The volume change behavior of natural gas hydrate-bearing sediment is essential as it influences settlement,strength,and stiffness,which directly affect the stability of hydrate reservoirs during hydrate extraction or...The volume change behavior of natural gas hydrate-bearing sediment is essential as it influences settlement,strength,and stiffness,which directly affect the stability of hydrate reservoirs during hydrate extraction or in response to environmental changes.The volume change is influenced not only by stress but also by the formation and dissociation of hydrates.This study adopted a customized apparatus for one-dimensional compression tests,allowing independent control of gas pressure and effective stress.Tests were conducted on samples with different hydrate saturations along various temperature-gas pressure-effective stress paths,yielding some conclusions related to compressibility and creep.An unusual phenomenon was observed under low-stress conditions:hydrate formation led to shrinkage rather than expansion.Three potential mechanisms behind this occurrence were discussed.As hydrate saturation increases,the yield stress rises while the compression and swelling indexes remain minimally affected.After hydrate dissociation,the compression curve of hydrate-bearing sediment drops to that of hydrate-free sediment.Once hydrate is formed,the compression curve of hydrate-free sediment gradually approaches that of hydrate-bearing sediment during the subsequent loading.Under low-stress conditions,the creep of both hydrate-free and hydrate-bearing sediments is very weak.However,when stress increases,significantly beyond the yield stress,the creep of both sediments increases significantly,with hydrate-bearing sediment exhibiting much greater creep than hydrate-free sediment.展开更多
The water-quenched(WQ)2195 Al−Li alloy was subjected to stretching at different temperatures,from room temperature(RT)to−196℃(CT),to investigate the effect of cryogenic deformation on the aging precipitation behavior...The water-quenched(WQ)2195 Al−Li alloy was subjected to stretching at different temperatures,from room temperature(RT)to−196℃(CT),to investigate the effect of cryogenic deformation on the aging precipitation behaviors and mechanical properties.The precipitation kinetics of the T1 phase and the microstructures in peak aging state were investigated through the differential scanning calorimetric(DSC)tests and electron microscopy observation.The results show that−196℃deformation produces a high dislocation density,which promotes the precipitation of the T1 phase and refines its sizes significantly.In addition,the grain boundary precipitates(GBPs)of−196℃-stretched samples are suppressed considerably due to the high dislocation density in the grain interiors,which increases the ductility.In comparison,the strength remains nearly constant.Thus,it is indicated that cryogenic forming has the potential to provide the shape and property control for the manufacture of critical components of aluminum alloys.展开更多
Microstructural characterization,mass loss tests,hydrogen evolution tests,electrochemical measurements,and corrosion morphology observations were conducted to investigate the effect of the secondary phases on the corr...Microstructural characterization,mass loss tests,hydrogen evolution tests,electrochemical measurements,and corrosion morphology observations were conducted to investigate the effect of the secondary phases on the corrosion behavior of the as-cast Mg−7Sn−1Zn−1Y(TZW711)alloy after solution treatment(T4)and aging treatment(T6).The results show that the T4-TZW711 alloy possesses the highest corrosion resistance in the early corrosion stage.This is because the dissolution of Mg2Sn reduces the cathodic current density and increases the charge transfer resistance(Rct).When the corrosion time is prolonged,the undissolved and clustered MgSnY phase will peel off from the T4-TZW711 alloy surface,thereby increasing the corrosion rate of the alloy.After aging treatment,the undissolved MgSnY phase is dispersed,which results in a lower localized corrosion sensitivity of T6-TZW711 alloy than that of the T4-TZW711 alloy,suggesting that the T6 treatment can enhance the corrosion resistance of Mg−7Sn−1Zn−1Y alloys.展开更多
Understanding the phase behavior of hydrocarbons and their mixtures,especially under confinement,is crucial for the extraction of shale oil and gas.In this study,we employed molecular dynamics simulations to investiga...Understanding the phase behavior of hydrocarbons and their mixtures,especially under confinement,is crucial for the extraction of shale oil and gas.In this study,we employed molecular dynamics simulations to investigate the phase behaviors of three typical hydrocarbons(methane,pentane,and octane)in the bulk phase and in nanopores.We find that the confinement effect can alter the phase behavior of a single-component hydrocarbon.For the mixture of methane and octane in nanopores,a rather high proportion of methane could inhibit the capillary condensation of octane.We also studied the influence of phase behavior on the recovery dynamics of hydrocarbon mixtures from blind nanopores of different sizes at different gas-oil ratios.The capillary condensation of the heavy hydrocarbon components in the nanopore throat could hinder the transport of light.These findings increase the understanding of the occurrence states of shale oil and gas and their migration through nanopore throats,providing practical guidance for shale oil and gas development.展开更多
Considering the interactions between fluid molecules and pore walls,variations in critical properties,capillary forces,and the influence of the adsorbed phase,this study investigates the phase behavior of the CO_(2)-s...Considering the interactions between fluid molecules and pore walls,variations in critical properties,capillary forces,and the influence of the adsorbed phase,this study investigates the phase behavior of the CO_(2)-shale oil within nanopores by utilizing a modified Peng-Robinson(PR)equation of state alongside a three-phase(gas-liquid-adsorbed)equilibrium calculation method.The results reveal that nano-confinement effects of the pores lead to a decrease in both critical temperature and critical pressure of fluids as pore size diminishes.Specifically,CO_(2) acts to inhibit the reduction of the critical temperature of the system while promoting the decrease in critical pressure.Furthermore,an increase in the mole fraction of CO_(2) causes the critical point of the system to shift leftward and reduces the area of the phase envelope.In the shale reservoirs of Block A in Gulong of the Daqing Oilfield,China,pronounced confinement effects are observed.At a pore diameter of 10 nm,reservoir fluids progressively exhibit characteristics typical of condensate gas reservoirs.Notably,the CO_(2) content in liquid in 10 nm pores increases by 20.0%compared to that in 100 nm pores,while the CO_(2) content in gas decreases by 10.8%.These findings indicate that confinement effects enhance CO_(2) mass transfer within nanopores,thereby facilitating CO_(2) sequestration and improving microscopic oil recovery.展开更多
Magnesium matrix composites with both high strength and ductility have been achieved by introducing pure Ti particles.However,the properties of the surfaces of the composites need to be improved by surface technology,...Magnesium matrix composites with both high strength and ductility have been achieved by introducing pure Ti particles.However,the properties of the surfaces of the composites need to be improved by surface technology,such as micro-arc oxidation(MAO).In this study,we investigated the influence of the Ti-reinforcement phase on coating growth and evolution by subjecting both AZ91 alloy and AZ91/Ti composite to MAO treatment using silicate-based and phosphate-based electrolytes.Results revealed that the Ti-reinforcement phase influenced the MAO process,altering discharge behavior,and leading to a decreased cell voltage.The vigorous discharge of the Ti-reinforcement phase induced the formation of coating discharge channels,concurrently dissolving and oxidizing Ti-reinforcement to produce a composite ceramic coating with TiO2.The MAO coating on the AZ91/Ti composite exhibited a dark blue macromorphology and distinctive local micromorphological anomalies.In silicate electrolyte,a“volcano-like”localized morphology centered on the discharge channel emerged.In contrast,treatment in phosphate-based electrolyte resulted in a coating morphology similar to typical porous ceramic coatings,with visible radial discharge micropores at the reinforcement phase location.Compared to the AZ91 alloy,the coating on the AZ91/Ti composite exhibited lower thickness and higher porosity.MAO treatment reduced the self-corrosion current density of the AZ91/Ti surface by two orders of magnitude.The silicate coating demonstrated better corrosion resistance than the phosphate coating,attributed to its lower porosity.The formation mechanism of MAO coatings on AZ91/Ti composites in phosphate-based and silicate-based electrolytes was proposed.展开更多
High-strength Al-Zn-Mg-Cu alloys are widely utilized,but their strength deteriorates as strengthening precipitates coarsen rapidly at elevated temperatures,limiting their applications above 150℃.This study systematic...High-strength Al-Zn-Mg-Cu alloys are widely utilized,but their strength deteriorates as strengthening precipitates coarsen rapidly at elevated temperatures,limiting their applications above 150℃.This study systematically investigates the microstructure evolution and its impact on the properties of peak-aged Al-Zn-Mg-Cu alloys with varying Zn/Mg ratios during thermal exposure at a series of temperatures from 150 to 300℃ for 500 h.The results reveal that alloys A1 and A2 with an optimal Zn/Mg ratio(1.50-2.14)and relatively lower(Zn+Mg)content(7.0-8.8 wt.%),exhibit superior heat resistance properties compared to the other three alloys.Despite having lower strength relative to alloys with higher solute content,peak-aged alloys A1 and A2 retain the highest strength after thermal exposure.This performance is attributed to the high proportion(over 80%)of T'/T phases in the precipitates for alloys A1 and A2,which demonstrate better thermal stability in comparison to η'/η phases.Additionally,the lower solute content reduces the driving force for diffusion of Zn and Mg atoms,thus inhibiting the coarsening of precipitates.Moreover,the study elucidates that the coarsening mechanism of precipitates transitions from interfacial diffusion control at 150℃ to matrix diffusion control at 200-300℃.These insights into the composition-dependent coarsening behavior of precipitates in dual-phase strengthened Al-Zn-Mg-Cu alloys offer valuable guidance for designing heat-resistant aluminum alloys with enhanced performance at elevated temperatures.展开更多
Comprehensive understanding of the direct transformation pathway from graphite to diamond under high temperature and high pressure has long been one of the fundamental goals in materials science.Despite considerable e...Comprehensive understanding of the direct transformation pathway from graphite to diamond under high temperature and high pressure has long been one of the fundamental goals in materials science.Despite considerable experimental and theoretical progress,current experimental studies have mainly focused on the local microstructural characterizations of recovered samples,which has certain limitations for hightemperature and high-pressure products,which often exhibit diversity.Here,we report on the pressure-induced phase transition behavior of natural single-crystal graphite under three distinct pressure-transmitting media from a macroscopic perspective using in situ two-dimensional Raman spectroscopy,scanning electron microscopy,and atomic force microscopy.The surface evolution process of graphite before and after the phase transition is captured,revealing that pressure-induced surface textures can impede the continuity of the phase transition process across the entire single crystal.Our results provide a fresh perspective for studying the phase transition behavior of graphite and greatly deepen our understanding of this behavior,which will be helpful in guiding further high-temperature and high-pressure syntheses of carbon allotropes.展开更多
The serrated flow behavior,known as the Portevin-Le Chatelier(PLC)effect,is commonly observed during high-temperature deformation.In this study,we report a serrated flow behavior in FeCoCrNiMo0.2 high-entropy alloy(HE...The serrated flow behavior,known as the Portevin-Le Chatelier(PLC)effect,is commonly observed during high-temperature deformation.In this study,we report a serrated flow behavior in FeCoCrNiMo0.2 high-entropy alloy(HEA),which is mediated by nano-twinning and phase transformation at cryogenic temperatures.During uniaxial tensile deformation at 77 K,the alloy exhibited the formation of high-density deformation nano-twinning,cross-twinning,stacking faults(SFs)and Lomer-Cottrell locks(L-C locks).Additionally,the lower stacking fault energy(SFE)at low temperatures promotes the formation of the 9R phase.The high-density twin boundaries effectively hinder dislocation movement,leading to the instability of plastic deformation and promoting the serrated flow behavior.Furthermore,the rapid and unstable transformation of the 9R phase contributes to the pronounced serrated flow behavior.Nano-twinning,SFs,cross-twinning,L-C locks and 9R phase collectively induce a dynamic Hall-Petch effect,enhancing the strength-ductility synergy and strain-hardening ability of deformed alloy at 77 K.Our work provides valuable insights into the mechanism of tensile deformation at cryogenic temperatures in single-phase FCC HEA.展开更多
The toughness of thermoplastic polymers such as polypropylene(PP)can be improved by adding elastomers-based toughening agents,and the phase morphology of these toughening agents is very important for the strength and ...The toughness of thermoplastic polymers such as polypropylene(PP)can be improved by adding elastomers-based toughening agents,and the phase morphology of these toughening agents is very important for the strength and toughness of PP.The low-temperature toughness of PP was improved by inserting high-density polyethylene(HDPE)between PP and polystyrene-b-ethylene-co-propyleneb-polystyrene(SEPS)to form an unusual SEPS@HDPE core–shell structure,with SEPS as the core and HDPE as the shell.Based on the microtopography and rheological behavior characterization,HDPE in PP/SEPS/HDPE composites was found to serve as an emulsifier,decrease the size of SEPS particles,and promote the homogeneous dispersion of dispersed phase particles in the matrix.An increase in the HDPE content shifted the toughening mechanism of PP composites from cavitation to matrix shear yielding.The reduction in the distance between the dispersed core–shell structure particles promoted shear yielding in the PP composites,leading to increased toughness.The creation of an intermediate HDPE layer with a moderate modulus was crucial for dispersing stress concentrations and significantly improving toughness without compromising the tensile strength.These findings will facilitate the fabrication of high-toughness PP products at low temperatures.展开更多
Shape memory alloys(SMAs)and shape memory ceramics(SMCs)exhibit high recovery ability due to the martensitic transformation,which complicates the fracture mechanism of SMAs and SMCs.The phase field method,as a powerfu...Shape memory alloys(SMAs)and shape memory ceramics(SMCs)exhibit high recovery ability due to the martensitic transformation,which complicates the fracture mechanism of SMAs and SMCs.The phase field method,as a powerful numerical simulation tool,can efficiently resolve the microstructural evolution,multi-field coupling effects,and fracture behavior of SMAs and SMCs.This review begins by presenting the fundamental theoretical framework of the fracture phase field method as applied to SMAs and SMCs,covering key aspects such as the phase field modeling of martensitic transformation and brittle fracture.Subsequently,it systematically examines the phase field simulations of fracture behaviors in SMAs and SMCs,with particular emphasis on how crystallographic orientation,grain size,and grain boundary properties influence the crack propagation.Additionally,the interplay between martensite transformation and fracture mechanisms is analyzed to provide deeper insights into the material responses under mechanical loading.Finally,the review explores future prospects and emerging trends in phase field simulations of SMA and SMC fracture behavior,along with potential advancements in the fracture phase field method itself,including multi-physics coupling and enhanced computational efficiency for large-scale simulations.展开更多
Shale reservoirs have abundant bedding structures,which deeply alter the mechanical properties of rocks,and thus affect the reservoir stimulation performance.Previous research mostly focuses on the effects of parallel...Shale reservoirs have abundant bedding structures,which deeply alter the mechanical properties of rocks,and thus affect the reservoir stimulation performance.Previous research mostly focuses on the effects of parallel bedding on fracture propagation,while the mechanical properties and mechanisms of fracture propagation remain unclear for rocks with complex wavy bedding(e.g.China’s continentalorigin Gulong shale).Herein,a mixed phase-field fracture model of the wavy-bedding shale was applied,based on the local tension-compression decomposition phase field method(PFM)and geometric structure generation algorithm for the bedding with controllable morphological features.The parametric analysis of fracture propagation behaviors in the case of abundant complex bedding structures showed that with wavy bedding,the vertical fracture propagation rate is far higher than the horizontal propagation rate.Moreover,the development of branch fractures is suppressed during the fracturing process of the wavy-bedding sample,and the stimulated volume is limited,which is different from the characteristic of parallel bedding that promotes horizontal fracture initiation and propagation.The results showed that larger amplitudes,higher frequencies,higher inclination angles,and larger strengths of wavy bedding all promote the formation of vertical penetrating fractures and suppress the growth of branch fractures.Under such circumstances,it is hard to create a well-connected fracture network after fracturing.This research may provide a theoretical basis for understanding fracture behaviors in rocks with such complex wavy bedding.展开更多
Shape memory alloys(SMAs)are unique materials that exhibit the ability to recover their original shape upon heating after being deformed at low temperatures.Due to their remarkable properties,such as high strength,exc...Shape memory alloys(SMAs)are unique materials that exhibit the ability to recover their original shape upon heating after being deformed at low temperatures.Due to their remarkable properties,such as high strength,excellent fatigue resistance,and the ability to undergo significant recoverable deformation,SMAs have found extensive applications in various fields,including biomedical devices,robotics,aerospace,automotive industries,and smart textiles.This paper provides a comprehensive overview of the phase transformation behavior and smart applications of SMAs,focusing on the underlying mechanisms,characteristics,and technological advancements in SMA-based devices.It explores the various phases involved in SMA behavior,including the martensitic and austenitic phases,thermoelastic transformations,and stress-induced phase transformations.Furthermore,this paper discusses the applications of SMAs in smart technologies,including their use in medical devices,actuators,sensors,and energy harvesting systems.By exploring the key factors influencing phase transformations,this study highlights the potential of SMAs in designing next-generation smart materials and systems.展开更多
1.Introduction.Ni-Mn-X(X=Ga,In,Sn,or Sb)Heusler alloys have versatile properties[1-4],such as shape memory effect[1],superelastic-ity[5],magnetocaloric effect[3],elastocaloric effect[6],and even multicaloric effect[7]...1.Introduction.Ni-Mn-X(X=Ga,In,Sn,or Sb)Heusler alloys have versatile properties[1-4],such as shape memory effect[1],superelastic-ity[5],magnetocaloric effect[3],elastocaloric effect[6],and even multicaloric effect[7],that indicate their potential for use in actu-ators,sensors,micropumps,energy harvesters,and solid-state re-frigeration[8-10].Among the alloys,Ni-Mn-Sn-based alloys are environment-friendly and cost-effective[6,7,11],and hence,they have received widespread attention.展开更多
In-situ tensile tests were conducted on a chemically corroded third-generation single-crystal superalloy DD9 at 980 and 1100℃.The phase transformation in the surface areas during the tensile process was analyzed usin...In-situ tensile tests were conducted on a chemically corroded third-generation single-crystal superalloy DD9 at 980 and 1100℃.The phase transformation in the surface areas during the tensile process was analyzed using field emission scanning electron microscope,energy dispersive X-ray spectroscope,electron probe X-ray microanalysis,and transmission electron microscope.The phase transformation mechanism on the surface and the influence mechanism were studied through observation and dynamic calculation.During tensile tests at elevated temperatures,chemical corrosion promotes the precipitation of topologically close-packed(tcp)μphase andσphase on the alloy surface.Both the precipitation amount and size of these two phases on the surface at 1100℃are greater than those at 980℃.The precipitation of tcp phase on the alloy surface results in the formation of an influence layer on the surface area,and the distribution characteristics of alloying elements are significantly different from those of the substrate.The depth of the influence layer at 1100℃is greater than that at 980℃.The precipitation of tcp phase prompts the phase transition fromγphase toγ′phase around the tcp phase.展开更多
Microemulsions are usually used to prepare nanomaterials.The fo rmation behavior of microemulsions is crucial to the preparation of nanomaterials.Water in the internal phase is usually replaced by electrolyte solution...Microemulsions are usually used to prepare nanomaterials.The fo rmation behavior of microemulsions is crucial to the preparation of nanomaterials.Water in the internal phase is usually replaced by electrolyte solutions to prepare nanomaterials.Knowing the effects of electrolyte solution on the phase behavior of microemulsion is significant to the nanomaterial preparation.Microemulsion systems were studied by a conductivity method with cyclohexane as oil,Triton X-100 as surfactant,hexanol as cosurfactant,and deionized water or the electrolyte solutions of Cu(Ac)_(2)and Zn(Ac)_(2)as aqueous phases.The results showed that the replacement of water with electrolyte solution had a strong effect on the phase behavior of microemulsion system.The O/W microemulsion zone in water system was not observed in the studied electrolyte system.The shape and area of the corresponding phase zone in electrolyte system were different from that in water system.The microemulsion regions of electrolyte solution systems were always larger than that of water system.Zn(Ac)_(2)showed a larger microemulsion region than Cu(Ac)_(2)at 0.1 mol·L^(-1).The microemulsion phase region formed by 0.1 mol·L^(-1)Zn(Ac)_(2)+0.1 mol·L^(-1)Cu(Ac)_(2)was smaller than that formed by 0.1 mol·L^(-1)Zn(Ac)_(2)or 0.1 mol·L^(-1)Cu(Ac)_(2)lonely.With the increase of electrolyte concentration in the electrolyte solution and the rise of temperature,the microemulsion region shrank gradually.The changes of interactions between different components in the system should be responsible to the variation of phase behavior.The results provide important information for the microemulsion system with electrolyte solution as aqueous phase.展开更多
The effects of temperature and Re content on the mechanical properties,dislocation morphology,and deformation mechanism of γ-γ′phases nickel-based single crystal superalloys are investigated by using the molecular ...The effects of temperature and Re content on the mechanical properties,dislocation morphology,and deformation mechanism of γ-γ′phases nickel-based single crystal superalloys are investigated by using the molecular dynamics method through the model of γ-γ′phases containing hole defect.The addition of Re makes the dislocation distribution tend towards the γ phase.The higher the Re content,the earlier theγphase yields,while the γ′phase yields later.Dislocation bends under the combined action of the applied force and the resistance of the Re atoms to form a bend point.The Re atoms are located at the bend points and strengthen the alloy by fixing the dislocation and preventing it from cutting the γ′phase.Dislocations nucleate first in the γ phase,causing theγphase to deform plastically before the γ′phase.As the strain increases,the dislocation length first remains unchanged,then increases rapidly,and finally fluctuates and changes.The dislocation lengths in the γ phase are larger than those in the γ′phase at different temperatures.The dislocation length shows a decreasing tendency with the increase of the temperature.Temperature can affect movement of the dislocation,and superalloys have different plastic deformation mechanisms at low,medium and high temperatures.展开更多
Face-centered cubic(FCC)equi-atomic multi-principal element alloys(MPEAs)exhibit excellent mechan-ical properties over a broad temperature range from cryogenic temperatures(CTs)to room temperature(RT).Specifically,whi...Face-centered cubic(FCC)equi-atomic multi-principal element alloys(MPEAs)exhibit excellent mechan-ical properties over a broad temperature range from cryogenic temperatures(CTs)to room temperature(RT).Specifically,while the deformation mechanism is dominated solely by dislocation slip at RT,the re-duction in stacking fault energy(SFE)at CTs leads to enhanced strain hardening with deformation twin-ning.This study employs in-situ neutron diffraction to reveal the temperature-dependent deformation be-havior of the FCC/body-centered cubic(BCC)dual-phase(DP)Al7(CoNiV)93 medium-entropy alloy(MEA),which possesses a matrix exhibiting deformation behavior analogous to that of representative equi-atomic MPEAs.Alongside the increased lattice friction stress associated with reduced temperature as a thermal component,deformation twinning at liquid nitrogen temperature(LNT)facilitates dislocation activity in the FCC matrix,leading to additional strain hardening induced by the dynamic Hall-Petch effect.This would give the appearance that the improved strengthening/hardening behaviors at LNT,compared to RT,are primarily attributable to the FCC phase.In contrast,the BCC precipitates are governed solely by dislocation slip for plastic deformation at both 77 K and 298 K,exhibiting a similar trend in dislocation density evolution.Nevertheless,empirical and quantitative findings indicate that the intrinsically high Peierls-Nabarro barriers in the BCC precipitates exhibit pronounced temperature-dependent lattice fric-tion stress,suggesting that the BCC precipitates play a more significant role in the temperature-dependent strengthening/hardening behaviors for the DP-MEA.This study provides a comprehensive understanding of deformation behavior by thoroughly analyzing temperature-dependent strengthening/hardening mech-anisms across various DP-MPEA systems,offering valuable guidelines for future alloy design.展开更多
The insufficient damping capabilities of aluminum alloy under low temperatures(<120℃)were addressed by developing high-damping laminated composites of NiTip/5052Al.This is achieved through the incorporation of var...The insufficient damping capabilities of aluminum alloy under low temperatures(<120℃)were addressed by developing high-damping laminated composites of NiTip/5052Al.This is achieved through the incorporation of varied pre-aging states of NiTi particles into the 5052Al matrix using a rolling composite technique.The aim is to enhance the application scope of aluminum alloy for vibration and noise reduction.The results demonstrated a distinct and integrated interface between the particle layer and the 5052Al alloy,with numerous interparticle interfaces within the particle layer.Increasing the aging temperature of the NiTi particles from 450 to 550℃ shifted the phase transition peaks of the composites to lower temperatures.The damping capacity of the laminated NiTip/5052Al composites notably surpasses that of the 5052Al alloy.At 28 and 66℃,the phase transformation damping peaks of the pre-aged NiTi particle layer reinforced 5052Al matrix composites are 1.93 and 2 times those of the 5052Al alloy at the corresponding temperatures,respectively.The collaborative impact of interparticle interface damping mechanism and the phase transformation damping mechanism of NiTi-reinforced particles significantly amplify the low-temperature damping performance of the laminated NiTip/5052Al composites.展开更多
The phase transformation of galena in H_(2)SO_(4)-Fe_(2)(SO_(4))_(3) system under oxygen pressure was investigated.Results indicated that the critical conditions for the phase transformation of galena into lead jarosi...The phase transformation of galena in H_(2)SO_(4)-Fe_(2)(SO_(4))_(3) system under oxygen pressure was investigated.Results indicated that the critical conditions for the phase transformation of galena into lead jarosite(Pb-J)were 130℃,30 g/L H_(2)SO_(4),15 g/L Fe^(3+),and an oxygen partial pressure of 0.4 MPa.Furthermore,increased Fe^(3+)concentration and oxygen partial pressure did not enhance jarosite formation.Conversely,lowering the temperature and increasing the H_(2)SO_(4) concentration facilitated PbSO_(4) formation and inhibited its further conversion to Pb-J.Additionally,the effects of potassium sulfate,sodium sulfate,and high concentrations of zinc sulfate on the phase transformation of galena were examined through leaching tests,XRD,SEM-EDS,and FT-IR analyses.All three sulfates inhibited the conversion of galena to Pb-J.Among these,potassium sulfate prevented Pb-J formation and converted it more thoroughly into potassium jarosite.However,high concentrations of zinc sulfate facilitated the crystallization of both PbSO_(4) and Pb-J,which altered the morphology of the product.Zinc ions coprecipitated with Pb-J,thereby integrating into the product.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.42171135)the Science and Technology Program of CNOOC Research Institute(Grant No.2023OTKK03)the“CUG Scholar”Scientific Research Funds at China University of Geosciences(Project No.2022098).
文摘The volume change behavior of natural gas hydrate-bearing sediment is essential as it influences settlement,strength,and stiffness,which directly affect the stability of hydrate reservoirs during hydrate extraction or in response to environmental changes.The volume change is influenced not only by stress but also by the formation and dissociation of hydrates.This study adopted a customized apparatus for one-dimensional compression tests,allowing independent control of gas pressure and effective stress.Tests were conducted on samples with different hydrate saturations along various temperature-gas pressure-effective stress paths,yielding some conclusions related to compressibility and creep.An unusual phenomenon was observed under low-stress conditions:hydrate formation led to shrinkage rather than expansion.Three potential mechanisms behind this occurrence were discussed.As hydrate saturation increases,the yield stress rises while the compression and swelling indexes remain minimally affected.After hydrate dissociation,the compression curve of hydrate-bearing sediment drops to that of hydrate-free sediment.Once hydrate is formed,the compression curve of hydrate-free sediment gradually approaches that of hydrate-bearing sediment during the subsequent loading.Under low-stress conditions,the creep of both hydrate-free and hydrate-bearing sediments is very weak.However,when stress increases,significantly beyond the yield stress,the creep of both sediments increases significantly,with hydrate-bearing sediment exhibiting much greater creep than hydrate-free sediment.
基金financially supported by the National Key Research and Development Program of China (No. 2019YFA0708801)the National Natural Science Foundation of China (No. 51875125)。
文摘The water-quenched(WQ)2195 Al−Li alloy was subjected to stretching at different temperatures,from room temperature(RT)to−196℃(CT),to investigate the effect of cryogenic deformation on the aging precipitation behaviors and mechanical properties.The precipitation kinetics of the T1 phase and the microstructures in peak aging state were investigated through the differential scanning calorimetric(DSC)tests and electron microscopy observation.The results show that−196℃deformation produces a high dislocation density,which promotes the precipitation of the T1 phase and refines its sizes significantly.In addition,the grain boundary precipitates(GBPs)of−196℃-stretched samples are suppressed considerably due to the high dislocation density in the grain interiors,which increases the ductility.In comparison,the strength remains nearly constant.Thus,it is indicated that cryogenic forming has the potential to provide the shape and property control for the manufacture of critical components of aluminum alloys.
基金National Natural Science Foundation of China(Nos.52301041,52022017,52065009,52371005)Special Fund for Special Posts of Guizhou University,China(No.[2023]26)+1 种基金Science and Technology Planning Project of Guizhou Province,China(No.ZK2021269)Fundamental Research Funds for the Central Universities,China(No.DUT23YG104)。
文摘Microstructural characterization,mass loss tests,hydrogen evolution tests,electrochemical measurements,and corrosion morphology observations were conducted to investigate the effect of the secondary phases on the corrosion behavior of the as-cast Mg−7Sn−1Zn−1Y(TZW711)alloy after solution treatment(T4)and aging treatment(T6).The results show that the T4-TZW711 alloy possesses the highest corrosion resistance in the early corrosion stage.This is because the dissolution of Mg2Sn reduces the cathodic current density and increases the charge transfer resistance(Rct).When the corrosion time is prolonged,the undissolved and clustered MgSnY phase will peel off from the T4-TZW711 alloy surface,thereby increasing the corrosion rate of the alloy.After aging treatment,the undissolved MgSnY phase is dispersed,which results in a lower localized corrosion sensitivity of T6-TZW711 alloy than that of the T4-TZW711 alloy,suggesting that the T6 treatment can enhance the corrosion resistance of Mg−7Sn−1Zn−1Y alloys.
基金supported by the National Natural Science Foundation of China(Grant Nos.U22B2075 and 12241203)。
文摘Understanding the phase behavior of hydrocarbons and their mixtures,especially under confinement,is crucial for the extraction of shale oil and gas.In this study,we employed molecular dynamics simulations to investigate the phase behaviors of three typical hydrocarbons(methane,pentane,and octane)in the bulk phase and in nanopores.We find that the confinement effect can alter the phase behavior of a single-component hydrocarbon.For the mixture of methane and octane in nanopores,a rather high proportion of methane could inhibit the capillary condensation of octane.We also studied the influence of phase behavior on the recovery dynamics of hydrocarbon mixtures from blind nanopores of different sizes at different gas-oil ratios.The capillary condensation of the heavy hydrocarbon components in the nanopore throat could hinder the transport of light.These findings increase the understanding of the occurrence states of shale oil and gas and their migration through nanopore throats,providing practical guidance for shale oil and gas development.
基金Supported by the National Natural Science Foundation of China Joint Fund(U22B2075).
文摘Considering the interactions between fluid molecules and pore walls,variations in critical properties,capillary forces,and the influence of the adsorbed phase,this study investigates the phase behavior of the CO_(2)-shale oil within nanopores by utilizing a modified Peng-Robinson(PR)equation of state alongside a three-phase(gas-liquid-adsorbed)equilibrium calculation method.The results reveal that nano-confinement effects of the pores lead to a decrease in both critical temperature and critical pressure of fluids as pore size diminishes.Specifically,CO_(2) acts to inhibit the reduction of the critical temperature of the system while promoting the decrease in critical pressure.Furthermore,an increase in the mole fraction of CO_(2) causes the critical point of the system to shift leftward and reduces the area of the phase envelope.In the shale reservoirs of Block A in Gulong of the Daqing Oilfield,China,pronounced confinement effects are observed.At a pore diameter of 10 nm,reservoir fluids progressively exhibit characteristics typical of condensate gas reservoirs.Notably,the CO_(2) content in liquid in 10 nm pores increases by 20.0%compared to that in 100 nm pores,while the CO_(2) content in gas decreases by 10.8%.These findings indicate that confinement effects enhance CO_(2) mass transfer within nanopores,thereby facilitating CO_(2) sequestration and improving microscopic oil recovery.
基金supported by the Guangdong Major Project of Basic and Applied Basic Research(Grant No.2020B0301030006).
文摘Magnesium matrix composites with both high strength and ductility have been achieved by introducing pure Ti particles.However,the properties of the surfaces of the composites need to be improved by surface technology,such as micro-arc oxidation(MAO).In this study,we investigated the influence of the Ti-reinforcement phase on coating growth and evolution by subjecting both AZ91 alloy and AZ91/Ti composite to MAO treatment using silicate-based and phosphate-based electrolytes.Results revealed that the Ti-reinforcement phase influenced the MAO process,altering discharge behavior,and leading to a decreased cell voltage.The vigorous discharge of the Ti-reinforcement phase induced the formation of coating discharge channels,concurrently dissolving and oxidizing Ti-reinforcement to produce a composite ceramic coating with TiO2.The MAO coating on the AZ91/Ti composite exhibited a dark blue macromorphology and distinctive local micromorphological anomalies.In silicate electrolyte,a“volcano-like”localized morphology centered on the discharge channel emerged.In contrast,treatment in phosphate-based electrolyte resulted in a coating morphology similar to typical porous ceramic coatings,with visible radial discharge micropores at the reinforcement phase location.Compared to the AZ91 alloy,the coating on the AZ91/Ti composite exhibited lower thickness and higher porosity.MAO treatment reduced the self-corrosion current density of the AZ91/Ti surface by two orders of magnitude.The silicate coating demonstrated better corrosion resistance than the phosphate coating,attributed to its lower porosity.The formation mechanism of MAO coatings on AZ91/Ti composites in phosphate-based and silicate-based electrolytes was proposed.
基金supported by the Natural Science Foundation of Chongqing(Nos.CSTB2022NSCQ-LZX0002 and CSTB2022NSCQ-BHX0624)the Chongqing Key Project for Technological Innovation and Application(No.CSTB2022TIAD-KPX0073)+1 种基金the Opening Project of State Key Laboratory for Advanced Metals and Materials(No.2022-Z03)the Science and Technology Research Program of Chongqing Municipal Education Commission(No.KJQN202200810).
文摘High-strength Al-Zn-Mg-Cu alloys are widely utilized,but their strength deteriorates as strengthening precipitates coarsen rapidly at elevated temperatures,limiting their applications above 150℃.This study systematically investigates the microstructure evolution and its impact on the properties of peak-aged Al-Zn-Mg-Cu alloys with varying Zn/Mg ratios during thermal exposure at a series of temperatures from 150 to 300℃ for 500 h.The results reveal that alloys A1 and A2 with an optimal Zn/Mg ratio(1.50-2.14)and relatively lower(Zn+Mg)content(7.0-8.8 wt.%),exhibit superior heat resistance properties compared to the other three alloys.Despite having lower strength relative to alloys with higher solute content,peak-aged alloys A1 and A2 retain the highest strength after thermal exposure.This performance is attributed to the high proportion(over 80%)of T'/T phases in the precipitates for alloys A1 and A2,which demonstrate better thermal stability in comparison to η'/η phases.Additionally,the lower solute content reduces the driving force for diffusion of Zn and Mg atoms,thus inhibiting the coarsening of precipitates.Moreover,the study elucidates that the coarsening mechanism of precipitates transitions from interfacial diffusion control at 150℃ to matrix diffusion control at 200-300℃.These insights into the composition-dependent coarsening behavior of precipitates in dual-phase strengthened Al-Zn-Mg-Cu alloys offer valuable guidance for designing heat-resistant aluminum alloys with enhanced performance at elevated temperatures.
基金support from the National Science Fund for Distinguished Young Scholars(Grant No.T2225027)the NSAF(Grant No.U1930401)+1 种基金the National Key R&D Program of China(MOST)(Grant No.2023YFA1406500)the National Natural Science Foundation of China(NSFC)(Grant No.61674045).
文摘Comprehensive understanding of the direct transformation pathway from graphite to diamond under high temperature and high pressure has long been one of the fundamental goals in materials science.Despite considerable experimental and theoretical progress,current experimental studies have mainly focused on the local microstructural characterizations of recovered samples,which has certain limitations for hightemperature and high-pressure products,which often exhibit diversity.Here,we report on the pressure-induced phase transition behavior of natural single-crystal graphite under three distinct pressure-transmitting media from a macroscopic perspective using in situ two-dimensional Raman spectroscopy,scanning electron microscopy,and atomic force microscopy.The surface evolution process of graphite before and after the phase transition is captured,revealing that pressure-induced surface textures can impede the continuity of the phase transition process across the entire single crystal.Our results provide a fresh perspective for studying the phase transition behavior of graphite and greatly deepen our understanding of this behavior,which will be helpful in guiding further high-temperature and high-pressure syntheses of carbon allotropes.
基金supported by the National Natural Science Foundation of China(Nos.52474403,52364050 and 52301137)Guizhou Provincial Program on Commercialization of Scientific and Technological Achievements(No.[2023]001)+2 种基金Guizhou Province Science and Technology Project(No.[2022]050)Guiyang city Science and Technology Project(No.[2023]48-16)the Central Government in Guidance of Local Science and Technology Development Funds(No.[2024]032).
文摘The serrated flow behavior,known as the Portevin-Le Chatelier(PLC)effect,is commonly observed during high-temperature deformation.In this study,we report a serrated flow behavior in FeCoCrNiMo0.2 high-entropy alloy(HEA),which is mediated by nano-twinning and phase transformation at cryogenic temperatures.During uniaxial tensile deformation at 77 K,the alloy exhibited the formation of high-density deformation nano-twinning,cross-twinning,stacking faults(SFs)and Lomer-Cottrell locks(L-C locks).Additionally,the lower stacking fault energy(SFE)at low temperatures promotes the formation of the 9R phase.The high-density twin boundaries effectively hinder dislocation movement,leading to the instability of plastic deformation and promoting the serrated flow behavior.Furthermore,the rapid and unstable transformation of the 9R phase contributes to the pronounced serrated flow behavior.Nano-twinning,SFs,cross-twinning,L-C locks and 9R phase collectively induce a dynamic Hall-Petch effect,enhancing the strength-ductility synergy and strain-hardening ability of deformed alloy at 77 K.Our work provides valuable insights into the mechanism of tensile deformation at cryogenic temperatures in single-phase FCC HEA.
基金supported by the Taiyuan Major Science and Technology Project Fund in 2021,Fund for Shanxi“1331 Project,”Key Research and Development Program of Shanxi Province(202102040201011)the Zhanjiang Marine Equipment and Marine Biological Industry Unveiled the Talent Team Project(2021E05034).
文摘The toughness of thermoplastic polymers such as polypropylene(PP)can be improved by adding elastomers-based toughening agents,and the phase morphology of these toughening agents is very important for the strength and toughness of PP.The low-temperature toughness of PP was improved by inserting high-density polyethylene(HDPE)between PP and polystyrene-b-ethylene-co-propyleneb-polystyrene(SEPS)to form an unusual SEPS@HDPE core–shell structure,with SEPS as the core and HDPE as the shell.Based on the microtopography and rheological behavior characterization,HDPE in PP/SEPS/HDPE composites was found to serve as an emulsifier,decrease the size of SEPS particles,and promote the homogeneous dispersion of dispersed phase particles in the matrix.An increase in the HDPE content shifted the toughening mechanism of PP composites from cavitation to matrix shear yielding.The reduction in the distance between the dispersed core–shell structure particles promoted shear yielding in the PP composites,leading to increased toughness.The creation of an intermediate HDPE layer with a moderate modulus was crucial for dispersing stress concentrations and significantly improving toughness without compromising the tensile strength.These findings will facilitate the fabrication of high-toughness PP products at low temperatures.
基金supported by the National Natural Science Foundation of China(12202294)the Sichuan Science and Technology Program(2024NSFSC1346).
文摘Shape memory alloys(SMAs)and shape memory ceramics(SMCs)exhibit high recovery ability due to the martensitic transformation,which complicates the fracture mechanism of SMAs and SMCs.The phase field method,as a powerful numerical simulation tool,can efficiently resolve the microstructural evolution,multi-field coupling effects,and fracture behavior of SMAs and SMCs.This review begins by presenting the fundamental theoretical framework of the fracture phase field method as applied to SMAs and SMCs,covering key aspects such as the phase field modeling of martensitic transformation and brittle fracture.Subsequently,it systematically examines the phase field simulations of fracture behaviors in SMAs and SMCs,with particular emphasis on how crystallographic orientation,grain size,and grain boundary properties influence the crack propagation.Additionally,the interplay between martensite transformation and fracture mechanisms is analyzed to provide deeper insights into the material responses under mechanical loading.Finally,the review explores future prospects and emerging trends in phase field simulations of SMA and SMC fracture behavior,along with potential advancements in the fracture phase field method itself,including multi-physics coupling and enhanced computational efficiency for large-scale simulations.
基金supported by the Technology Project of CNPC(Grant No.2023ZZ08)the National Natural Science Foundation of China(Grant No.52274058)the USTC Research Funds of the Double First-Class Initiative(Grant No.YD2090002025).
文摘Shale reservoirs have abundant bedding structures,which deeply alter the mechanical properties of rocks,and thus affect the reservoir stimulation performance.Previous research mostly focuses on the effects of parallel bedding on fracture propagation,while the mechanical properties and mechanisms of fracture propagation remain unclear for rocks with complex wavy bedding(e.g.China’s continentalorigin Gulong shale).Herein,a mixed phase-field fracture model of the wavy-bedding shale was applied,based on the local tension-compression decomposition phase field method(PFM)and geometric structure generation algorithm for the bedding with controllable morphological features.The parametric analysis of fracture propagation behaviors in the case of abundant complex bedding structures showed that with wavy bedding,the vertical fracture propagation rate is far higher than the horizontal propagation rate.Moreover,the development of branch fractures is suppressed during the fracturing process of the wavy-bedding sample,and the stimulated volume is limited,which is different from the characteristic of parallel bedding that promotes horizontal fracture initiation and propagation.The results showed that larger amplitudes,higher frequencies,higher inclination angles,and larger strengths of wavy bedding all promote the formation of vertical penetrating fractures and suppress the growth of branch fractures.Under such circumstances,it is hard to create a well-connected fracture network after fracturing.This research may provide a theoretical basis for understanding fracture behaviors in rocks with such complex wavy bedding.
文摘Shape memory alloys(SMAs)are unique materials that exhibit the ability to recover their original shape upon heating after being deformed at low temperatures.Due to their remarkable properties,such as high strength,excellent fatigue resistance,and the ability to undergo significant recoverable deformation,SMAs have found extensive applications in various fields,including biomedical devices,robotics,aerospace,automotive industries,and smart textiles.This paper provides a comprehensive overview of the phase transformation behavior and smart applications of SMAs,focusing on the underlying mechanisms,characteristics,and technological advancements in SMA-based devices.It explores the various phases involved in SMA behavior,including the martensitic and austenitic phases,thermoelastic transformations,and stress-induced phase transformations.Furthermore,this paper discusses the applications of SMAs in smart technologies,including their use in medical devices,actuators,sensors,and energy harvesting systems.By exploring the key factors influencing phase transformations,this study highlights the potential of SMAs in designing next-generation smart materials and systems.
基金supported by the National Key R&D Pro-gram of China(No.2022YFB3805701)National Natural Science Foundation of China(NSFC)(No.52371182,51701052,52192592,52192593)+1 种基金Young Elite Scientists Sponsorship Program by CAST(No.2019QNRC001)the Heilongjiang Touyan Innovation Team Program.
文摘1.Introduction.Ni-Mn-X(X=Ga,In,Sn,or Sb)Heusler alloys have versatile properties[1-4],such as shape memory effect[1],superelastic-ity[5],magnetocaloric effect[3],elastocaloric effect[6],and even multicaloric effect[7],that indicate their potential for use in actu-ators,sensors,micropumps,energy harvesters,and solid-state re-frigeration[8-10].Among the alloys,Ni-Mn-Sn-based alloys are environment-friendly and cost-effective[6,7,11],and hence,they have received widespread attention.
文摘In-situ tensile tests were conducted on a chemically corroded third-generation single-crystal superalloy DD9 at 980 and 1100℃.The phase transformation in the surface areas during the tensile process was analyzed using field emission scanning electron microscope,energy dispersive X-ray spectroscope,electron probe X-ray microanalysis,and transmission electron microscope.The phase transformation mechanism on the surface and the influence mechanism were studied through observation and dynamic calculation.During tensile tests at elevated temperatures,chemical corrosion promotes the precipitation of topologically close-packed(tcp)μphase andσphase on the alloy surface.Both the precipitation amount and size of these two phases on the surface at 1100℃are greater than those at 980℃.The precipitation of tcp phase on the alloy surface results in the formation of an influence layer on the surface area,and the distribution characteristics of alloying elements are significantly different from those of the substrate.The depth of the influence layer at 1100℃is greater than that at 980℃.The precipitation of tcp phase prompts the phase transition fromγphase toγ′phase around the tcp phase.
基金funded by the National Natural Science Foundation of China(22078203)fundamental research funds for the central universities(2022SCUH0041)。
文摘Microemulsions are usually used to prepare nanomaterials.The fo rmation behavior of microemulsions is crucial to the preparation of nanomaterials.Water in the internal phase is usually replaced by electrolyte solutions to prepare nanomaterials.Knowing the effects of electrolyte solution on the phase behavior of microemulsion is significant to the nanomaterial preparation.Microemulsion systems were studied by a conductivity method with cyclohexane as oil,Triton X-100 as surfactant,hexanol as cosurfactant,and deionized water or the electrolyte solutions of Cu(Ac)_(2)and Zn(Ac)_(2)as aqueous phases.The results showed that the replacement of water with electrolyte solution had a strong effect on the phase behavior of microemulsion system.The O/W microemulsion zone in water system was not observed in the studied electrolyte system.The shape and area of the corresponding phase zone in electrolyte system were different from that in water system.The microemulsion regions of electrolyte solution systems were always larger than that of water system.Zn(Ac)_(2)showed a larger microemulsion region than Cu(Ac)_(2)at 0.1 mol·L^(-1).The microemulsion phase region formed by 0.1 mol·L^(-1)Zn(Ac)_(2)+0.1 mol·L^(-1)Cu(Ac)_(2)was smaller than that formed by 0.1 mol·L^(-1)Zn(Ac)_(2)or 0.1 mol·L^(-1)Cu(Ac)_(2)lonely.With the increase of electrolyte concentration in the electrolyte solution and the rise of temperature,the microemulsion region shrank gradually.The changes of interactions between different components in the system should be responsible to the variation of phase behavior.The results provide important information for the microemulsion system with electrolyte solution as aqueous phase.
基金Project supported by the Xi’an Science and Technology Plan Project of Shaanxi Province of China(Grant No.23GXFW0086).
文摘The effects of temperature and Re content on the mechanical properties,dislocation morphology,and deformation mechanism of γ-γ′phases nickel-based single crystal superalloys are investigated by using the molecular dynamics method through the model of γ-γ′phases containing hole defect.The addition of Re makes the dislocation distribution tend towards the γ phase.The higher the Re content,the earlier theγphase yields,while the γ′phase yields later.Dislocation bends under the combined action of the applied force and the resistance of the Re atoms to form a bend point.The Re atoms are located at the bend points and strengthen the alloy by fixing the dislocation and preventing it from cutting the γ′phase.Dislocations nucleate first in the γ phase,causing theγphase to deform plastically before the γ′phase.As the strain increases,the dislocation length first remains unchanged,then increases rapidly,and finally fluctuates and changes.The dislocation lengths in the γ phase are larger than those in the γ′phase at different temperatures.The dislocation length shows a decreasing tendency with the increase of the temperature.Temperature can affect movement of the dislocation,and superalloys have different plastic deformation mechanisms at low,medium and high temperatures.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIP)(Nos.NRF-2021R1A2C3006662,NRF-2022R1A5A1030054,and RS-2023-00281246)supported by the Basic Science Research Program‘Fostering the Next Generation of Researchers(Ph.D.Candidate)’through the NRF funded by the Ministry of Edu-cation(No.RS-2023-00275651).
文摘Face-centered cubic(FCC)equi-atomic multi-principal element alloys(MPEAs)exhibit excellent mechan-ical properties over a broad temperature range from cryogenic temperatures(CTs)to room temperature(RT).Specifically,while the deformation mechanism is dominated solely by dislocation slip at RT,the re-duction in stacking fault energy(SFE)at CTs leads to enhanced strain hardening with deformation twin-ning.This study employs in-situ neutron diffraction to reveal the temperature-dependent deformation be-havior of the FCC/body-centered cubic(BCC)dual-phase(DP)Al7(CoNiV)93 medium-entropy alloy(MEA),which possesses a matrix exhibiting deformation behavior analogous to that of representative equi-atomic MPEAs.Alongside the increased lattice friction stress associated with reduced temperature as a thermal component,deformation twinning at liquid nitrogen temperature(LNT)facilitates dislocation activity in the FCC matrix,leading to additional strain hardening induced by the dynamic Hall-Petch effect.This would give the appearance that the improved strengthening/hardening behaviors at LNT,compared to RT,are primarily attributable to the FCC phase.In contrast,the BCC precipitates are governed solely by dislocation slip for plastic deformation at both 77 K and 298 K,exhibiting a similar trend in dislocation density evolution.Nevertheless,empirical and quantitative findings indicate that the intrinsically high Peierls-Nabarro barriers in the BCC precipitates exhibit pronounced temperature-dependent lattice fric-tion stress,suggesting that the BCC precipitates play a more significant role in the temperature-dependent strengthening/hardening behaviors for the DP-MEA.This study provides a comprehensive understanding of deformation behavior by thoroughly analyzing temperature-dependent strengthening/hardening mech-anisms across various DP-MPEA systems,offering valuable guidelines for future alloy design.
基金National Natural Science Foundation of China (No. 52061011)Guangxi Natural Science Foundation,China (No. 2022GXNSFAA035574)Innovation Project of Guangxi Graduate Education,China (No. YCSW2023361)。
文摘The insufficient damping capabilities of aluminum alloy under low temperatures(<120℃)were addressed by developing high-damping laminated composites of NiTip/5052Al.This is achieved through the incorporation of varied pre-aging states of NiTi particles into the 5052Al matrix using a rolling composite technique.The aim is to enhance the application scope of aluminum alloy for vibration and noise reduction.The results demonstrated a distinct and integrated interface between the particle layer and the 5052Al alloy,with numerous interparticle interfaces within the particle layer.Increasing the aging temperature of the NiTi particles from 450 to 550℃ shifted the phase transition peaks of the composites to lower temperatures.The damping capacity of the laminated NiTip/5052Al composites notably surpasses that of the 5052Al alloy.At 28 and 66℃,the phase transformation damping peaks of the pre-aged NiTi particle layer reinforced 5052Al matrix composites are 1.93 and 2 times those of the 5052Al alloy at the corresponding temperatures,respectively.The collaborative impact of interparticle interface damping mechanism and the phase transformation damping mechanism of NiTi-reinforced particles significantly amplify the low-temperature damping performance of the laminated NiTip/5052Al composites.
基金Projects(2023AG05008,202302AB080012)supported by the Yunnan Major Scientific and Technological Program,ChinaProject(202405AC350015)supported by the Science and Technology Talent Programme of Yunnan Province,China。
文摘The phase transformation of galena in H_(2)SO_(4)-Fe_(2)(SO_(4))_(3) system under oxygen pressure was investigated.Results indicated that the critical conditions for the phase transformation of galena into lead jarosite(Pb-J)were 130℃,30 g/L H_(2)SO_(4),15 g/L Fe^(3+),and an oxygen partial pressure of 0.4 MPa.Furthermore,increased Fe^(3+)concentration and oxygen partial pressure did not enhance jarosite formation.Conversely,lowering the temperature and increasing the H_(2)SO_(4) concentration facilitated PbSO_(4) formation and inhibited its further conversion to Pb-J.Additionally,the effects of potassium sulfate,sodium sulfate,and high concentrations of zinc sulfate on the phase transformation of galena were examined through leaching tests,XRD,SEM-EDS,and FT-IR analyses.All three sulfates inhibited the conversion of galena to Pb-J.Among these,potassium sulfate prevented Pb-J formation and converted it more thoroughly into potassium jarosite.However,high concentrations of zinc sulfate facilitated the crystallization of both PbSO_(4) and Pb-J,which altered the morphology of the product.Zinc ions coprecipitated with Pb-J,thereby integrating into the product.
