead to distinct behaviors during in vitro digestion and fermentation.These findings highlight the potential of medicinal plant starches in functional ingredients and industrial processes.
基金National Natural Science Foundation of China(52071274)Key Research and Development Projects of Shaanxi Province(2023-YBGY-442)Science and Technology Nova Project-Innovative Talent Promotion Program of Shaanxi Province(2020KJXX-062)。
文摘To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretreatment was employed to construct a Ta_(2)O_(5)ceramic layer on the Ta12W alloy surface.Subsequently,a slurry spraying-vacuum sintering method was used to prepare a Si-Cr-Ti-Zr coating on the pretreated substrate.Comparative studies were conducted on the microstructure,phase composition,and isothermal oxidation resistance(at 1600℃)of the as-prepared coatings with and without the micro-arc oxidation ceramic layer.The results show that the Ta_(2)O_(5)layer prepared at 400 V is more continuous and has smaller pores than that prepared at 350 V.After microarc oxidation pretreatment,the Si-Cr-Ti-Zr coating on Ta12W alloy consists of three distinct layers:an upper layer dominated by Ti_(5)Si_(3),Ta_(5)Si_(3),and ZrSi;a middle layer dominated by TaSi_(2);a coating/substrate interfacial reaction layer dominated by Ta_(5)Si_(3).Both the Si-Cr-Ti-Zr coatings with and without the Ta_(2)O_(5)ceramic layer do not fail after isothermal oxidation at 1600℃for 5 h.Notably,the addition of the Ta2O5 ceramic layer reduces the high-temperature oxidation rate of the coating.
文摘Herein,antibacterial silver‑doped fluorescent carbon dots(Ag‑CDs)were synthesized through a stepwise hydrothermal method,with polyethyleneimine(PEI),citric acid(CA),and silver nitrate(AgNO3)serving as precursors.The applicability and antimicrobial efficacy of these nanomaterials were systematically investigated for metal ion sensing.Experimental evidence demonstrated that the Ag‑CDs exhibited a pronounced fluorescence quenching response toward ferric ions(Fe^(3+)),enabling their quantitative determination via a linear concentration‑dependent relationship.These Ag‑CDs exhibited significant inhibitory effects on biofilm growth and disruption for both Escherichia coli and Staphylococcus aureus.Mechanism investigations indicate that Ag‑CDs induced the death of Escherichia coli and Pseudomonas aeruginosa by disrupting their bacterial morphology and structure,triggering the generation of intracellular reactive oxygen species(ROS),and impairing their antioxidant defense system.
