Cold deformation treatment of Cu-bearing stainless steel through a cold rolling process combined with electric pulse treatment(EPT)can significantly improve the microstructure and formability of cold-rolled Cu-bearing...Cold deformation treatment of Cu-bearing stainless steel through a cold rolling process combined with electric pulse treatment(EPT)can significantly improve the microstructure and formability of cold-rolled Cu-bearing stainless steel.The microstructure after EPT was characterized by scanning electron microscopy,transmission electron microscopy,and in-situ tensile testing.It is found that compared with conventional heat treatment,EPT process can significantly promote the nucleation rate and mobility at grain boundaries of the deformed samples,greatly accelerating the recovery and static recrystallization of Cu-bearing stainless steel samples at lower temperatures and contributing to the recovery of anisotropy and the re-molding of deformed samples.Microstructural characterization and theoretical analyses show that the rapid recrystallization during EPT process is caused not only by Joule heating effects but also by non-thermal effects that accelerate grain boundary migration and dislocation destruction and regeneration.In addition,EPT process significantly accelerated the nucleation and precipitation growth of Cu-rich phase.The coarsening of Cu-rich phase during EPT process is due to not only the high vacancy diffusion coefficient under the action of the electric pulse but also the increase in the vacancy diffusion flux induced by the electromigration in the process of the electric pulse.展开更多
A full-sectional microstructure characterization method was developed to investigate the formation of coarse slag rims during the continuous casting of hypo-peritectic steel.The cross-sectional microstructural analysi...A full-sectional microstructure characterization method was developed to investigate the formation of coarse slag rims during the continuous casting of hypo-peritectic steel.The cross-sectional microstructural analysis of typical slag rims for two highly crystalline powders revealed that their formation was primarily driven by the solidification of the liquid slag.Distinct differences were observed in the microstructures of slag rims from the two powders.Powder A(characterized by a higher breaking temperature and viscosity)displayed alternating lamellar microstructures of coarse and fine phases,with the coarse phases composed of akermanite-gehlenite transition phases.In contrast,powder B(with a lower breaking temperature and viscosity)predominantly comprised regular akermanite-gehlenite crystals interspersed with a certain amount of glassy phases.Numerical simulations of a three-phase fluid flow coupled with heat transfer indicate that slag rim formation correlates with mold oscillation.Solidification of the liquid slag at the slag rim front predominantly occurs during the negative stroke of the mold oscillation.The average heating rate during the ascending stage of the mold reaches approximately 100 K·s^(−1),whereas the average cooling rate during the descending stage attains 400 K·s^(−1).This temperature variation leads to the formation of lamellar microstructures,whereas the ascending stage promotes the formation of coarse structures and thicker slag rims.Based on the powder properties,two distinct formation pathways exist for highly crystalline mold powders.For the powders with a higher breaking temperature,higher viscosity,and narrower solidification range(powder A),coarse microstructures and thicker slag rims were preferentially formed.For powders with lower breaking temperature and viscosity and wider solidification ranges(powder B),the liquid slag resisted rapid solidification,and the extended mushy zone allowed the partial liquid slag to persist at the slag rim front,promoting the formation of a thin slag rim.This study enhances the understanding of slag rim formation in highly crystalline mold powders and provides critical insights into the control of longitudinal surface cracks in hypo-peritectic steel.展开更多
Tungsten heavy alloys(WHAs)prepared using laser additive manufacturing(AM)exhibit intricate ge-ometries,albeit with limited mechanical properties.Here we designed a high-strength WHA featuring a FeCrCoNi high entropy ...Tungsten heavy alloys(WHAs)prepared using laser additive manufacturing(AM)exhibit intricate ge-ometries,albeit with limited mechanical properties.Here we designed a high-strength WHA featuring a FeCrCoNi high entropy alloy(HEA)binder via the laser metal deposition(LMD)technique.Due to the distinctive thermal cycle and rapid cooling rate,the as-deposited alloys exhibit microstructures with hy-poeutectic,eutectic-like,and spot-like characteristics.To elucidate this phenomenon,the solidification paths were delineated and analyzed by combining microstructural characterization and phase equilib-rium simulation.Theμphase precipitated out from the supersaturated solid solution,thereby nucleating massive dislocations on the FeCrCoNi matrix to increase the work hardening rate.Furthermore,theμphase formed an ultrafine intermetallic compound(IMC)layer around the W grain,reducing the hole or crack between the W grain and FeCrCoNi matrix.Attributed to the precipitation strengthening,the solid solution of the FeCrCoNi binder,along with the load-bearing strength of W,the developed alloy achieved ultrahigh compressive stress and strain of 2047 MPa and 32%respectively at room temperature.These findings contribute valuable insights to the advancement of additive manufacturing for tungsten alloys,leveraging their excellent properties.展开更多
Refractory high/medium-entropy alloys(RH/MEAs)are known for their outstanding performance at el-evated temperatures;however,they usually exhibit poor room-temperature plasticity,which can be at-tributed to the non-uni...Refractory high/medium-entropy alloys(RH/MEAs)are known for their outstanding performance at el-evated temperatures;however,they usually exhibit poor room-temperature plasticity,which can be at-tributed to the non-uniform deformation that occurs at room temperature.Once cracks nucleate,they will rapidly propagate into vertical splitting cracks.Here,we introduce multiple phases including FCC and HCP phases into the NbMoTa RMEA via appropriate addition of carbon.The results show that multiple-phase synergy effectively suppresses non-uniform deformation,thereby delaying the onset of vertical splitting cracks.An optimal combination of compressive strength-plasticity is achieved by the(NbMoTa)_(92.5)C_(7.5) alloy.The significant improvement in room-temperature mechanical properties can be attributed to its hierarchical microstructure:in the mesoscale,the BCC matrix is divided by eutectic structures;while at the microscale,the BCC matrix is further refined by abundant lath-like FCC precipitates.The FCC precip-itates contain high-density stacking faults,acting as a dislocation source under compressive loading.The HCP phase in the eutectic microstructures,in turn,acts as a strong barrier to dislocation movement and simultaneously increases the dislocation storage capacity.These findings open a new route to tailor the microstructure and mechanical properties of RH/MEAs.展开更多
ZnO thin films with varying Ta concentrations were fabricated through magnetron sputtering.The crystallinity and surface morphology of the ZnO films are significantly influenced by the incorporation of Ta,as evidenced...ZnO thin films with varying Ta concentrations were fabricated through magnetron sputtering.The crystallinity and surface morphology of the ZnO films are significantly influenced by the incorporation of Ta,as evidenced by the X-ray diffraction and scanning electron microscopy results.The lattice constants,as determined by X-ray diffraction,contradict the disparity in Ta and Zn ion radii,which is attributed to the impact of interstitial defects.This inconsistency introduces variations in carrier concentration in this experiment compared with prior studies.Subsequent exploration of the luminescent characteristics and emission mechanism of defect levels in Ta-doped ZnO films was conducted through photoluminescence.Furthermore,the factors influencing the bandgap are discussed.展开更多
The complex non-equilibrium solidification effects of the laser powder bed fusion(LPBF)combined with the high solubility of rare-earth(RE)elements,provide a new advanced powder metallurgy process for Mg RE alloys with...The complex non-equilibrium solidification effects of the laser powder bed fusion(LPBF)combined with the high solubility of rare-earth(RE)elements,provide a new advanced powder metallurgy process for Mg RE alloys with outstanding mechanical performances.However,its creep mechanism has not been revealed yet.The present study systematically investigates and evaluates the high-temperature creep mechanism of LPBFed WE43 alloy under varying temperatures and applied stress conditions.In addition,it thoroughly elucidates the interactions and evolution mechanisms between precipitates and disloca-tions during the creep process.Subject to residual stresses and thermal cycling,theβphase is formed in the form of“precipitation chains”(PCs)within the grains.The metastable phasesβ″,β′,andβ_(1) in-situ precipitate between the PCs.The creep resistance of the(LPBFed)WE43 alloy is governed by the evolution of precipitates and their interactions with dislocations during the creep.Under creep condi-tions at 200℃,a large number of<c+a>anddislocations undergo climb and cross-slip behaviors within the grains.During the climb and cross-slip of dislocations,the Orowan strengthening effect ofβ″,the cutting mechanisms ofβ′andβ_(1) phases relative to dislocations,and the dislocation barriers formed by theβphase arrays collectively impart excellent creep resistance to the WE43 alloy.As creep time progresses,dislocations accumulate within the grains,and theβandβ_(1) phases promote the forma-tion of subgrain boundaries,further triggering discontinuous dynamic recrystallization behaviors during the creep process.Furthermore,influenced by the directional diffusion of elements,precipitates dynami-cally form around the grain boundaries of recrystallized grains,thereby enhancing the resistance to grain boundary sliding.When the creep temperature increases to 250℃ or 300℃,a large number of<c+a>dislocations,accompanied by the dissolution of metastable phases and elemental re-diffusion,transform during the creep process into stacking faults(SFs).SFs not only exhibit high thermal stability but also act as effective dislocation barriers at high temperatures through lattice mismatch mechanisms.However,under high-temperature conditions,thermal activation leads to the dissolution of unstable metastable phases,promoting rapid coarsening and transformation of precipitates into various morphologies ofβphases,thereby causing a catastrophic decline in creep performance.At the same time,high tempera-tures further exacerbate elemental diffusion,resulting in precipitate-free zones near grain boundaries,thereby inducing crack initiation.Therefore,the creep resistance of as-deposited alloys decreases signif-icantly at higher temperatures.Building on this,the future development trends of LPBFed WE43 alloys are envisioned,where homogenizing heterostructures or introducing high aspect ratio precipitates and high-density SFs prior to creep can be regarded as a promising approach for enhancing creep resistance in LPBFed WE43 alloys.展开更多
The fracture mechanisms of coarse-grained heat-affected zone(CGHAZ)for Mg and Mg–Ca deoxidized high-strength low-alloy(HSLA)steels after high heat input welding(HHIW)were investigated based on the microstructures,cra...The fracture mechanisms of coarse-grained heat-affected zone(CGHAZ)for Mg and Mg–Ca deoxidized high-strength low-alloy(HSLA)steels after high heat input welding(HHIW)were investigated based on the microstructures,crack behaviors and mechanical properties.Compared to Mg–Ca steel,the proportion of intergranular acicular ferrites(IAFs)and polygonal ferrites(PFs)in Mg steel increases from 59.97%to 90.16%.The high-angle grain boundaries(HAGBs)and geometrically necessary dislocations density increase from 55.5%and 4.30×10^(14) m^(-2)to 70.4%and 5.48×10^(14) m^(–2),respectively,while effective grain size decreases from 9.46 to 8.12μm.The area fraction of radial zone in Mg steel decreases from 80.8%to 37.7%and cleavage plane is smaller with more curved and finer tearing ridges.The inclusions distributed at the center of cleavage planes and along river lines can serve as crack initiation sites.The zigzag pattern of primary crack propagation path has width of 476μm and the length of secondary cracks remains below 10μm.These cracks are deflected or arrested by IAFs,PFs and HAGBs,and tend to propagate along{110}plane family.These factors contribute to superior overall mechanical properties of Mg steel,especially increasing low-temperature impact toughness from 23 to 175 J.展开更多
YBa_(2)Cu_(3)O_(7-x)(YBCO)films with low microwave surface resistance(RS)are essential for high temperature superconducting microwave devices.The oxygen pressure during deposition has been found to influence RS signif...YBa_(2)Cu_(3)O_(7-x)(YBCO)films with low microwave surface resistance(RS)are essential for high temperature superconducting microwave devices.The oxygen pressure during deposition has been found to influence RS significantly.In this work,we deposited highly c-axis aligned YBCO films on single crystal MgO(001)substrates under different oxygen pressures via pulsed laser ablation.Their detailed microstructure was characterized with three-dimensional reciprocal space mapping(3D-RSM)method and their microwave surface resistance was also measured with resonant cavity perturbation method.We found that the variation of oxygen pressure can affect film microstructure,including grain orientation distribution and the concentration of crystal defects.The microstructure modulation can explain RS dependence on the oxygen pressure.展开更多
The low coercivity is the major factor inhibiting the large-scale commercial utilization of Nd-Ce-Fe-B sintered magnets.In this work,we achieved a record-high coercivity of 15.04 kOe in Ga-doped Nd-Ce-Fe-B sintered ma...The low coercivity is the major factor inhibiting the large-scale commercial utilization of Nd-Ce-Fe-B sintered magnets.In this work,we achieved a record-high coercivity of 15.04 kOe in Ga-doped Nd-Ce-Fe-B sintered magnets with 30 wt%Ce replacing Nd,demonstrating enormous potential.The Ga-doped Nd-Ce-Fe-B magnets with higher boron(HB)and lower boron(LB)content are designed.The coercivity of the HB magnet increases slightly from 10.80 to 12.26 kOe after annealing,attributed to the optimized distribution of grain boundary(GB)phases.In contrast,the coercivity of the LB magnet remarkably increases from 8.13 to 15.04 kOe after annealing.Microstructural observations indicate that the narrow GB phase in the as-sintered magnet is rich in Fe,and the strong exchange coupling of adjacent grains resulted in low coercivity.The evolution of Ga-rich phases reveals a potential formation mechanism of the RE_(6)Fe_(13)Ga phase,that is the RE-Fe amorphous phase and REGa phase in the as-sintered magnet combine to form the RE_(6)Fe_(13)Ga phase and RE-Ga amorphous phase during post-sinter annealing(RE:rare earth).Moreover,the GB phase of the annealed magnet transforms into a Fe-lean phase with a thickness of 16.4 nm.Magnetization and demagnetization behavior characterizations reveal that the exchange decoupling of adjacent grains induced by the optimized GB phases is the main reason for the remarkable coercivity enhancement,which is also validated by micromagnetic simulations.展开更多
It is rather difficult for titanium alloy ultra-thick plates to achieve superior weld formation and excellent mechanical properties along the weld penetration direction due to the large fluctuations of the molten pool...It is rather difficult for titanium alloy ultra-thick plates to achieve superior weld formation and excellent mechanical properties along the weld penetration direction due to the large fluctuations of the molten pool,largely limiting their engineering application.In this study,106-mm-thick Ti-6Al-4V ELI alloy plates were successfully butt welded via electron beam welding(EBW).The defect-free EBW joint with full penetration was obtained.The precipitated secondary α(α_(s))in heat affected zone(HAZ),αlamellae in fusion line(FL)and α′martensite in fusion zone(FZ)increased the α_(s)/β,α/β and α′/β interfaces,respectively,resulting in the higher microhardness and impact energy values(57 J in the HAZ,62 J in the FL and 51.9 J in the FZ)than those in the base material(BM).The impact energy of the joint in this study was higher than that for Ti-6Al-4V ELI alloy joints as reported,which was mainly attributed to the formation of the relatively thickerαphase and finer interlamellar spacing in this study,enhancing the resistance to crack propagation.Furthermore,the average fracture toughness(90.2 MPa m^(1/2))of the FZ was higher than that of the BM(74.2 MPa m^(1/2)).This study provides references for the welding application of titanium alloy ultra-thick plates in the manufacture of large-sized components.展开更多
The influence of homogenization parameters on element segregation,dendritic structure,and the precipitate evolution in the GH3535-0.08wt%Y alloy was investigated.Additionally,some specific homogenization parameters we...The influence of homogenization parameters on element segregation,dendritic structure,and the precipitate evolution in the GH3535-0.08wt%Y alloy was investigated.Additionally,some specific homogenization parameters were maintained constant throughout the experiments.Results indicate that the heat treatment at 1150℃for 10 h is the optimal homogenization condition.Following this optimal treatment,dendrite structures and element segregation are eliminated.Furthermore,both SiC and Y_(5)Si_(3)precipitates in the as-cast alloy decrease significantly.Conversely,the homogenization at 1188℃induces overheating defects within the alloy.Although SiC and Y_(5)Si_(3)phases also decrease,some large M6C phases can still be observed,adversely affecting subsequent forging processes.展开更多
To investigate the influence of Al-Zn-Mg-Cu alloy with as-homogenized and as-rolled initial microstructures on the tensile flow behavior,isothermal tensile tests were conducted on a GLEEBLE-3500 isothermal simulator a...To investigate the influence of Al-Zn-Mg-Cu alloy with as-homogenized and as-rolled initial microstructures on the tensile flow behavior,isothermal tensile tests were conducted on a GLEEBLE-3500 isothermal simulator at temperatures of 380-440℃and strain rates of 0.05-1 s^(−1).The Johnson-Cook model,Hensel-Spittel model,strain-compensated Arrhenius model,and critical fracture strain model were established.Results show that through the evaluation of the models using the correlation coefficient(R)and the average absolute relative error,the strain-compensated Arrhenius model can represent the flow behavior of the alloy more accurately.Shear bands are more pronounced in the as-homogenized specimens,whereas dynamic recrystallization is predominantly observed in as-rolled specimens.Fracture morphology analysis reveals that a mixed fracture mechanism is prevalent in the as-homogenized specimen,whereas a ductile fracture mechanism is predominant in the as-rolled specimen.The processing maps indicate that the unstable region is reduced in the as-rolled specimens compared with that in the as-homogenized specimens.The optimal hot working windows for the as-homogenized and as-rolled specimens are determined as 410-440℃/0.14-1 s^(−1)and 380-400℃/0.05-0.29 s^(−1),respectively.展开更多
Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively invest...Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively investigated.Macroscopic morphology,microstructure,and interfacial structure of the joints were analyzed using scanning electron microscope,energy dispersive spectrometer,and X-ray diffractometer(XRD).The results show that magnetic pulse welding of dissimilar Mg/Fe metals is achieved using an Al interlayer,which acts as a bridge for deformation and diffusion.Specifically,the AZ31B/AA1060 interface exhibits a typical wavy morphology,and a transition zone exists at the joint interface,which may result in an extremely complex microstructure.The microstructure of this transition zone differs from that of AZ31B magnesium and 1060 Al alloys,and it is identified as brittle intermetallic compounds(IMCs)Al_(3)Mg_(2) and Al_(12)Mg_(17).The transition zone is mainly distributed on the Al side,with the maximum thickness of Al-side transition layer reaching approximately 13.53μm.Incomplete melting layers with varying thicknesses are observed at the primary weld interface,while micron-sized hole defects appear in the transition zone of the secondary weld interface.The AA1060/DC56D interface is mainly straight,with only a small number of discontinuous transition zones distributed intermittently along the interface.These transition zones are characterized by the presence of the brittle IMC FeAl_(3),with a maximum thickness of about 4μm.展开更多
The Guanxian-Anxian fault zone in the Longmen Shan,Sichuan,China,exhibits long-term creep-slip but ruptured during the 2008 Wenchuan earthquake,challenging the view that creeping faults rarely generate strong earthqua...The Guanxian-Anxian fault zone in the Longmen Shan,Sichuan,China,exhibits long-term creep-slip but ruptured during the 2008 Wenchuan earthquake,challenging the view that creeping faults rarely generate strong earthquakes.To investigate the transition from creep-slip to stick-slip,we analyzed fault rocks from the WFSD-3,using microstructural observations,XRD,μXRF,Raman spectroscopy,and quartz grain size statistics.Fault rocks show intense foliation,pressure-solution structures,and abundant clay minerals,reflecting long-term aseismic creep.At the interface between black and gray fault gouges at~1249.98 m,microstructures indicate stick-slip behavior,including truncated grains,angular fragments,and finer grain sizes.Here,clay content drops sharply while strong minerals(quartz,feldspar,calcite,dolomite)increase.Elemental mapping shows Al and K enriched in black gouge,whereas Ca and Si in gray gouge;Raman spectroscopy indicates possible graphitization;the finest quartz grains occur in black gouge.These features mark co-seismic principal slip zone of the Wenchuan earthquake.We propose that fluid-driven transformation of strong minerals into clays facilitates creep-slip,whereas localized precipitation of strong minerals strengthens the fault,causing stress accumulation and controlling the creep-slip to stick-slip transition.This mechanism has implications for reassessing seismic hazards of creeping faults.展开更多
Heterogeneous nucleation,characterized by its low nucleation barrier and controllable nucleation sites,has been widely employed to manipulate the microstructures and properties of metallic materials.In recent years,th...Heterogeneous nucleation,characterized by its low nucleation barrier and controllable nucleation sites,has been widely employed to manipulate the microstructures and properties of metallic materials.In recent years,the dispersion of inclusions,carbides,and microstructure refinement in steel have emerged as one of the key research directions in the development of high-quality steel.The current research status regarding the regulation of inclusions,carbides,and microstructures in steel through heterogeneous nucleation are reviewed.The key points and challenges in refining the second phase and microstructure in steel using inclusion particles are highlighted,aiming to provide inspiration and references for future scholars.Deoxidized inclusions,when refined and dispersed,exhibit favorable lattice matching with second phases(e.g.,nitrides,sulfides,carbides)in steel.This characteristic serves as the fundamental mechanism for achieving refinement of the second phase.Concurrently,the solid-solution alloying effect from deoxidizing metals contributes to second-phase refinement,an aspect that requires prioritized investigation.In addition to the single heterogeneous nucleation refinement effect,the two-stage heterogeneous nucleation refinement of the second phase and microstructure offers a new approach for follow-up research.Notably,second-phase particles added as heterogeneous nucleation sites via external addition often require surface modification to ensure their stable retention in steel at high temperatures,which remains a major challenge restricting the widespread application of this method.Currently,the explanation of heterogeneous nucleation phenomena primarily relies on empirical calculations of lattice mismatch between the substrate and the nucleating phase,which cannot fully elucidate the quantitative relationship on the interface between the substrate and the nucleation phase.On this basis,quantifying the electronic structure and nucleation barrier at the interface between the substrate and the nucleation phase is a critical direction worthy of increased attention in the future.展开更多
In current research,Li_(2)O-Al_(2)O_(3)-SiO_(2)glass-ceramics were prepared by conventional meltquenching and subsequent heat treatment method.The effect of Al_(2)O_(3)content on microstructures,thermal properties,cry...In current research,Li_(2)O-Al_(2)O_(3)-SiO_(2)glass-ceramics were prepared by conventional meltquenching and subsequent heat treatment method.The effect of Al_(2)O_(3)content on microstructures,thermal properties,crystallization behaviours and mechanical properties were investigated.FTIR,Raman spectroscopy and nuclear magnetic resonance spectroscopy microstructure analysis showed that the silico-oxygen network was damaged,while the increase of[AlO_(4)]content repaired the glass network,and finally made the glass network have better connectivity,with the decrease of SiO_(2).The thermal analysis confirmed the increasing glass transition and crystallization temperatures from growing Al_(2)O_(3)content.In addition,different crystal phases can be precipitated in the glass matrix,such as LiAlSi_(4)O_(10),Li_(2)Si_(2)O_(5) in glass with low Al_(2)O_(3)content,the combination of Li_xAl_xSi_(1-x)O_(2),LiAlSi_(3)O_(8),Li_(2)SiO_(3)in glass with intermediate Al_(2)O_(3)content,and the combination of LiAlSi_(2)O_(6),SiO_(2)in glass with high Al_(2)O_(3)content.The hardness of as-prepared glass gradually increases with the increase of the Al_(2)O_(3)content.The Vickers hardness of the glass-ceramics is highly dependent on the Al_(2)O_(3)content in the glass and the heat treatment temperatures,reaching a maximum of 10.11 GPa.Scanning electron microscope images show that the crystals change from spherical to massive and finally to sheet.The change of glass structure,crystal phase and morphology is the main reason for the different mechanical properties.展开更多
The Cu-12Fe alloy has attracted significant attention due to its excellent electrical conductivity and electromagnetic shielding capability,high strength,cost-effectiveness,and recyclability.In the present work,the Cu...The Cu-12Fe alloy has attracted significant attention due to its excellent electrical conductivity and electromagnetic shielding capability,high strength,cost-effectiveness,and recyclability.In the present work,the Cu-12Fe alloy strip with the thickness of 2.4 mm was successfully produced by twin-roll strip casting.The microstructure and properties of the Cu-12Fe alloy were tailored by cold rolling and aging treatment.The tensile strength of the as-cast strip is approximately 328 MPa and its elongation is 25%.The Fe phase randomly dispersed in the matrix,and the average size of Fe-rich phase is 2μm.Besides,enrichment of Fe phase is observed in the central layer of the strip,results in the formation of the“sandwich structure”.Moreover,the as-cast strip of Cu-12Fe was directly cold-rolled from 2.4 to 0.12 mm.The directly cold-rolled sample after aging at 450℃for 16 h(ProcessⅠ)shows excellent electrical conductivity of 69.5%IACS,the tensile strength and elongation are 513 MPa and 3.8%,the saturation magnetic flux density is 20.1 emu·g^(-1),and the coercive force is 25.2 Oe.In ProcessⅡ,the as-cast strip firstly cold-rolled to 1.2 mm,then aged at 500℃for 1.5 h,followed by cold rolling to 0.12 mm,finally aged at 450℃for 16 h.The sample after ProcessⅡshows the electrical conductivity of 66.3%IACS,the tensile strength of 533 MPa,an elongation of 3.5%,saturation magnetic flux density of 21.4 emu·g^(-1),and the coercive force of 22.3 Oe.展开更多
The microstructure of high Nb-TiAl alloys was optimized by the addition of a small amount of Ta elements to further improve their properties.A series of Ti46Al1.5Cr8Nb-xTa(x=0.2,0.4,0.6,0.8,1.0,at.%)alloys were prepar...The microstructure of high Nb-TiAl alloys was optimized by the addition of a small amount of Ta elements to further improve their properties.A series of Ti46Al1.5Cr8Nb-xTa(x=0.2,0.4,0.6,0.8,1.0,at.%)alloys were prepared by vacuum arc melting.The microstructure,mechanical properties,and related influencing mechanisms were systematically investigated.The results indicate that the solidification microstructure of the Ti46Al1.5Cr8Nb-xTa alloys comprises theγ-TiAl phase,α_(2)-Ti_(3)Al phase,and B2 phase.As the Ta content increases from 0.2 at.%to 1.0 at.%,the content ofα_(2)phase and B2 phase increases,while theγphase content decreases.Among them,the B2 phase shows the most pronounced change,being significantly refined,with its content increasing from 12.49%to 21.91%.In addition,the average size of the lamellar colony decreases from 160.65 to 94.44μm.The addition of the Ta element shifts the solidification path toward lower aluminum concentrations,leading to changes in phase content.The tantalum-induced increase in the B2 phase and enhanced supercooling at the solidification front provide the basis for lamellar colony refinement.Compressive testing at room temperature reveals that the Ti46 Al1.5 Cr8 Nb0.4 Ta alloy exhibits optimal compressive properties,achieving a compressive strength of 2,434 MPa and a compressive strain of 33.1%.The improvement of its properties is attributed to a combination of lamellar colony refinement,solid solution strengthening resulting from the incorporation of Ta element,and a reduction in the c/a of theγphase.展开更多
Quantitative analysis of aluminum-silicon(Al-Si)alloy microstructure is crucial for evaluating and controlling alloy performance.Conventional analysis methods rely on manual segmentation,which is inefficient and subje...Quantitative analysis of aluminum-silicon(Al-Si)alloy microstructure is crucial for evaluating and controlling alloy performance.Conventional analysis methods rely on manual segmentation,which is inefficient and subjective,while fully supervised deep learning approaches require extensive and expensive pixel-level annotated data.Furthermore,existing semi-supervised methods still face challenges in handling the adhesion of adjacent primary silicon particles and effectively utilizing consistency in unlabeled data.To address these issues,this paper proposes a novel semi-supervised framework for Al-Si alloy microstructure image segmentation.First,we introduce a Rotational Uncertainty Correction Strategy(RUCS).This strategy employs multi-angle rotational perturbations andMonte Carlo sampling to assess prediction consistency,generating a pixel-wise confidence weight map.By integrating this map into the loss function,the model dynamically focuses on high-confidence regions,thereby improving generalization ability while reducing manual annotation pressure.Second,we design a Boundary EnhancementModule(BEM)to strengthen boundary feature extraction through erosion difference and multi-scale dilated convolutions.This module guides the model to focus on the boundary regions of adjacent particles,effectively resolving particle adhesion and improving segmentation accuracy.Systematic experiments were conducted on the Aluminum-Silicon Alloy Microstructure Dataset(ASAD).Results indicate that the proposed method performs exceptionally well with scarce labeled data.Specifically,using only 5%labeled data,our method improves the Jaccard index and Adjusted Rand Index(ARI)by 2.84 and 1.57 percentage points,respectively,and reduces the Variation of Information(VI)by 8.65 compared to stateof-the-art semi-supervised models,approaching the performance levels of 10%labeled data.These results demonstrate that the proposed method significantly enhances the accuracy and robustness of quantitative microstructure analysis while reducing annotation costs.展开更多
The synergistic effects of corrosion and impact loading on the microstructure evolution and dynamic mechanical properties of ultrahigh-strength AerMet 100 steel are investigated.Through integrated experiments and mode...The synergistic effects of corrosion and impact loading on the microstructure evolution and dynamic mechanical properties of ultrahigh-strength AerMet 100 steel are investigated.Through integrated experiments and modeling,the result reveals that the corrosion leads to grain refinement and a reduction in the proportion of low-angle grain boundaries.Notably,corrosion promotes austenite enrichment(increasing from 1.8%to 13.9%)through selective dissolution of the martensitic matrix,while repetitive impacts reverse this trend(reducing to 0.1%)through stress-induced martensitic transformation.Fracture analysis demonstrates corrosion-induced ductile-to-brittle transition,with quasi-cleavage features dominating after prolonged corrosion.A physics-based dynamic yield strength model with<3%prediction error relative to impact tests is developed.These findings establish microstructure-property relationships of AerMet 100 steel under multi-field coupling,providing critical guidance for designing corrosion-resistant ultrahigh-strength steels in marine-impact environments.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52305401 and 52475391)National Key Research and Development Program of China(2024YFB3714301)+1 种基金the Fundamental Research Program of Shanxi Province(202303011211004,TZLH20230818001)Engineering Research Center of the Ministry of Education.
文摘Cold deformation treatment of Cu-bearing stainless steel through a cold rolling process combined with electric pulse treatment(EPT)can significantly improve the microstructure and formability of cold-rolled Cu-bearing stainless steel.The microstructure after EPT was characterized by scanning electron microscopy,transmission electron microscopy,and in-situ tensile testing.It is found that compared with conventional heat treatment,EPT process can significantly promote the nucleation rate and mobility at grain boundaries of the deformed samples,greatly accelerating the recovery and static recrystallization of Cu-bearing stainless steel samples at lower temperatures and contributing to the recovery of anisotropy and the re-molding of deformed samples.Microstructural characterization and theoretical analyses show that the rapid recrystallization during EPT process is caused not only by Joule heating effects but also by non-thermal effects that accelerate grain boundary migration and dislocation destruction and regeneration.In addition,EPT process significantly accelerated the nucleation and precipitation growth of Cu-rich phase.The coarsening of Cu-rich phase during EPT process is due to not only the high vacancy diffusion coefficient under the action of the electric pulse but also the increase in the vacancy diffusion flux induced by the electromigration in the process of the electric pulse.
基金supported by the National Natural Science Foundation of China(No.52274318).
文摘A full-sectional microstructure characterization method was developed to investigate the formation of coarse slag rims during the continuous casting of hypo-peritectic steel.The cross-sectional microstructural analysis of typical slag rims for two highly crystalline powders revealed that their formation was primarily driven by the solidification of the liquid slag.Distinct differences were observed in the microstructures of slag rims from the two powders.Powder A(characterized by a higher breaking temperature and viscosity)displayed alternating lamellar microstructures of coarse and fine phases,with the coarse phases composed of akermanite-gehlenite transition phases.In contrast,powder B(with a lower breaking temperature and viscosity)predominantly comprised regular akermanite-gehlenite crystals interspersed with a certain amount of glassy phases.Numerical simulations of a three-phase fluid flow coupled with heat transfer indicate that slag rim formation correlates with mold oscillation.Solidification of the liquid slag at the slag rim front predominantly occurs during the negative stroke of the mold oscillation.The average heating rate during the ascending stage of the mold reaches approximately 100 K·s^(−1),whereas the average cooling rate during the descending stage attains 400 K·s^(−1).This temperature variation leads to the formation of lamellar microstructures,whereas the ascending stage promotes the formation of coarse structures and thicker slag rims.Based on the powder properties,two distinct formation pathways exist for highly crystalline mold powders.For the powders with a higher breaking temperature,higher viscosity,and narrower solidification range(powder A),coarse microstructures and thicker slag rims were preferentially formed.For powders with lower breaking temperature and viscosity and wider solidification ranges(powder B),the liquid slag resisted rapid solidification,and the extended mushy zone allowed the partial liquid slag to persist at the slag rim front,promoting the formation of a thin slag rim.This study enhances the understanding of slag rim formation in highly crystalline mold powders and provides critical insights into the control of longitudinal surface cracks in hypo-peritectic steel.
基金financially suppoted by the National Natural Sci-ence Foundation of China(No.52371041).
文摘Tungsten heavy alloys(WHAs)prepared using laser additive manufacturing(AM)exhibit intricate ge-ometries,albeit with limited mechanical properties.Here we designed a high-strength WHA featuring a FeCrCoNi high entropy alloy(HEA)binder via the laser metal deposition(LMD)technique.Due to the distinctive thermal cycle and rapid cooling rate,the as-deposited alloys exhibit microstructures with hy-poeutectic,eutectic-like,and spot-like characteristics.To elucidate this phenomenon,the solidification paths were delineated and analyzed by combining microstructural characterization and phase equilib-rium simulation.Theμphase precipitated out from the supersaturated solid solution,thereby nucleating massive dislocations on the FeCrCoNi matrix to increase the work hardening rate.Furthermore,theμphase formed an ultrafine intermetallic compound(IMC)layer around the W grain,reducing the hole or crack between the W grain and FeCrCoNi matrix.Attributed to the precipitation strengthening,the solid solution of the FeCrCoNi binder,along with the load-bearing strength of W,the developed alloy achieved ultrahigh compressive stress and strain of 2047 MPa and 32%respectively at room temperature.These findings contribute valuable insights to the advancement of additive manufacturing for tungsten alloys,leveraging their excellent properties.
基金financial support from the Na-tional Natural Science Foundation of China(No.52231006)National Key Research and Development Program of China(No.2017YFB0702003)the National Natural Science Foundation of China(No.51871217).
文摘Refractory high/medium-entropy alloys(RH/MEAs)are known for their outstanding performance at el-evated temperatures;however,they usually exhibit poor room-temperature plasticity,which can be at-tributed to the non-uniform deformation that occurs at room temperature.Once cracks nucleate,they will rapidly propagate into vertical splitting cracks.Here,we introduce multiple phases including FCC and HCP phases into the NbMoTa RMEA via appropriate addition of carbon.The results show that multiple-phase synergy effectively suppresses non-uniform deformation,thereby delaying the onset of vertical splitting cracks.An optimal combination of compressive strength-plasticity is achieved by the(NbMoTa)_(92.5)C_(7.5) alloy.The significant improvement in room-temperature mechanical properties can be attributed to its hierarchical microstructure:in the mesoscale,the BCC matrix is divided by eutectic structures;while at the microscale,the BCC matrix is further refined by abundant lath-like FCC precipitates.The FCC precip-itates contain high-density stacking faults,acting as a dislocation source under compressive loading.The HCP phase in the eutectic microstructures,in turn,acts as a strong barrier to dislocation movement and simultaneously increases the dislocation storage capacity.These findings open a new route to tailor the microstructure and mechanical properties of RH/MEAs.
基金supported by the National Natural Science Foundation of China(61774140).
文摘ZnO thin films with varying Ta concentrations were fabricated through magnetron sputtering.The crystallinity and surface morphology of the ZnO films are significantly influenced by the incorporation of Ta,as evidenced by the X-ray diffraction and scanning electron microscopy results.The lattice constants,as determined by X-ray diffraction,contradict the disparity in Ta and Zn ion radii,which is attributed to the impact of interstitial defects.This inconsistency introduces variations in carrier concentration in this experiment compared with prior studies.Subsequent exploration of the luminescent characteristics and emission mechanism of defect levels in Ta-doped ZnO films was conducted through photoluminescence.Furthermore,the factors influencing the bandgap are discussed.
基金financially supported by the National Natu-ral Science Foundation of China(Nos.52201105 and 52475324)the National Key Research and Development Program of China(Nos.2023YFB3408003 and 2023YFB3308001)+4 种基金the Graduate Sci-entific Research and Innovation Foundation of Chongqing(No.CYB23018)the Innovation Support Program for Overseas Re-turnees in Chongqing(No.cx2023061)the Research Project from Chongqing Key Laboratory of High-performance Structural Additive Manufacturing(No.02090011044158)the Chengdu Key Research and Development Support Program(No.2023-YF11-00077-HZ)the Fundamental Research Foundation for the Central Universities in China(Nos.2024IAIS-QN012 and 2023CDJKYJH049)。
文摘The complex non-equilibrium solidification effects of the laser powder bed fusion(LPBF)combined with the high solubility of rare-earth(RE)elements,provide a new advanced powder metallurgy process for Mg RE alloys with outstanding mechanical performances.However,its creep mechanism has not been revealed yet.The present study systematically investigates and evaluates the high-temperature creep mechanism of LPBFed WE43 alloy under varying temperatures and applied stress conditions.In addition,it thoroughly elucidates the interactions and evolution mechanisms between precipitates and disloca-tions during the creep process.Subject to residual stresses and thermal cycling,theβphase is formed in the form of“precipitation chains”(PCs)within the grains.The metastable phasesβ″,β′,andβ_(1) in-situ precipitate between the PCs.The creep resistance of the(LPBFed)WE43 alloy is governed by the evolution of precipitates and their interactions with dislocations during the creep.Under creep condi-tions at 200℃,a large number of<c+a>anddislocations undergo climb and cross-slip behaviors within the grains.During the climb and cross-slip of dislocations,the Orowan strengthening effect ofβ″,the cutting mechanisms ofβ′andβ_(1) phases relative to dislocations,and the dislocation barriers formed by theβphase arrays collectively impart excellent creep resistance to the WE43 alloy.As creep time progresses,dislocations accumulate within the grains,and theβandβ_(1) phases promote the forma-tion of subgrain boundaries,further triggering discontinuous dynamic recrystallization behaviors during the creep process.Furthermore,influenced by the directional diffusion of elements,precipitates dynami-cally form around the grain boundaries of recrystallized grains,thereby enhancing the resistance to grain boundary sliding.When the creep temperature increases to 250℃ or 300℃,a large number of<c+a>dislocations,accompanied by the dissolution of metastable phases and elemental re-diffusion,transform during the creep process into stacking faults(SFs).SFs not only exhibit high thermal stability but also act as effective dislocation barriers at high temperatures through lattice mismatch mechanisms.However,under high-temperature conditions,thermal activation leads to the dissolution of unstable metastable phases,promoting rapid coarsening and transformation of precipitates into various morphologies ofβphases,thereby causing a catastrophic decline in creep performance.At the same time,high tempera-tures further exacerbate elemental diffusion,resulting in precipitate-free zones near grain boundaries,thereby inducing crack initiation.Therefore,the creep resistance of as-deposited alloys decreases signif-icantly at higher temperatures.Building on this,the future development trends of LPBFed WE43 alloys are envisioned,where homogenizing heterostructures or introducing high aspect ratio precipitates and high-density SFs prior to creep can be regarded as a promising approach for enhancing creep resistance in LPBFed WE43 alloys.
基金financial support by the National Natural Science Foundation of China(No.52474361)the Independent Research Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(No.SKLASS 2023-Z01)the Science and Technology Commission of Shanghai Municipality(No.19DZ2270200).
文摘The fracture mechanisms of coarse-grained heat-affected zone(CGHAZ)for Mg and Mg–Ca deoxidized high-strength low-alloy(HSLA)steels after high heat input welding(HHIW)were investigated based on the microstructures,crack behaviors and mechanical properties.Compared to Mg–Ca steel,the proportion of intergranular acicular ferrites(IAFs)and polygonal ferrites(PFs)in Mg steel increases from 59.97%to 90.16%.The high-angle grain boundaries(HAGBs)and geometrically necessary dislocations density increase from 55.5%and 4.30×10^(14) m^(-2)to 70.4%and 5.48×10^(14) m^(–2),respectively,while effective grain size decreases from 9.46 to 8.12μm.The area fraction of radial zone in Mg steel decreases from 80.8%to 37.7%and cleavage plane is smaller with more curved and finer tearing ridges.The inclusions distributed at the center of cleavage planes and along river lines can serve as crack initiation sites.The zigzag pattern of primary crack propagation path has width of 476μm and the length of secondary cracks remains below 10μm.These cracks are deflected or arrested by IAFs,PFs and HAGBs,and tend to propagate along{110}plane family.These factors contribute to superior overall mechanical properties of Mg steel,especially increasing low-temperature impact toughness from 23 to 175 J.
基金Project support by the National Key Research and Development Program of China(Grant No.2022YFA1603900)the National Natural Science Foundation of China–Beijing Joint Fund(Grant No.U23A6015)+1 种基金Central University Basic Research Fund of China(Grant No.E1E40207X2)the Funds from University of Chinese Academy of Sciences(Grant Nos.E1EG0210X2 and 118900M018).
文摘YBa_(2)Cu_(3)O_(7-x)(YBCO)films with low microwave surface resistance(RS)are essential for high temperature superconducting microwave devices.The oxygen pressure during deposition has been found to influence RS significantly.In this work,we deposited highly c-axis aligned YBCO films on single crystal MgO(001)substrates under different oxygen pressures via pulsed laser ablation.Their detailed microstructure was characterized with three-dimensional reciprocal space mapping(3D-RSM)method and their microwave surface resistance was also measured with resonant cavity perturbation method.We found that the variation of oxygen pressure can affect film microstructure,including grain orientation distribution and the concentration of crystal defects.The microstructure modulation can explain RS dependence on the oxygen pressure.
基金supported by the National Natural Science Foundation of China(Nos.52261037,52088101)the Key research project of Jiangxi Province(No.20203ABC28W006)the Double-Thousand Plan of Jiangxi Province(No.jxsq2023101057).
文摘The low coercivity is the major factor inhibiting the large-scale commercial utilization of Nd-Ce-Fe-B sintered magnets.In this work,we achieved a record-high coercivity of 15.04 kOe in Ga-doped Nd-Ce-Fe-B sintered magnets with 30 wt%Ce replacing Nd,demonstrating enormous potential.The Ga-doped Nd-Ce-Fe-B magnets with higher boron(HB)and lower boron(LB)content are designed.The coercivity of the HB magnet increases slightly from 10.80 to 12.26 kOe after annealing,attributed to the optimized distribution of grain boundary(GB)phases.In contrast,the coercivity of the LB magnet remarkably increases from 8.13 to 15.04 kOe after annealing.Microstructural observations indicate that the narrow GB phase in the as-sintered magnet is rich in Fe,and the strong exchange coupling of adjacent grains resulted in low coercivity.The evolution of Ga-rich phases reveals a potential formation mechanism of the RE_(6)Fe_(13)Ga phase,that is the RE-Fe amorphous phase and REGa phase in the as-sintered magnet combine to form the RE_(6)Fe_(13)Ga phase and RE-Ga amorphous phase during post-sinter annealing(RE:rare earth).Moreover,the GB phase of the annealed magnet transforms into a Fe-lean phase with a thickness of 16.4 nm.Magnetization and demagnetization behavior characterizations reveal that the exchange decoupling of adjacent grains induced by the optimized GB phases is the main reason for the remarkable coercivity enhancement,which is also validated by micromagnetic simulations.
基金supported by the National Key Research and Development Program of China(No.2023YFC2810700)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2021193)+2 种基金the Liaoning Province Excellent Youth Foundation(No.2024JH3/10200021)the Liaoning Revitalization Talents Program(No.XLYC2403094)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(No.PTYQ2024YZ0009).
文摘It is rather difficult for titanium alloy ultra-thick plates to achieve superior weld formation and excellent mechanical properties along the weld penetration direction due to the large fluctuations of the molten pool,largely limiting their engineering application.In this study,106-mm-thick Ti-6Al-4V ELI alloy plates were successfully butt welded via electron beam welding(EBW).The defect-free EBW joint with full penetration was obtained.The precipitated secondary α(α_(s))in heat affected zone(HAZ),αlamellae in fusion line(FL)and α′martensite in fusion zone(FZ)increased the α_(s)/β,α/β and α′/β interfaces,respectively,resulting in the higher microhardness and impact energy values(57 J in the HAZ,62 J in the FL and 51.9 J in the FZ)than those in the base material(BM).The impact energy of the joint in this study was higher than that for Ti-6Al-4V ELI alloy joints as reported,which was mainly attributed to the formation of the relatively thickerαphase and finer interlamellar spacing in this study,enhancing the resistance to crack propagation.Furthermore,the average fracture toughness(90.2 MPa m^(1/2))of the FZ was higher than that of the BM(74.2 MPa m^(1/2)).This study provides references for the welding application of titanium alloy ultra-thick plates in the manufacture of large-sized components.
基金National Natural Science Foundation of China(51801227,52071331)。
文摘The influence of homogenization parameters on element segregation,dendritic structure,and the precipitate evolution in the GH3535-0.08wt%Y alloy was investigated.Additionally,some specific homogenization parameters were maintained constant throughout the experiments.Results indicate that the heat treatment at 1150℃for 10 h is the optimal homogenization condition.Following this optimal treatment,dendrite structures and element segregation are eliminated.Furthermore,both SiC and Y_(5)Si_(3)precipitates in the as-cast alloy decrease significantly.Conversely,the homogenization at 1188℃induces overheating defects within the alloy.Although SiC and Y_(5)Si_(3)phases also decrease,some large M6C phases can still be observed,adversely affecting subsequent forging processes.
文摘To investigate the influence of Al-Zn-Mg-Cu alloy with as-homogenized and as-rolled initial microstructures on the tensile flow behavior,isothermal tensile tests were conducted on a GLEEBLE-3500 isothermal simulator at temperatures of 380-440℃and strain rates of 0.05-1 s^(−1).The Johnson-Cook model,Hensel-Spittel model,strain-compensated Arrhenius model,and critical fracture strain model were established.Results show that through the evaluation of the models using the correlation coefficient(R)and the average absolute relative error,the strain-compensated Arrhenius model can represent the flow behavior of the alloy more accurately.Shear bands are more pronounced in the as-homogenized specimens,whereas dynamic recrystallization is predominantly observed in as-rolled specimens.Fracture morphology analysis reveals that a mixed fracture mechanism is prevalent in the as-homogenized specimen,whereas a ductile fracture mechanism is predominant in the as-rolled specimen.The processing maps indicate that the unstable region is reduced in the as-rolled specimens compared with that in the as-homogenized specimens.The optimal hot working windows for the as-homogenized and as-rolled specimens are determined as 410-440℃/0.14-1 s^(−1)and 380-400℃/0.05-0.29 s^(−1),respectively.
文摘Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively investigated.Macroscopic morphology,microstructure,and interfacial structure of the joints were analyzed using scanning electron microscope,energy dispersive spectrometer,and X-ray diffractometer(XRD).The results show that magnetic pulse welding of dissimilar Mg/Fe metals is achieved using an Al interlayer,which acts as a bridge for deformation and diffusion.Specifically,the AZ31B/AA1060 interface exhibits a typical wavy morphology,and a transition zone exists at the joint interface,which may result in an extremely complex microstructure.The microstructure of this transition zone differs from that of AZ31B magnesium and 1060 Al alloys,and it is identified as brittle intermetallic compounds(IMCs)Al_(3)Mg_(2) and Al_(12)Mg_(17).The transition zone is mainly distributed on the Al side,with the maximum thickness of Al-side transition layer reaching approximately 13.53μm.Incomplete melting layers with varying thicknesses are observed at the primary weld interface,while micron-sized hole defects appear in the transition zone of the secondary weld interface.The AA1060/DC56D interface is mainly straight,with only a small number of discontinuous transition zones distributed intermittently along the interface.These transition zones are characterized by the presence of the brittle IMC FeAl_(3),with a maximum thickness of about 4μm.
基金supported by the National Natural Science Foundation of China(42230312,42272270,42172262,42372266)the Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(2024ZD1000500)the China Geological Survey Project(DD20240041).
文摘The Guanxian-Anxian fault zone in the Longmen Shan,Sichuan,China,exhibits long-term creep-slip but ruptured during the 2008 Wenchuan earthquake,challenging the view that creeping faults rarely generate strong earthquakes.To investigate the transition from creep-slip to stick-slip,we analyzed fault rocks from the WFSD-3,using microstructural observations,XRD,μXRF,Raman spectroscopy,and quartz grain size statistics.Fault rocks show intense foliation,pressure-solution structures,and abundant clay minerals,reflecting long-term aseismic creep.At the interface between black and gray fault gouges at~1249.98 m,microstructures indicate stick-slip behavior,including truncated grains,angular fragments,and finer grain sizes.Here,clay content drops sharply while strong minerals(quartz,feldspar,calcite,dolomite)increase.Elemental mapping shows Al and K enriched in black gouge,whereas Ca and Si in gray gouge;Raman spectroscopy indicates possible graphitization;the finest quartz grains occur in black gouge.These features mark co-seismic principal slip zone of the Wenchuan earthquake.We propose that fluid-driven transformation of strong minerals into clays facilitates creep-slip,whereas localized precipitation of strong minerals strengthens the fault,causing stress accumulation and controlling the creep-slip to stick-slip transition.This mechanism has implications for reassessing seismic hazards of creeping faults.
基金supported by the National Natural Science Foundation of China(No.52304358)Young Elite Scientists Sponsorship Program by CAST(No.YESS20230462).
文摘Heterogeneous nucleation,characterized by its low nucleation barrier and controllable nucleation sites,has been widely employed to manipulate the microstructures and properties of metallic materials.In recent years,the dispersion of inclusions,carbides,and microstructure refinement in steel have emerged as one of the key research directions in the development of high-quality steel.The current research status regarding the regulation of inclusions,carbides,and microstructures in steel through heterogeneous nucleation are reviewed.The key points and challenges in refining the second phase and microstructure in steel using inclusion particles are highlighted,aiming to provide inspiration and references for future scholars.Deoxidized inclusions,when refined and dispersed,exhibit favorable lattice matching with second phases(e.g.,nitrides,sulfides,carbides)in steel.This characteristic serves as the fundamental mechanism for achieving refinement of the second phase.Concurrently,the solid-solution alloying effect from deoxidizing metals contributes to second-phase refinement,an aspect that requires prioritized investigation.In addition to the single heterogeneous nucleation refinement effect,the two-stage heterogeneous nucleation refinement of the second phase and microstructure offers a new approach for follow-up research.Notably,second-phase particles added as heterogeneous nucleation sites via external addition often require surface modification to ensure their stable retention in steel at high temperatures,which remains a major challenge restricting the widespread application of this method.Currently,the explanation of heterogeneous nucleation phenomena primarily relies on empirical calculations of lattice mismatch between the substrate and the nucleating phase,which cannot fully elucidate the quantitative relationship on the interface between the substrate and the nucleation phase.On this basis,quantifying the electronic structure and nucleation barrier at the interface between the substrate and the nucleation phase is a critical direction worthy of increased attention in the future.
基金Funded by the National Key Research Program(No.2024-1129-954-112)National Natural Science Foundation of China(No.52372033)Guangxi Science and Technology Major Program(No.AA24263054)。
文摘In current research,Li_(2)O-Al_(2)O_(3)-SiO_(2)glass-ceramics were prepared by conventional meltquenching and subsequent heat treatment method.The effect of Al_(2)O_(3)content on microstructures,thermal properties,crystallization behaviours and mechanical properties were investigated.FTIR,Raman spectroscopy and nuclear magnetic resonance spectroscopy microstructure analysis showed that the silico-oxygen network was damaged,while the increase of[AlO_(4)]content repaired the glass network,and finally made the glass network have better connectivity,with the decrease of SiO_(2).The thermal analysis confirmed the increasing glass transition and crystallization temperatures from growing Al_(2)O_(3)content.In addition,different crystal phases can be precipitated in the glass matrix,such as LiAlSi_(4)O_(10),Li_(2)Si_(2)O_(5) in glass with low Al_(2)O_(3)content,the combination of Li_xAl_xSi_(1-x)O_(2),LiAlSi_(3)O_(8),Li_(2)SiO_(3)in glass with intermediate Al_(2)O_(3)content,and the combination of LiAlSi_(2)O_(6),SiO_(2)in glass with high Al_(2)O_(3)content.The hardness of as-prepared glass gradually increases with the increase of the Al_(2)O_(3)content.The Vickers hardness of the glass-ceramics is highly dependent on the Al_(2)O_(3)content in the glass and the heat treatment temperatures,reaching a maximum of 10.11 GPa.Scanning electron microscope images show that the crystals change from spherical to massive and finally to sheet.The change of glass structure,crystal phase and morphology is the main reason for the different mechanical properties.
基金financially supported by the Natural Science Foundation of Liaoning Province of China(2022-MS-109)the Key Research and Development Program of Liaoning Province(2023JH2/101800045)the Ministry of Science and Technology of the Peoples Republic of China(ZZ2021006).
文摘The Cu-12Fe alloy has attracted significant attention due to its excellent electrical conductivity and electromagnetic shielding capability,high strength,cost-effectiveness,and recyclability.In the present work,the Cu-12Fe alloy strip with the thickness of 2.4 mm was successfully produced by twin-roll strip casting.The microstructure and properties of the Cu-12Fe alloy were tailored by cold rolling and aging treatment.The tensile strength of the as-cast strip is approximately 328 MPa and its elongation is 25%.The Fe phase randomly dispersed in the matrix,and the average size of Fe-rich phase is 2μm.Besides,enrichment of Fe phase is observed in the central layer of the strip,results in the formation of the“sandwich structure”.Moreover,the as-cast strip of Cu-12Fe was directly cold-rolled from 2.4 to 0.12 mm.The directly cold-rolled sample after aging at 450℃for 16 h(ProcessⅠ)shows excellent electrical conductivity of 69.5%IACS,the tensile strength and elongation are 513 MPa and 3.8%,the saturation magnetic flux density is 20.1 emu·g^(-1),and the coercive force is 25.2 Oe.In ProcessⅡ,the as-cast strip firstly cold-rolled to 1.2 mm,then aged at 500℃for 1.5 h,followed by cold rolling to 0.12 mm,finally aged at 450℃for 16 h.The sample after ProcessⅡshows the electrical conductivity of 66.3%IACS,the tensile strength of 533 MPa,an elongation of 3.5%,saturation magnetic flux density of 21.4 emu·g^(-1),and the coercive force of 22.3 Oe.
基金the financial support by the Major Science and Technology Achievement Transformation Project in Heilongjiang Province(No.ZC2023SH0075)the National Natural Science Foundation of China(Nos.52425401,U2441255,52474377,and 52371015)+1 种基金the Young Elite Scientists Sponsorship·Program by CAST(No.2021QNRC001)the Henan Provincial Key Research and Development&Promotion Special Program(No.251111231400)。
文摘The microstructure of high Nb-TiAl alloys was optimized by the addition of a small amount of Ta elements to further improve their properties.A series of Ti46Al1.5Cr8Nb-xTa(x=0.2,0.4,0.6,0.8,1.0,at.%)alloys were prepared by vacuum arc melting.The microstructure,mechanical properties,and related influencing mechanisms were systematically investigated.The results indicate that the solidification microstructure of the Ti46Al1.5Cr8Nb-xTa alloys comprises theγ-TiAl phase,α_(2)-Ti_(3)Al phase,and B2 phase.As the Ta content increases from 0.2 at.%to 1.0 at.%,the content ofα_(2)phase and B2 phase increases,while theγphase content decreases.Among them,the B2 phase shows the most pronounced change,being significantly refined,with its content increasing from 12.49%to 21.91%.In addition,the average size of the lamellar colony decreases from 160.65 to 94.44μm.The addition of the Ta element shifts the solidification path toward lower aluminum concentrations,leading to changes in phase content.The tantalum-induced increase in the B2 phase and enhanced supercooling at the solidification front provide the basis for lamellar colony refinement.Compressive testing at room temperature reveals that the Ti46 Al1.5 Cr8 Nb0.4 Ta alloy exhibits optimal compressive properties,achieving a compressive strength of 2,434 MPa and a compressive strain of 33.1%.The improvement of its properties is attributed to a combination of lamellar colony refinement,solid solution strengthening resulting from the incorporation of Ta element,and a reduction in the c/a of theγphase.
基金funded by the National Natural Science Foundation of China (52061020).
文摘Quantitative analysis of aluminum-silicon(Al-Si)alloy microstructure is crucial for evaluating and controlling alloy performance.Conventional analysis methods rely on manual segmentation,which is inefficient and subjective,while fully supervised deep learning approaches require extensive and expensive pixel-level annotated data.Furthermore,existing semi-supervised methods still face challenges in handling the adhesion of adjacent primary silicon particles and effectively utilizing consistency in unlabeled data.To address these issues,this paper proposes a novel semi-supervised framework for Al-Si alloy microstructure image segmentation.First,we introduce a Rotational Uncertainty Correction Strategy(RUCS).This strategy employs multi-angle rotational perturbations andMonte Carlo sampling to assess prediction consistency,generating a pixel-wise confidence weight map.By integrating this map into the loss function,the model dynamically focuses on high-confidence regions,thereby improving generalization ability while reducing manual annotation pressure.Second,we design a Boundary EnhancementModule(BEM)to strengthen boundary feature extraction through erosion difference and multi-scale dilated convolutions.This module guides the model to focus on the boundary regions of adjacent particles,effectively resolving particle adhesion and improving segmentation accuracy.Systematic experiments were conducted on the Aluminum-Silicon Alloy Microstructure Dataset(ASAD).Results indicate that the proposed method performs exceptionally well with scarce labeled data.Specifically,using only 5%labeled data,our method improves the Jaccard index and Adjusted Rand Index(ARI)by 2.84 and 1.57 percentage points,respectively,and reduces the Variation of Information(VI)by 8.65 compared to stateof-the-art semi-supervised models,approaching the performance levels of 10%labeled data.These results demonstrate that the proposed method significantly enhances the accuracy and robustness of quantitative microstructure analysis while reducing annotation costs.
基金supported by the National Natural Science Foundation of China(12522203,12532003 and U2267252)National Technological Basic Research Program of China,the Development and Application Project of Ship CAE Softwarethe Science and Technology Innovation 2035 Major Project of Yongjiang under Grant(2025Z009).
文摘The synergistic effects of corrosion and impact loading on the microstructure evolution and dynamic mechanical properties of ultrahigh-strength AerMet 100 steel are investigated.Through integrated experiments and modeling,the result reveals that the corrosion leads to grain refinement and a reduction in the proportion of low-angle grain boundaries.Notably,corrosion promotes austenite enrichment(increasing from 1.8%to 13.9%)through selective dissolution of the martensitic matrix,while repetitive impacts reverse this trend(reducing to 0.1%)through stress-induced martensitic transformation.Fracture analysis demonstrates corrosion-induced ductile-to-brittle transition,with quasi-cleavage features dominating after prolonged corrosion.A physics-based dynamic yield strength model with<3%prediction error relative to impact tests is developed.These findings establish microstructure-property relationships of AerMet 100 steel under multi-field coupling,providing critical guidance for designing corrosion-resistant ultrahigh-strength steels in marine-impact environments.
