查看更多>>摘要：Shock compression and spallation damage of a face-center cubic phase high-entropy alloy(HEA)Al0.1CoCrFeNi were investigated via plate impact experiments along with free surface velocity mea-surements.Postmortem samples were characterized with transmission electron microscopy and electron backscatter diffraction.The Hugoniot equation of state and spall strength at different impact strengths were determined.There exists a power-law relation between spall strength and strain rate.The spall strength of Al0.1CoCrFeNi HEA is about 50％higher than those of previously studied HEAs and compa-rable to those widely applied structural stainless steels at the same shock stress.Dislocation glide and stacking faults are the important deformation mechanisms in the Al0.1CoCrFeNi HEA.Nanotwins are only observed at high shock stress.Damage in the Al0.1CoCrFeNi HEA is ductile in nature.Voids are nucleated preferentially in grain interiors,and the intragranular voids show a strong dependence on grain boundary misorientation and peak stress.
查看更多>>摘要：Desired microstructure and surface integrity are critical to achieving the high performance of addi-tively manufactured components.In the present work,the hybrid post-processes of magnetic abra-sive finishing(MAF)and post-heat treatment(HT)were applied to the additively manufactured Inconel 718 superalloys.Their hybrid effects and influencing mechanism on the surface quality and mechan-ical properties of the additively manufactured samples have been studied comparatively.The results show that the MAF process effectively reduces the surface roughness by more than an order of mag-nitude due to the flexibility and geometric consistency of the magnetic particles and abrasives with the finished surfaces.The proper sequence of MAF and HT obtains enhanced mechanical properties for the homogenized-MAF-aged sample with the yield strength of 1147 MPa,the ultimate tensile strength of 1334 MPa,and the elongation of 22.9％,which exceeds the standard wrought material.The sur-face integrity,compressive residual stress field,and grain refinement induced by the MAF and subse-quent aging heat treatment increase the cracking resistance and delay the fracture failure,which sig-nificantly benefits the mechanical properties.The MAF process combined with proper post-heat treat-ment provides an effective pathway to improve the mechanical properties of additively manufactured materials.
查看更多>>摘要：A superiority in interfacial bonding is favorable to fabricate high-strength conductive composites for elec-trical contact applications.In the present work,high strength and high conductivity multi-scale metallic glass composites(including micron-scale CuZrAl metallic glass reinforcement,hundred-nanometer-scale CuCrZr crystalline grain matrix,and nano-scale precipitated phase)were fabricated by a one-step spark plasma sintering(SPS).The strength and conductivity of the bulk copper matrix metallic glass compos-ites(BCMGCs)were enhanced simultaneously with the increase in the sintering pressure of the SPS.The excellent performance is attributed to the improved interfacial bonding between the metallic glass re-inforcement and the copper alloy matrix due to the high pressure assisted by temperature and pulsed current.In particular,the precipitation of nanoprecipitates at the interface further reduces the interfacial resistance and improves the mechanical properties of the composites.This work broadens the horizon for the selection and optimization of reinforcements and manufacturing processes for high-performance electrical contact materials(ECMs).
查看更多>>摘要：The martensite start temperature is a critical parameter for steels with metastable austenite.Although numerous models have been developed to predict the martensite start(Ms)temperature,the complexity of the martensitic transformation greatly limits their performance and extensibility.In this work,we ap-ply deep data mining of thermodynamic calculations and deep learning to develop a generic model for Ms prediction.Deep data mining was used to establish a hierarchical database with three levels of in-formation.Then,a convolutional neural network model,which can accurately treat the hierarchical data structure,was used to obtain the final model.By integrating thermodynamic calculations,traditional ma-chine learning and deep learning modeling,the final predictor model shows excellent generalizability and extensibility,i.e.model performance both within and beyond the composition range of the original database.The effects of 15 alloying elements were considered successfully using the proposed method-ology.The work suggests that,with the help of deep data mining considering the physical mechanisms,deep learning methods can partially mitigate the challenge with limited data in materials science and provide a means for solving complex problems with small databases.
查看更多>>摘要：Low alloying Mg-2Gd-0.5(Cu/Ni)alloys for sealing tools in the oil and gas industry were prepared.The differences in the effects of minor Cu and Ni additions on microstructures and properties of the Mg-2Gd alloy were compared.The results showed that adding Ni was more effective than adding Cu in re-fining grain sizes,strengthening the basal fiber texture,and promoting the formation of LPSO phases,resulting in higher strength.The tensile yield strength/elongation of the Mg-2Gd-0.5Cu alloy,Mg-2Gd-0.25Cu-0.25Ni alloy,and Mg-2Gd-0.5Ni alloy was 146 MPa/23.7％,175 MPa/23.1％,and 248 MPa/18.2％,re-spectively.The decreased elongation was attributed to the basal fiber texture and the presence of coarse LPSO phases.In terms of the corrosion rate in 3.5 wt.％NaCl solution,it rose from 112 mm y-1 for the Mg-2Gd-0.5Cu alloy to 269 mm y-1 for the Mg-2Gd-0.25Cu-0.25Ni alloy and 490 mm y1 for the Mg-2Gd-0.5Ni alloy,indicating that the addition of Ni instead of Cu showed a more significant promoting effect on the degradability of Mg alloys,which was related to more refined grains,the stronger basal fiber texture,and a larger amount of LPSO phases.
查看更多>>摘要：In this work,we put forward a scheme to exquisitely design and selectively synthesize the core@shell structured MSe2/FeSe2@MoSe2(M = Co,Ni)flower-like multicomponent nanocomposites(MCNCs)through a simple two-step hydrothermal reaction on the surfaces of MFe204 nanospheres with the cer-tain amounts of Mo and Se sources.With increasing the amounts of Mo and Se sources,the obtained core@shelll structured MSe2/FeSe2@MoSe2(M = Co,Ni)MCNCs with the enhanced content of MoSe2 and improved flower-like geometry morphology could be produced on a large scale.The obtained results re-vealed that the as-prepared samples displayed improved comprehensive microwave absorption properties(CMAPs)with the increased amounts of Mo and Se sources.The as-prepared CoSe2/FeSe2@MoSe2 and NiSe2/FeSe2@MoSe2 MCNCs with the well-defined flower-like morphology could simultaneously present the outstanding CMAPs in terms of strong absorption capability,wide absorption bandwidth,and thin matching thicknesses,which mainly originated from the conduction loss and flower-like geometry mor-phology.Therefore,the findings not only develop the very desirable candidates for high-performance microwave absorption materials but also pave a new way for optimizing the CMAPs through tailoring morphology engineering.
Qingfeng WuZhijun WangFeng HeZhongsheng Yang Junjie Li...
71-81页
查看更多>>摘要：In traditional physical metallurgy,once recrystallization occurs,it will proceed to 100％along with time even at relatively low temperatures,resulting in the limited thermal stability of partially recrystallized al-loys.Here,we proposed the strategy of achieving the endless recrystallization state at high temperature(～0.6Tm)in high entropy alloys for the first time.The partially recrystallized microstructures remained stable after annealing at 700℃ for 1440 h toward endless recrystallization with kinetics analysis.Ben-efiting from the ultra-thermostable heterostructures,the alloy exhibited excellent mechanical properties of～1.6 GPa tensile strength at room temperature and～1.1 GPa tensile strength at 600℃ even after exposure at 700℃ for 720 h.The kinetics of recovery,recrystallization,grain growth,and precipitate coarsening were quantitatively analyzed to uncover the mechanisms of endless recrystallization.The re-sults revealed that the stable state of 50％recrystallization at 700℃ can be attributed to the precipitates inhibited recrystallization and the continued recovery decreased stored energy in the non-recrystallized regions.Furthermore,the grain size was stable in the recrystallized regions due to the strong pinning ef-fect of the intergranular precipitates with slow coarsening rates.These findings created a brand-new state of endless recrystallization with the combination of recovery and recrystallization,which can significantly broaden the service temperature range of heterogeneous materials.
查看更多>>摘要：Although many material designs or strategic methods have been proposed for treating oil spills and oily wastewater,the complex oily state,dealing with the harsh operating conditions of oil-water separation(such as the recovery of viscous spilled crude oil,bacteria-containing oily wastewa-ter,and removal of spilled oil under fire),and the autorecycling of oil and absorption materials re-main a great challenge.This work proposed an ingenious design strategy of"several birds with one stone"to prepare pH/thermoresponsive flame-retardant/photothermal bactericidal P-Fe304-polydopamine(PDA)@melamine-formaldehyde(MF)foams.This design makes the foams remarkably effective in the re-covery of spilled viscous crude oil as well as in the separation of bacteria-containing oily emulsions,par-ticularly for instant fire extinguishing by magnetically controlled oil absorption as well as for fire alarms.The photothermal effect and pH response induce a change in the surface wettability of the foams,facil-itating excellent autoadsorption/desorption of the spilled oil.The photothermal bactericidal activity and fouling resistance of the foam are beneficial to the separation of bacteria-containing oily wastewater.Outstanding flame-retardant properties and maneuverable magnetic control enable the foam to rapidly recover the spilled oil in a large range of fires,extinguish fires instantly,and facilitate early fire warn-ing.The proposed strategy is expected to inspire further research on treating oil spills under complex conditions.
查看更多>>摘要：A universal numerical model based on the particle size distribution(PSD)approach has been developed for the simulation of precipitation kinetics in multicomponent alloys during isothermal ageing.Nucleation was implemented utilizing the classical nucleation theory(CNT).Growth and coarsening were modeled by a single growth kinetics equation,which is constructed based on the interfacial diffusion flux balance and the capillarity effect.Only partial off-diagonal terms in the diffusion matrix(diffusion of individual components in the matrix)were taken into account in the calculations to minimize the computational cost while coupling with CALPHAD to extract thermodynamics equilibrium around the interface.A new feature of the model is the incorporation of a more realistic spatial site distribution via a Voronoi con-struction in the characteristic cell,for the purpose of modifying the diffusion distance.Computational predictions of the precipitate dimensions and the precipitation kinetics were compared with the atom probe tomography(APT)measurements on ternary Ni-AI-Cr alloys isothermally aged at 873 K.It is found that the temporal evolution of the dimensions and composition of the precipitates is well captured,as is the dependence on changes in the alloy composition.The new modification with Voronoi construction demonstrates that the overall precipitation kinetics depends on the density and the spatial site distribu-tion of precipitates.The ability to handle sophisticated alloy chemistries by quantitative equations,the compositional sensitivity of microstructural characteristics emerging from the simulation results,and the ability to visualize the spatial distribution of precipitates make the work very promising for multicompo-nent alloy design and optimization.
查看更多>>摘要：The assemblages of unicellular microalgae and bacteria in phytoplankton communities can generally re-sult in biodeterioration of metals in marine environment.In this study,the self-promoted biofouling mechanism underneath red-tide alga Phaeodactylum tricornutum and its symbiotic bacterium Bacillus alti-tudinis was systematically revealed.The mutualistic interaction of the bacteria and algae quadrupled the corrosion rate in comparison to the individual effect of the bacterium or algal strain alone.Reversely,the corroded metal appeared to be an accelerator that can stimulate the activity of the P.tricornutum and aggravate the biological pollution based on the result of 62.3％up-regulation of the key photosynthesis genes.The corrosion-biofouling-accelerated corrosion-deteriorated biofouling formed a vicious cycle.
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