As a prototypical high-energy-density reactive material system,metastable intermolecular composites(MICs)have attracted considerable interest owing to their customizable component configurations and interfacial archit...As a prototypical high-energy-density reactive material system,metastable intermolecular composites(MICs)have attracted considerable interest owing to their customizable component configurations and interfacial architectures.Nevertheless,their energy release characteristics are fundamentally constrained by the formation of condensed-phase products with elevated boiling points,thereby diminishing their efficacy in applications requiring rapid pressure generation or shock wave propagation.Herein,we demonstrate a molecular-level fluorination approach that enables oxygen substitution by fluorine within bismuth oxide crystalline frameworks,yielding ternary BixOyFz crystals with atomically precise F/O stoichiometric control through systematic solvent polarity engineering.This energetics system,designed through a multilevel regulation strategy,realizes stepwise redox reactions of Al–F and Al–O during energy release,with the partitioning between these redox pathways being precisely allocable through hierarchical regulation.Furthermore,the pre-ignition reaction(PIR)between BixOyFz and Al2O3(the inert passivation shell of Al)weakens the passivation layer,lowering the ignition threshold.The in situ generation of low-boiling-point AlF3 promotes rapid gas expansion,leading to significantly enhanced pressurization rates and deflagration wave velocities under confinement compared to conventional strategies.To evaluate energy output capabilities and validate potential safety-protection applications,the system successfully achieved instantaneous destruction of SD chips,enabling secure data erasure.This work establishes crystalline lattice fluorination as a generalized materials design strategy to transcend intrinsic limitations of MICs systems in component selection and reaction thermodynamics,providing new paradigms for adaptive energetic architectures and transient microelectromechanical applications.展开更多
Laser powder bed fusion(LPBF)is an attractive additive manufacturing technology for preparing high-performance high-entropy alloys(HEAs)engineering components.Unfortunately,the existence of inherent thermal residual s...Laser powder bed fusion(LPBF)is an attractive additive manufacturing technology for preparing high-performance high-entropy alloys(HEAs)engineering components.Unfortunately,the existence of inherent thermal residual stress and non-equilibrium microstructures in the additively manufactured components results in unsatisfactory mechanical properties.Herein,we propose a novel strengthening strategy,namely deep cryogenic treatment(DCT)followed by laser shock peening(LSP),to tailor the microstructures and enhance performances of an LPBF additively manufactured metastable HEA.The post-treatment effects of DCT+LSP on the LPBF-fabricated Fe_(50)Mn_(30)Co_(10)Cr_(10)HEA are evaluated in terms of microstructural modifications,residual stress,and microhardness redistribution,as well as tensile properties.Results indicate that a gradient heterogeneous structure is formed on the as-built sample surface,featuring gradient variations in grain size,martensitic phase content,and dislocation density,due to the grain refinement and martensitic phase transformation under DCT+LSP.The initial tensile residual stress on the surface is fully transformed into compressive stress,achieving a peak of-289 MPa,and the surface microhardness attains a maximum of 380.8 HV.The various strengthening mechanisms of gradient heterogeneous structures,as well as the multiple effects of heterodeformation-induced(HDI)hardening,transformation-induced plasticity(TRIP),and twinning-induced plasticity(TWIP),are responsible for achieving strength-ductility synergy.This work provides a practical pathway and valuable scientific insights for enhancing the mechanical behaviors of additively manufactured metastable HEAs via microstructural engineering.展开更多
High-pressure β-Sn germanium may transform into diverse metastable allotropes with distinctive nanostructures and unique physical properties via multiple pathways under decompression.However,the mechanism and transit...High-pressure β-Sn germanium may transform into diverse metastable allotropes with distinctive nanostructures and unique physical properties via multiple pathways under decompression.However,the mechanism and transition kinetics remain poorly understood.Here,we investigate the formation of metastable phases and nanostructures in germanium via controllable transition pathways of β-Sn Ge under rapid decompression at different rates.High-resolution transmission electron microscopy reveals three distinct metastable phases with the distinctive nanostructures:an almost perfect st12 Ge crystal,nanosized bc8/r8 structures with amorphous boundaries,and amorphous Ge with nanosized clusters (0.8–2.5 nm).Fast in situ x-ray diffraction and x-ray absorption measurements indicate that these nanostructured products form in certain pressure regions via distinct kinetic pathways and are strongly correlated with nucleation rates and electronic transitions mediated by compression rate,temperature,and stress.This work provides deep insight into the controllable synthesis of metastable materials with unique crystal symmetries and nanostructures for potential applications.展开更多
This study investigates the development of novel high-entropy alloys(HEAs)with enhanced mechanical properties through an innovative fabrication method of direct energy deposition(DED).The focus is on the creation of m...This study investigates the development of novel high-entropy alloys(HEAs)with enhanced mechanical properties through an innovative fabrication method of direct energy deposition(DED).The focus is on the creation of metastable core-shell precipitation-strengthened HEAs that exhibit a unique multi-stage terrace-like slip wave toughening mechanism,a novel approach to improving both strength and ductility simultaneously.Mechanical testing reveals that the developed HEAs exhibit superior mechanical proper-ties,including high yield strength,ultimate tensile strength,and exceptional ductility.The improvement in these properties is attributed to the multi-stage terrace-like slip wave toughening mechanism activated by the unique microstructural features.This toughening mechanism involves the sequential activation of slip systems,facilitated by the stress concentration around the core-shell precipitates and the subsequent propagation of slip waves across the material.The terrace-like pattern of these slip waves enhances the material's ability to deform plastically,providing a significant toughening effect while maintaining high strength levels.Furthermore,the study delves into the fundamental interactions between the microstruc-tural elements and the deformation mechanisms.It elucidates how the core-shell precipitates and the matrix cooperate to distribute stress uniformly,delay the onset of necking,and prevent premature failure.This synergistic interaction between the microstructural features and the slip wave toughening mecha-nism is central to the remarkable balance of strength and ductility achieved in the HEAs.The introduction of a multi-stage terrace-like slip wave toughening mechanism offers a new pathway to designing HEAs with an exceptional amalgamation of strength and ductility.展开更多
The effect of hot deformation onα-phase precipitation during the subsequent heat treatment,as well as the mechanical properties of TB18 Ti-alloy,was investigated.Results show that the round bar obtained by the dual-p...The effect of hot deformation onα-phase precipitation during the subsequent heat treatment,as well as the mechanical properties of TB18 Ti-alloy,was investigated.Results show that the round bar obtained by the dual-phase field forging of the cast ingot exhibits uniform composition distribution on its cross-section.However,various degrees of deformation are detected at different positions on the cross-section,which is attributed to the characteristics of the forging process.Under the forging condition,the microstructure is mainly composed ofβ-phase matrix and coarsened discontinuous primaryα-phases.After solution and following artificial aging treatment,the primaryα-phases disappear,while needle-like secondaryα-phases precipitate in the matrix.Additionally,dispersed white zones are observed in the samples after aging,which are analyzed to be the precipitation-free zones of secondaryα-phase.Despite a uniform compositional distribution among various regions,these dispersed white zones exhibit higher content and larger size in the positions that have undergone lower forging deformation.It indicates that the insufficient forging deformation inhibits the precipitation of the secondaryα-phase,ultimately resulting in the lower strengthening effect by heat treatment.Thus,consistent with the characteristics of the forging process,a periodic variation of sample in strength is detected along the circumferential direction of the forged round bar.展开更多
The spray-deposition was used to produce billets of Mg-4Al-1.5Zn-3Ca-1Nd(A alloy)and Mg-13Al-3Zn-3Ca-1Nd(B alloy),and evolution of deformation substructure and Mg_(x)Zn_(y)Ca_(z)metastable phase in fine-grained(3μm)M...The spray-deposition was used to produce billets of Mg-4Al-1.5Zn-3Ca-1Nd(A alloy)and Mg-13Al-3Zn-3Ca-1Nd(B alloy),and evolution of deformation substructure and Mg_(x)Zn_(y)Ca_(z)metastable phase in fine-grained(3μm)Mg alloys was investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and electron backscattered diffraction(EBSD).It was found that different dislocation configurations were formed in A and B alloys.Redundant free dislocations(RFDs)and dislocation tangles were the ways to form deformation substructure in A alloy,no RFDs except dislocation tangles were found in B alloy.The interaction between nano-scale second phase particles(nano-scale C15 andβ-Mg_(17)(Al,Zn)_(12)phase)and different dislocation configurations had a significant effect on the deformation substructures formation.The mass transfer of Mg_(x)Zn_(y)Ca_(z)metastable phases and the stacking order of stacking faults were conducive to the Mg-Nd-Zn typed long period stacking ordered(LPSO)phases formation.Nano-scale C15 phases,Mg-Nd-Zn typed LPSO phases,c/a ratio,β-Mg_(17)(Al,Zn)_(12)phases were the key factors influencing the formation of textures.Different textures and grain boundary features(GB features)had a significant effect on k-value.The non-basal textures were the main factor affecting k-value in A alloy,while the high-angle grain boundary(HAGB)was the main factor affecting k-value in B alloy.展开更多
The extensive applications of cubic silicon in flexible transistors and infrared detectors are greatly hindered by its intrinsic properties.Metastable silicon phases,such as Si-Ⅲ,Ⅳ,andⅫ,prepared using extreme press...The extensive applications of cubic silicon in flexible transistors and infrared detectors are greatly hindered by its intrinsic properties.Metastable silicon phases,such as Si-Ⅲ,Ⅳ,andⅫ,prepared using extreme pressure methods,provide a unique“genetic bank”with diverse structures and exotic characteristics.However,exploration of their inherent physical properties remains underdeveloped.Herein,we demonstrate the phase engineering strategy to modulate the thermal conductivity and mechanical properties of metastable silicon.The thermal conductivity,obtained via the Raman optothermal approach,exhibits broad tunability across various Si-Ⅰ,Ⅲ,Ⅻ,andⅣphases.The hardness and Young's modulus of Si-Ⅳare significantly greater than those of the Si-Ⅲ/Ⅻmixture,as confirmed by the nanoindentation technique.Moreover,it was found that pressure-induced structural defects can substantially degrade the thermal and mechanical properties of silicon.This systematic investigation offers a feasible route for designing novel semiconductors and further advancing their desirable applications in advanced nanodevices and mechanical transducers.展开更多
The electrolysis of alkaline seawater is critical for sustainable hydrogen production but is hindered by the sluggish oxygen evolution reaction in saline environments.Advanced electrocatalysts with tailored structures...The electrolysis of alkaline seawater is critical for sustainable hydrogen production but is hindered by the sluggish oxygen evolution reaction in saline environments.Advanced electrocatalysts with tailored structures and electronic properties are essential,and phase engineering provides a transformative approach by modulating crystallographic symmetry and electronic configurations.Two-dimensional(2D)LaMnO_(3) perovskites show promise due to their exposed active sites and tunable electronic properties.However,the conventional stable rhombohedral phase limits oxygen diffusion despite good electron transport.Unconventional metastable phases with superior symmetry enhance lattice oxygen activity in saline environments but are challenging to synthesize.Herein,we propose a microwave shock method incorporating Co atoms to rapidly produce 2D LaMnO_(3) in rhombohedral,hexagonal,and metastable cubic phases.This strategy circumvents the limitations of high-temperature synthesis,preserving the 2D morphology while enabling the formation of metastable cubic phases.The metastable cubic phase exhibits superior OER activity and stability even in alkaline seawater due to optimal symmetry,interlayer spacing,and Mn-O covalency.X-ray absorption spectroscopy and theoretical calculations further highlight its balanced oxygen adsorption and desorption.This work underscores the role of metastable phase engineering in advancing seawater electrolysis and establishes a scalable route for designing high-performance 2D electrocatalysts.展开更多
In recent years,aqueous aluminum ion batteries have been widely studied owing to their abundant energy storage and high theo retical capacity.An in-depth study of vanadium oxide materials is necessary to address the p...In recent years,aqueous aluminum ion batteries have been widely studied owing to their abundant energy storage and high theo retical capacity.An in-depth study of vanadium oxide materials is necessary to address the precipitation of insoluble products covered cathode surface and the slow reaction kinetics.Therefore,a method using a simple one-step hydrothermal preparation and oxalic acid to regulate oxygen vacancies has been reported.A high starting capacity(400 mAh g^(-1))can be achieved by Ov-V2O5,and it is capable of undergoing 200 cycles at 0.4 A g^(-1),with a termination discharge capacity of103 mAh g^(-1).Mechanism analysis demonstrated that metastable structures(AlxV2O5and HxV2O5)were constructed through the insertion of Al^(3+)/H^(+)during discharging,which existed in the lattice intercalation with V2O5.The incorporation of oxygen vacancies lowers the reaction energy barrier while improving the ion transport efficiency.In addition,the metastable structure allows the electrostatic interaction between Al3+and the main backbone to establish protection and optimize the transport channel.In parallel,this work exploits ex-situ characterization and DFT to obtain a profound insight into the instrumental effect of oxygen vacancies in the construction of metastable structures during in-situ electrochemical activation,with a view to better understanding the mechanism of the synergistic participation of Al3+and H+in the reaction.This work not only reports a method for cathode materials to modulate oxygen vacancies,but also lays the foundation for a deeper understanding of the metastable structure of vanadium oxides.展开更多
The phase metastability and precipitation are now considered to be an important strategy in designing Fe-rich high entropy alloys(HEAs).In this study,the influence of silicon addition on the initial and straininduced ...The phase metastability and precipitation are now considered to be an important strategy in designing Fe-rich high entropy alloys(HEAs).In this study,the influence of silicon addition on the initial and straininduced microstructure evolution and related mechanical property of Fe52−xMn27Cr15Co6Six(x=0,0.3,0.5,1.0,1.5,at.%)HEAs was systematically investigated by utilizing the in-depth microstructural characterization coupled with X-ray diffractometer(XRD),secondary electron microscopy(SEM),and transmission electron microscopy(TEM).The addition of Si to Fe52−xMn27Cr15Co6Six HEAs facilitates the triplex structure consisting of fcc-γmatrix,thermally-inducedε-martensite and sigma phase(σ).The lattice distortion energy by Si atoms is suggested to promote the formation ofσphase consisting of Cr,Si and Co and consequently influence the metastability of the matrix.In 0.3 at.%Si HEA,the strain-induced bodycentered tetragonal(bct)-typeα’-martensite were observed at the intersection of bi-directional straininducedε-martensite laths,enhancing the ultimate tensile strength to∼851 MPa from∼618.3 MPa with ductility increment(∼73.1%from∼71%).In 0.3 at.%Si and 0.5 at.%Si alloys,the granular-typeσphase was observed both at grain boundaries and in grain interior,and the size of granular-typeσphase at grain boundary and intra-granularσphase were found to be similar.The deformation mode altered from the transformation-induced plasticity(TRIP)to twinning-induced plasticity(TWIP)with an increase of Si content to 1.5 at.%,due to the enhanced fcc-γstability induced by the compositional modulation driven by increasedσphase formation.The propagation of microcracks inside brittleσphase could be suppressed by homogeneous slip through strain-induced martensite transformation(SIMT)in HEAs with low Si addition of 0.3at.%-0.5 at.%.展开更多
Reinforcing bars in concrete structures in marine environment are prone to pitting corrosion,which threatens the safety of engineering structures.In order to effectively mitigate the pitting corrosion of reinforcing b...Reinforcing bars in concrete structures in marine environment are prone to pitting corrosion,which threatens the safety of engineering structures.In order to effectively mitigate the pitting corrosion of reinforcing bars,the electrochemical testing and atomic force microscopy are adopted,the effect of triethanolamine dodecylbenzene sulfonate(TDS)on metastable pitting behavior of 304 stainless steel(304 SS)in simulated concrete pore solutions(SCPS)with chlorine contamination was studied.The results show that the corrosion potential(Ecorr)and breakdown potential(Eb)increased with the growth of the TDS concentrations.Statistical cha-racteristics of metastable pits suggested that as the TDS concentrations increased in the SCPS,the parameters were all decreased.The Mott-Schottky tests exhibited that,although the donor density(ND)diminished,the thickness of the space charge layer(W)increased with increasing TDS concentrations.Investigation results showed that TDS inhibited the sprouting and growth of metastable pits,and with greater TDS concentration,it becomes more difficult for metastable pits to transfer into stable pits in the SCPS,the generated stable passive film prevented the sprouting of pitting corrosion,It is recommended to use TDS with a concentration of not less than 3.364×10^(-4) mol/L in engineering,so that the sensitivity of passivation film of 304SS to chloride erosion is reduced.展开更多
By employing micrometer-diameter microelectrodes, the metastable pitting corrosion behavior of Co_(68.15)Fe_(4.35)Si_(12.5)B_(12)Cr_(3) metallic glasses (MGs) exposed to 0.6 mol/L NaCl solution was investigated to cla...By employing micrometer-diameter microelectrodes, the metastable pitting corrosion behavior of Co_(68.15)Fe_(4.35)Si_(12.5)B_(12)Cr_(3) metallic glasses (MGs) exposed to 0.6 mol/L NaCl solution was investigated to clarify the correlation between metastable pitting and structural heterogeneity in MGs. Thermally induced degeneration of structural heterogeneity inhibits the initiation, decelerates the growth kinetics, and accelerates the repassivation kinetics of metastable pits while also decreasing the probability of transition from metastability to stability. This enhanced resistance to pitting corrosion is attributed to a reduction in active pitting precursor sites and a decrease in electrochemical activity caused by the structural homogenization of MGs.展开更多
High-strength steel with excellent ductility is pivotal for the formability and safety of critical structural components.Here,a heterogeneous metastable lamellar steel,composed of alternating lamellar ferrite and aust...High-strength steel with excellent ductility is pivotal for the formability and safety of critical structural components.Here,a heterogeneous metastable lamellar steel,composed of alternating lamellar ferrite and austenite aligned with the rolling direction,was developed through an innovative combination of warm rolling and immediate annealing processes.This novel design overcomes the strength-ductility trade-off,achieving high ultimate tensile strength(∼1.2 GPa)and excellent uniform elongation(∼78%),pushing the product of ultimate tensile strength and uniform elongation to an ultra-high level(>90 GPa%).The high tensile strength is attributed to ultrafine lamellar grains and significant work hardening induced by the hetero-deformation and transformation-induced plasticity(TRIP)effect.The exceptional ductility is a result of the synergy of multiple plasticity mechanisms,including(i)the inherent plastic deformation ability of lamellar microstructure and the hetero-deformation-induced hardening in the early deformation period,(ii)the persistent TRIP effect induced by the lamellar austenite with high mechanical stability and the elimination of strain localization caused by prolonged strain hardening due to the coordinated deformation of lamellar austenite and ferrite in the middle deformation period,and(iii)delamination cracking in the late deformation period.This approach adopted in current work offers a straightforward and economically feasible pathway for fabricating advanced high-strength steel with superior performance.展开更多
To improve the yield strength of metastableβ-Ti alloys with transformation-induced plasticity(TRIP)and twinning-induced plasticity effects,a novel strategy combining heterostructure strengthening with the TRIP effect...To improve the yield strength of metastableβ-Ti alloys with transformation-induced plasticity(TRIP)and twinning-induced plasticity effects,a novel strategy combining heterostructure strengthening with the TRIP effect was developed.A metastableβ-Ti alloy with a nominal composition of Ti-4Mo-3Cr-1Fe-1Al was used as the base alloy.By adjusting the annealing temperature after cold rolling,heterostructured samples comprising soft recrystallizedβ-grains and hard un-recrystallizedβ-grains andα-phase were prepared.Compared with the homogeneous coarse-grained sample,the yield strength of the heterostructured sample significantly increased from 610 to905 MPa,while maintaining excellent plasticity(32.7%),overcoming the traditional trade-off between strength and ductility.The observed high yield strength is attributed to significant back-stress strengthening caused by the accumulation of a large number of geometrically necessary dislocations at the interfaces between the soft and hard regions.Meanwhile,the exceptional plasticity is attributed to the activation of stress-induced martensite(SIM)within the metastableβmatrix.The sequential activation of dislocation slips and SIM is achieved through the construction of a heterostructured structure.This work provides a new strategy for designing metastableβ-Ti alloys with high strength and plasticity by coupling heterostructure strengthening and transformation-induced plasticity.展开更多
High porosity and high brittleness are the main reasons that limit the long-term service life of the alumina-titanium oxide composite coating.Herein,a metastable nanostructured aluminatitanium oxide composite coating ...High porosity and high brittleness are the main reasons that limit the long-term service life of the alumina-titanium oxide composite coating.Herein,a metastable nanostructured aluminatitanium oxide composite coating with high density and high properties was synthesized by plasma spraying of TiO_(2)-Al composite powder.The main phases of the metastable nanostructured alumina-titanium oxide wereγ-Al_(2)O_(3),TiO and AlTiO_(2).The coating,as prepared,contains various metastable microstructures,such as fine-grained,intra-/inter-granular,and"self-locking"microstructures.These metastable microstruc-tures are important for the improvement of hardness and toughness of the coating.Compared with other alumina-based composite coatings,the metastable nanostructured aluminatitanium oxide composite coating showed the most impressive overall performance.The reinforcing and toughening mechanism of the metastable alumina-titanium oxide composite coating included fine grain strengthening and self-toughening of the metastable microstructure.展开更多
Laser processing of Al-Ge eutectic alloys is used to produce two different metastable intermetallic-matrix nano-scale lamellar composite microstructures:(ⅰ)β_(1)(monoclinic)Al_(6)Ge_(5)(60 vol%)-α(FCC)Al(40 vol%),a...Laser processing of Al-Ge eutectic alloys is used to produce two different metastable intermetallic-matrix nano-scale lamellar composite microstructures:(ⅰ)β_(1)(monoclinic)Al_(6)Ge_(5)(60 vol%)-α(FCC)Al(40 vol%),and(ⅱ)β_(2)(monoclinic)AIGe(67 vol%)-α(FCC)Al(33 vol%).Nanoindentation and micropillar compres-sion tests were performed to characterize mechanical behavior and compare with the equilibrium struc-ture of as-cast diamond cubic Ge(42 vol%)-FCC Al(58 vol%)micrometer-scale eutectic composite.The as-processed and deformed microstructures were characterized by scanning/transmission electron mi-croscopy.Bothβ_(1)-αandβ_(2)-αeutectics exhibit high compressive flow strengths of≈1 GPa and 1.2 GPa respectively,whereas the maximum compressive flow strength of Al-Ge eutectic is about 450 MPa.In spite of complex monoclinic structures and higher volume fraction of intermetallic phase as compared to metallic,bothβ_(1)-αandβ_(2)-αcomposite microstructures have higher level of plastic deformability than as-cast Al-Ge.The microstructure with the highest strength,β_(2)-α,also exhibits the highest plastic strain to failure attributed to a gradual strain softening behavior due to interaction of micro shear cracks with nano-twins in theβ_(2)(monoclinic)AlGe phase,whereas theβ_(1)(monoclinic)Al_(6)Ge_(5) phase without the nano-twins exhibits sudden fracture by a sharp crack.In the Al-richαphases in bothβ_(1)-αandβ_(2)-αmicrostructures,nanoscale Ge-rich clusters were observed that led to profuse stacking faults post defor-mation.Density functional theory calculations suggest that Ge solutes can lower stacking fault energy of FCC Al,thereby promoting partial dislocation glide in Al.This study highlights unusual mechanisms that impart plastic deformability at ultra-high yield strengths in intermetallic-metal composites with a low-symmetry intermetallic matrix phase.展开更多
To overcome the strength-plasticity trade-offin the structural titanium alloys,a novel metastableβti-tanium alloy Ti-5Mo-4Cr-1V-1Zr(Ti-5411)with high strength and high plasticity was designed by the d-electrons theor...To overcome the strength-plasticity trade-offin the structural titanium alloys,a novel metastableβti-tanium alloy Ti-5Mo-4Cr-1V-1Zr(Ti-5411)with high strength and high plasticity was designed by the d-electrons theory,average electron-to-atom ratio(e/α^(-))and atomic radius difference(Δr^(-))theory.Com-bined in-situ scanning electron microscope(SEM)and electron backscatter diffraction(EBSD),the defor-mation mechanisms of the novel Ti-5411 metastableβtitanium alloy were systematically investigated.The results show that the Ti-5411 alloy exhibits excellent yield strength(∼689 MPa),tensile strength(∼930 MPa)and total elongation(∼39%).The in-situ tension indicates that slip activities,crystal rota-tion,stress induced martensite(SIM)α''transformation and{332}<113>deformation twin are the major deformation mechanisms of Ti-5411 alloy.Besides,with the increase of strain degree(0-0.5 mm displace-ment),deformation twins increase,widen and interlace.At 0.35 mm tensile displacement,the orientation of theβgrains rotates∼6.65°to accommodate the increased macrostrain.Additionally,martensiteα''also assists the nucleation of twins.Some{332}<113>twins grow and merge by consuming martensiteα''during deformation,and the residual martensiteα''remains in the merged twins.展开更多
Elinvar alloys exhibit temperature-independent elastic modulus within a specific temperature range,known as the Elinvar effect,which was first observed in Fe-Ni alloys[1].The unique temperature-independent elastic mod...Elinvar alloys exhibit temperature-independent elastic modulus within a specific temperature range,known as the Elinvar effect,which was first observed in Fe-Ni alloys[1].The unique temperature-independent elastic modulus makes Elinvar alloys highly desirable in precision-control applications,including aerospace,electronics,and optical instruments.Currently,most of the used and studied Elinvar alloys are ferromagnetic alloys(FeNi and Fe-Pt)and antiferromagnetic alloys(Fe-Mn and γ-MnCu)[2–4].The Elinvar effect in these alloys typically originates from magnetostriction or magnetoelastic effects,which are magnetic fieldor magnetic transition-dependent[5].Consequently,these Elinvar alloys cannot function properly in the presence of a magnetic field owing to their Elinvar effect being closely tied to magnetic phase transition.Therefore,developing non-magneticdependent Elinvar alloys is highly essential to widen their practical applications.展开更多
Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback co...Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback control on nuclear spin precession in a metastability exchange optical pumping(MEOP)-based polarized^(3)He system.We analyze the effects of feedback theoretically and validate our predictions experimentally.With optimized feedback parameters,the spin coherence time T_(2)is extended by an order of magnitude.When the feedback strength surpasses a critical threshold,robust maser oscillations are spontaneously excited,demonstrating remarkable resistance to environmental noise and maintaining stable oscillation.This proof-of-principle experiment highlights the viability of MEOP-based^(3)He spin oscillators,especially in low-frequency domains.The operational simplicity and easy integration associated with MEOP-based systems make them particularly promising for fast,high-precision magnetic field measurements.展开更多
The precipitation behavior and its influence on the electrical resistivity of the Al-0.96Mg2Si alloy during aging were investigated with in-situ resistivity measurement and transmission electron microscopy （TEM）. Th...The precipitation behavior and its influence on the electrical resistivity of the Al-0.96Mg2Si alloy during aging were investigated with in-situ resistivity measurement and transmission electron microscopy （TEM）. The precipitates of the peak aged alloy include both β＂ and if, but the amount ratio of β＂ to β＂ varies with the aging temperature and time increasing. The precipitates during aging at 175 ℃ are dominated by needle-like β＂ phases （including pre-β＂ phase）, the size of which increases with the time prolonging, but does not increase substantially after further aging. The evolution of electrical conductivity is directly related to such microstructural evolution. However, the hardness of the alloy stays at the peak value for a long term. When the alloy is aged at 195 ℃, the ratio of β＂ to β＇ becomes the main factor to influence relative resistivity （Ap） value. The higher the temperature is, the smaller the ratio is, and the faster the Ap value decreases. Moreover, the hardness peak drops with the decrease of the ratio. With the size and distribution parameters measured from TEM images, a semi-quantitative relationship between precipitates and the electrical resistivity was established.展开更多
基金supported by the National Natural Science Foundation of China,China(Grant No.22305100,No.22405104)the Hubei Provincial International Science and Technology Cooperation Program Project(Grant No.2023EHA014)+4 种基金the National Foreign Experts Program(Grant No.Y20240022,H20240275)the Hubei Natural Science Foundation(Grant No.2025AFB460)the Hubei Provincial Department of Education Scientific Research Project(Grant No.F2023033,Q20234414)the Wuhan Natural Science Foundation Exploration Project(Chenguang Program)(Grant No.2025040601020173)the Jianghan University Scientific Research Startup Fund(Grant No.PBSKL-2022-QD-08,No.PBSKL-2024-QD-03).
文摘As a prototypical high-energy-density reactive material system,metastable intermolecular composites(MICs)have attracted considerable interest owing to their customizable component configurations and interfacial architectures.Nevertheless,their energy release characteristics are fundamentally constrained by the formation of condensed-phase products with elevated boiling points,thereby diminishing their efficacy in applications requiring rapid pressure generation or shock wave propagation.Herein,we demonstrate a molecular-level fluorination approach that enables oxygen substitution by fluorine within bismuth oxide crystalline frameworks,yielding ternary BixOyFz crystals with atomically precise F/O stoichiometric control through systematic solvent polarity engineering.This energetics system,designed through a multilevel regulation strategy,realizes stepwise redox reactions of Al–F and Al–O during energy release,with the partitioning between these redox pathways being precisely allocable through hierarchical regulation.Furthermore,the pre-ignition reaction(PIR)between BixOyFz and Al2O3(the inert passivation shell of Al)weakens the passivation layer,lowering the ignition threshold.The in situ generation of low-boiling-point AlF3 promotes rapid gas expansion,leading to significantly enhanced pressurization rates and deflagration wave velocities under confinement compared to conventional strategies.To evaluate energy output capabilities and validate potential safety-protection applications,the system successfully achieved instantaneous destruction of SD chips,enabling secure data erasure.This work establishes crystalline lattice fluorination as a generalized materials design strategy to transcend intrinsic limitations of MICs systems in component selection and reaction thermodynamics,providing new paradigms for adaptive energetic architectures and transient microelectromechanical applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.52205467 and U21A20138)Youth Science Foundation of Jiangsu Province(Grant No.BK20220531)Science and Technology Planning Project of Zhenjiang-International Scientific and Technological Cooperation(Grant No.GJ2023014)。
文摘Laser powder bed fusion(LPBF)is an attractive additive manufacturing technology for preparing high-performance high-entropy alloys(HEAs)engineering components.Unfortunately,the existence of inherent thermal residual stress and non-equilibrium microstructures in the additively manufactured components results in unsatisfactory mechanical properties.Herein,we propose a novel strengthening strategy,namely deep cryogenic treatment(DCT)followed by laser shock peening(LSP),to tailor the microstructures and enhance performances of an LPBF additively manufactured metastable HEA.The post-treatment effects of DCT+LSP on the LPBF-fabricated Fe_(50)Mn_(30)Co_(10)Cr_(10)HEA are evaluated in terms of microstructural modifications,residual stress,and microhardness redistribution,as well as tensile properties.Results indicate that a gradient heterogeneous structure is formed on the as-built sample surface,featuring gradient variations in grain size,martensitic phase content,and dislocation density,due to the grain refinement and martensitic phase transformation under DCT+LSP.The initial tensile residual stress on the surface is fully transformed into compressive stress,achieving a peak of-289 MPa,and the surface microhardness attains a maximum of 380.8 HV.The various strengthening mechanisms of gradient heterogeneous structures,as well as the multiple effects of heterodeformation-induced(HDI)hardening,transformation-induced plasticity(TRIP),and twinning-induced plasticity(TWIP),are responsible for achieving strength-ductility synergy.This work provides a practical pathway and valuable scientific insights for enhancing the mechanical behaviors of additively manufactured metastable HEAs via microstructural engineering.
基金supported by the National Nature Science Foundation of China(NSFC)(Grant No.11974033)Xuqiang Liu acknowledges support from the National Postdoctoral Foundation Project of China under Grant No.GZC20230215+2 种基金the National Nature Science Foundation of China under Grants No.12404001The XRD measurements at room and high temperatures were performed at the 4W2 HPStation of the Beijing Synchrotron Radiation Facility(BSRF)and beamline 15U1 of the Shanghai Synchrotron Radiation Facility(SSRF)In situ high-pressure,low-temperature XRD measurements were conducted at sector 16 ID-B,HPCAT of the Advanced Photon Source,and were supported by DOE-NNSA under Award No.DE-NA0001974.
文摘High-pressure β-Sn germanium may transform into diverse metastable allotropes with distinctive nanostructures and unique physical properties via multiple pathways under decompression.However,the mechanism and transition kinetics remain poorly understood.Here,we investigate the formation of metastable phases and nanostructures in germanium via controllable transition pathways of β-Sn Ge under rapid decompression at different rates.High-resolution transmission electron microscopy reveals three distinct metastable phases with the distinctive nanostructures:an almost perfect st12 Ge crystal,nanosized bc8/r8 structures with amorphous boundaries,and amorphous Ge with nanosized clusters (0.8–2.5 nm).Fast in situ x-ray diffraction and x-ray absorption measurements indicate that these nanostructured products form in certain pressure regions via distinct kinetic pathways and are strongly correlated with nucleation rates and electronic transitions mediated by compression rate,temperature,and stress.This work provides deep insight into the controllable synthesis of metastable materials with unique crystal symmetries and nanostructures for potential applications.
文摘This study investigates the development of novel high-entropy alloys(HEAs)with enhanced mechanical properties through an innovative fabrication method of direct energy deposition(DED).The focus is on the creation of metastable core-shell precipitation-strengthened HEAs that exhibit a unique multi-stage terrace-like slip wave toughening mechanism,a novel approach to improving both strength and ductility simultaneously.Mechanical testing reveals that the developed HEAs exhibit superior mechanical proper-ties,including high yield strength,ultimate tensile strength,and exceptional ductility.The improvement in these properties is attributed to the multi-stage terrace-like slip wave toughening mechanism activated by the unique microstructural features.This toughening mechanism involves the sequential activation of slip systems,facilitated by the stress concentration around the core-shell precipitates and the subsequent propagation of slip waves across the material.The terrace-like pattern of these slip waves enhances the material's ability to deform plastically,providing a significant toughening effect while maintaining high strength levels.Furthermore,the study delves into the fundamental interactions between the microstruc-tural elements and the deformation mechanisms.It elucidates how the core-shell precipitates and the matrix cooperate to distribute stress uniformly,delay the onset of necking,and prevent premature failure.This synergistic interaction between the microstructural features and the slip wave toughening mecha-nism is central to the remarkable balance of strength and ductility achieved in the HEAs.The introduction of a multi-stage terrace-like slip wave toughening mechanism offers a new pathway to designing HEAs with an exceptional amalgamation of strength and ductility.
基金Qin Chuangyuan Cites High-Level Innovation,Entrepreneurship Talent Project(QCYRCXM-2023-003)Innovation Capability Support Program of Shaanxi(2022KJXX-84)。
文摘The effect of hot deformation onα-phase precipitation during the subsequent heat treatment,as well as the mechanical properties of TB18 Ti-alloy,was investigated.Results show that the round bar obtained by the dual-phase field forging of the cast ingot exhibits uniform composition distribution on its cross-section.However,various degrees of deformation are detected at different positions on the cross-section,which is attributed to the characteristics of the forging process.Under the forging condition,the microstructure is mainly composed ofβ-phase matrix and coarsened discontinuous primaryα-phases.After solution and following artificial aging treatment,the primaryα-phases disappear,while needle-like secondaryα-phases precipitate in the matrix.Additionally,dispersed white zones are observed in the samples after aging,which are analyzed to be the precipitation-free zones of secondaryα-phase.Despite a uniform compositional distribution among various regions,these dispersed white zones exhibit higher content and larger size in the positions that have undergone lower forging deformation.It indicates that the insufficient forging deformation inhibits the precipitation of the secondaryα-phase,ultimately resulting in the lower strengthening effect by heat treatment.Thus,consistent with the characteristics of the forging process,a periodic variation of sample in strength is detected along the circumferential direction of the forged round bar.
基金financial support by the National Natural Science Foundation of China(No.51364032)the Inner Mongolia Natural Science Foundation(No.2022MS05028)。
文摘The spray-deposition was used to produce billets of Mg-4Al-1.5Zn-3Ca-1Nd(A alloy)and Mg-13Al-3Zn-3Ca-1Nd(B alloy),and evolution of deformation substructure and Mg_(x)Zn_(y)Ca_(z)metastable phase in fine-grained(3μm)Mg alloys was investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and electron backscattered diffraction(EBSD).It was found that different dislocation configurations were formed in A and B alloys.Redundant free dislocations(RFDs)and dislocation tangles were the ways to form deformation substructure in A alloy,no RFDs except dislocation tangles were found in B alloy.The interaction between nano-scale second phase particles(nano-scale C15 andβ-Mg_(17)(Al,Zn)_(12)phase)and different dislocation configurations had a significant effect on the deformation substructures formation.The mass transfer of Mg_(x)Zn_(y)Ca_(z)metastable phases and the stacking order of stacking faults were conducive to the Mg-Nd-Zn typed long period stacking ordered(LPSO)phases formation.Nano-scale C15 phases,Mg-Nd-Zn typed LPSO phases,c/a ratio,β-Mg_(17)(Al,Zn)_(12)phases were the key factors influencing the formation of textures.Different textures and grain boundary features(GB features)had a significant effect on k-value.The non-basal textures were the main factor affecting k-value in A alloy,while the high-angle grain boundary(HAGB)was the main factor affecting k-value in B alloy.
基金supported by the National Natural Science Foundation of China(Grant Nos.52472040,52072032,and 12090031)the 173 JCJQ program(Grant No.2021JCJQ-JJ-0159)。
文摘The extensive applications of cubic silicon in flexible transistors and infrared detectors are greatly hindered by its intrinsic properties.Metastable silicon phases,such as Si-Ⅲ,Ⅳ,andⅫ,prepared using extreme pressure methods,provide a unique“genetic bank”with diverse structures and exotic characteristics.However,exploration of their inherent physical properties remains underdeveloped.Herein,we demonstrate the phase engineering strategy to modulate the thermal conductivity and mechanical properties of metastable silicon.The thermal conductivity,obtained via the Raman optothermal approach,exhibits broad tunability across various Si-Ⅰ,Ⅲ,Ⅻ,andⅣphases.The hardness and Young's modulus of Si-Ⅳare significantly greater than those of the Si-Ⅲ/Ⅻmixture,as confirmed by the nanoindentation technique.Moreover,it was found that pressure-induced structural defects can substantially degrade the thermal and mechanical properties of silicon.This systematic investigation offers a feasible route for designing novel semiconductors and further advancing their desirable applications in advanced nanodevices and mechanical transducers.
文摘The electrolysis of alkaline seawater is critical for sustainable hydrogen production but is hindered by the sluggish oxygen evolution reaction in saline environments.Advanced electrocatalysts with tailored structures and electronic properties are essential,and phase engineering provides a transformative approach by modulating crystallographic symmetry and electronic configurations.Two-dimensional(2D)LaMnO_(3) perovskites show promise due to their exposed active sites and tunable electronic properties.However,the conventional stable rhombohedral phase limits oxygen diffusion despite good electron transport.Unconventional metastable phases with superior symmetry enhance lattice oxygen activity in saline environments but are challenging to synthesize.Herein,we propose a microwave shock method incorporating Co atoms to rapidly produce 2D LaMnO_(3) in rhombohedral,hexagonal,and metastable cubic phases.This strategy circumvents the limitations of high-temperature synthesis,preserving the 2D morphology while enabling the formation of metastable cubic phases.The metastable cubic phase exhibits superior OER activity and stability even in alkaline seawater due to optimal symmetry,interlayer spacing,and Mn-O covalency.X-ray absorption spectroscopy and theoretical calculations further highlight its balanced oxygen adsorption and desorption.This work underscores the role of metastable phase engineering in advancing seawater electrolysis and establishes a scalable route for designing high-performance 2D electrocatalysts.
基金financially supported by the National Natural Science Foundation of China(52102233)Science and Technology Project of Hebei Education Department(QN2023019).
文摘In recent years,aqueous aluminum ion batteries have been widely studied owing to their abundant energy storage and high theo retical capacity.An in-depth study of vanadium oxide materials is necessary to address the precipitation of insoluble products covered cathode surface and the slow reaction kinetics.Therefore,a method using a simple one-step hydrothermal preparation and oxalic acid to regulate oxygen vacancies has been reported.A high starting capacity(400 mAh g^(-1))can be achieved by Ov-V2O5,and it is capable of undergoing 200 cycles at 0.4 A g^(-1),with a termination discharge capacity of103 mAh g^(-1).Mechanism analysis demonstrated that metastable structures(AlxV2O5and HxV2O5)were constructed through the insertion of Al^(3+)/H^(+)during discharging,which existed in the lattice intercalation with V2O5.The incorporation of oxygen vacancies lowers the reaction energy barrier while improving the ion transport efficiency.In addition,the metastable structure allows the electrostatic interaction between Al3+and the main backbone to establish protection and optimize the transport channel.In parallel,this work exploits ex-situ characterization and DFT to obtain a profound insight into the instrumental effect of oxygen vacancies in the construction of metastable structures during in-situ electrochemical activation,with a view to better understanding the mechanism of the synergistic participation of Al3+and H+in the reaction.This work not only reports a method for cathode materials to modulate oxygen vacancies,but also lays the foundation for a deeper understanding of the metastable structure of vanadium oxides.
基金financially supported by the National Research Foundation of Korea(NRF)grants funded by the Korean Govern-ment(Nos.RS-2023-00281246 and RS-2024-00398068)the grant(No.360-05-01-PNK9690)by the Department of Hydrogen Materials Evaluation at Korea Institute of Materials Science(KIMS).
文摘The phase metastability and precipitation are now considered to be an important strategy in designing Fe-rich high entropy alloys(HEAs).In this study,the influence of silicon addition on the initial and straininduced microstructure evolution and related mechanical property of Fe52−xMn27Cr15Co6Six(x=0,0.3,0.5,1.0,1.5,at.%)HEAs was systematically investigated by utilizing the in-depth microstructural characterization coupled with X-ray diffractometer(XRD),secondary electron microscopy(SEM),and transmission electron microscopy(TEM).The addition of Si to Fe52−xMn27Cr15Co6Six HEAs facilitates the triplex structure consisting of fcc-γmatrix,thermally-inducedε-martensite and sigma phase(σ).The lattice distortion energy by Si atoms is suggested to promote the formation ofσphase consisting of Cr,Si and Co and consequently influence the metastability of the matrix.In 0.3 at.%Si HEA,the strain-induced bodycentered tetragonal(bct)-typeα’-martensite were observed at the intersection of bi-directional straininducedε-martensite laths,enhancing the ultimate tensile strength to∼851 MPa from∼618.3 MPa with ductility increment(∼73.1%from∼71%).In 0.3 at.%Si and 0.5 at.%Si alloys,the granular-typeσphase was observed both at grain boundaries and in grain interior,and the size of granular-typeσphase at grain boundary and intra-granularσphase were found to be similar.The deformation mode altered from the transformation-induced plasticity(TRIP)to twinning-induced plasticity(TWIP)with an increase of Si content to 1.5 at.%,due to the enhanced fcc-γstability induced by the compositional modulation driven by increasedσphase formation.The propagation of microcracks inside brittleσphase could be suppressed by homogeneous slip through strain-induced martensite transformation(SIMT)in HEAs with low Si addition of 0.3at.%-0.5 at.%.
基金supports from the National Natural Science Foundation of China(Nos.51509081,52208241).
文摘Reinforcing bars in concrete structures in marine environment are prone to pitting corrosion,which threatens the safety of engineering structures.In order to effectively mitigate the pitting corrosion of reinforcing bars,the electrochemical testing and atomic force microscopy are adopted,the effect of triethanolamine dodecylbenzene sulfonate(TDS)on metastable pitting behavior of 304 stainless steel(304 SS)in simulated concrete pore solutions(SCPS)with chlorine contamination was studied.The results show that the corrosion potential(Ecorr)and breakdown potential(Eb)increased with the growth of the TDS concentrations.Statistical cha-racteristics of metastable pits suggested that as the TDS concentrations increased in the SCPS,the parameters were all decreased.The Mott-Schottky tests exhibited that,although the donor density(ND)diminished,the thickness of the space charge layer(W)increased with increasing TDS concentrations.Investigation results showed that TDS inhibited the sprouting and growth of metastable pits,and with greater TDS concentration,it becomes more difficult for metastable pits to transfer into stable pits in the SCPS,the generated stable passive film prevented the sprouting of pitting corrosion,It is recommended to use TDS with a concentration of not less than 3.364×10^(-4) mol/L in engineering,so that the sensitivity of passivation film of 304SS to chloride erosion is reduced.
基金supported by the National Natural Science Foun-dation of China(No.52401222)Zhejiang Provincial Natural Sci-ence Foundation(LQN25E010011)+2 种基金Ningbo Natural Science Founda-tion(2024J073)Ningbo Major Special Projects of the Plan“Science and Technology Innovation 2025"(No.2022Z107)Ningbo Key Research and Development Program(No.2023Z097).
文摘By employing micrometer-diameter microelectrodes, the metastable pitting corrosion behavior of Co_(68.15)Fe_(4.35)Si_(12.5)B_(12)Cr_(3) metallic glasses (MGs) exposed to 0.6 mol/L NaCl solution was investigated to clarify the correlation between metastable pitting and structural heterogeneity in MGs. Thermally induced degeneration of structural heterogeneity inhibits the initiation, decelerates the growth kinetics, and accelerates the repassivation kinetics of metastable pits while also decreasing the probability of transition from metastability to stability. This enhanced resistance to pitting corrosion is attributed to a reduction in active pitting precursor sites and a decrease in electrochemical activity caused by the structural homogenization of MGs.
基金support from the National Natural Science Foundation of China(Grant No.52304389)the China Postdoctoral Science Foundation(No.2022M720402)+2 种基金Huibin Wu and Gang Niu appreciate the support from the Fundamental Research Funds for the Central Universities(No.FRF-BD-23-01)Na Gong appreciates the support from the Structural Metal Alloy Program(SMAP,No.A18B1b0061)Gang Niu is grateful to Hatem S.Zurob for his insightful recommendation and expressive discussion.
文摘High-strength steel with excellent ductility is pivotal for the formability and safety of critical structural components.Here,a heterogeneous metastable lamellar steel,composed of alternating lamellar ferrite and austenite aligned with the rolling direction,was developed through an innovative combination of warm rolling and immediate annealing processes.This novel design overcomes the strength-ductility trade-off,achieving high ultimate tensile strength(∼1.2 GPa)and excellent uniform elongation(∼78%),pushing the product of ultimate tensile strength and uniform elongation to an ultra-high level(>90 GPa%).The high tensile strength is attributed to ultrafine lamellar grains and significant work hardening induced by the hetero-deformation and transformation-induced plasticity(TRIP)effect.The exceptional ductility is a result of the synergy of multiple plasticity mechanisms,including(i)the inherent plastic deformation ability of lamellar microstructure and the hetero-deformation-induced hardening in the early deformation period,(ii)the persistent TRIP effect induced by the lamellar austenite with high mechanical stability and the elimination of strain localization caused by prolonged strain hardening due to the coordinated deformation of lamellar austenite and ferrite in the middle deformation period,and(iii)delamination cracking in the late deformation period.This approach adopted in current work offers a straightforward and economically feasible pathway for fabricating advanced high-strength steel with superior performance.
基金financially supported by the National Natural Science Foundation of China(No.52071339)
文摘To improve the yield strength of metastableβ-Ti alloys with transformation-induced plasticity(TRIP)and twinning-induced plasticity effects,a novel strategy combining heterostructure strengthening with the TRIP effect was developed.A metastableβ-Ti alloy with a nominal composition of Ti-4Mo-3Cr-1Fe-1Al was used as the base alloy.By adjusting the annealing temperature after cold rolling,heterostructured samples comprising soft recrystallizedβ-grains and hard un-recrystallizedβ-grains andα-phase were prepared.Compared with the homogeneous coarse-grained sample,the yield strength of the heterostructured sample significantly increased from 610 to905 MPa,while maintaining excellent plasticity(32.7%),overcoming the traditional trade-off between strength and ductility.The observed high yield strength is attributed to significant back-stress strengthening caused by the accumulation of a large number of geometrically necessary dislocations at the interfaces between the soft and hard regions.Meanwhile,the exceptional plasticity is attributed to the activation of stress-induced martensite(SIM)within the metastableβmatrix.The sequential activation of dislocation slips and SIM is achieved through the construction of a heterostructured structure.This work provides a new strategy for designing metastableβ-Ti alloys with high strength and plasticity by coupling heterostructure strengthening and transformation-induced plasticity.
基金supported by the National Natural Science Foundation of China(Nos.52371063 and 52072110)the Natural Science Foundation of Hebei Province(No.E2018202034)+1 种基金the Central Funds Guiding the Local Science and Technology Development of Hebei Province(No.236Z7610G)the Graduate Innovation Project of Hebei Province(No.CXZZBS2022035).
文摘High porosity and high brittleness are the main reasons that limit the long-term service life of the alumina-titanium oxide composite coating.Herein,a metastable nanostructured aluminatitanium oxide composite coating with high density and high properties was synthesized by plasma spraying of TiO_(2)-Al composite powder.The main phases of the metastable nanostructured alumina-titanium oxide wereγ-Al_(2)O_(3),TiO and AlTiO_(2).The coating,as prepared,contains various metastable microstructures,such as fine-grained,intra-/inter-granular,and"self-locking"microstructures.These metastable microstruc-tures are important for the improvement of hardness and toughness of the coating.Compared with other alumina-based composite coatings,the metastable nanostructured aluminatitanium oxide composite coating showed the most impressive overall performance.The reinforcing and toughening mechanism of the metastable alumina-titanium oxide composite coating included fine grain strengthening and self-toughening of the metastable microstructure.
基金funded by DOE,Office of Science,Office of Basic Energy Sciences with the grant number of DE-SC0016808.
文摘Laser processing of Al-Ge eutectic alloys is used to produce two different metastable intermetallic-matrix nano-scale lamellar composite microstructures:(ⅰ)β_(1)(monoclinic)Al_(6)Ge_(5)(60 vol%)-α(FCC)Al(40 vol%),and(ⅱ)β_(2)(monoclinic)AIGe(67 vol%)-α(FCC)Al(33 vol%).Nanoindentation and micropillar compres-sion tests were performed to characterize mechanical behavior and compare with the equilibrium struc-ture of as-cast diamond cubic Ge(42 vol%)-FCC Al(58 vol%)micrometer-scale eutectic composite.The as-processed and deformed microstructures were characterized by scanning/transmission electron mi-croscopy.Bothβ_(1)-αandβ_(2)-αeutectics exhibit high compressive flow strengths of≈1 GPa and 1.2 GPa respectively,whereas the maximum compressive flow strength of Al-Ge eutectic is about 450 MPa.In spite of complex monoclinic structures and higher volume fraction of intermetallic phase as compared to metallic,bothβ_(1)-αandβ_(2)-αcomposite microstructures have higher level of plastic deformability than as-cast Al-Ge.The microstructure with the highest strength,β_(2)-α,also exhibits the highest plastic strain to failure attributed to a gradual strain softening behavior due to interaction of micro shear cracks with nano-twins in theβ_(2)(monoclinic)AlGe phase,whereas theβ_(1)(monoclinic)Al_(6)Ge_(5) phase without the nano-twins exhibits sudden fracture by a sharp crack.In the Al-richαphases in bothβ_(1)-αandβ_(2)-αmicrostructures,nanoscale Ge-rich clusters were observed that led to profuse stacking faults post defor-mation.Density functional theory calculations suggest that Ge solutes can lower stacking fault energy of FCC Al,thereby promoting partial dislocation glide in Al.This study highlights unusual mechanisms that impart plastic deformability at ultra-high yield strengths in intermetallic-metal composites with a low-symmetry intermetallic matrix phase.
基金supported by the National Natural Science Foundation of China(Nos.52104372,52374332)the Postdoctoral Research Foundation of China(Nos.2019M651129,2019TQ0053)the Fundamental Research Funds for the Central Universities(No.N2324003-02).
文摘To overcome the strength-plasticity trade-offin the structural titanium alloys,a novel metastableβti-tanium alloy Ti-5Mo-4Cr-1V-1Zr(Ti-5411)with high strength and high plasticity was designed by the d-electrons theory,average electron-to-atom ratio(e/α^(-))and atomic radius difference(Δr^(-))theory.Com-bined in-situ scanning electron microscope(SEM)and electron backscatter diffraction(EBSD),the defor-mation mechanisms of the novel Ti-5411 metastableβtitanium alloy were systematically investigated.The results show that the Ti-5411 alloy exhibits excellent yield strength(∼689 MPa),tensile strength(∼930 MPa)and total elongation(∼39%).The in-situ tension indicates that slip activities,crystal rota-tion,stress induced martensite(SIM)α''transformation and{332}<113>deformation twin are the major deformation mechanisms of Ti-5411 alloy.Besides,with the increase of strain degree(0-0.5 mm displace-ment),deformation twins increase,widen and interlace.At 0.35 mm tensile displacement,the orientation of theβgrains rotates∼6.65°to accommodate the increased macrostrain.Additionally,martensiteα''also assists the nucleation of twins.Some{332}<113>twins grow and merge by consuming martensiteα''during deformation,and the residual martensiteα''remains in the merged twins.
基金financially supported by the National Natural Science Foundation of China(No.52401161)the Natural Science Foundation of Sichuan Province for Young Scholars(No.24NSFSC6582)+3 种基金the Postdoctoral Fellowship Program of CPSF(No.GZC20231761)the National Natural Science Foundation of China(No.52271249)the Key Research and Development Program of Shaanxi(No.2023-YBGY-488)the Xi'an Talent Plan(No.XAYC240016).
文摘Elinvar alloys exhibit temperature-independent elastic modulus within a specific temperature range,known as the Elinvar effect,which was first observed in Fe-Ni alloys[1].The unique temperature-independent elastic modulus makes Elinvar alloys highly desirable in precision-control applications,including aerospace,electronics,and optical instruments.Currently,most of the used and studied Elinvar alloys are ferromagnetic alloys(FeNi and Fe-Pt)and antiferromagnetic alloys(Fe-Mn and γ-MnCu)[2–4].The Elinvar effect in these alloys typically originates from magnetostriction or magnetoelastic effects,which are magnetic fieldor magnetic transition-dependent[5].Consequently,these Elinvar alloys cannot function properly in the presence of a magnetic field owing to their Elinvar effect being closely tied to magnetic phase transition.Therefore,developing non-magneticdependent Elinvar alloys is highly essential to widen their practical applications.
基金supported by the National Natural Science Foundation of China(Grant No.U2230207)。
文摘Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback control on nuclear spin precession in a metastability exchange optical pumping(MEOP)-based polarized^(3)He system.We analyze the effects of feedback theoretically and validate our predictions experimentally.With optimized feedback parameters,the spin coherence time T_(2)is extended by an order of magnitude.When the feedback strength surpasses a critical threshold,robust maser oscillations are spontaneously excited,demonstrating remarkable resistance to environmental noise and maintaining stable oscillation.This proof-of-principle experiment highlights the viability of MEOP-based^(3)He spin oscillators,especially in low-frequency domains.The operational simplicity and easy integration associated with MEOP-based systems make them particularly promising for fast,high-precision magnetic field measurements.
基金Project(51105139)supported by the National Natural Science Foundation of ChinaProject(2010CB731706)supported by the National Basic Research Program of China
文摘The precipitation behavior and its influence on the electrical resistivity of the Al-0.96Mg2Si alloy during aging were investigated with in-situ resistivity measurement and transmission electron microscopy （TEM）. The precipitates of the peak aged alloy include both β＂ and if, but the amount ratio of β＂ to β＂ varies with the aging temperature and time increasing. The precipitates during aging at 175 ℃ are dominated by needle-like β＂ phases （including pre-β＂ phase）, the size of which increases with the time prolonging, but does not increase substantially after further aging. The evolution of electrical conductivity is directly related to such microstructural evolution. However, the hardness of the alloy stays at the peak value for a long term. When the alloy is aged at 195 ℃, the ratio of β＂ to β＇ becomes the main factor to influence relative resistivity （Ap） value. The higher the temperature is, the smaller the ratio is, and the faster the Ap value decreases. Moreover, the hardness peak drops with the decrease of the ratio. With the size and distribution parameters measured from TEM images, a semi-quantitative relationship between precipitates and the electrical resistivity was established.
