The effect of quenching rate on the electrical conductivity and microstructure of thick plates of incumbent AA7050 was investigated by employing Jominy end quench test. The electrical conductivity measurement and micr...The effect of quenching rate on the electrical conductivity and microstructure of thick plates of incumbent AA7050 was investigated by employing Jominy end quench test. The electrical conductivity measurement and microstructural observation were conducted at different distances from the quenched end. The results indicate that the average cooling rates decrease with increasing the distance from the quenched end of the bar in the quench sensitive temperature range. However, the electrical conductivity increases with the increase of distance from the quenched end. The surface parts of the plate were fully recrystallized, while partial recrystallization took place at the quarter and center parts of the plate. The quench induced grain boundary precipitates became remarkably coarser and discontinuously distributed with increasing distance from the quenched end of the bar. Plenty of heterogeneous precipitates were observed to nucleate on A13Zr dispersoids when the distance from the quenched end was greater than 38mm.展开更多
A cyclic quenching treatment(CQT)succeeded in turning a 2.3 GPa maraging steel with a Charpy impact energy of 9 J into a new grade with the same strength but a Charpy impact energy of 20 J upon 4 cyclic treatments.The...A cyclic quenching treatment(CQT)succeeded in turning a 2.3 GPa maraging steel with a Charpy impact energy of 9 J into a new grade with the same strength but a Charpy impact energy of 20 J upon 4 cyclic treatments.The improvement of mechanical properties is attributed to the refinement and increased chemical heterogeneity of the martensitic substructure,rather than the refinement of prior austenite grain(PAG),as well as the Transformation-Induced Plasticity(TRIP)effect facilitated by small austenite grains.The role of local segregation of Ni during CQT in the formation of Ni-rich austenite grains,Ni-rich martensite laths and Ni-poor martensite laths,was investigated and verified by DICTRA simulations.This study highlights the important influence of Ni partitioning behavior during CQT,providing insights into microstructural evolution and mechanical properties.展开更多
The effects of quenching and aging （T6, T7 and RRA） on the microstructural evolution of an A1-Zn-Mg-Cu alloy were investigated by hardness test, optical microscopy （OM）, transmission electron microscopy （TEM） an...The effects of quenching and aging （T6, T7 and RRA） on the microstructural evolution of an A1-Zn-Mg-Cu alloy were investigated by hardness test, optical microscopy （OM）, transmission electron microscopy （TEM） and differential scanning calorimetry （DSC） measurements. It is found that the hardness of T6 aged sample after water-quenching is the highest. The quench sensitivities of T7 and RRA are almost the same, which are 1.2% higher than that of T6. TEM observation shows that the quench sensitivity for the studied alloy is mainly caused by heterogeneous precipitation during slow quenching. Many r/phases precipitate on A13Zr dispersoids inside recrystallized grains and at （sub） grain boundaries, while T and S phases form in the substructure with high density of dislocations and defects. After aging, the η＇ precipitates are coarser in the vicinity of equilibrium r/phase. However, the size and morphology of the precipitates show different characteristics among T6, T7 and RRA treatments. The DSC results are highly consistent with the TEM observation. The DSC curves of T6 aged samples are different from those of T7 and RRA aged samples, which also reflects the differences on the microstructure.展开更多
The effect of homogenization time on quench sensitivity of a cast 7085 aluminum alloy was investigated by means of end-quenching test, optical microscope （OM）, scanning electron microscope （SEM） and transmission e...The effect of homogenization time on quench sensitivity of a cast 7085 aluminum alloy was investigated by means of end-quenching test, optical microscope （OM）, scanning electron microscope （SEM） and transmission electron microscope （TEM）. The results show that with the increase of homogenization time from 48 h to 384 h, quench sensitivity increased slightly as the largest difference in the hardness was increased from 5.2% to 6.9% in the end-quenched and aged specimens. Prolonging homogenization had little effect on the grain structure, but improved the dissolution of soluble T phase and resulted in larger Al3Zr dispersoids with a low number density. Some small quench-induced η phase particles on Al3Zr dispersoids were observed inside grains during slow quenching, which decreased hardness after subsequent aging. The change in the character of Al3Zr dispersoids exerted slight influence on quench sensitivity.展开更多
This paper deals with reaction-diffusion equations involving nonstandard growth conditions, subject to homogeneous Neumann boundary conditions. The complete clas- sification is established for simultaneous and non-sim...This paper deals with reaction-diffusion equations involving nonstandard growth conditions, subject to homogeneous Neumann boundary conditions. The complete clas- sification is established for simultaneous and non-simultaneous quenching under suitable assumptions on initial data. Moreover, quenching sets and quenching rates are obtained.展开更多
The quench sensitivity of 6351 alloy was determined by the time temperature-transformation（TTT） curves and time temperature-property（TTP） curves by an interrupted quench technique with measurement of as-aged hardn...The quench sensitivity of 6351 alloy was determined by the time temperature-transformation（TTT） curves and time temperature-property（TTP） curves by an interrupted quench technique with measurement of as-aged hardness and as-quenched electro-conductivity.The microstructure transformation during isothermal treatment was studied by the transmission electron microscopy（TEM） and Avrami equation.The results showed that the electro-conductivity of the 6351 alloy increased and the hardness decreased with prolonging the holding time at a certain isothermal temperature.The TEM observation indicated that the supersaturated solid solution decomposed and needles β″ precipitated at the initial stage of isothermal holding.With the prolongation of holding time at the nose temperature,rod β＇ and plate β phases formed.The isothermal transformation rate at 360℃ was the fastest,and became slow at 280℃ and reached the slowest at 440℃.The nose temperatures of the TTT and TTP curves were about 360℃ and the high quench sensitive temperature range was 230 430℃.The quench factor analysis indicated that the cooling rate should be more than 15℃/s in the quench sensitive areas in order to get optimal mechanical properties.展开更多
In the field of Raman spectroscopy detection,the quest for a non–noble metal,recyclable,and highly sensitive detection substrate is of utmost importance.In this work,a new crystalline and noble metal–free substrate ...In the field of Raman spectroscopy detection,the quest for a non–noble metal,recyclable,and highly sensitive detection substrate is of utmost importance.In this work,a new crystalline and noble metal–free substrate of[Bi(DMF)_(8)][PMo_(12)O_(40)](Bi–PMo_(12))is designed,which is composed of[PMo_(12)O_(40)]^(3−)and solvated[Bi(DMF)_(8)]^(3+)cations.Mechanistic studies have revealed that Raman scattering quenching phenomenon arises from two main factors.Firstly,it arises from the absorption of the scattered light due to the transition of a single electron in the reduced state of MoV between 4d orbitals.Secondly,after the interaction between the substrate and hydrazine,the surface undergoes varying degrees of roughening,leading to an impact on the scattered light intensity.These two effects collectively contribute to the detection of low concentrations of N_(2)H_(4).As a result,Bi–PMo_(12)opens up a novel Raman scattering quenching mechanism to realize the detection of reduced N_(2)H_(4)small molecules.A remarkably low detection limit of 4.5×10^(−9)ppm for N_(2)H_(4)is achieved on the Bi–PMo_(12)substrate.This detection has a lower concentration than the currently known SERS detection of N_(2)H_(4).Moreover,Bi–PMo_(12)can be recovered and reused through recrystallization,achieving a recovery rate of up to ca.51%.This study reveals the underlying potential of crystalline polyoxometalate materials in the field of Raman detection,thus opening up new avenues for highly sensitive analysis using Raman techniques.展开更多
Due to the nonunitary time evolution and possibly complex energy eigenvalues in non-Hermitian systems,it is still under debate how to properly deal with the dynamics of time-dependent non-Hermitian Hamiltonian.Recentl...Due to the nonunitary time evolution and possibly complex energy eigenvalues in non-Hermitian systems,it is still under debate how to properly deal with the dynamics of time-dependent non-Hermitian Hamiltonian.Recently a quantum metric framework has been proposed to study the dynamics of generated defects of a non-Hermitian system under linear quench.Here,we provide an explicit expression for the endowed Hamiltonian under quantum metric for a general twolevel non-Hermitian system.Then we propose two exactly solvable models for the study of nonadiabatic dynamics of non-Hermitian systems,and analyze the defect production using the metric method.We find that,in contrast to the direct normalization method,the metric method can reproduce the symmetry of generated defects.The power-law scaling of generated defects with respect to quench time is also obtained.展开更多
The microstructure evolution and mechanical properties of a Fe-0.12C-0.2Si-1.6Mn-0.3Cr-0.0025B(wt.%)steel with different initial microstructures,i.e.,hot rolled(HR)and cold rolled-annealed(CRA),were studied through op...The microstructure evolution and mechanical properties of a Fe-0.12C-0.2Si-1.6Mn-0.3Cr-0.0025B(wt.%)steel with different initial microstructures,i.e.,hot rolled(HR)and cold rolled-annealed(CRA),were studied through optical microscopy,scanning electron microscopy,electron channeling contrast imaging,microhardness and room temperature uniaxial tensile tests.After water quenching from 930℃ to room temperature,a fully martensitic microstructure was obtained in both as-quenched HR and CRA specimens,which shows a microhardness of 480±5 HV,and no significant difference in microstructure and microhardness was observed.Tensile test results show that the product of tensile strength and total elongation(UTS×TE)of the as-quenched HR specimen,i.e.,24.1 GPa%,is higher than that of the as-quenched CRA specimen,i.e.,18.9 GPa%.While,after being tempered at 300℃,the martensitic microstructures and mechanical properties of the two as-quenched specimens change significantly due to the synergy role of the matrix phase softening and the precipitation strengthening.Concerning the maximum UTS×TE,it is 18.9 GPa%obtained in the as-quenched CRA one,while that is 24.4 GPa%obtained in the HR specimen after tempered at 300℃ for 5 min.展开更多
The effect of hot deformation on the quench sensitivity of the 7085 alloy was studied through hardness testing and microstructure characterization.The findings indicate that hot deformation enhances the quench sensiti...The effect of hot deformation on the quench sensitivity of the 7085 alloy was studied through hardness testing and microstructure characterization.The findings indicate that hot deformation enhances the quench sensitivity of the 7085 alloy,with the hardness difference between water quenching and air cooling increasing from 5.4%(before hot deformation)to 10.4%(after hot deformation).In the undeformed samples,the Al3Zr particles within the grains exhibit better coherent with the Al matrix.During slow quenching,only theηphase is observed on Al3Zr particles and at the grain boundaries.Hot deformation leads to a mass of recrystallization and the formation of subgrains with high dislocation density.This results in an increase in the types,quantities,and sizes of heterogeneous precipitates during quenching.In the slow quenching process,high angle grain boundaries are best for the nucleation and growth of theηphase.Secondly,a substantial quantity ofηand T phases precipitate on the non-coherent Al3Zr phase within the recrystallized grains.The locations with high dislocation density subgrains(boundaries)serve as nucleation positions for theηand T phases precipitating.Additionally,the Y phase is observed to precipitate at dislocation sites within the subgrains.展开更多
Formamidinium lead bromide(FAPbBr_(3))perovskite nanocrystals(NCs)are promising for display and lighting due to their ultra-pure green emission.However,the thermal quenching will exacerbate their performance degradati...Formamidinium lead bromide(FAPbBr_(3))perovskite nanocrystals(NCs)are promising for display and lighting due to their ultra-pure green emission.However,the thermal quenching will exacerbate their performance degradation in practical applications,which is a common issue for halide perovskites.Here,we reported the heat-resistant FAPbBr_(3)NCs prepared by a ligand-engineered room-temperature synthesis strategy.An aromatic amine,specificallyβ-phenylethylamine(PEA)or 3-fluorophenylethylamine(3-F-PEA),was incoporated as the short-chain ligand to expedite the crystallization rate and control the size distribution of FAPbBr_(3)NCs.Employing this ligand engineering approach,we synthesized high quality FAPbBr_(3)NCs with uniform grain size and reduced long-chain alkyl ligands,resulting in substantially suppressed thermal quenching and enhanced carrier transportation in the perovskite NCs films.Most notably,more than 90%of the room temperature PL intensity in the 3-F-PEA modified FAPbBr_(3)NCs film was preserved at 380 K.Consequently,we fabricated ultra-pure green EL devices with a room temperature external quantum efficiency(EQE)as high as 21.9%at the luminance of above 1,000 cd m^(-2),and demonstrated less than 10%loss in EQE at 343 K.This study introduces a novel room temperature method to synthesize efficient FAPbBr_(3)NCs with exceptional thermal stability,paving the way for advanced optoelectronic device applications.展开更多
High-performance 24CrNiMo steel was fabricated using Laser Powder Bed Fusion (LPBF). Subsequent quenching treatment was applied and the influence of quenching temperatures on micro-structure evolution and properties w...High-performance 24CrNiMo steel was fabricated using Laser Powder Bed Fusion (LPBF). Subsequent quenching treatment was applied and the influence of quenching temperatures on micro-structure evolution and properties was systematically characterised and analysed. The micro-structure of the as-built steel consisted of two parts. The first part comprised martensite with twins combined with ω-Fe nano-particles, and the second part consisted of lower bainite in the molten pool, as well as upper bainite, granular bainite and tempered martensite in the heat-affected zone. With the quenching temperatures varying from 800℃ to 950℃, the micro-structure gradually transformed from acicular ferrite + martensite to tempered martensite +θ-Fe3C carbides, and the grain size exhibited noticeable growth. Moreover, quenching treatments could eliminate the anisotropy and inhomogeneity of the micro-structure. The rod-shaped nanosized η-Fe2C and θ-Fe3C precipitates were clearly observed, which were converted from ω-Fe and distributed at multiple angles in the lath. The size and number of nano-precipitates, triggered by the high self-tempering degree of martensite, gradually increased. The relationships among grain size, the twins, dislocation density and nano-precipitation and the dramatically improved performance of quenched samples were analysed using strengthening mechanisms. After quenching at 850℃, the as-built 24CrNiMo steel attained ultra-high mechanical properties including hardness, Ultimate Tensile Strength (UTS), Elongation (El) and impact energy with values of 480.9 HV_(1), 1611.4 MPa, 9.8% and 42.8 J, respectively. Meanwhile, both the wear and thermal fatigue resistance increased by approximately 40%. This study demonstrated that LPBF-fabricated 24CrNiMo steel, with matching good performances, can be achieved using a subsequent one-step quenching process.展开更多
A martensitic initial microstructure before hot forming was prepared by direct quenching after hot rolling of the hot formed steel and the effect of such initial microstructure on mechanical properties of steel was an...A martensitic initial microstructure before hot forming was prepared by direct quenching after hot rolling of the hot formed steel and the effect of such initial microstructure on mechanical properties of steel was analyzed. The process of direct quenching after hot rolling which replaced the steps of coiling and cold rolling was termed as compact process. As the temperature before direct quenching falls within the non-recrystallization range, the deformed austenite grains exhibit flattened morphology along the hot rolling direction, and the high-density dislocations and significant strain energy in deformed austenite are inherited by directly quenched martensite. Moreover, due to promotion of austenite nucleation and subsequent recrystallization during the reverse transformation process in hot forming, both reversed austenite grains and martensite laths are significantly refined. Compared to the conventional process with an initial microstructure consisting of fully recrystallized ferrite and cementite, the compact process reduces average prior austenite grain sizes from 12.5 to 5.5 μm and martensite lath widths from 202 to 123 nm. Additionally, the compact process results in a higher density of dislocations in test steel, leading to maximum yield strength (1294 MPa) and ultimate tensile strength (2266 MPa). Compared to conventional process, this compact process significantly improves the mechanical properties of the hot formed steels while simplifying the production.展开更多
The microstructure and mechanical properties of 2524 Al alloy after quenching in liquid nitrogen(LN_(2))were investigated by TEM and compared with those of cold water quenching.The results show that the LN_(2) quenchi...The microstructure and mechanical properties of 2524 Al alloy after quenching in liquid nitrogen(LN_(2))were investigated by TEM and compared with those of cold water quenching.The results show that the LN_(2) quenching process effectively induces the formation of dislocation loops.These loops become large and unevenly distribute after aging for 15 min.Furthermore,such loops become rapidly immobilized by the precipitation of coarse S phases after 1 h aging.The alloy quenched in LN_(2) demonstrates superior peak hardness and displays a more rapid response to subsequent aging treatments compared with the cold water-quenched one.Despite the short aging time,LN_(2)-quenched sample achieves tensile strength of 488 MPa.This enhanced strength is attributed to the strengthening effect of numerous finely dispersed Guinier-Preston-Bagaryatsky(GPB)zones,in conjunction with the inhomogeneous formation of S phase on the dislocation loops.展开更多
The present work aims to investigate the effects of quenching, lamellarizing, and tempering(QLT)heat treatment on the microstructure and mechanical properties of ZG14Ni3Cr1Mo V high-strength low-alloy(HSLA) steel by c...The present work aims to investigate the effects of quenching, lamellarizing, and tempering(QLT)heat treatment on the microstructure and mechanical properties of ZG14Ni3Cr1Mo V high-strength low-alloy(HSLA) steel by comparing with traditional quenching and tempering(QT) heat treatment. Following the various QLT heat treatments, a dual-phase microstructure consisting of “soft” ferrite and “hard” tempered bainite is obtained, exhibiting significantly refined grain sizes(38.87 to 46.51 μm for QLT samples) compared to QT samples(64.93 μm). As the lamellar quenching temperature increases from 750 ℃ to 810 ℃, the yield strength and tensile strength of the QLT samples increase, although they remain lower than those of the QT samples. Conversely, elongation at fracture, reduction of area, and the product of strength and elongation synergy decrease, yet consistently exceed QT levels. Notably, the QLT samples demonstrate superior cryogenic impact toughness within the range of-80 ℃ to-120 ℃, achieving optimal values after 910 ℃ quenching + 780 ℃ lamellar quenching + 670 ℃ tempering: 215.97 J at-80 ℃, 207.80 J at-100℃, and 183.17 J at-120 ℃. This exceptional cryogenic toughness is attributed to two key mechanisms in the dual-phase microstructure:(i) a low dislocation density that suppresses crack initiation, and(ii) crack-tip passivation by soft ferrite, coupled with crack deflection and hindrance at high-angle grain boundaries(HAGBs). The results establish QLT as a viable method for enhancing cryogenic toughness in ZG14Ni3Cr1Mo V HSLA steels.展开更多
Quorum quenching (QQ)-based strategies are efficient for biofouling control.However,the feasibility of using QQ bacteria in antibiotic-stressed membrane bioreactors (MBRs) remains unknown.In this study,we isolated thr...Quorum quenching (QQ)-based strategies are efficient for biofouling control.However,the feasibility of using QQ bacteria in antibiotic-stressed membrane bioreactors (MBRs) remains unknown.In this study,we isolated three novel QQ strains (Bacillus sp.QX01 and QX03,Delftia sp.QX14) from the activated sludge of an actual MBR.They can degrade 11 N-acylhomoserine lactones (AHLs) with high efficiencies and rates through intracellular QQ pathways involving putative acylases and lactonases.Running two lab-scale MBRs,we found that introducing antibiotics (sulfamethoxazole,azithromycin,and ciprofloxacin,each at100μg/L) shortened the fouling cycle by 71.4%.However,the immobilized inoculation of QX01 into one MBR extended the fouling cycle by 1.5-2.0 times.Quantitative detection revealed that QX01 significantly reduced the concentrations of two AHLs (C4-HSL and C8-HSL),which were positively correlated with the contents of extracellular polymeric substances(EPS)(Pearson’s r=0.62-0.83,P<0.01).This suggests that QX01 could perform its QQ activity robustly under antibiotic stress,thereby inhibiting EPS production (proteins especially) and biofilm formation.Moreover,QX01 notably altered the succession patterns of both sludge and fouling communities,with more pronounced effects on abundant taxa.Genera associated with AHL synthesis and EPS production,such as Terrimonas and Rhodobacter,were significantly depleted,contributing to the mitigated biofouling.Additionally,QX01 increased the bacterial community diversity (evenness especially),which was inhibited by antibiotics.Overall,we demonstrate that the novel QQ bacteria could be effective for biofouling control in antibiotic-stressed MBRs,though future work is needed to develop practical approaches for prolonging QQ activity.展开更多
The rapid development of nanotechnology has significantly revolutionized wearable electronics and expanded their functionality.Through introducing innovative solutions for energy harvesting and autonomous sensing,this...The rapid development of nanotechnology has significantly revolutionized wearable electronics and expanded their functionality.Through introducing innovative solutions for energy harvesting and autonomous sensing,this research presents a cost-effective strategy to enhance the performance of triboelectric nanogenerators(TENGs).The TENG was fabricated from polyvinylidene fluoride(PVDF)and N,N'-poly(methyl methacrylate)(PMMA)blend with a porous structure via a novel optimized quenching method.The developed approach results in a highβ-phase content(85.7%)PVDF/3wt.%PMMA porous blend,known for its superior piezoelectric properties.PVDF/3wt.%PMMA modified porous TENG demonstrates remarkable electrical output,with a dielectric constant of 40 and an open-circuit voltage of approximately 600 V.The porous matrix notably increases durability,enduring over 36000 operational cycles without performance degradation.Moreover,practical applications were explored in this research,including powering LEDs and pacemakers with a maximum power output of 750mWm^(-2).Also,TENG served as a self-powered tactile sensor for robotic applications in various temperature conditions.The work highlights the potential of the PVDF/PMMA porous blend to utilize the next-generation self-powered sensors and power small electronic devices.展开更多
Amphiphiles,including surfactants,have emerged as indispensable elements in materials science and pharmaceutical science,and their functions are highly relying on the critical micelle concentration(CMC)[1,2].Numerous ...Amphiphiles,including surfactants,have emerged as indispensable elements in materials science and pharmaceutical science,and their functions are highly relying on the critical micelle concentration(CMC)[1,2].Numerous fluorimetry-based probes have been developed to measure CMCs[3](Fig.S1).However,CMC measurements using these probes suffer from a time-consuming and laborious procedure and large uncertainties,primarily due to their poor photo-stabilities and highly fluctuating fluorescence backgrounds.展开更多
Based on three-dimensional quantum electrodynamics theory,a set of truncated Dyson-Schwinger（D-S） equations are solved to study photon and fermion propagators with the effect of vacuum polarization.Numerical studies...Based on three-dimensional quantum electrodynamics theory,a set of truncated Dyson-Schwinger（D-S） equations are solved to study photon and fermion propagators with the effect of vacuum polarization.Numerical studies show that condensation and the value of fermion mass depends heavily on how the D-S equations are truncated.By solving a set of coupled D-S equations,it is also found that the fermion propagator shows a clear dependence on the order parameter.The truncated D-S equations under unquenched approximation are used to study the mass-function and chiral condensation of the fermions.The results under the unquenched approximation are clearly different from the ones under quenched approximation.With the increase in the order parameter,the fermion condensation in the unquenched approximation decreases when 0≤ξ5,while it increases when ξ5.However,nothing like this is observed in the quenched approximation,which indicates that there may be flaws in the quenched approximations.展开更多
This paper deals with the quenching behavior of positive solutions to the Newton filtration equations coupled with boundary singularities.We determine quenching rates for non-simultaneous quenching at first,and then e...This paper deals with the quenching behavior of positive solutions to the Newton filtration equations coupled with boundary singularities.We determine quenching rates for non-simultaneous quenching at first,and then establish the criteria to identify the simultaneous and non-simultaneous quenching in terms of the parameters involved.展开更多
基金Project (50904010) supported by the National Natural Science Foundation of ChinaProject (2010DFB50340) supported by the China International Science and Technology Cooperation
文摘The effect of quenching rate on the electrical conductivity and microstructure of thick plates of incumbent AA7050 was investigated by employing Jominy end quench test. The electrical conductivity measurement and microstructural observation were conducted at different distances from the quenched end. The results indicate that the average cooling rates decrease with increasing the distance from the quenched end of the bar in the quench sensitive temperature range. However, the electrical conductivity increases with the increase of distance from the quenched end. The surface parts of the plate were fully recrystallized, while partial recrystallization took place at the quarter and center parts of the plate. The quench induced grain boundary precipitates became remarkably coarser and discontinuously distributed with increasing distance from the quenched end of the bar. Plenty of heterogeneous precipitates were observed to nucleate on A13Zr dispersoids when the distance from the quenched end was greater than 38mm.
基金sponsored by the National Natural Science Foun-dation of China(Grant Nos.52271122,52203384).
文摘A cyclic quenching treatment(CQT)succeeded in turning a 2.3 GPa maraging steel with a Charpy impact energy of 9 J into a new grade with the same strength but a Charpy impact energy of 20 J upon 4 cyclic treatments.The improvement of mechanical properties is attributed to the refinement and increased chemical heterogeneity of the martensitic substructure,rather than the refinement of prior austenite grain(PAG),as well as the Transformation-Induced Plasticity(TRIP)effect facilitated by small austenite grains.The role of local segregation of Ni during CQT in the formation of Ni-rich austenite grains,Ni-rich martensite laths and Ni-poor martensite laths,was investigated and verified by DICTRA simulations.This study highlights the important influence of Ni partitioning behavior during CQT,providing insights into microstructural evolution and mechanical properties.
基金Project (201012200238) supported by the Freedom Inquiry Program of Central South University,ChinaProject (2012CB61950) supported by the National Basic Research Program of China
文摘The effects of quenching and aging （T6, T7 and RRA） on the microstructural evolution of an A1-Zn-Mg-Cu alloy were investigated by hardness test, optical microscopy （OM）, transmission electron microscopy （TEM） and differential scanning calorimetry （DSC） measurements. It is found that the hardness of T6 aged sample after water-quenching is the highest. The quench sensitivities of T7 and RRA are almost the same, which are 1.2% higher than that of T6. TEM observation shows that the quench sensitivity for the studied alloy is mainly caused by heterogeneous precipitation during slow quenching. Many r/phases precipitate on A13Zr dispersoids inside recrystallized grains and at （sub） grain boundaries, while T and S phases form in the substructure with high density of dislocations and defects. After aging, the η＇ precipitates are coarser in the vicinity of equilibrium r/phase. However, the size and morphology of the precipitates show different characteristics among T6, T7 and RRA treatments. The DSC results are highly consistent with the TEM observation. The DSC curves of T6 aged samples are different from those of T7 and RRA aged samples, which also reflects the differences on the microstructure.
基金Project(2012CB619500)supported by the National Basic Research Program of ChinaProject supported by Yuying Project of Central South University
文摘The effect of homogenization time on quench sensitivity of a cast 7085 aluminum alloy was investigated by means of end-quenching test, optical microscope （OM）, scanning electron microscope （SEM） and transmission electron microscope （TEM）. The results show that with the increase of homogenization time from 48 h to 384 h, quench sensitivity increased slightly as the largest difference in the hardness was increased from 5.2% to 6.9% in the end-quenched and aged specimens. Prolonging homogenization had little effect on the grain structure, but improved the dissolution of soluble T phase and resulted in larger Al3Zr dispersoids with a low number density. Some small quench-induced η phase particles on Al3Zr dispersoids were observed inside grains during slow quenching, which decreased hardness after subsequent aging. The change in the character of Al3Zr dispersoids exerted slight influence on quench sensitivity.
文摘This paper deals with reaction-diffusion equations involving nonstandard growth conditions, subject to homogeneous Neumann boundary conditions. The complete clas- sification is established for simultaneous and non-simultaneous quenching under suitable assumptions on initial data. Moreover, quenching sets and quenching rates are obtained.
基金Project(2012M511552) supported by China Postdoctoral Science FoundationProject(2009A080205001) supported by the State Key Fundamental Research Program of China
文摘The quench sensitivity of 6351 alloy was determined by the time temperature-transformation（TTT） curves and time temperature-property（TTP） curves by an interrupted quench technique with measurement of as-aged hardness and as-quenched electro-conductivity.The microstructure transformation during isothermal treatment was studied by the transmission electron microscopy（TEM） and Avrami equation.The results showed that the electro-conductivity of the 6351 alloy increased and the hardness decreased with prolonging the holding time at a certain isothermal temperature.The TEM observation indicated that the supersaturated solid solution decomposed and needles β″ precipitated at the initial stage of isothermal holding.With the prolongation of holding time at the nose temperature,rod β＇ and plate β phases formed.The isothermal transformation rate at 360℃ was the fastest,and became slow at 280℃ and reached the slowest at 440℃.The nose temperatures of the TTT and TTP curves were about 360℃ and the high quench sensitive temperature range was 230 430℃.The quench factor analysis indicated that the cooling rate should be more than 15℃/s in the quench sensitive areas in order to get optimal mechanical properties.
基金the financial support from the National Natural Science Foundation of China(No.21971085)the Natural Science Foundation of Shandong Province(No.ZR2021MB008)。
文摘In the field of Raman spectroscopy detection,the quest for a non–noble metal,recyclable,and highly sensitive detection substrate is of utmost importance.In this work,a new crystalline and noble metal–free substrate of[Bi(DMF)_(8)][PMo_(12)O_(40)](Bi–PMo_(12))is designed,which is composed of[PMo_(12)O_(40)]^(3−)and solvated[Bi(DMF)_(8)]^(3+)cations.Mechanistic studies have revealed that Raman scattering quenching phenomenon arises from two main factors.Firstly,it arises from the absorption of the scattered light due to the transition of a single electron in the reduced state of MoV between 4d orbitals.Secondly,after the interaction between the substrate and hydrazine,the surface undergoes varying degrees of roughening,leading to an impact on the scattered light intensity.These two effects collectively contribute to the detection of low concentrations of N_(2)H_(4).As a result,Bi–PMo_(12)opens up a novel Raman scattering quenching mechanism to realize the detection of reduced N_(2)H_(4)small molecules.A remarkably low detection limit of 4.5×10^(−9)ppm for N_(2)H_(4)is achieved on the Bi–PMo_(12)substrate.This detection has a lower concentration than the currently known SERS detection of N_(2)H_(4).Moreover,Bi–PMo_(12)can be recovered and reused through recrystallization,achieving a recovery rate of up to ca.51%.This study reveals the underlying potential of crystalline polyoxometalate materials in the field of Raman detection,thus opening up new avenues for highly sensitive analysis using Raman techniques.
基金supported by the National Key Research and Development Program of the Ministry of Science and Technology of China(Grant No.2021YFA1200700)the National Natural Science Foundation of China(Grant Nos.11905054 and 12275075)the Fundamental Research Funds for the Central Universities of China.
文摘Due to the nonunitary time evolution and possibly complex energy eigenvalues in non-Hermitian systems,it is still under debate how to properly deal with the dynamics of time-dependent non-Hermitian Hamiltonian.Recently a quantum metric framework has been proposed to study the dynamics of generated defects of a non-Hermitian system under linear quench.Here,we provide an explicit expression for the endowed Hamiltonian under quantum metric for a general twolevel non-Hermitian system.Then we propose two exactly solvable models for the study of nonadiabatic dynamics of non-Hermitian systems,and analyze the defect production using the metric method.We find that,in contrast to the direct normalization method,the metric method can reproduce the symmetry of generated defects.The power-law scaling of generated defects with respect to quench time is also obtained.
基金Chongqing Natural Science Foundation(No.CSTB2022NSCQ-MSX1394)Graduate Research and Innovation Foundation of Chongqing,China(Grant No.CYS22008)+2 种基金Open Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(SKLASS 2023-10)the Science and Technology Commission of Shanghai Municipality(No.19DZ2270200)the Open Project of the Large Casting and Forging Manufacturing Technology Engineering Center of Shanghai Institute of Mechanical and Electrical Engineering,State Key Laboratory of Vanadium and Titanium Resources Open Fund(No.2022P4FZG04A).
文摘The microstructure evolution and mechanical properties of a Fe-0.12C-0.2Si-1.6Mn-0.3Cr-0.0025B(wt.%)steel with different initial microstructures,i.e.,hot rolled(HR)and cold rolled-annealed(CRA),were studied through optical microscopy,scanning electron microscopy,electron channeling contrast imaging,microhardness and room temperature uniaxial tensile tests.After water quenching from 930℃ to room temperature,a fully martensitic microstructure was obtained in both as-quenched HR and CRA specimens,which shows a microhardness of 480±5 HV,and no significant difference in microstructure and microhardness was observed.Tensile test results show that the product of tensile strength and total elongation(UTS×TE)of the as-quenched HR specimen,i.e.,24.1 GPa%,is higher than that of the as-quenched CRA specimen,i.e.,18.9 GPa%.While,after being tempered at 300℃,the martensitic microstructures and mechanical properties of the two as-quenched specimens change significantly due to the synergy role of the matrix phase softening and the precipitation strengthening.Concerning the maximum UTS×TE,it is 18.9 GPa%obtained in the as-quenched CRA one,while that is 24.4 GPa%obtained in the HR specimen after tempered at 300℃ for 5 min.
基金Project(52205421)supported by the National Natural Science Foundation of ChinaProject(AA23023028)supported by the Guangxi Science and Technology Major Project,China+2 种基金Projects(2022B0909070001,2020B010186001)supported by the Key Research and Development Projects of Guangdong Province,ChinaProject(2021B0101220006)supported by the Guangdong Key Areas Research and Development Program“Chip,Software and Computing”Major Project,ChinaProjects(2021RC2087,2022JJ30570)supported by the Science and Technology Innovation Program of Hunan Province,China。
文摘The effect of hot deformation on the quench sensitivity of the 7085 alloy was studied through hardness testing and microstructure characterization.The findings indicate that hot deformation enhances the quench sensitivity of the 7085 alloy,with the hardness difference between water quenching and air cooling increasing from 5.4%(before hot deformation)to 10.4%(after hot deformation).In the undeformed samples,the Al3Zr particles within the grains exhibit better coherent with the Al matrix.During slow quenching,only theηphase is observed on Al3Zr particles and at the grain boundaries.Hot deformation leads to a mass of recrystallization and the formation of subgrains with high dislocation density.This results in an increase in the types,quantities,and sizes of heterogeneous precipitates during quenching.In the slow quenching process,high angle grain boundaries are best for the nucleation and growth of theηphase.Secondly,a substantial quantity ofηand T phases precipitate on the non-coherent Al3Zr phase within the recrystallized grains.The locations with high dislocation density subgrains(boundaries)serve as nucleation positions for theηand T phases precipitating.Additionally,the Y phase is observed to precipitate at dislocation sites within the subgrains.
基金support from the National Key Research and Development Program of China(2022YFE0206000)the National Natural Science Foundation of China(U2001219,51973064)+3 种基金the Guangdong Basic and Applied Basic Research Foundation(2023B1515040003,2024A1515010262)the Natural Science Foundation of Guangdong Province(2023B1212060003)the Open Project Program of Wuhan National Laboratory for Optoelectronics(NO.2021WNLOKF014)the State Key Lab of Luminescent Materials and Devices,South China University of Technology(Skllmd-2023-05).
文摘Formamidinium lead bromide(FAPbBr_(3))perovskite nanocrystals(NCs)are promising for display and lighting due to their ultra-pure green emission.However,the thermal quenching will exacerbate their performance degradation in practical applications,which is a common issue for halide perovskites.Here,we reported the heat-resistant FAPbBr_(3)NCs prepared by a ligand-engineered room-temperature synthesis strategy.An aromatic amine,specificallyβ-phenylethylamine(PEA)or 3-fluorophenylethylamine(3-F-PEA),was incoporated as the short-chain ligand to expedite the crystallization rate and control the size distribution of FAPbBr_(3)NCs.Employing this ligand engineering approach,we synthesized high quality FAPbBr_(3)NCs with uniform grain size and reduced long-chain alkyl ligands,resulting in substantially suppressed thermal quenching and enhanced carrier transportation in the perovskite NCs films.Most notably,more than 90%of the room temperature PL intensity in the 3-F-PEA modified FAPbBr_(3)NCs film was preserved at 380 K.Consequently,we fabricated ultra-pure green EL devices with a room temperature external quantum efficiency(EQE)as high as 21.9%at the luminance of above 1,000 cd m^(-2),and demonstrated less than 10%loss in EQE at 343 K.This study introduces a novel room temperature method to synthesize efficient FAPbBr_(3)NCs with exceptional thermal stability,paving the way for advanced optoelectronic device applications.
基金co-supported by the National Key Research and Development Program of China (No. 2022YFB4600500)the National Natural Science Foundation of China (No. 52235006)
文摘High-performance 24CrNiMo steel was fabricated using Laser Powder Bed Fusion (LPBF). Subsequent quenching treatment was applied and the influence of quenching temperatures on micro-structure evolution and properties was systematically characterised and analysed. The micro-structure of the as-built steel consisted of two parts. The first part comprised martensite with twins combined with ω-Fe nano-particles, and the second part consisted of lower bainite in the molten pool, as well as upper bainite, granular bainite and tempered martensite in the heat-affected zone. With the quenching temperatures varying from 800℃ to 950℃, the micro-structure gradually transformed from acicular ferrite + martensite to tempered martensite +θ-Fe3C carbides, and the grain size exhibited noticeable growth. Moreover, quenching treatments could eliminate the anisotropy and inhomogeneity of the micro-structure. The rod-shaped nanosized η-Fe2C and θ-Fe3C precipitates were clearly observed, which were converted from ω-Fe and distributed at multiple angles in the lath. The size and number of nano-precipitates, triggered by the high self-tempering degree of martensite, gradually increased. The relationships among grain size, the twins, dislocation density and nano-precipitation and the dramatically improved performance of quenched samples were analysed using strengthening mechanisms. After quenching at 850℃, the as-built 24CrNiMo steel attained ultra-high mechanical properties including hardness, Ultimate Tensile Strength (UTS), Elongation (El) and impact energy with values of 480.9 HV_(1), 1611.4 MPa, 9.8% and 42.8 J, respectively. Meanwhile, both the wear and thermal fatigue resistance increased by approximately 40%. This study demonstrated that LPBF-fabricated 24CrNiMo steel, with matching good performances, can be achieved using a subsequent one-step quenching process.
基金financial support from the National Natural Science Foundation of China(No.52274372)the National Key Research and Development Program of China(No.2021YFB3702404).
文摘A martensitic initial microstructure before hot forming was prepared by direct quenching after hot rolling of the hot formed steel and the effect of such initial microstructure on mechanical properties of steel was analyzed. The process of direct quenching after hot rolling which replaced the steps of coiling and cold rolling was termed as compact process. As the temperature before direct quenching falls within the non-recrystallization range, the deformed austenite grains exhibit flattened morphology along the hot rolling direction, and the high-density dislocations and significant strain energy in deformed austenite are inherited by directly quenched martensite. Moreover, due to promotion of austenite nucleation and subsequent recrystallization during the reverse transformation process in hot forming, both reversed austenite grains and martensite laths are significantly refined. Compared to the conventional process with an initial microstructure consisting of fully recrystallized ferrite and cementite, the compact process reduces average prior austenite grain sizes from 12.5 to 5.5 μm and martensite lath widths from 202 to 123 nm. Additionally, the compact process results in a higher density of dislocations in test steel, leading to maximum yield strength (1294 MPa) and ultimate tensile strength (2266 MPa). Compared to conventional process, this compact process significantly improves the mechanical properties of the hot formed steels while simplifying the production.
基金supported by the National Natural Science Foundation of China(No.52001106)the Natural Science Foundation of Hebei Province,China(No.E2022202158).
文摘The microstructure and mechanical properties of 2524 Al alloy after quenching in liquid nitrogen(LN_(2))were investigated by TEM and compared with those of cold water quenching.The results show that the LN_(2) quenching process effectively induces the formation of dislocation loops.These loops become large and unevenly distribute after aging for 15 min.Furthermore,such loops become rapidly immobilized by the precipitation of coarse S phases after 1 h aging.The alloy quenched in LN_(2) demonstrates superior peak hardness and displays a more rapid response to subsequent aging treatments compared with the cold water-quenched one.Despite the short aging time,LN_(2)-quenched sample achieves tensile strength of 488 MPa.This enhanced strength is attributed to the strengthening effect of numerous finely dispersed Guinier-Preston-Bagaryatsky(GPB)zones,in conjunction with the inhomogeneous formation of S phase on the dislocation loops.
基金supported by the Science and Technology Planning Joint Program of Liaoning Province(Applied Basic Research Project,No.2023JH2/101700054).
文摘The present work aims to investigate the effects of quenching, lamellarizing, and tempering(QLT)heat treatment on the microstructure and mechanical properties of ZG14Ni3Cr1Mo V high-strength low-alloy(HSLA) steel by comparing with traditional quenching and tempering(QT) heat treatment. Following the various QLT heat treatments, a dual-phase microstructure consisting of “soft” ferrite and “hard” tempered bainite is obtained, exhibiting significantly refined grain sizes(38.87 to 46.51 μm for QLT samples) compared to QT samples(64.93 μm). As the lamellar quenching temperature increases from 750 ℃ to 810 ℃, the yield strength and tensile strength of the QLT samples increase, although they remain lower than those of the QT samples. Conversely, elongation at fracture, reduction of area, and the product of strength and elongation synergy decrease, yet consistently exceed QT levels. Notably, the QLT samples demonstrate superior cryogenic impact toughness within the range of-80 ℃ to-120 ℃, achieving optimal values after 910 ℃ quenching + 780 ℃ lamellar quenching + 670 ℃ tempering: 215.97 J at-80 ℃, 207.80 J at-100℃, and 183.17 J at-120 ℃. This exceptional cryogenic toughness is attributed to two key mechanisms in the dual-phase microstructure:(i) a low dislocation density that suppresses crack initiation, and(ii) crack-tip passivation by soft ferrite, coupled with crack deflection and hindrance at high-angle grain boundaries(HAGBs). The results establish QLT as a viable method for enhancing cryogenic toughness in ZG14Ni3Cr1Mo V HSLA steels.
基金supported by the National Natural Science Foundation of China (Nos.51938001 and 52300073)。
文摘Quorum quenching (QQ)-based strategies are efficient for biofouling control.However,the feasibility of using QQ bacteria in antibiotic-stressed membrane bioreactors (MBRs) remains unknown.In this study,we isolated three novel QQ strains (Bacillus sp.QX01 and QX03,Delftia sp.QX14) from the activated sludge of an actual MBR.They can degrade 11 N-acylhomoserine lactones (AHLs) with high efficiencies and rates through intracellular QQ pathways involving putative acylases and lactonases.Running two lab-scale MBRs,we found that introducing antibiotics (sulfamethoxazole,azithromycin,and ciprofloxacin,each at100μg/L) shortened the fouling cycle by 71.4%.However,the immobilized inoculation of QX01 into one MBR extended the fouling cycle by 1.5-2.0 times.Quantitative detection revealed that QX01 significantly reduced the concentrations of two AHLs (C4-HSL and C8-HSL),which were positively correlated with the contents of extracellular polymeric substances(EPS)(Pearson’s r=0.62-0.83,P<0.01).This suggests that QX01 could perform its QQ activity robustly under antibiotic stress,thereby inhibiting EPS production (proteins especially) and biofilm formation.Moreover,QX01 notably altered the succession patterns of both sludge and fouling communities,with more pronounced effects on abundant taxa.Genera associated with AHL synthesis and EPS production,such as Terrimonas and Rhodobacter,were significantly depleted,contributing to the mitigated biofouling.Additionally,QX01 increased the bacterial community diversity (evenness especially),which was inhibited by antibiotics.Overall,we demonstrate that the novel QQ bacteria could be effective for biofouling control in antibiotic-stressed MBRs,though future work is needed to develop practical approaches for prolonging QQ activity.
基金supported by the research projects AP14869428 from the Ministry of Science and Higher Education of the Republic of Kazakhstan20122022FD4135 from Nazarbayev University.
文摘The rapid development of nanotechnology has significantly revolutionized wearable electronics and expanded their functionality.Through introducing innovative solutions for energy harvesting and autonomous sensing,this research presents a cost-effective strategy to enhance the performance of triboelectric nanogenerators(TENGs).The TENG was fabricated from polyvinylidene fluoride(PVDF)and N,N'-poly(methyl methacrylate)(PMMA)blend with a porous structure via a novel optimized quenching method.The developed approach results in a highβ-phase content(85.7%)PVDF/3wt.%PMMA porous blend,known for its superior piezoelectric properties.PVDF/3wt.%PMMA modified porous TENG demonstrates remarkable electrical output,with a dielectric constant of 40 and an open-circuit voltage of approximately 600 V.The porous matrix notably increases durability,enduring over 36000 operational cycles without performance degradation.Moreover,practical applications were explored in this research,including powering LEDs and pacemakers with a maximum power output of 750mWm^(-2).Also,TENG served as a self-powered tactile sensor for robotic applications in various temperature conditions.The work highlights the potential of the PVDF/PMMA porous blend to utilize the next-generation self-powered sensors and power small electronic devices.
基金supported by Shanghai Municipal Commission of Science and Technology,China(Grant No.:19XD1400300)the National Natural Science Foundation of China(Grant Nos.:821040821,82273867,and 82030107).
文摘Amphiphiles,including surfactants,have emerged as indispensable elements in materials science and pharmaceutical science,and their functions are highly relying on the critical micelle concentration(CMC)[1,2].Numerous fluorimetry-based probes have been developed to measure CMCs[3](Fig.S1).However,CMC measurements using these probes suffer from a time-consuming and laborious procedure and large uncertainties,primarily due to their poor photo-stabilities and highly fluctuating fluorescence backgrounds.
基金The Science Foundation of Southeast University,the National Natural Science Foundation of China (No. 11047005)
文摘Based on three-dimensional quantum electrodynamics theory,a set of truncated Dyson-Schwinger（D-S） equations are solved to study photon and fermion propagators with the effect of vacuum polarization.Numerical studies show that condensation and the value of fermion mass depends heavily on how the D-S equations are truncated.By solving a set of coupled D-S equations,it is also found that the fermion propagator shows a clear dependence on the order parameter.The truncated D-S equations under unquenched approximation are used to study the mass-function and chiral condensation of the fermions.The results under the unquenched approximation are clearly different from the ones under quenched approximation.With the increase in the order parameter,the fermion condensation in the unquenched approximation decreases when 0≤ξ5,while it increases when ξ5.However,nothing like this is observed in the quenched approximation,which indicates that there may be flaws in the quenched approximations.
基金Supported by the National Natural Science Foundation of China(10771024,11101060,11171048)
文摘This paper deals with the quenching behavior of positive solutions to the Newton filtration equations coupled with boundary singularities.We determine quenching rates for non-simultaneous quenching at first,and then establish the criteria to identify the simultaneous and non-simultaneous quenching in terms of the parameters involved.
