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 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
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
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
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
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
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
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
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
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
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
Development of new materials with high hydrogen storage capacity and reversible hydrogen sorp-tion performances under mild conditions has very high value in both fundamental and application aspects.In the past years,s...Development of new materials with high hydrogen storage capacity and reversible hydrogen sorp-tion performances under mild conditions has very high value in both fundamental and application aspects.In the past years,some new systems with metastable structures,such as ultra-fine nanocrystalline alloys,amorphous alloys,nanoglass alloys,immiscible alloys,high-entropy alloys,have been abundantly studied as hydrogen storage mate-rials.Many new hydrogen storage properties either from the kinetics or thermodynamics aspects have been reported.In this review,recent advances of studies on metastable alloys for hydrogen storage applications have been comprehensively reviewed.The materials preparation methods to synthesize metastable hydrogen storage alloys are firstly reviewed.Afterwards,hydrogen storage prop-erties of the metastable alloys are summarized and dis-cussed,focusing on the unique kinetics and thermodynamics properties by forming of such unique metastable structures.For examples,superior hydrogena-tion kinetics and higher hydrogen storage capacity have been achieved in Mg-based amorphous and nanoglass alloys.Destabilized thermodynamics properties can be obtained in the immiscible Mg-Mn and Mg-Zr alloys.In addition to highlighting the recent achievements of metastable alloys in the field of hydrogen storage,the remaining challenges and trends of the emerging research are also discussed.展开更多
Fe based cast alloys with double phases structure of m etastable austenite m atrix an d eutecticcarbide M7 C3 were provided with the excellent properties of high abrasion resistance andhigher i m pact toughness . ...Fe based cast alloys with double phases structure of m etastable austenite m atrix an d eutecticcarbide M7 C3 were provided with the excellent properties of high abrasion resistance andhigher i m pact toughness . An i m portant reason of high abrasion resistance is hard ness violentincreasing on the m atrix surface because of w ear easily induced m artensite transfor m ation . The exploitation and applications of m etastable austenite m atrix wear alloys of Fe C Cr Nisyste m and Fe C Cr Mn system were described in this paper . The excellent properties of thesealloys w ill be sufficiently indicated by authors’exa m ples . To exploit a class of these alloyswith high abrasion resistance and various im pact toughness for m eeting the requirem ent of dif ferent environ ment , the proble m of the structure design of metastable austenite m atrix wearalloy w as also described in this paper .展开更多
The solubility, metastable zone width, and induction time of analgin for unseeded batch cooling crystallization in ethanol–aqueous system were experimentally determined. The solubility data could be well described by...The solubility, metastable zone width, and induction time of analgin for unseeded batch cooling crystallization in ethanol–aqueous system were experimentally determined. The solubility data could be well described by the van't Hoff equation model. The metastable zone width at various cooling rates was measured, and some parameters of nucleation kinetic were calculated using the Ny'vlt theory. Furthermore, the induction period of various temperatures and supersaturation ratios was also measured. According to classical nucleation theory, some nucleation parameters and interfacial energy was calculated through the induction time(t_(ind)) data. Homogeneous nucleation tended to occur when the supersaturation is high, whereas heterogeneous nucleation was more likely to occur when the supersaturation is low.展开更多
The microstructure and mechanical properties evolution of AISI 301LN metastable austenitic stainless steels during cold rolling were investigated. A wide range of cold thickness reduction (10%-80%) was carried out in ...The microstructure and mechanical properties evolution of AISI 301LN metastable austenitic stainless steels during cold rolling were investigated. A wide range of cold thickness reduction (10%-80%) was carried out in a four-high rolling mill at ambient temperature. The X-ray and Feritscope MP30 were used to identify the strain-induced α′-martensite phase and its volume fraction, respectively. The microstructure was observed by optical micrograph and the mechanical properties were determined by tensile tests and microhardness. The results show that the strain-induced α′-martensite nucleated at the shear bands intersections and the growth of α′-martensite occurred by the repeated nucleation of new embryos. The volume fraction of strain-induced α′-martensite increased with increasing the cold rolling reduction. In addition, the percentage increased in the tensile strength is the same as that of hardness. The ratio between the average tensile strength and the average microhardness was found to range between 2.82 and 3.17.展开更多
The hot deformation characteristics of as-forged Ti−3.5Al−5Mo−6V−3Cr−2Sn−0.5Fe−0.1B−0.1C alloy within a temperature range from 750 to 910℃and a strain rate range from 0.001 to 1 s^(-1) were investigated by hot compre...The hot deformation characteristics of as-forged Ti−3.5Al−5Mo−6V−3Cr−2Sn−0.5Fe−0.1B−0.1C alloy within a temperature range from 750 to 910℃and a strain rate range from 0.001 to 1 s^(-1) were investigated by hot compression tests.The stress−strain curves show that the flow stress decreases with the increase of temperature and the decrease of strain rate.The microstructure is sensitive to deformation parameters.The dynamic recrystallization(DRX)grains appear while the temperature reaches 790℃at a constant strain rate of 0.001 s^(-1) and strain rate is not higher than 0.1 s^(-1) at a constant temperature of 910℃.The work-hardening rateθis calculated and it is found that DRX prefers to happen at high temperature and low strain rate.The constitutive equation and processing map were obtained.The average activation energy of the alloy is 242.78 kJ/mol and there are few unstable regions on the processing map,which indicates excellent hot workability.At the strain rate of 0.1 s^(-1),the stress−strain curves show an abnormal shape where there are two stress peaks simultaneously.This can be attributed to the alternation of hardening effect,which results from the continuous dynamic recrystallization(CDRX)and the rotation of DRX grains,and dynamic softening mechanism.展开更多
Airborne silicate pollutants in flight corridors pose a serious threat to aviation safety whose severity is directly linked to the wettability of molten silicates on thermal barrier coatings(TBCs)at high temperatures(...Airborne silicate pollutants in flight corridors pose a serious threat to aviation safety whose severity is directly linked to the wettability of molten silicates on thermal barrier coatings(TBCs)at high temperatures(1200–2000℃).Despite its importance,the wettability of silicate melt on TBCs has not been well investigated.In particular,the surface morphology characteristics of TBCs can be expected to have a first-order effect on the wettability of silicate melt on such TBCs.Here,a series of atmospheric plasma spray(APS)yttria-stabilized zirconia(YSZ)TBCs with varying surface roughness were generated through the application of mechanical polishing.The metastable nonwetting behavior of three representative types of airborne silicate ash(volcanic ash,fly ash and a synthetic calcium–magnesium–aluminum–silicates(CMAS)powder)on these TBCs with varying surface roughness was investigated.It was observed that the smoother the surface of TBCs was,the larger the contact angle was with the molten silicate melts,and consequently,the smaller the area of damage was on the TBCs.Thus,the reduction in TBCs surface roughness(here via mechanical polishing)led to an improvement in the wetting and spreading resistance of TBCs to silicate melts at high temperature.In support of these observations and conclusions,the surface morphology of the TBC(both before and after polishing)had been characterized,and the mechanism of the surface roughness-dependence of wettability had been discussed.These results should contribute to reducing the deposition rate of silicate melt on TBCs,thus extending the lifetime of turbine blades and reducing maintenance costs.展开更多
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.
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(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 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.
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(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 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.
基金financially supported by Guangdong Basic and Applied Basic Research Foundation (No. 2019A1515011985)the National Natural Science Foundation of China (Nos.52071157,51801078,52001070 and 52001079)+3 种基金the Natural Science Foundation of Jiangsu Province (No.BK20180986)the Natural Science Foundation of Guangxi Province (No. 2019GXNSFB A185004)Guangzhou Science and Technology Association Young Talent Lifting Project (No.X20200301071)the Open Fund of the Guangdong Provincial Key Laboratory of Advance Energy Storage Materials (No.AESM202102)
文摘Development of new materials with high hydrogen storage capacity and reversible hydrogen sorp-tion performances under mild conditions has very high value in both fundamental and application aspects.In the past years,some new systems with metastable structures,such as ultra-fine nanocrystalline alloys,amorphous alloys,nanoglass alloys,immiscible alloys,high-entropy alloys,have been abundantly studied as hydrogen storage mate-rials.Many new hydrogen storage properties either from the kinetics or thermodynamics aspects have been reported.In this review,recent advances of studies on metastable alloys for hydrogen storage applications have been comprehensively reviewed.The materials preparation methods to synthesize metastable hydrogen storage alloys are firstly reviewed.Afterwards,hydrogen storage prop-erties of the metastable alloys are summarized and dis-cussed,focusing on the unique kinetics and thermodynamics properties by forming of such unique metastable structures.For examples,superior hydrogena-tion kinetics and higher hydrogen storage capacity have been achieved in Mg-based amorphous and nanoglass alloys.Destabilized thermodynamics properties can be obtained in the immiscible Mg-Mn and Mg-Zr alloys.In addition to highlighting the recent achievements of metastable alloys in the field of hydrogen storage,the remaining challenges and trends of the emerging research are also discussed.
文摘Fe based cast alloys with double phases structure of m etastable austenite m atrix an d eutecticcarbide M7 C3 were provided with the excellent properties of high abrasion resistance andhigher i m pact toughness . An i m portant reason of high abrasion resistance is hard ness violentincreasing on the m atrix surface because of w ear easily induced m artensite transfor m ation . The exploitation and applications of m etastable austenite m atrix wear alloys of Fe C Cr Nisyste m and Fe C Cr Mn system were described in this paper . The excellent properties of thesealloys w ill be sufficiently indicated by authors’exa m ples . To exploit a class of these alloyswith high abrasion resistance and various im pact toughness for m eeting the requirem ent of dif ferent environ ment , the proble m of the structure design of metastable austenite m atrix wearalloy w as also described in this paper .
基金Supported by the National Natural Science Foundation of China(21206109)China Ministry of Science and Major National Scientific Instrument Development Project(21527812)
文摘The solubility, metastable zone width, and induction time of analgin for unseeded batch cooling crystallization in ethanol–aqueous system were experimentally determined. The solubility data could be well described by the van't Hoff equation model. The metastable zone width at various cooling rates was measured, and some parameters of nucleation kinetic were calculated using the Ny'vlt theory. Furthermore, the induction period of various temperatures and supersaturation ratios was also measured. According to classical nucleation theory, some nucleation parameters and interfacial energy was calculated through the induction time(t_(ind)) data. Homogeneous nucleation tended to occur when the supersaturation is high, whereas heterogeneous nucleation was more likely to occur when the supersaturation is low.
基金Item Sponsored by National High-Tech Research and Development Program (863 Program) of China (2008AA030702)
文摘The microstructure and mechanical properties evolution of AISI 301LN metastable austenitic stainless steels during cold rolling were investigated. A wide range of cold thickness reduction (10%-80%) was carried out in a four-high rolling mill at ambient temperature. The X-ray and Feritscope MP30 were used to identify the strain-induced α′-martensite phase and its volume fraction, respectively. The microstructure was observed by optical micrograph and the mechanical properties were determined by tensile tests and microhardness. The results show that the strain-induced α′-martensite nucleated at the shear bands intersections and the growth of α′-martensite occurred by the repeated nucleation of new embryos. The volume fraction of strain-induced α′-martensite increased with increasing the cold rolling reduction. In addition, the percentage increased in the tensile strength is the same as that of hardness. The ratio between the average tensile strength and the average microhardness was found to range between 2.82 and 3.17.
文摘The hot deformation characteristics of as-forged Ti−3.5Al−5Mo−6V−3Cr−2Sn−0.5Fe−0.1B−0.1C alloy within a temperature range from 750 to 910℃and a strain rate range from 0.001 to 1 s^(-1) were investigated by hot compression tests.The stress−strain curves show that the flow stress decreases with the increase of temperature and the decrease of strain rate.The microstructure is sensitive to deformation parameters.The dynamic recrystallization(DRX)grains appear while the temperature reaches 790℃at a constant strain rate of 0.001 s^(-1) and strain rate is not higher than 0.1 s^(-1) at a constant temperature of 910℃.The work-hardening rateθis calculated and it is found that DRX prefers to happen at high temperature and low strain rate.The constitutive equation and processing map were obtained.The average activation energy of the alloy is 242.78 kJ/mol and there are few unstable regions on the processing map,which indicates excellent hot workability.At the strain rate of 0.1 s^(-1),the stress−strain curves show an abnormal shape where there are two stress peaks simultaneously.This can be attributed to the alternation of hardening effect,which results from the continuous dynamic recrystallization(CDRX)and the rotation of DRX grains,and dynamic softening mechanism.
基金This study was financially supported by the National Science and Technology Major Project(No.2017-VI-0010-0081)the Program of the Ministry of Education of China for Introducing Talents of Discipline to Universities(No.B17002)+2 种基金the National Natural Science Foundation of China(No.51901011)the“Freigeist”Fellowship of the Volkswagenstiftung on“Volcanic Ash Deposition in Jet Engines”(VADJEs,No.89705)China Scholarship Council(CSC).
文摘Airborne silicate pollutants in flight corridors pose a serious threat to aviation safety whose severity is directly linked to the wettability of molten silicates on thermal barrier coatings(TBCs)at high temperatures(1200–2000℃).Despite its importance,the wettability of silicate melt on TBCs has not been well investigated.In particular,the surface morphology characteristics of TBCs can be expected to have a first-order effect on the wettability of silicate melt on such TBCs.Here,a series of atmospheric plasma spray(APS)yttria-stabilized zirconia(YSZ)TBCs with varying surface roughness were generated through the application of mechanical polishing.The metastable nonwetting behavior of three representative types of airborne silicate ash(volcanic ash,fly ash and a synthetic calcium–magnesium–aluminum–silicates(CMAS)powder)on these TBCs with varying surface roughness was investigated.It was observed that the smoother the surface of TBCs was,the larger the contact angle was with the molten silicate melts,and consequently,the smaller the area of damage was on the TBCs.Thus,the reduction in TBCs surface roughness(here via mechanical polishing)led to an improvement in the wetting and spreading resistance of TBCs to silicate melts at high temperature.In support of these observations and conclusions,the surface morphology of the TBC(both before and after polishing)had been characterized,and the mechanism of the surface roughness-dependence of wettability had been discussed.These results should contribute to reducing the deposition rate of silicate melt on TBCs,thus extending the lifetime of turbine blades and reducing maintenance costs.
