Tungsten heavy alloys(WHAs)prepared using laser additive manufacturing(AM)exhibit intricate ge-ometries,albeit with limited mechanical properties.Here we designed a high-strength WHA featuring a FeCrCoNi high entropy ...Tungsten heavy alloys(WHAs)prepared using laser additive manufacturing(AM)exhibit intricate ge-ometries,albeit with limited mechanical properties.Here we designed a high-strength WHA featuring a FeCrCoNi high entropy alloy(HEA)binder via the laser metal deposition(LMD)technique.Due to the distinctive thermal cycle and rapid cooling rate,the as-deposited alloys exhibit microstructures with hy-poeutectic,eutectic-like,and spot-like characteristics.To elucidate this phenomenon,the solidification paths were delineated and analyzed by combining microstructural characterization and phase equilib-rium simulation.Theμphase precipitated out from the supersaturated solid solution,thereby nucleating massive dislocations on the FeCrCoNi matrix to increase the work hardening rate.Furthermore,theμphase formed an ultrafine intermetallic compound(IMC)layer around the W grain,reducing the hole or crack between the W grain and FeCrCoNi matrix.Attributed to the precipitation strengthening,the solid solution of the FeCrCoNi binder,along with the load-bearing strength of W,the developed alloy achieved ultrahigh compressive stress and strain of 2047 MPa and 32%respectively at room temperature.These findings contribute valuable insights to the advancement of additive manufacturing for tungsten alloys,leveraging their excellent properties.展开更多
Refractory high/medium-entropy alloys(RH/MEAs)are known for their outstanding performance at el-evated temperatures;however,they usually exhibit poor room-temperature plasticity,which can be at-tributed to the non-uni...Refractory high/medium-entropy alloys(RH/MEAs)are known for their outstanding performance at el-evated temperatures;however,they usually exhibit poor room-temperature plasticity,which can be at-tributed to the non-uniform deformation that occurs at room temperature.Once cracks nucleate,they will rapidly propagate into vertical splitting cracks.Here,we introduce multiple phases including FCC and HCP phases into the NbMoTa RMEA via appropriate addition of carbon.The results show that multiple-phase synergy effectively suppresses non-uniform deformation,thereby delaying the onset of vertical splitting cracks.An optimal combination of compressive strength-plasticity is achieved by the(NbMoTa)_(92.5)C_(7.5) alloy.The significant improvement in room-temperature mechanical properties can be attributed to its hierarchical microstructure:in the mesoscale,the BCC matrix is divided by eutectic structures;while at the microscale,the BCC matrix is further refined by abundant lath-like FCC precipitates.The FCC precip-itates contain high-density stacking faults,acting as a dislocation source under compressive loading.The HCP phase in the eutectic microstructures,in turn,acts as a strong barrier to dislocation movement and simultaneously increases the dislocation storage capacity.These findings open a new route to tailor the microstructure and mechanical properties of RH/MEAs.展开更多
ZnO thin films with varying Ta concentrations were fabricated through magnetron sputtering.The crystallinity and surface morphology of the ZnO films are significantly influenced by the incorporation of Ta,as evidenced...ZnO thin films with varying Ta concentrations were fabricated through magnetron sputtering.The crystallinity and surface morphology of the ZnO films are significantly influenced by the incorporation of Ta,as evidenced by the X-ray diffraction and scanning electron microscopy results.The lattice constants,as determined by X-ray diffraction,contradict the disparity in Ta and Zn ion radii,which is attributed to the impact of interstitial defects.This inconsistency introduces variations in carrier concentration in this experiment compared with prior studies.Subsequent exploration of the luminescent characteristics and emission mechanism of defect levels in Ta-doped ZnO films was conducted through photoluminescence.Furthermore,the factors influencing the bandgap are discussed.展开更多
The fracture mechanisms of coarse-grained heat-affected zone(CGHAZ)for Mg and Mg–Ca deoxidized high-strength low-alloy(HSLA)steels after high heat input welding(HHIW)were investigated based on the microstructures,cra...The fracture mechanisms of coarse-grained heat-affected zone(CGHAZ)for Mg and Mg–Ca deoxidized high-strength low-alloy(HSLA)steels after high heat input welding(HHIW)were investigated based on the microstructures,crack behaviors and mechanical properties.Compared to Mg–Ca steel,the proportion of intergranular acicular ferrites(IAFs)and polygonal ferrites(PFs)in Mg steel increases from 59.97%to 90.16%.The high-angle grain boundaries(HAGBs)and geometrically necessary dislocations density increase from 55.5%and 4.30×10^(14) m^(-2)to 70.4%and 5.48×10^(14) m^(–2),respectively,while effective grain size decreases from 9.46 to 8.12μm.The area fraction of radial zone in Mg steel decreases from 80.8%to 37.7%and cleavage plane is smaller with more curved and finer tearing ridges.The inclusions distributed at the center of cleavage planes and along river lines can serve as crack initiation sites.The zigzag pattern of primary crack propagation path has width of 476μm and the length of secondary cracks remains below 10μm.These cracks are deflected or arrested by IAFs,PFs and HAGBs,and tend to propagate along{110}plane family.These factors contribute to superior overall mechanical properties of Mg steel,especially increasing low-temperature impact toughness from 23 to 175 J.展开更多
YBa_(2)Cu_(3)O_(7-x)(YBCO)films with low microwave surface resistance(RS)are essential for high temperature superconducting microwave devices.The oxygen pressure during deposition has been found to influence RS signif...YBa_(2)Cu_(3)O_(7-x)(YBCO)films with low microwave surface resistance(RS)are essential for high temperature superconducting microwave devices.The oxygen pressure during deposition has been found to influence RS significantly.In this work,we deposited highly c-axis aligned YBCO films on single crystal MgO(001)substrates under different oxygen pressures via pulsed laser ablation.Their detailed microstructure was characterized with three-dimensional reciprocal space mapping(3D-RSM)method and their microwave surface resistance was also measured with resonant cavity perturbation method.We found that the variation of oxygen pressure can affect film microstructure,including grain orientation distribution and the concentration of crystal defects.The microstructure modulation can explain RS dependence on the oxygen pressure.展开更多
The low coercivity is the major factor inhibiting the large-scale commercial utilization of Nd-Ce-Fe-B sintered magnets.In this work,we achieved a record-high coercivity of 15.04 kOe in Ga-doped Nd-Ce-Fe-B sintered ma...The low coercivity is the major factor inhibiting the large-scale commercial utilization of Nd-Ce-Fe-B sintered magnets.In this work,we achieved a record-high coercivity of 15.04 kOe in Ga-doped Nd-Ce-Fe-B sintered magnets with 30 wt%Ce replacing Nd,demonstrating enormous potential.The Ga-doped Nd-Ce-Fe-B magnets with higher boron(HB)and lower boron(LB)content are designed.The coercivity of the HB magnet increases slightly from 10.80 to 12.26 kOe after annealing,attributed to the optimized distribution of grain boundary(GB)phases.In contrast,the coercivity of the LB magnet remarkably increases from 8.13 to 15.04 kOe after annealing.Microstructural observations indicate that the narrow GB phase in the as-sintered magnet is rich in Fe,and the strong exchange coupling of adjacent grains resulted in low coercivity.The evolution of Ga-rich phases reveals a potential formation mechanism of the RE_(6)Fe_(13)Ga phase,that is the RE-Fe amorphous phase and REGa phase in the as-sintered magnet combine to form the RE_(6)Fe_(13)Ga phase and RE-Ga amorphous phase during post-sinter annealing(RE:rare earth).Moreover,the GB phase of the annealed magnet transforms into a Fe-lean phase with a thickness of 16.4 nm.Magnetization and demagnetization behavior characterizations reveal that the exchange decoupling of adjacent grains induced by the optimized GB phases is the main reason for the remarkable coercivity enhancement,which is also validated by micromagnetic simulations.展开更多
It is rather difficult for titanium alloy ultra-thick plates to achieve superior weld formation and excellent mechanical properties along the weld penetration direction due to the large fluctuations of the molten pool...It is rather difficult for titanium alloy ultra-thick plates to achieve superior weld formation and excellent mechanical properties along the weld penetration direction due to the large fluctuations of the molten pool,largely limiting their engineering application.In this study,106-mm-thick Ti-6Al-4V ELI alloy plates were successfully butt welded via electron beam welding(EBW).The defect-free EBW joint with full penetration was obtained.The precipitated secondary α(α_(s))in heat affected zone(HAZ),αlamellae in fusion line(FL)and α′martensite in fusion zone(FZ)increased the α_(s)/β,α/β and α′/β interfaces,respectively,resulting in the higher microhardness and impact energy values(57 J in the HAZ,62 J in the FL and 51.9 J in the FZ)than those in the base material(BM).The impact energy of the joint in this study was higher than that for Ti-6Al-4V ELI alloy joints as reported,which was mainly attributed to the formation of the relatively thickerαphase and finer interlamellar spacing in this study,enhancing the resistance to crack propagation.Furthermore,the average fracture toughness(90.2 MPa m^(1/2))of the FZ was higher than that of the BM(74.2 MPa m^(1/2)).This study provides references for the welding application of titanium alloy ultra-thick plates in the manufacture of large-sized components.展开更多
Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively invest...Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively investigated.Macroscopic morphology,microstructure,and interfacial structure of the joints were analyzed using scanning electron microscope,energy dispersive spectrometer,and X-ray diffractometer(XRD).The results show that magnetic pulse welding of dissimilar Mg/Fe metals is achieved using an Al interlayer,which acts as a bridge for deformation and diffusion.Specifically,the AZ31B/AA1060 interface exhibits a typical wavy morphology,and a transition zone exists at the joint interface,which may result in an extremely complex microstructure.The microstructure of this transition zone differs from that of AZ31B magnesium and 1060 Al alloys,and it is identified as brittle intermetallic compounds(IMCs)Al_(3)Mg_(2) and Al_(12)Mg_(17).The transition zone is mainly distributed on the Al side,with the maximum thickness of Al-side transition layer reaching approximately 13.53μm.Incomplete melting layers with varying thicknesses are observed at the primary weld interface,while micron-sized hole defects appear in the transition zone of the secondary weld interface.The AA1060/DC56D interface is mainly straight,with only a small number of discontinuous transition zones distributed intermittently along the interface.These transition zones are characterized by the presence of the brittle IMC FeAl_(3),with a maximum thickness of about 4μm.展开更多
The rapid advancements in computer vision(CV)technology have transformed the traditional approaches to material microstructure analysis.This review outlines the history of CV and explores the applications of deep-lear...The rapid advancements in computer vision(CV)technology have transformed the traditional approaches to material microstructure analysis.This review outlines the history of CV and explores the applications of deep-learning(DL)-driven CV in four key areas of materials science:microstructure-based performance prediction,microstructure information generation,microstructure defect detection,and crystal structure-based property prediction.The CV has significantly reduced the cost of traditional experimental methods used in material performance prediction.Moreover,recent progress made in generating microstructure images and detecting microstructural defects using CV has led to increased efficiency and reliability in material performance assessments.The DL-driven CV models can accelerate the design of new materials with optimized performance by integrating predictions based on both crystal and microstructural data,thereby allowing for the discovery and innovation of next-generation materials.Finally,the review provides insights into the rapid interdisciplinary developments in the field of materials science and future prospects.展开更多
The age-hardening response,mechanical,and corrosion-resistant properties of AA7085 alloys with and without the addition of 0.3 wt.%scandium(Sc)were compared.Using advanced techniques such as aberration-corrected trans...The age-hardening response,mechanical,and corrosion-resistant properties of AA7085 alloys with and without the addition of 0.3 wt.%scandium(Sc)were compared.Using advanced techniques such as aberration-corrected transmission electron microscopy and first-principles calculations,the underlying micromechanisms of Sc microalloying were revealed.Results show that the increase in strength of the AA7085-Sc alloy is mainly attributed to the decreased Al grain size and increased number density of both Al_(3)Sc@Al_(3)(Sc,Zr)core−shell nanoparticles and Sc-containingη_(p) and GP−η_(p) nanoprecipitates.Strong strain fields and evident electron transfer from Zr to the neighboring matrix Al atoms exist at the Al_(3)Sc@Al_(3)(Sc,Zr)/Al interface.The Sc doping in GP−η_(p) andη_(p) suppresses the GP−η_(p)→η_(p) transformation.Modified corrosion resistance of the AA7085-Sc alloy compared with AA7085 alloy is associated with the fine grain boundary precipitates ofη_(p)hases and narrow precipitation free zone.The reasons of property changes of AA7085 alloy after Sc microalloying are explored based on the multiscale microstructural characterization.展开更多
A new method was proposed for preparing AZ31/1060 composite plates with a corrugated interface,which involved cold-pressing a corrugated surface on the Al plate and then hot-pressing the assembled Mg/Al plate.The resu...A new method was proposed for preparing AZ31/1060 composite plates with a corrugated interface,which involved cold-pressing a corrugated surface on the Al plate and then hot-pressing the assembled Mg/Al plate.The results show that cold-pressing produces intense plastic deformation near the corrugated surface of the Al plate,which promotes dynamic recrystallization of the Al substrate near the interface during the subsequent hot-pressing.In addition,the initial corrugation on the surface of the Al plate also changes the local stress state near the interface during hot pressing,which has a large effect on the texture components of the substrates near the corrugated interface.The construction of the corrugated interface can greatly enhance the shear strength by 2−4 times due to the increased contact area and the strong“mechanical gearing”effect.Moreover,the mechanical properties are largely depended on the orientation relationship between corrugated direction and loading direction.展开更多
The dependence of shrinkage porosities on microstructure characteristics of Mg−12Al alloy was investigated.The distribution,morphology,size,and number density of shrinkage porosities were analyzed under different cool...The dependence of shrinkage porosities on microstructure characteristics of Mg−12Al alloy was investigated.The distribution,morphology,size,and number density of shrinkage porosities were analyzed under different cooling rates.The relationship between shrinkage porosities and microstructure characteristics was discussed in terms of temperature conditions,feeding channel characteristics,and feeding capacity.Further,the feeding behavior of the residual liquid phase in the solid skeleton was quantified by introducing permeability.Results show a strong correlation between the solid microstructure skeleton and shrinkage porosity characteristics.An increase in permeability corresponds to a declining number density of shrinkage porosities.This study aims to provide a more complete understanding how to reduce shrinkage porosities by controlling microstructure characteristics.展开更多
This study investigated enhancing the wear resistance of Ti6Al4V alloys for medical applications by incorporating Ti C nanoreinforcements using advanced spark plasma sintering(SPS). The addition of up to 2.5wt% Ti C s...This study investigated enhancing the wear resistance of Ti6Al4V alloys for medical applications by incorporating Ti C nanoreinforcements using advanced spark plasma sintering(SPS). The addition of up to 2.5wt% Ti C significantly improved the mechanical properties, including a notable 18.2% increase in hardness(HV 332). Fretting wear tests against 316L stainless steel(SS316L) balls demonstrated a 20wt%–22wt% reduction in wear volume in the Ti6Al4V/Ti C composites compared with the monolithic alloy. Microstructural analysis revealed that Ti C reinforcement controlled the grain orientation and reduced the β-phase content, which contributed to enhanced mechanical properties. The monolithic alloy exhibited a Widmanstätten lamellar microstructure, while increasing the Ti C content modified the wear mechanisms from ploughing and adhesion(0–0.5wt%) to pitting and abrasion(1wt%–2.5wt%). At higher reinforcement levels, the formation of a robust oxide layer through tribo-oxide treatment effectively reduced the wear volume by minimizing the abrasive effects and plastic deformation. This study highlights the potential of SPS-mediated Ti C reinforcement as a transformative approach for improving the performance of Ti6Al4V alloys, paving the way for advanced medical applications.展开更多
The dissimilar 2B06 and 7B04 Al alloy joints were prepared by refill friction stir spot welding(RFSSW),and the microstructural evolution and corrosion behavior of the joints were investigated.Based on microstructural ...The dissimilar 2B06 and 7B04 Al alloy joints were prepared by refill friction stir spot welding(RFSSW),and the microstructural evolution and corrosion behavior of the joints were investigated.Based on microstructural analysis,the welded joints exhibit distinct microstructural zones,including the stir zone(SZ),thermomechanically affected zone(TMAZ),and heat-affected zone(HAZ).The grain size of each zone is in the order of HAZ>TMAZ>SZ.Notably,the TMAZ and HAZ contain significantly larger secondary-phase particles compared to the SZ,with particle size in the HAZ increasing at higher rotational speeds.Electrochemical tests indicate that corrosion susceptibility follows the sequence of HAZ>TMAZ>SZ>BM,with greater sensitivity observed at increased rotational speeds.Post-corrosion mechanical performance degradation primarily arises from crevice corrosion at joint overlaps,but not from the changes in the microstructure.展开更多
Pure metal Fe films with thickness of about 100nm were deposited on Si （100） substrates by DC magnetron sputtering. Annealing was subsequently performed in a vacuum furnace in the temperature range of 600-1000℃ for...Pure metal Fe films with thickness of about 100nm were deposited on Si （100） substrates by DC magnetron sputtering. Annealing was subsequently performed in a vacuum furnace in the temperature range of 600-1000℃ for 2h. The samples were characterized by means of Rutherford backscattering （RBS） with 3MeV carbon ions. The RBS data were fitted with SIMNRA 6.0, and the results show the atomic interdiffusion in Fe/Si systems. The microstructures and crystal structures were characterized by scanning electron microscope and X-ray diffrac- tion. The effects of annealing on atomic interdiffusion, silicide formation, and microstructures in Fe/Si systems were analyzed.展开更多
Ti-doped graphite-like carbon （Ti-GLC） films were synthesized successfully by magnetron sputtering technique. The compositions, microstructures and properties of the Ti-doped GLC films dependent on the parameter of ...Ti-doped graphite-like carbon （Ti-GLC） films were synthesized successfully by magnetron sputtering technique. The compositions, microstructures and properties of the Ti-doped GLC films dependent on the parameter of Ti target current were systemically investigated by Raman spectra, X-ray photoelectron spectroscopy （XPS）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, atomic force microscopy （AFM）, nanoindentation and ball-on-disk tribometer. With the increase of the Ti target current, the ratio of sp2 bond and the content of Ti as well as the film hardness and compressive internal stress increase, but the high content of the Ti would result in the loose film due to the formation of the squamose structure. Less incorporated Ti reduces the friction of the GLC film in dry-sliding condition, while pure GLC film exhibits the lowest friction coefficient in water-lubricated condition. Ti-GLC film deposited with low Ti target current shows high wear resistance in both dry-sliding and water-lubricated conditions.展开更多
Copper （Cu） doped beryllium （Be） thin films were deposited on silicon substrates by using a simple ion beam sputtering method, which can also realize the varying of Cu doping concentration. Detailed morphological ...Copper （Cu） doped beryllium （Be） thin films were deposited on silicon substrates by using a simple ion beam sputtering method, which can also realize the varying of Cu doping concentration. Detailed morphological and structural characterizations of the samples clearly disclose a microstructure evolution of films upon doping Cu. Doping Cu can effectively suppress film grain growth, causing a small grain size as well as uniform size distribution. Furthermore, doping Cu affects the crystallographic texture of film, which leads to the formation of more compact film structure. In particular, the surface smoothness of the doped films is significantly improved, which makes them promising candidates for various applications.展开更多
The microstructure and properties of TZP ceramics fabricated from spray dried powder differing in granule morphology and deformability are determined.The effects of the feed slurry solids con...The microstructure and properties of TZP ceramics fabricated from spray dried powder differing in granule morphology and deformability are determined.The effects of the feed slurry solids content on the granule character are discussed.The lower solid content results in hard and tough ‘donut’ shaped granules that resist deformation during compaction.The microphotograph shows that relatively large intergranular pores formed by incomplete deformation of granules persist during sintering and are the major strength limiting defects in fired material.Sintered material produced from uniform and deformable granules has a homogeneous microstructure and relatively high mean strength.展开更多
Vanadium carbide/titanium carbide （VC/TiC） superlattice films were synthesized by magnetron sputtering method. The effects of modulation period on the microstructure evolution and mechanical properties were investig...Vanadium carbide/titanium carbide （VC/TiC） superlattice films were synthesized by magnetron sputtering method. The effects of modulation period on the microstructure evolution and mechanical properties were investigated by EDXA, XRD, HRTEM and nano-indentation. The results reveal that the VC/TiC superlattice films form an epitaxial structure when their modulation period is less than a critical value, accompanied with a remarkable increase in hardness. Further increasing the modulation period, the hardness of superlattices decreases slowly to the rule-of-mixture value due to the destruction of epitaxial structures. The XRD results reveal that three-directional strains are generated in superlattices when the epitaxial structure is formed, which may change the modulus of constituent layers. This may explain the remarkable hardness enhancement of VC/TiC superlattices.展开更多
The rare earth influence on the as-cast micro structures and mechanical properties of aluminum alloys attracted great attentions in the last decades.But up to date no reports can be found on the effect of microalloyin...The rare earth influence on the as-cast micro structures and mechanical properties of aluminum alloys attracted great attentions in the last decades.But up to date no reports can be found on the effect of microalloying element La(La addition is below 0.1 wt.%) on the solidification of hypoeutectic Al-Si alloys.This study carried out solidification experiments with Al-6 Si alloys micro-alloyed by element La.The α-Al grain refinement,the eutectic Si modification and the tensile properties improvement caused by microalloying element La were investigated.The effect mechanisms of La were discussed.It is demonstrated that the addition of La as low as 100 ppm can deprave the more effective heterogeneous nucleation conditions for the eutectic Si caused by the impurity P.The addition of 0.06 wt.% La is sufficient to achieve an ideal α-Al grain refinement,eutectic Si modification and ductility improvement of the alloys.LaAlSi phase forms in the Al-Si alloy with the additive amount of La higher than 0.06 wt.%.It has a tetragonal structure.Micro-alloying element La refines the α-Al grains by working as a surfactant and modifies the eutectic Si by promoting the formation of the significant multiple Si twins.展开更多
基金financially suppoted by the National Natural Sci-ence Foundation of China(No.52371041).
文摘Tungsten heavy alloys(WHAs)prepared using laser additive manufacturing(AM)exhibit intricate ge-ometries,albeit with limited mechanical properties.Here we designed a high-strength WHA featuring a FeCrCoNi high entropy alloy(HEA)binder via the laser metal deposition(LMD)technique.Due to the distinctive thermal cycle and rapid cooling rate,the as-deposited alloys exhibit microstructures with hy-poeutectic,eutectic-like,and spot-like characteristics.To elucidate this phenomenon,the solidification paths were delineated and analyzed by combining microstructural characterization and phase equilib-rium simulation.Theμphase precipitated out from the supersaturated solid solution,thereby nucleating massive dislocations on the FeCrCoNi matrix to increase the work hardening rate.Furthermore,theμphase formed an ultrafine intermetallic compound(IMC)layer around the W grain,reducing the hole or crack between the W grain and FeCrCoNi matrix.Attributed to the precipitation strengthening,the solid solution of the FeCrCoNi binder,along with the load-bearing strength of W,the developed alloy achieved ultrahigh compressive stress and strain of 2047 MPa and 32%respectively at room temperature.These findings contribute valuable insights to the advancement of additive manufacturing for tungsten alloys,leveraging their excellent properties.
基金financial support from the Na-tional Natural Science Foundation of China(No.52231006)National Key Research and Development Program of China(No.2017YFB0702003)the National Natural Science Foundation of China(No.51871217).
文摘Refractory high/medium-entropy alloys(RH/MEAs)are known for their outstanding performance at el-evated temperatures;however,they usually exhibit poor room-temperature plasticity,which can be at-tributed to the non-uniform deformation that occurs at room temperature.Once cracks nucleate,they will rapidly propagate into vertical splitting cracks.Here,we introduce multiple phases including FCC and HCP phases into the NbMoTa RMEA via appropriate addition of carbon.The results show that multiple-phase synergy effectively suppresses non-uniform deformation,thereby delaying the onset of vertical splitting cracks.An optimal combination of compressive strength-plasticity is achieved by the(NbMoTa)_(92.5)C_(7.5) alloy.The significant improvement in room-temperature mechanical properties can be attributed to its hierarchical microstructure:in the mesoscale,the BCC matrix is divided by eutectic structures;while at the microscale,the BCC matrix is further refined by abundant lath-like FCC precipitates.The FCC precip-itates contain high-density stacking faults,acting as a dislocation source under compressive loading.The HCP phase in the eutectic microstructures,in turn,acts as a strong barrier to dislocation movement and simultaneously increases the dislocation storage capacity.These findings open a new route to tailor the microstructure and mechanical properties of RH/MEAs.
基金supported by the National Natural Science Foundation of China(61774140).
文摘ZnO thin films with varying Ta concentrations were fabricated through magnetron sputtering.The crystallinity and surface morphology of the ZnO films are significantly influenced by the incorporation of Ta,as evidenced by the X-ray diffraction and scanning electron microscopy results.The lattice constants,as determined by X-ray diffraction,contradict the disparity in Ta and Zn ion radii,which is attributed to the impact of interstitial defects.This inconsistency introduces variations in carrier concentration in this experiment compared with prior studies.Subsequent exploration of the luminescent characteristics and emission mechanism of defect levels in Ta-doped ZnO films was conducted through photoluminescence.Furthermore,the factors influencing the bandgap are discussed.
基金financial support by the National Natural Science Foundation of China(No.52474361)the Independent Research Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(No.SKLASS 2023-Z01)the Science and Technology Commission of Shanghai Municipality(No.19DZ2270200).
文摘The fracture mechanisms of coarse-grained heat-affected zone(CGHAZ)for Mg and Mg–Ca deoxidized high-strength low-alloy(HSLA)steels after high heat input welding(HHIW)were investigated based on the microstructures,crack behaviors and mechanical properties.Compared to Mg–Ca steel,the proportion of intergranular acicular ferrites(IAFs)and polygonal ferrites(PFs)in Mg steel increases from 59.97%to 90.16%.The high-angle grain boundaries(HAGBs)and geometrically necessary dislocations density increase from 55.5%and 4.30×10^(14) m^(-2)to 70.4%and 5.48×10^(14) m^(–2),respectively,while effective grain size decreases from 9.46 to 8.12μm.The area fraction of radial zone in Mg steel decreases from 80.8%to 37.7%and cleavage plane is smaller with more curved and finer tearing ridges.The inclusions distributed at the center of cleavage planes and along river lines can serve as crack initiation sites.The zigzag pattern of primary crack propagation path has width of 476μm and the length of secondary cracks remains below 10μm.These cracks are deflected or arrested by IAFs,PFs and HAGBs,and tend to propagate along{110}plane family.These factors contribute to superior overall mechanical properties of Mg steel,especially increasing low-temperature impact toughness from 23 to 175 J.
基金Project support by the National Key Research and Development Program of China(Grant No.2022YFA1603900)the National Natural Science Foundation of China–Beijing Joint Fund(Grant No.U23A6015)+1 种基金Central University Basic Research Fund of China(Grant No.E1E40207X2)the Funds from University of Chinese Academy of Sciences(Grant Nos.E1EG0210X2 and 118900M018).
文摘YBa_(2)Cu_(3)O_(7-x)(YBCO)films with low microwave surface resistance(RS)are essential for high temperature superconducting microwave devices.The oxygen pressure during deposition has been found to influence RS significantly.In this work,we deposited highly c-axis aligned YBCO films on single crystal MgO(001)substrates under different oxygen pressures via pulsed laser ablation.Their detailed microstructure was characterized with three-dimensional reciprocal space mapping(3D-RSM)method and their microwave surface resistance was also measured with resonant cavity perturbation method.We found that the variation of oxygen pressure can affect film microstructure,including grain orientation distribution and the concentration of crystal defects.The microstructure modulation can explain RS dependence on the oxygen pressure.
基金supported by the National Natural Science Foundation of China(Nos.52261037,52088101)the Key research project of Jiangxi Province(No.20203ABC28W006)the Double-Thousand Plan of Jiangxi Province(No.jxsq2023101057).
文摘The low coercivity is the major factor inhibiting the large-scale commercial utilization of Nd-Ce-Fe-B sintered magnets.In this work,we achieved a record-high coercivity of 15.04 kOe in Ga-doped Nd-Ce-Fe-B sintered magnets with 30 wt%Ce replacing Nd,demonstrating enormous potential.The Ga-doped Nd-Ce-Fe-B magnets with higher boron(HB)and lower boron(LB)content are designed.The coercivity of the HB magnet increases slightly from 10.80 to 12.26 kOe after annealing,attributed to the optimized distribution of grain boundary(GB)phases.In contrast,the coercivity of the LB magnet remarkably increases from 8.13 to 15.04 kOe after annealing.Microstructural observations indicate that the narrow GB phase in the as-sintered magnet is rich in Fe,and the strong exchange coupling of adjacent grains resulted in low coercivity.The evolution of Ga-rich phases reveals a potential formation mechanism of the RE_(6)Fe_(13)Ga phase,that is the RE-Fe amorphous phase and REGa phase in the as-sintered magnet combine to form the RE_(6)Fe_(13)Ga phase and RE-Ga amorphous phase during post-sinter annealing(RE:rare earth).Moreover,the GB phase of the annealed magnet transforms into a Fe-lean phase with a thickness of 16.4 nm.Magnetization and demagnetization behavior characterizations reveal that the exchange decoupling of adjacent grains induced by the optimized GB phases is the main reason for the remarkable coercivity enhancement,which is also validated by micromagnetic simulations.
基金supported by the National Key Research and Development Program of China(No.2023YFC2810700)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2021193)+2 种基金the Liaoning Province Excellent Youth Foundation(No.2024JH3/10200021)the Liaoning Revitalization Talents Program(No.XLYC2403094)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(No.PTYQ2024YZ0009).
文摘It is rather difficult for titanium alloy ultra-thick plates to achieve superior weld formation and excellent mechanical properties along the weld penetration direction due to the large fluctuations of the molten pool,largely limiting their engineering application.In this study,106-mm-thick Ti-6Al-4V ELI alloy plates were successfully butt welded via electron beam welding(EBW).The defect-free EBW joint with full penetration was obtained.The precipitated secondary α(α_(s))in heat affected zone(HAZ),αlamellae in fusion line(FL)and α′martensite in fusion zone(FZ)increased the α_(s)/β,α/β and α′/β interfaces,respectively,resulting in the higher microhardness and impact energy values(57 J in the HAZ,62 J in the FL and 51.9 J in the FZ)than those in the base material(BM).The impact energy of the joint in this study was higher than that for Ti-6Al-4V ELI alloy joints as reported,which was mainly attributed to the formation of the relatively thickerαphase and finer interlamellar spacing in this study,enhancing the resistance to crack propagation.Furthermore,the average fracture toughness(90.2 MPa m^(1/2))of the FZ was higher than that of the BM(74.2 MPa m^(1/2)).This study provides references for the welding application of titanium alloy ultra-thick plates in the manufacture of large-sized components.
文摘Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively investigated.Macroscopic morphology,microstructure,and interfacial structure of the joints were analyzed using scanning electron microscope,energy dispersive spectrometer,and X-ray diffractometer(XRD).The results show that magnetic pulse welding of dissimilar Mg/Fe metals is achieved using an Al interlayer,which acts as a bridge for deformation and diffusion.Specifically,the AZ31B/AA1060 interface exhibits a typical wavy morphology,and a transition zone exists at the joint interface,which may result in an extremely complex microstructure.The microstructure of this transition zone differs from that of AZ31B magnesium and 1060 Al alloys,and it is identified as brittle intermetallic compounds(IMCs)Al_(3)Mg_(2) and Al_(12)Mg_(17).The transition zone is mainly distributed on the Al side,with the maximum thickness of Al-side transition layer reaching approximately 13.53μm.Incomplete melting layers with varying thicknesses are observed at the primary weld interface,while micron-sized hole defects appear in the transition zone of the secondary weld interface.The AA1060/DC56D interface is mainly straight,with only a small number of discontinuous transition zones distributed intermittently along the interface.These transition zones are characterized by the presence of the brittle IMC FeAl_(3),with a maximum thickness of about 4μm.
基金financially supported by the National Science Fund for Distinguished Young Scholars,China(No.52025041)the National Natural Science Foundation of China(Nos.52450003,U2341267,and 52174294)+1 种基金the National Postdoctoral Program for Innovative Talents,China(No.BX20240437)the Fundamental Research Funds for the Central Universities,China(Nos.FRF-IDRY-23-037 and FRF-TP-20-02C2)。
文摘The rapid advancements in computer vision(CV)technology have transformed the traditional approaches to material microstructure analysis.This review outlines the history of CV and explores the applications of deep-learning(DL)-driven CV in four key areas of materials science:microstructure-based performance prediction,microstructure information generation,microstructure defect detection,and crystal structure-based property prediction.The CV has significantly reduced the cost of traditional experimental methods used in material performance prediction.Moreover,recent progress made in generating microstructure images and detecting microstructural defects using CV has led to increased efficiency and reliability in material performance assessments.The DL-driven CV models can accelerate the design of new materials with optimized performance by integrating predictions based on both crystal and microstructural data,thereby allowing for the discovery and innovation of next-generation materials.Finally,the review provides insights into the rapid interdisciplinary developments in the field of materials science and future prospects.
基金the support from the National Natural Science Foundation of China (Nos. U20A20274, 52061003)the Natural Science Foundation of Yunnan Province, China (No. 202301AT070209)the Science and Technology Major Project of Yunnan Province, China (No. 202102AG050017)。
文摘The age-hardening response,mechanical,and corrosion-resistant properties of AA7085 alloys with and without the addition of 0.3 wt.%scandium(Sc)were compared.Using advanced techniques such as aberration-corrected transmission electron microscopy and first-principles calculations,the underlying micromechanisms of Sc microalloying were revealed.Results show that the increase in strength of the AA7085-Sc alloy is mainly attributed to the decreased Al grain size and increased number density of both Al_(3)Sc@Al_(3)(Sc,Zr)core−shell nanoparticles and Sc-containingη_(p) and GP−η_(p) nanoprecipitates.Strong strain fields and evident electron transfer from Zr to the neighboring matrix Al atoms exist at the Al_(3)Sc@Al_(3)(Sc,Zr)/Al interface.The Sc doping in GP−η_(p) andη_(p) suppresses the GP−η_(p)→η_(p) transformation.Modified corrosion resistance of the AA7085-Sc alloy compared with AA7085 alloy is associated with the fine grain boundary precipitates ofη_(p)hases and narrow precipitation free zone.The reasons of property changes of AA7085 alloy after Sc microalloying are explored based on the multiscale microstructural characterization.
基金supported by Guangdong Major Project of Basic and Applied Basic Research, China (No. 2020B0301030006)Fundamental Research Funds for the Central Universities, China (No. SWU-XDJH202313)+1 种基金Chongqing Postdoctoral Science Foundation Funded Project, China (No. 2112012728014435)the Chongqing Postgraduate Research and Innovation Project, China (No. CYS23197)。
文摘A new method was proposed for preparing AZ31/1060 composite plates with a corrugated interface,which involved cold-pressing a corrugated surface on the Al plate and then hot-pressing the assembled Mg/Al plate.The results show that cold-pressing produces intense plastic deformation near the corrugated surface of the Al plate,which promotes dynamic recrystallization of the Al substrate near the interface during the subsequent hot-pressing.In addition,the initial corrugation on the surface of the Al plate also changes the local stress state near the interface during hot pressing,which has a large effect on the texture components of the substrates near the corrugated interface.The construction of the corrugated interface can greatly enhance the shear strength by 2−4 times due to the increased contact area and the strong“mechanical gearing”effect.Moreover,the mechanical properties are largely depended on the orientation relationship between corrugated direction and loading direction.
基金financially supported by the National Key Research and Development Program of China(No.2021YFB3701000)the National Natural Science Foundation of China(Nos.52471118,52101125,U2037601,and U21A2048)Young Elite Scientists Sponsorship Program by CAST,China(No.2022QNRC001)。
文摘The dependence of shrinkage porosities on microstructure characteristics of Mg−12Al alloy was investigated.The distribution,morphology,size,and number density of shrinkage porosities were analyzed under different cooling rates.The relationship between shrinkage porosities and microstructure characteristics was discussed in terms of temperature conditions,feeding channel characteristics,and feeding capacity.Further,the feeding behavior of the residual liquid phase in the solid skeleton was quantified by introducing permeability.Results show a strong correlation between the solid microstructure skeleton and shrinkage porosity characteristics.An increase in permeability corresponds to a declining number density of shrinkage porosities.This study aims to provide a more complete understanding how to reduce shrinkage porosities by controlling microstructure characteristics.
文摘This study investigated enhancing the wear resistance of Ti6Al4V alloys for medical applications by incorporating Ti C nanoreinforcements using advanced spark plasma sintering(SPS). The addition of up to 2.5wt% Ti C significantly improved the mechanical properties, including a notable 18.2% increase in hardness(HV 332). Fretting wear tests against 316L stainless steel(SS316L) balls demonstrated a 20wt%–22wt% reduction in wear volume in the Ti6Al4V/Ti C composites compared with the monolithic alloy. Microstructural analysis revealed that Ti C reinforcement controlled the grain orientation and reduced the β-phase content, which contributed to enhanced mechanical properties. The monolithic alloy exhibited a Widmanstätten lamellar microstructure, while increasing the Ti C content modified the wear mechanisms from ploughing and adhesion(0–0.5wt%) to pitting and abrasion(1wt%–2.5wt%). At higher reinforcement levels, the formation of a robust oxide layer through tribo-oxide treatment effectively reduced the wear volume by minimizing the abrasive effects and plastic deformation. This study highlights the potential of SPS-mediated Ti C reinforcement as a transformative approach for improving the performance of Ti6Al4V alloys, paving the way for advanced medical applications.
基金supported by the National Natural Science Foundation of China (Nos. 52075449, 51975480)。
文摘The dissimilar 2B06 and 7B04 Al alloy joints were prepared by refill friction stir spot welding(RFSSW),and the microstructural evolution and corrosion behavior of the joints were investigated.Based on microstructural analysis,the welded joints exhibit distinct microstructural zones,including the stir zone(SZ),thermomechanically affected zone(TMAZ),and heat-affected zone(HAZ).The grain size of each zone is in the order of HAZ>TMAZ>SZ.Notably,the TMAZ and HAZ contain significantly larger secondary-phase particles compared to the SZ,with particle size in the HAZ increasing at higher rotational speeds.Electrochemical tests indicate that corrosion susceptibility follows the sequence of HAZ>TMAZ>SZ>BM,with greater sensitivity observed at increased rotational speeds.Post-corrosion mechanical performance degradation primarily arises from crevice corrosion at joint overlaps,but not from the changes in the microstructure.
文摘Pure metal Fe films with thickness of about 100nm were deposited on Si （100） substrates by DC magnetron sputtering. Annealing was subsequently performed in a vacuum furnace in the temperature range of 600-1000℃ for 2h. The samples were characterized by means of Rutherford backscattering （RBS） with 3MeV carbon ions. The RBS data were fitted with SIMNRA 6.0, and the results show the atomic interdiffusion in Fe/Si systems. The microstructures and crystal structures were characterized by scanning electron microscope and X-ray diffrac- tion. The effects of annealing on atomic interdiffusion, silicide formation, and microstructures in Fe/Si systems were analyzed.
基金Project (50905178) supported by the National Natural Science Foundation of ChinaProject (2011CB706603) supported by the National Basic Research Program of China
文摘Ti-doped graphite-like carbon （Ti-GLC） films were synthesized successfully by magnetron sputtering technique. The compositions, microstructures and properties of the Ti-doped GLC films dependent on the parameter of Ti target current were systemically investigated by Raman spectra, X-ray photoelectron spectroscopy （XPS）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, atomic force microscopy （AFM）, nanoindentation and ball-on-disk tribometer. With the increase of the Ti target current, the ratio of sp2 bond and the content of Ti as well as the film hardness and compressive internal stress increase, but the high content of the Ti would result in the loose film due to the formation of the squamose structure. Less incorporated Ti reduces the friction of the GLC film in dry-sliding condition, while pure GLC film exhibits the lowest friction coefficient in water-lubricated condition. Ti-GLC film deposited with low Ti target current shows high wear resistance in both dry-sliding and water-lubricated conditions.
基金Project (60908023) supported by the National Natural Science Foundation of China
文摘Copper （Cu） doped beryllium （Be） thin films were deposited on silicon substrates by using a simple ion beam sputtering method, which can also realize the varying of Cu doping concentration. Detailed morphological and structural characterizations of the samples clearly disclose a microstructure evolution of films upon doping Cu. Doping Cu can effectively suppress film grain growth, causing a small grain size as well as uniform size distribution. Furthermore, doping Cu affects the crystallographic texture of film, which leads to the formation of more compact film structure. In particular, the surface smoothness of the doped films is significantly improved, which makes them promising candidates for various applications.
文摘The microstructure and properties of TZP ceramics fabricated from spray dried powder differing in granule morphology and deformability are determined.The effects of the feed slurry solids content on the granule character are discussed.The lower solid content results in hard and tough ‘donut’ shaped granules that resist deformation during compaction.The microphotograph shows that relatively large intergranular pores formed by incomplete deformation of granules persist during sintering and are the major strength limiting defects in fired material.Sintered material produced from uniform and deformable granules has a homogeneous microstructure and relatively high mean strength.
基金Project(51201187)supported by the National Natural Science Foundation of China
文摘Vanadium carbide/titanium carbide （VC/TiC） superlattice films were synthesized by magnetron sputtering method. The effects of modulation period on the microstructure evolution and mechanical properties were investigated by EDXA, XRD, HRTEM and nano-indentation. The results reveal that the VC/TiC superlattice films form an epitaxial structure when their modulation period is less than a critical value, accompanied with a remarkable increase in hardness. Further increasing the modulation period, the hardness of superlattices decreases slowly to the rule-of-mixture value due to the destruction of epitaxial structures. The XRD results reveal that three-directional strains are generated in superlattices when the epitaxial structure is formed, which may change the modulus of constituent layers. This may explain the remarkable hardness enhancement of VC/TiC superlattices.
基金supported by the National Natural Science Foundation of China [grant numbers 51771210,51901231]the Science and technology project of the headquarters of SGCC [grant number5500-201924129A-0-0-00]+1 种基金Chinese Academy of Sciences Strategic Priority Program on Space Science [grant number XDA15013800]China’s Manned Space Station Project [grant number TGJZ800-2-RW024]。
文摘The rare earth influence on the as-cast micro structures and mechanical properties of aluminum alloys attracted great attentions in the last decades.But up to date no reports can be found on the effect of microalloying element La(La addition is below 0.1 wt.%) on the solidification of hypoeutectic Al-Si alloys.This study carried out solidification experiments with Al-6 Si alloys micro-alloyed by element La.The α-Al grain refinement,the eutectic Si modification and the tensile properties improvement caused by microalloying element La were investigated.The effect mechanisms of La were discussed.It is demonstrated that the addition of La as low as 100 ppm can deprave the more effective heterogeneous nucleation conditions for the eutectic Si caused by the impurity P.The addition of 0.06 wt.% La is sufficient to achieve an ideal α-Al grain refinement,eutectic Si modification and ductility improvement of the alloys.LaAlSi phase forms in the Al-Si alloy with the additive amount of La higher than 0.06 wt.%.It has a tetragonal structure.Micro-alloying element La refines the α-Al grains by working as a surfactant and modifies the eutectic Si by promoting the formation of the significant multiple Si twins.
