Developing megahertz(MHz)electromagnetic wave(EMW)absorption materials with broadband absorption,multi-temperature adaptability,and facile preparation method remains a challenge.Herein,nanocrystalline FeCoNiCr_(0.4)Cu...Developing megahertz(MHz)electromagnetic wave(EMW)absorption materials with broadband absorption,multi-temperature adaptability,and facile preparation method remains a challenge.Herein,nanocrystalline FeCoNiCr_(0.4)Cu_(0.2) high-entropy alloy powders(HEAs)with both large aspect ratios and thin intergranular amorphous layers are constructed by a multistage mechanical alloying strategy,aiming to achieve excellent and temperature-stable permeability and EMW absorption.A single-phase face-centered cubic structure with good ductility and high crystallinity is obtained as wet milling precursors,via precisely controlling dry milling time.Then,HEAs are flattened to improve aspect ratios by synergistically regulating wet milling time.FeCoNiCr_(0.4)Cu_(0.2) HEAs with dry milling 20 h and wet milling 5 h(D20)exhibit higher and more stable permeability because of larger aspect ratios and thinner intergranular amorphous layers.The maximum reflection loss(RL)of D20/SiO_(2) composites is greater than-7 dB with 5 mm thickness,and EMW absorption bandwidth(RL<-7 dB)can maintain between 523 and 600 MHz from-50 to 150℃.Furthermore,relying on the“cocktail effect”of HEAs,D20 sample also exhibits excellent corrosion resistance and high Curie temperature.This work provides a facile and tunable strategy to design MHz electromagnetic absorbers with temperature stability,broadband,and resistance to harsh environments.展开更多
The microstructure and tensile properties of the as-cast and as-rolled Mg-4.5Sn-5Zn alloys by adding various Sc content were investigated.Improvement of the tensile properties in as-cast Sc-containing alloys is attrib...The microstructure and tensile properties of the as-cast and as-rolled Mg-4.5Sn-5Zn alloys by adding various Sc content were investigated.Improvement of the tensile properties in as-cast Sc-containing alloys is attributed to the grain refinement and modification of secondary phase morphology.Three types of precipitates,namely spherical Mg2Sn,rod-like MgZn and Sc-rich phases were dispersed in the matrix of the Sc added M g-4.5Sn-5Zn alloys after hot rolling deformation.In addition,weakening and deflecting of the basal texture in as-rolled alloys were found and were attributed to Sc addition.Further increasing the Sc addition rate to 0.4 wt.%,however,resulted in the clustering of the Sc-rich phases and was found to reduce the tensile properties of the alloy,especially the elongation.The as-rolled Mg-4.5Sn-5Zn-0.3Sc alloy exhibits an optimum combination of tensile properties.The ultimate tensile strength,yield strength and elongation are 293.0MPa,164.2Mpa and 21.5%,respectively,and the elongation is about 68%higher than that of Sc-free alloy.展开更多
High-temperature electromagnetic(EM) protection materials integrated of multiple EM protection mechanisms and functions are regarded as desirable candidates for solving EM interference over a wide temperature range.In...High-temperature electromagnetic(EM) protection materials integrated of multiple EM protection mechanisms and functions are regarded as desirable candidates for solving EM interference over a wide temperature range.In this work,a novel microwave modulator is fabricated by introducing carbonyl iron particles(CIP)/resin into channels of carbonized wood(C-wood).Innovatively,the spaced arrangement of two microwave absorbents not only achieves a synergistic enhancement of magnetic and dielectric losses,but also breaks the translational invariance of EM characteristics in the horizontal direction to obtain multiple phase discontinuities in the frequency range of 8.2-18.0 GHz achieving modulation of reflected wave radiation direction.Accordingly,CIP/C-wood microwave modulator demonstrates the maximum effective bandwidth of 5.2 GHz and the maximum EM protection efficiency over 97% with a thickness of only 1.5 mm in the temperature range 298-673 K.Besides,CIP/C-wood microwave modulator shows stable and low thermal conductivities,as well as monotonic electrical conductivity-temperature characteristics,therefore it can also achieve thermal infrared stealth and working temperature monitoring in wide temperature ranges.This work provides an inspiration for the design of high-temperature EM protection materials with multiple EM protection mechanisms and functions.展开更多
The effect of rolling and forging on the microstructure and corrosion behavior of LZ91 alloy was investigated using an electron probe micro-analyzer,immersion and electrochemical tests.Results showed that the area fra...The effect of rolling and forging on the microstructure and corrosion behavior of LZ91 alloy was investigated using an electron probe micro-analyzer,immersion and electrochemical tests.Results showed that the area fraction of theβ-Li phase remained unchanged,and the grain size of theβ-Li phase decreased after forging.The as-rolled forged alloy(FR-LZ91)exhibited the highest area fraction of theβ-Li phase and the longest grains.The corrosion resistance of the forged LZ91 alloy increased due to grain refinement that prevented further corrosion during the immersion test.Among the experimental alloys,FR-LZ91 showed the highest resistance of corrosion film and charge transfer resistance values due to its protective film caused by the high area fraction of theβ-Li phase.展开更多
Objective:Circulating cell-free Epstein-Barr virus(EBV)DNA has been shown to be a valuable biomarker for population screening and prognostic surveillance for nasopharyngeal carcinoma(NPC).Despite important insights in...Objective:Circulating cell-free Epstein-Barr virus(EBV)DNA has been shown to be a valuable biomarker for population screening and prognostic surveillance for nasopharyngeal carcinoma(NPC).Despite important insights into the biology of persistence,few studies have addressed the clinical significance of cell-based EBV-DNA loads in peripheral blood cells(PBCs).Methods:A prospective observational cohort study was conducted involving 1,063 newly diagnosed,locoregionally-advanced NPC patients at Sun Yat-sen University Cancer Center from 2005 to 2007.Cox regression analysis was conducted to identify the association of PBC EBV DNA loads to overall survival(OS)and other prognostic outcomes.Prognostic nomograms were developed based on PBC EBV DNA loads to predict survival outcomes for NPC patients.Results:After a median follow-up of 108 months,patients with higher PBC EBV-DNA loads had significantly worse OS[hazard ratio(HR)of medium,medium-high,and high vs.low were 1.50,1.52,and 1.85 respectively;Ptrend<0.001].Similar results were found for progression-free survival and distant metastasis-free survival.The concordance index of the prognostic nomogram for predicting OS in the training set and validation set were 0.70 and 0.66,respectively.Our data showed that the PBC EBV DNA load was an independent and robust survival biomarker,which remained significant even after adjusting for plasma EBV DNA loads in a subset of 205 patients of the cohort(HR:1.88;P=0.025).Importantly,a combination of PBC EBV DNA load and plasma EBV DNA load improved the predicted OS.Conclusions:The EBV-DNA load in PBCs may be an independent prognosis marker for NPC patients.展开更多
Bioinspired by Nepenthes, lubricant infused surfaces(LIS) have attracted widespread attention in the field of anticorrosion. However,the lubricant coating has some disadvantages such as complex construction processing...Bioinspired by Nepenthes, lubricant infused surfaces(LIS) have attracted widespread attention in the field of anticorrosion. However,the lubricant coating has some disadvantages such as complex construction processing and easy loss of oil phase in air or dynamic water phase. In this study, oleogel is infused into a lotus leaf inspired super-hydrophobic matrix to form an oleogel infused surface(OIS) for enhancing corrosion resistance of active Mg-Li alloy. For reserving oleogel, firstly, a facile one-step electrodeposition method is used to construct super-hydrophobic surface(SHS) composed by samarium/myristic acid complex micro-nano flower structure onto Mg-Li alloy.The coating exhibits excellent superhydrophobic property at a static contact angle of 160° by applying 30 V electrolysis for 30 min. The protection efficiency of single SHS highly relates with the metal itself. For short period immersion in water phase, SHS can afford protection to Mg-Li alloy. However, the long-term immersion will see the rapid failure of SHS, and the high activity of Mg-Li alloy is one main reason.We assume that SHS cannot be a good choice for protecting Mg-Li alloy. Then, a Nepenthes inspired liquid coating is formed by infusing oleogel into the micro-nano structure by a spin-coating method. The liquid coating performs prominent corrosion resistance with Rctreaching as high as 1.51 × 10^(10)Ω cm^(2). After the mechanical damage from the external environment, the liquid coating can realize self-repair through thermal assistance, and the liquid coating can still restore Rctup to 1.24 × 10^(10)Ω cm^(2) after healing. The corrosion resistance of the liquid coating remains strong by showing Rctas high as 1.14 × 10^(9)Ω cm^(2), even after immersion in representative corrosive 3.5 wt% Na Cl solution for 30 d.展开更多
In this study,the real 3D model of the feather shaft that is composed of medulla and cortex is characterized by X-ray computer tomography,and the structural features are quantitatively analyzed.Compression and tensile...In this study,the real 3D model of the feather shaft that is composed of medulla and cortex is characterized by X-ray computer tomography,and the structural features are quantitatively analyzed.Compression and tensile tests are conducted to evaluate the mechanical performance of the feather shaft and cortex at different regions.The analysis of the 3D model shows that the medulla accounts for∼70%of the shaft volume and exhibits a closed-cell foam-like structure,with a porosity of 59%.The cells in the medulla show dodecahedron and decahedron morphology and have an equivalent diameter of∼30μm.In axial compression,the presence of medulla enhances the shaft stability.Especially,the combined effect of the medulla and cortex increases the buckling strength of the middle and distal shaft by 77%and 141%,respectively,compared to the calculated value of the shaft using linear mixed rule.The tensile properties of the cortex along the shaft axis are anisotropic because of the different fiber structures.As the fiber orientation gradually becomes uniform in the axial direction,the Young’s modulus and tensile strength of the cortex on the dorsal gradually increase from calamus to the distal shaft,and the fracture mode changes from tortuous fracture to V-shaped fracture.The cortex on the lateral shows the opposite trend,that is the distal shaft becomes weaker due to fiber tangles.展开更多
Obtaining an appropriate grain size is crucial for Al alloys or Al matrix composites prior to processing,as it significantly influences the mechanical properties of components and workability during the manufacturing ...Obtaining an appropriate grain size is crucial for Al alloys or Al matrix composites prior to processing,as it significantly influences the mechanical properties of components and workability during the manufacturing process.TiB_(2)particles are exceptional grain refiners in Al and serve as excellent reinforcement particles for particulate-reinforced aluminum matrix composites.However,the optimal particle content for achieving excellent refinement and strengthening effects depends on the matrix composition and requires further investigation.Additionally,homogenization is essential for mitigating the element segregation in the ingot.Although it is anticipated that adding suitable particles can effectively inhibit undesired grain growth during homogenization,comprehensive investigations on this aspect are currently lacking.Therefore,TiB_(2)/2219Al matrix composites with varying reinforcement contents(0,1,3,5 wt%)were fabricated through traditional casting followed by homogenization treatment to address these research gaps.The effects of reinforcement content and homogenization treatment on the microstructure and mechanical properties of in-situ TiB_(2)/2219Al composites were investigated.The results demonstrate a gradual strengthening of the refining effect with increasing particle concentration.Moreover,composites containing 3 wt%TiB_(2)particles exhibit superior comprehensive mechanical properties in both as-cast and homogenized state.Additionally,potential orientation relationships are observed and calculated between undissolved Al_(2)Cu eutectic phase and submicron or nanometer-sized TiB_(2)particles,resulting in a mixture structure with enhanced bonding strength.This mixture structure is continuously distributed along grain boundaries during solidification,forming a three-dimensional cellular network that acts as primary retarding forces for grain growth during homogenization.Furthermore,the established homogenization kinetic equations were further utilized to analyze the correlation between homogenization time and grain size,as well as the influence of homogenization temperature.展开更多
The semi-solid stir casting method is adopted to prepare 10 wt%SiC_(p)/Mg-6Zn-0.5Ca-xAl(x=0,1,3 and 5 wt%)composites,and the microstructure evolution and mechanical property of composites with various Al content are i...The semi-solid stir casting method is adopted to prepare 10 wt%SiC_(p)/Mg-6Zn-0.5Ca-xAl(x=0,1,3 and 5 wt%)composites,and the microstructure evolution and mechanical property of composites with various Al content are investigated.The results show that the addition of 3 wt%Al improves the distribution of SiC_(p),whereas the SiC_(p) cluster occurs again with Al content greater than 3%.An abnormal phenomenon of twinning is observed in the cast composites in this work.The SiC_(p)/Mg-6Zn-0.5Ca composite possesses the highest twin content of~23%,for which tension twins(TTW)and compression twins(CTW)account for~19%and~3%,respectively.The CTW is only observed in ZXA600 composite.The addition of Al has an inhibiting effect for the generation and growth of twins.The content of twin decreases firstly and then increases with increase of Al content.The lowest twin content is obtained as Al increases to 3 wt%.It is found the existence of twin is detrimental to the mechanical property of composites.As-cast SiC_(p)/Mg-6Zn-0.5Ca-3Al composite with the lowest twin content exhibits the optimal mechanical property of yield strength,ultimate tensile strength and elongation for 100 MPa,188 MPa and 4.4%,respectively.The outstanding mechanical property is attributed to the uniform distribution of SiC_(p),the low twin content and the well-distributed fine second phases.展开更多
The high lattice thermal conductivity of half-Heuslers(HHs)restricts the further enhancement of their thermoelectric figure-of-merit(ZT).In this study,multiscale scattering centers,such as point defects,dislocations,a...The high lattice thermal conductivity of half-Heuslers(HHs)restricts the further enhancement of their thermoelectric figure-of-merit(ZT).In this study,multiscale scattering centers,such as point defects,dislocations,and nanoprecipitates,are synchronously introduced in a n-type ZrNiSn-based HH matrix through Nb doping and Hf substitution.The lattice thermal conductivity is substantially decreased from 4.55(for the pristine ZrNiSn)to 1.8 W·m^(−1)·K^(−1) at 1123 K via phonon scattering over a broad wavelength range through the adjustment of multiscale defects.This value is close to the theoretically estimated lowest thermal conductivity.The power factor(PF)is enhanced from 3.25(for the pristine ZrNiSn)to 5.01 mW·m^(−1)·K^(−2) for Zr_(0.66)Hf_(0.30)Nb_(0.04)NiSn at 1123 K owing to the donor doping and band regulation via Nb doping and Hf substitution.This can be ascribed to the synergistic interaction between the lowering of the lattice thermal conductivity and retention of the high PF.Consequently,a ZT value of as high as 1.06 is achieved for Zr_(0.66)Hf_(0.30)Nb_(0.04)NiSn at 1123 K.This work demonstrates that these actions are effective in jointly manipulating the transport of electrons and phonons,thereby improving the thermoelectric performance through defect engineering.展开更多
The thermoelectric(TE)performance of p-type ZrCoSb-based half-Heusler(HH)alloys has been improved tremendously in recent years;however,it remains challenging to find suitable n-type ZrCoSb-based HH alloys due to their...The thermoelectric(TE)performance of p-type ZrCoSb-based half-Heusler(HH)alloys has been improved tremendously in recent years;however,it remains challenging to find suitable n-type ZrCoSb-based HH alloys due to their high lattice thermal conductivity(κ_(L)).In this work,n-type Zr_(1−x)Ta_(x)Co_(1−x)Ni_(x)Sb HH alloys were firstly designed by multisite alloying.The evolution of the Raman peak proved that alloy scattering,phonon softening,anharmonicity,entropy-driven disorder,and precipitates had a combined effect on decreasingκ_(L)by 46.7%compared to that of pristine ZrCoSb.Subsequently,Hf_(0.75)Zr_(0.25)NiSn_(0.99)Sb_(0.01)was introduced into Zr_(0.88)Ta_(0.12)Co_(0.88)Ni_(0.12)Sb to further suppressκ_(L).Remarkably,the grain size of the biphasic HH alloys was refined by at least one order of magnitude.A biphasic high-entropy HH alloy with y=0.2 exhibited the minimumκ_(L)of∼2.44 W/(m·K)at 923 K,reducing by 67.7%compared to that of ZrCoSb.Consequently,(Zr_(0.88)Ta_(0.12)Co_(0.88)Ni_(0.12)Sb)_(0.9)(Hf_(0.75)Zr_(0.25)NiSn_(0.99)Sb_(0.01))_(0.1)exhibited the highest TE figure of merit(∼0.38)at 923 K.The cooperation between the entropy and biphasic microstructure resulted in multiscale defects,refined grains,and biphasic interfaces,which maximized the scattering of the multiwavelength phonons in HH alloys.This work provides a new strategy for further reducing the grain size andκ_(L)of medium-and high-entropy HH alloys.展开更多
Magnesium-lithium(Mg-Li)alloys are characteristic of great potentials for transformative weight reduction across diverse applications,from aeronautics and spacecraft to automobiles,electronics,and biomaterials.However...Magnesium-lithium(Mg-Li)alloys are characteristic of great potentials for transformative weight reduction across diverse applications,from aeronautics and spacecraft to automobiles,electronics,and biomaterials.However,commercial services on Mg-Li alloys remain chal-lenges given their poor corrosion resistance.This article critically reviews state-of-the-art progress of corrosion-resistant coatings for Mg-Li alloys,aiming to unlocking the full potential of such promising materials.The preparation techniques employed are summarized,the under-lying protective mechanisms are elucidated,and coating performances are critically evaluated.This review further highlights key challenges for future exploration and development,and provides insightful perspectives towards emerging frontiers in this dynamic domain.展开更多
Recently, high-entropy alloys(HEAs) or multi-principal-element alloys with unprecedented physical,chemical, and mechanical properties, have been considered as candidate materials used in advanced reactors due to their...Recently, high-entropy alloys(HEAs) or multi-principal-element alloys with unprecedented physical,chemical, and mechanical properties, have been considered as candidate materials used in advanced reactors due to their promising irradiation resistant behavior. Here, we report a new single-phase bodycentered cubic(BCC) structured Ti_2 ZrHfV_(0.5)Mo_(0.2) HEA possessing excellent irradiation resistance, i.e.,scarcely irradiation hardening and abnormal lattice constant reduction after helium-ion irradiation,which is completely different from conventional alloys. This is the first time to report the abnormal XRD phenomenon of metallic alloys and almost no hardening after irradiation. These excellent properties make it to be a potential candidate material used as core components in next-generation nuclear reactors. The particular irradiation tolerance derives from high density lattice vacancies/defects.展开更多
To evaluate the potential of high entropy alloys for marine applications,a new high entropy alloy coating of AlCrFeNiW_(0.2)Ti_(0.5)was designed and produced on Q235 steel via laser cladding.The microstructure,microha...To evaluate the potential of high entropy alloys for marine applications,a new high entropy alloy coating of AlCrFeNiW_(0.2)Ti_(0.5)was designed and produced on Q235 steel via laser cladding.The microstructure,microhardness and tribological performances sliding against YG6 cemented carbide,GCr15 steel and Si_(3)N_(4)ceramic in seawater were studied in detail.The AlCrFeNiW_(0.2)Ti_(0.5)coating showed an anomalous’sunflower-like’morphology and consisted of BCC and ordered B2 phases.The microhardness was approximately 692.5 HV,which was 5 times higher than substrate.The coating showed more excellent tribological performances than Q235 steel and SUS304,a typical material used in seawater environment,sliding against all three coupled balls in seawater.Besides,the wear and friction of AlCrFeNiW_(0.2)Ti_(0.5)coating sliding against YG6 in seawater were most mild.The main reason was the generation of Mg(OH)_(2),CaCO_(3),metal oxides and hydroxides and the formation of protective tribo-film on the worn surface of AlCrFeNiW_(0.2)Ti_(0.5)coating in the process of reciprocated sliding.This would effectively hinder the direct contact between the worn surfaces of AlCrFeNiW_(0.2)Ti_(0.5)coating and YG6 ball,resulting in a decrease of friction coefficient and wear rate.Thus the YG6 was an ideal coupled material for AlCrFeNiW_(0.2)Ti_(0.5)coating in seawater,and the coating would become a promising wear-resisting material in ocean environment.展开更多
The microstructure and mechanical properties of as-cast and isothermally annealed C_(x)Hf_(0.25)NbTaW_(0.5)(x=0,0.05,0.15,0.25)refractory high-entropy alloys(RHEAs)were studied.Both the as-cast and annealed RHEAs cons...The microstructure and mechanical properties of as-cast and isothermally annealed C_(x)Hf_(0.25)NbTaW_(0.5)(x=0,0.05,0.15,0.25)refractory high-entropy alloys(RHEAs)were studied.Both the as-cast and annealed RHEAs consisted of disordered body-centered cubic solid solution phase and metal carbide(MC)phase with a face-centered cubic crystal structure(Fm-3 m space group).The primary carbides were enriched with Hf and C elements and tended to form lamellar eutectic-like microstructure in the interdendrites.The lamellar eutectic-like structure in the interdendrites would be formed from the decomposition of sub-carbide M_(2)C under the influence of Hf element.After isothermal annealing,slatted carbides were precipitated on the matrix,and the distribution became more uniform with high C content.The formation of carbides strongly influenced the mechanical properties both at room and high temperatures.The yield strength values of C_(x)Hf_(0.25)NbTaW_(0.5) RHEA at 1473 and 1673 K were 792 and 749 MPa,respectively.The result had exceeded the high temperature mechanical properties of currently known RHEAs.Moreover,this RHEA exhibited high-temperature performance stability and excellent plasticity,exceeding 30 and 50%at room and elevated temperatures(above 1273 K),respectively.During thermal deformation,carbon-containing RHEAs obtained more severe work hardening than that of ACHO RHEAs,and required greater dynamic recrystallization to achieve the dynamic equilibrium.展开更多
In situ synchrotron X-ray radiography was used to study the effect of direct current(DC) on the grain nucleation and growth of Sn-50 wt.%Pb alloy. The results showed that applying DC adequately during solidification...In situ synchrotron X-ray radiography was used to study the effect of direct current(DC) on the grain nucleation and growth of Sn-50 wt.%Pb alloy. The results showed that applying DC adequately during solidification could effectively enhance the grain nucleation and inhibit its growth. Imaging of comparative experiments with varying DC intensity indicated that the final grain size, determined by the competition between grain nucleation and growth, was sensitively dependent on the DC intensity. It was found that the average grain size was decreased from 1632 to 567 μm with DC density of 1.5 A/mm^2 compared to the case without DC. Beyond this value, raising the current density may cause a significant decrease in the nucleation rate, and thus lead to a coarsening of the grain structure.展开更多
Contact infection of bacteria and viruses has been a critical threat to human health. The worldwideoutbreak of COVID-19 put forward urgent requirements for the research and development of the selfantibacterial materia...Contact infection of bacteria and viruses has been a critical threat to human health. The worldwideoutbreak of COVID-19 put forward urgent requirements for the research and development of the selfantibacterial materials, especially the antibacterial alloys. Based on the concept of high-entropy alloys, thepresent work designed and prepared a novel Co_(0.4)FeCr_(0.9)Cu_(0.3) antibacterial high-entropy alloy with superior antibacterial properties without intricate or rigorous annealing processes, which outperform the antibacterial stainless steels. The antibacterial tests presented a 99.97% antibacterial rate against Escherichiacoli and a 99.96% antibacterial rate against Staphylococcus aureus after 24 h. In contrast, the classic antibacterial copper-bearing stainless steel only performed the 71.50% and 80.84% antibacterial rate, respectively. The results of the reactive oxygen species analysis indicated that the copper ion release and theimmediate contact with copper-rich phase had a synergistic effect in enhancing antibacterial properties.Moreover, this alloy exhibited excellent corrosion resistance when compared with the classic antibacterialstainless steels, and the compression test indicated the yield strength of the alloy was 1015 MPa. Thesefindings generate fresh insights into guiding the designs of structure-function-integrated antibacterial alloys.展开更多
High entropy alloy has attracted increasing attentions.However,to enhance the alloy strength often leads to impairment of the ductility,or vice versa.Here we reported a heat treatment approach on AlCrFeNi2Ti0.5 high e...High entropy alloy has attracted increasing attentions.However,to enhance the alloy strength often leads to impairment of the ductility,or vice versa.Here we reported a heat treatment approach on AlCrFeNi2Ti0.5 high entropy alloy,which can elevate the strength and ductility simultaneously.An ingot of AlCrFeNi2Ti0.5 weighing 2.5 kg was firstly fabricated by medium frequency induction melting.Then samples from the same height of the bulk ingot were annealed for 6 h at 600,700,800 and 1000 ℃,respectively.After 1000 ℃ annealing,an optimal microstructure was obtained by using our approach which can make some precipitation particles distribute homogeneously in the dendrite interior while keep the interdendrite structure as a single solid solution phase.The mechanical test on this AlCrFeNi2Ti0.5 alloy sample showed that,the compressive fracture strength σbc was increased by about600 MPa and the plastic strain ep was doubled,compared with those of the as-cast sample.Our approach can be readily adapted to large-scale industrial production of high entropy alloys with high strength and ductility by proper annealing treatment.展开更多
B4Cp/6061Al composites have become important structural and functional materials and can be fabricated by powder metallurgy and subsequent hot rolling. In this work, the effects of the hot-pressing temperature on micr...B4Cp/6061Al composites have become important structural and functional materials and can be fabricated by powder metallurgy and subsequent hot rolling. In this work, the effects of the hot-pressing temperature on microstructures and mechanical behaviors of the B4Cp/6061Al composites were investigated. The results showed that compared with the T4 heat treated B4Cp/6061Al composite hot pressed at 560℃, the yield strength and failure strain of the composites hot pressed at 580℃ were increased to 235 MPa and 18.4%, respectively. This was associated with the interface bonding strength between the B4C particles and the matrix. However, the reaction products, identified to be MgAl2O4 phases, were detected in the composites hot pressed at 600℃. The formation of the MgAl2O4 phases resulted in the Mg depletion, thus reducing the yield strength to 203.5 MPa after the T4 heat treatment due to the effect of the solid solution strengthening being weakened. In addition, the variation of hardness and electrical conductivity was mainly related to the Mg content in the matrix. Based on the as-rolled microstructures observed by SEM, SR-μCT and fracture surfaces, the deformation schematic diagram was depicted to reflect the tensile deformation process of the composites.展开更多
基金the Supported by Program for the National Natural Science Foundation of China(No.52071053,U1704253,52103334)China Postdoctoral Science Foundation(2020M670748,2020M680946)the Fundamental Research Funds for the Central Universities(DUT20GF111).
文摘Developing megahertz(MHz)electromagnetic wave(EMW)absorption materials with broadband absorption,multi-temperature adaptability,and facile preparation method remains a challenge.Herein,nanocrystalline FeCoNiCr_(0.4)Cu_(0.2) high-entropy alloy powders(HEAs)with both large aspect ratios and thin intergranular amorphous layers are constructed by a multistage mechanical alloying strategy,aiming to achieve excellent and temperature-stable permeability and EMW absorption.A single-phase face-centered cubic structure with good ductility and high crystallinity is obtained as wet milling precursors,via precisely controlling dry milling time.Then,HEAs are flattened to improve aspect ratios by synergistically regulating wet milling time.FeCoNiCr_(0.4)Cu_(0.2) HEAs with dry milling 20 h and wet milling 5 h(D20)exhibit higher and more stable permeability because of larger aspect ratios and thinner intergranular amorphous layers.The maximum reflection loss(RL)of D20/SiO_(2) composites is greater than-7 dB with 5 mm thickness,and EMW absorption bandwidth(RL<-7 dB)can maintain between 523 and 600 MHz from-50 to 150℃.Furthermore,relying on the“cocktail effect”of HEAs,D20 sample also exhibits excellent corrosion resistance and high Curie temperature.This work provides a facile and tunable strategy to design MHz electromagnetic absorbers with temperature stability,broadband,and resistance to harsh environments.
基金the National Key Research and Development Programof China(No.2016YFB0701203)Fundamental Research Funds for the Central Universities(No.DUT18RC(3)042)+1 种基金National Natural Science Foundation of China(Nos.51525401,51774065,51601028,51690163,51574058)Dalian Support Plan for Innovation of Highlevel Talents(Top and Leading Talents,2015R013).
文摘The microstructure and tensile properties of the as-cast and as-rolled Mg-4.5Sn-5Zn alloys by adding various Sc content were investigated.Improvement of the tensile properties in as-cast Sc-containing alloys is attributed to the grain refinement and modification of secondary phase morphology.Three types of precipitates,namely spherical Mg2Sn,rod-like MgZn and Sc-rich phases were dispersed in the matrix of the Sc added M g-4.5Sn-5Zn alloys after hot rolling deformation.In addition,weakening and deflecting of the basal texture in as-rolled alloys were found and were attributed to Sc addition.Further increasing the Sc addition rate to 0.4 wt.%,however,resulted in the clustering of the Sc-rich phases and was found to reduce the tensile properties of the alloy,especially the elongation.The as-rolled Mg-4.5Sn-5Zn-0.3Sc alloy exhibits an optimum combination of tensile properties.The ultimate tensile strength,yield strength and elongation are 293.0MPa,164.2Mpa and 21.5%,respectively,and the elongation is about 68%higher than that of Sc-free alloy.
基金Supported by Program for the National Natural Science Foundation of China(No.52071053,U1704253)the Fundamental Research Funds for the Central Universities(DUT20GF111)the China Postdoctoral Science Foundation(2020M670748,2020M680946).
文摘High-temperature electromagnetic(EM) protection materials integrated of multiple EM protection mechanisms and functions are regarded as desirable candidates for solving EM interference over a wide temperature range.In this work,a novel microwave modulator is fabricated by introducing carbonyl iron particles(CIP)/resin into channels of carbonized wood(C-wood).Innovatively,the spaced arrangement of two microwave absorbents not only achieves a synergistic enhancement of magnetic and dielectric losses,but also breaks the translational invariance of EM characteristics in the horizontal direction to obtain multiple phase discontinuities in the frequency range of 8.2-18.0 GHz achieving modulation of reflected wave radiation direction.Accordingly,CIP/C-wood microwave modulator demonstrates the maximum effective bandwidth of 5.2 GHz and the maximum EM protection efficiency over 97% with a thickness of only 1.5 mm in the temperature range 298-673 K.Besides,CIP/C-wood microwave modulator shows stable and low thermal conductivities,as well as monotonic electrical conductivity-temperature characteristics,therefore it can also achieve thermal infrared stealth and working temperature monitoring in wide temperature ranges.This work provides an inspiration for the design of high-temperature EM protection materials with multiple EM protection mechanisms and functions.
基金financially supported by the National Natural Science Foundation of China (Nos. 52022017, 51974058, and 51927801)the Innovation Foundation of Science and Technology of Dalian, China (No. 2020RQ124)the Fundamental Research Funds for the Central Universities, China
文摘The effect of rolling and forging on the microstructure and corrosion behavior of LZ91 alloy was investigated using an electron probe micro-analyzer,immersion and electrochemical tests.Results showed that the area fraction of theβ-Li phase remained unchanged,and the grain size of theβ-Li phase decreased after forging.The as-rolled forged alloy(FR-LZ91)exhibited the highest area fraction of theβ-Li phase and the longest grains.The corrosion resistance of the forged LZ91 alloy increased due to grain refinement that prevented further corrosion during the immersion test.Among the experimental alloys,FR-LZ91 showed the highest resistance of corrosion film and charge transfer resistance values due to its protective film caused by the high area fraction of theβ-Li phase.
基金supported by grants from the National Key Research and Development Program of China(Grant No.2016YFC0902001)the Sino-Sweden Joint Research Program(Grant No.81861138006)+5 种基金the Science and Technology Planning Project of Guangzhou,China(Grant No.201804020094)the National Natural Science Foundation of China(Grant Nos.81973131,81903395,81803319,and 81502056)the National Science Fund for Distinguished Young Scholars of China(Grant No.81325018)the Key Project for International Cooperation and Exchange of the National Natural Science Foundation of China(Grant No.81220108022)the Natural Science Foundation of Guangdong Province(Grant No.2017A030312003)。
文摘Objective:Circulating cell-free Epstein-Barr virus(EBV)DNA has been shown to be a valuable biomarker for population screening and prognostic surveillance for nasopharyngeal carcinoma(NPC).Despite important insights into the biology of persistence,few studies have addressed the clinical significance of cell-based EBV-DNA loads in peripheral blood cells(PBCs).Methods:A prospective observational cohort study was conducted involving 1,063 newly diagnosed,locoregionally-advanced NPC patients at Sun Yat-sen University Cancer Center from 2005 to 2007.Cox regression analysis was conducted to identify the association of PBC EBV DNA loads to overall survival(OS)and other prognostic outcomes.Prognostic nomograms were developed based on PBC EBV DNA loads to predict survival outcomes for NPC patients.Results:After a median follow-up of 108 months,patients with higher PBC EBV-DNA loads had significantly worse OS[hazard ratio(HR)of medium,medium-high,and high vs.low were 1.50,1.52,and 1.85 respectively;Ptrend<0.001].Similar results were found for progression-free survival and distant metastasis-free survival.The concordance index of the prognostic nomogram for predicting OS in the training set and validation set were 0.70 and 0.66,respectively.Our data showed that the PBC EBV DNA load was an independent and robust survival biomarker,which remained significant even after adjusting for plasma EBV DNA loads in a subset of 205 patients of the cohort(HR:1.88;P=0.025).Importantly,a combination of PBC EBV DNA load and plasma EBV DNA load improved the predicted OS.Conclusions:The EBV-DNA load in PBCs may be an independent prognosis marker for NPC patients.
基金supported by the National Key Research and Development Program of China (2017YFA0403803)the National Natural Science Foundation of China [Grant Nos.52022017,52074172,51974058,51927801]+1 种基金the Innovation Foundation of Science and Technology of Dalian [Grant No.2020RQ124]Fundamental Research Funds for the Central Universities。
文摘Bioinspired by Nepenthes, lubricant infused surfaces(LIS) have attracted widespread attention in the field of anticorrosion. However,the lubricant coating has some disadvantages such as complex construction processing and easy loss of oil phase in air or dynamic water phase. In this study, oleogel is infused into a lotus leaf inspired super-hydrophobic matrix to form an oleogel infused surface(OIS) for enhancing corrosion resistance of active Mg-Li alloy. For reserving oleogel, firstly, a facile one-step electrodeposition method is used to construct super-hydrophobic surface(SHS) composed by samarium/myristic acid complex micro-nano flower structure onto Mg-Li alloy.The coating exhibits excellent superhydrophobic property at a static contact angle of 160° by applying 30 V electrolysis for 30 min. The protection efficiency of single SHS highly relates with the metal itself. For short period immersion in water phase, SHS can afford protection to Mg-Li alloy. However, the long-term immersion will see the rapid failure of SHS, and the high activity of Mg-Li alloy is one main reason.We assume that SHS cannot be a good choice for protecting Mg-Li alloy. Then, a Nepenthes inspired liquid coating is formed by infusing oleogel into the micro-nano structure by a spin-coating method. The liquid coating performs prominent corrosion resistance with Rctreaching as high as 1.51 × 10^(10)Ω cm^(2). After the mechanical damage from the external environment, the liquid coating can realize self-repair through thermal assistance, and the liquid coating can still restore Rctup to 1.24 × 10^(10)Ω cm^(2) after healing. The corrosion resistance of the liquid coating remains strong by showing Rctas high as 1.14 × 10^(9)Ω cm^(2), even after immersion in representative corrosive 3.5 wt% Na Cl solution for 30 d.
基金We acknowledge the financial support by the National Key Research and Development Program of China(No.2017YFA0403803)Liaoning Revitalization Talents Program(No.XLYC1808005)the fundamental research funds for the central universities.
文摘In this study,the real 3D model of the feather shaft that is composed of medulla and cortex is characterized by X-ray computer tomography,and the structural features are quantitatively analyzed.Compression and tensile tests are conducted to evaluate the mechanical performance of the feather shaft and cortex at different regions.The analysis of the 3D model shows that the medulla accounts for∼70%of the shaft volume and exhibits a closed-cell foam-like structure,with a porosity of 59%.The cells in the medulla show dodecahedron and decahedron morphology and have an equivalent diameter of∼30μm.In axial compression,the presence of medulla enhances the shaft stability.Especially,the combined effect of the medulla and cortex increases the buckling strength of the middle and distal shaft by 77%and 141%,respectively,compared to the calculated value of the shaft using linear mixed rule.The tensile properties of the cortex along the shaft axis are anisotropic because of the different fiber structures.As the fiber orientation gradually becomes uniform in the axial direction,the Young’s modulus and tensile strength of the cortex on the dorsal gradually increase from calamus to the distal shaft,and the fracture mode changes from tortuous fracture to V-shaped fracture.The cortex on the lateral shows the opposite trend,that is the distal shaft becomes weaker due to fiber tangles.
基金supported by the National Key Research and Development Program of China(No.2022YFB3400142)the National Natural Science Foundation of China(Nos.52174356,52022017,51927801,51971051,51901034 and U22A20174)+3 种基金the Science and Technology Plan Project of Liaoning Province(Nos.2022010005-JH6/1001 and 2022JH2/1013)the Innovation Foundation of Science and Technology of Dalian(Nos.2020JJ25CY002 and 2020J12GX037)the Major Science and Technology Projects of Longmen Laboratory(No.231100220400)the Fundamental Research Funds for the Central Universities.
文摘Obtaining an appropriate grain size is crucial for Al alloys or Al matrix composites prior to processing,as it significantly influences the mechanical properties of components and workability during the manufacturing process.TiB_(2)particles are exceptional grain refiners in Al and serve as excellent reinforcement particles for particulate-reinforced aluminum matrix composites.However,the optimal particle content for achieving excellent refinement and strengthening effects depends on the matrix composition and requires further investigation.Additionally,homogenization is essential for mitigating the element segregation in the ingot.Although it is anticipated that adding suitable particles can effectively inhibit undesired grain growth during homogenization,comprehensive investigations on this aspect are currently lacking.Therefore,TiB_(2)/2219Al matrix composites with varying reinforcement contents(0,1,3,5 wt%)were fabricated through traditional casting followed by homogenization treatment to address these research gaps.The effects of reinforcement content and homogenization treatment on the microstructure and mechanical properties of in-situ TiB_(2)/2219Al composites were investigated.The results demonstrate a gradual strengthening of the refining effect with increasing particle concentration.Moreover,composites containing 3 wt%TiB_(2)particles exhibit superior comprehensive mechanical properties in both as-cast and homogenized state.Additionally,potential orientation relationships are observed and calculated between undissolved Al_(2)Cu eutectic phase and submicron or nanometer-sized TiB_(2)particles,resulting in a mixture structure with enhanced bonding strength.This mixture structure is continuously distributed along grain boundaries during solidification,forming a three-dimensional cellular network that acts as primary retarding forces for grain growth during homogenization.Furthermore,the established homogenization kinetic equations were further utilized to analyze the correlation between homogenization time and grain size,as well as the influence of homogenization temperature.
基金supported by the National Natural Science Foundation of China (Grant Nos.51974058,52022017,52371005 and 51927801)the Fundamental Research Funds for the Central Universities.
文摘The semi-solid stir casting method is adopted to prepare 10 wt%SiC_(p)/Mg-6Zn-0.5Ca-xAl(x=0,1,3 and 5 wt%)composites,and the microstructure evolution and mechanical property of composites with various Al content are investigated.The results show that the addition of 3 wt%Al improves the distribution of SiC_(p),whereas the SiC_(p) cluster occurs again with Al content greater than 3%.An abnormal phenomenon of twinning is observed in the cast composites in this work.The SiC_(p)/Mg-6Zn-0.5Ca composite possesses the highest twin content of~23%,for which tension twins(TTW)and compression twins(CTW)account for~19%and~3%,respectively.The CTW is only observed in ZXA600 composite.The addition of Al has an inhibiting effect for the generation and growth of twins.The content of twin decreases firstly and then increases with increase of Al content.The lowest twin content is obtained as Al increases to 3 wt%.It is found the existence of twin is detrimental to the mechanical property of composites.As-cast SiC_(p)/Mg-6Zn-0.5Ca-3Al composite with the lowest twin content exhibits the optimal mechanical property of yield strength,ultimate tensile strength and elongation for 100 MPa,188 MPa and 4.4%,respectively.The outstanding mechanical property is attributed to the uniform distribution of SiC_(p),the low twin content and the well-distributed fine second phases.
基金supported by the Project funded by China Postdoctoral Science Foundation(BX2021048,2021M700661)the National Natural Science Foundation of China(Nos.52271025,51971052,51927801,U22A20174)the Liaoning Revitalization Talents Program(No.XLYC2007183).
文摘The high lattice thermal conductivity of half-Heuslers(HHs)restricts the further enhancement of their thermoelectric figure-of-merit(ZT).In this study,multiscale scattering centers,such as point defects,dislocations,and nanoprecipitates,are synchronously introduced in a n-type ZrNiSn-based HH matrix through Nb doping and Hf substitution.The lattice thermal conductivity is substantially decreased from 4.55(for the pristine ZrNiSn)to 1.8 W·m^(−1)·K^(−1) at 1123 K via phonon scattering over a broad wavelength range through the adjustment of multiscale defects.This value is close to the theoretically estimated lowest thermal conductivity.The power factor(PF)is enhanced from 3.25(for the pristine ZrNiSn)to 5.01 mW·m^(−1)·K^(−2) for Zr_(0.66)Hf_(0.30)Nb_(0.04)NiSn at 1123 K owing to the donor doping and band regulation via Nb doping and Hf substitution.This can be ascribed to the synergistic interaction between the lowering of the lattice thermal conductivity and retention of the high PF.Consequently,a ZT value of as high as 1.06 is achieved for Zr_(0.66)Hf_(0.30)Nb_(0.04)NiSn at 1123 K.This work demonstrates that these actions are effective in jointly manipulating the transport of electrons and phonons,thereby improving the thermoelectric performance through defect engineering.
基金supported by the National Natural Science Foundation of China(Grant Nos.52271025,51971052,51927801,51834009)the Liaoning Revitalization Talents Program(No.XLYC2007183).
文摘The thermoelectric(TE)performance of p-type ZrCoSb-based half-Heusler(HH)alloys has been improved tremendously in recent years;however,it remains challenging to find suitable n-type ZrCoSb-based HH alloys due to their high lattice thermal conductivity(κ_(L)).In this work,n-type Zr_(1−x)Ta_(x)Co_(1−x)Ni_(x)Sb HH alloys were firstly designed by multisite alloying.The evolution of the Raman peak proved that alloy scattering,phonon softening,anharmonicity,entropy-driven disorder,and precipitates had a combined effect on decreasingκ_(L)by 46.7%compared to that of pristine ZrCoSb.Subsequently,Hf_(0.75)Zr_(0.25)NiSn_(0.99)Sb_(0.01)was introduced into Zr_(0.88)Ta_(0.12)Co_(0.88)Ni_(0.12)Sb to further suppressκ_(L).Remarkably,the grain size of the biphasic HH alloys was refined by at least one order of magnitude.A biphasic high-entropy HH alloy with y=0.2 exhibited the minimumκ_(L)of∼2.44 W/(m·K)at 923 K,reducing by 67.7%compared to that of ZrCoSb.Consequently,(Zr_(0.88)Ta_(0.12)Co_(0.88)Ni_(0.12)Sb)_(0.9)(Hf_(0.75)Zr_(0.25)NiSn_(0.99)Sb_(0.01))_(0.1)exhibited the highest TE figure of merit(∼0.38)at 923 K.The cooperation between the entropy and biphasic microstructure resulted in multiscale defects,refined grains,and biphasic interfaces,which maximized the scattering of the multiwavelength phonons in HH alloys.This work provides a new strategy for further reducing the grain size andκ_(L)of medium-and high-entropy HH alloys.
基金supported by the National Natural Science Foundation of China(52371005 and 51927801)the Fundamental Research Funds for the Central Universities(DUT23YG104).E.G.thanks Xiaomi Foundation for support.
文摘Magnesium-lithium(Mg-Li)alloys are characteristic of great potentials for transformative weight reduction across diverse applications,from aeronautics and spacecraft to automobiles,electronics,and biomaterials.However,commercial services on Mg-Li alloys remain chal-lenges given their poor corrosion resistance.This article critically reviews state-of-the-art progress of corrosion-resistant coatings for Mg-Li alloys,aiming to unlocking the full potential of such promising materials.The preparation techniques employed are summarized,the under-lying protective mechanisms are elucidated,and coating performances are critically evaluated.This review further highlights key challenges for future exploration and development,and provides insightful perspectives towards emerging frontiers in this dynamic domain.
基金supported by the National Natural Science Foundation of China (Nos. 11605271, 51471044, 51525401, 51771201 and 51401208)Support Plan for Innovation of High-level Talents (Top and Leading Talents, 2015R013)Support Plan for Innovation of High-level Talents (Youth Technology Stars, 2016RQ005)
文摘Recently, high-entropy alloys(HEAs) or multi-principal-element alloys with unprecedented physical,chemical, and mechanical properties, have been considered as candidate materials used in advanced reactors due to their promising irradiation resistant behavior. Here, we report a new single-phase bodycentered cubic(BCC) structured Ti_2 ZrHfV_(0.5)Mo_(0.2) HEA possessing excellent irradiation resistance, i.e.,scarcely irradiation hardening and abnormal lattice constant reduction after helium-ion irradiation,which is completely different from conventional alloys. This is the first time to report the abnormal XRD phenomenon of metallic alloys and almost no hardening after irradiation. These excellent properties make it to be a potential candidate material used as core components in next-generation nuclear reactors. The particular irradiation tolerance derives from high density lattice vacancies/defects.
基金financially supported by the National Natural Science Foundation of China(Nos.51771041,51774065,51671044 and 51901116)the National Key Research and Development Program of China(No.2017YFA0403803)。
文摘To evaluate the potential of high entropy alloys for marine applications,a new high entropy alloy coating of AlCrFeNiW_(0.2)Ti_(0.5)was designed and produced on Q235 steel via laser cladding.The microstructure,microhardness and tribological performances sliding against YG6 cemented carbide,GCr15 steel and Si_(3)N_(4)ceramic in seawater were studied in detail.The AlCrFeNiW_(0.2)Ti_(0.5)coating showed an anomalous’sunflower-like’morphology and consisted of BCC and ordered B2 phases.The microhardness was approximately 692.5 HV,which was 5 times higher than substrate.The coating showed more excellent tribological performances than Q235 steel and SUS304,a typical material used in seawater environment,sliding against all three coupled balls in seawater.Besides,the wear and friction of AlCrFeNiW_(0.2)Ti_(0.5)coating sliding against YG6 in seawater were most mild.The main reason was the generation of Mg(OH)_(2),CaCO_(3),metal oxides and hydroxides and the formation of protective tribo-film on the worn surface of AlCrFeNiW_(0.2)Ti_(0.5)coating in the process of reciprocated sliding.This would effectively hinder the direct contact between the worn surfaces of AlCrFeNiW_(0.2)Ti_(0.5)coating and YG6 ball,resulting in a decrease of friction coefficient and wear rate.Thus the YG6 was an ideal coupled material for AlCrFeNiW_(0.2)Ti_(0.5)coating in seawater,and the coating would become a promising wear-resisting material in ocean environment.
基金supported by National MCF Energy Research and Development Program(No.2018YFE0312400)National Key Research and Development Program of China(Nos.2019YFA0209901 and 2018YFA0702901)+2 种基金Liao Ning Revitalization Talents Program(No.XLYC1807047)Fund of Science and Technology on Reactor Fuel and Materials Laboratory(No.6142A06190304)Fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP201902)。
文摘The microstructure and mechanical properties of as-cast and isothermally annealed C_(x)Hf_(0.25)NbTaW_(0.5)(x=0,0.05,0.15,0.25)refractory high-entropy alloys(RHEAs)were studied.Both the as-cast and annealed RHEAs consisted of disordered body-centered cubic solid solution phase and metal carbide(MC)phase with a face-centered cubic crystal structure(Fm-3 m space group).The primary carbides were enriched with Hf and C elements and tended to form lamellar eutectic-like microstructure in the interdendrites.The lamellar eutectic-like structure in the interdendrites would be formed from the decomposition of sub-carbide M_(2)C under the influence of Hf element.After isothermal annealing,slatted carbides were precipitated on the matrix,and the distribution became more uniform with high C content.The formation of carbides strongly influenced the mechanical properties both at room and high temperatures.The yield strength values of C_(x)Hf_(0.25)NbTaW_(0.5) RHEA at 1473 and 1673 K were 792 and 749 MPa,respectively.The result had exceeded the high temperature mechanical properties of currently known RHEAs.Moreover,this RHEA exhibited high-temperature performance stability and excellent plasticity,exceeding 30 and 50%at room and elevated temperatures(above 1273 K),respectively.During thermal deformation,carbon-containing RHEAs obtained more severe work hardening than that of ACHO RHEAs,and required greater dynamic recrystallization to achieve the dynamic equilibrium.
基金supported by the National Key Research and Development Program of China (No. 2016YFB0701203)the National Natural Science Foundation of China (Nos. 51525401, 51690163, 51601028, 51401044)Dalian Support Plan for Innovation of High-level Talents (Top and Leading Talents, 2015R013)
文摘In situ synchrotron X-ray radiography was used to study the effect of direct current(DC) on the grain nucleation and growth of Sn-50 wt.%Pb alloy. The results showed that applying DC adequately during solidification could effectively enhance the grain nucleation and inhibit its growth. Imaging of comparative experiments with varying DC intensity indicated that the final grain size, determined by the competition between grain nucleation and growth, was sensitively dependent on the DC intensity. It was found that the average grain size was decreased from 1632 to 567 μm with DC density of 1.5 A/mm^2 compared to the case without DC. Beyond this value, raising the current density may cause a significant decrease in the nucleation rate, and thus lead to a coarsening of the grain structure.
基金Supported by the National Key Research and Development Program of China(No.2019YFA0209901)National Natural Science Foundation of China(No.51822402 and U20A20278)+2 种基金Liao Ning Revitalization Talents Program(No.XLYC1807047)Major Special Project of“Scientific and Technological Innovation 2025 in Ningbo(No.2019B10086)Peter K.Liaw thanks the support from the National Science Foundation(DMR-1611180 and 1809640)with the program directors,Drs.Judith Yang,Gary Shiflet,and Diana Farkas.
文摘Contact infection of bacteria and viruses has been a critical threat to human health. The worldwideoutbreak of COVID-19 put forward urgent requirements for the research and development of the selfantibacterial materials, especially the antibacterial alloys. Based on the concept of high-entropy alloys, thepresent work designed and prepared a novel Co_(0.4)FeCr_(0.9)Cu_(0.3) antibacterial high-entropy alloy with superior antibacterial properties without intricate or rigorous annealing processes, which outperform the antibacterial stainless steels. The antibacterial tests presented a 99.97% antibacterial rate against Escherichiacoli and a 99.96% antibacterial rate against Staphylococcus aureus after 24 h. In contrast, the classic antibacterial copper-bearing stainless steel only performed the 71.50% and 80.84% antibacterial rate, respectively. The results of the reactive oxygen species analysis indicated that the copper ion release and theimmediate contact with copper-rich phase had a synergistic effect in enhancing antibacterial properties.Moreover, this alloy exhibited excellent corrosion resistance when compared with the classic antibacterialstainless steels, and the compression test indicated the yield strength of the alloy was 1015 MPa. Thesefindings generate fresh insights into guiding the designs of structure-function-integrated antibacterial alloys.
基金financially supported by the National Natural Science Foundation of China(U20A20278 and 52001051)the National Key Research and Development Program of China(2018YFA0702901 and 2019YFA0209901)+2 种基金Liao Ning Revitalization Talents Program(XLYC1807047)the Major Special Project of“Scientific and Technological Innovation 2025”in Ningbo(2019B10086)the project funded by China Postdoctoral Science Foundation(2021T140082)。
基金supported by the National Natural Science Foundation of China(Nos.51134013,51071035,51375070 and 51104029)the Fundamental Research Funds for the Central Universities
文摘High entropy alloy has attracted increasing attentions.However,to enhance the alloy strength often leads to impairment of the ductility,or vice versa.Here we reported a heat treatment approach on AlCrFeNi2Ti0.5 high entropy alloy,which can elevate the strength and ductility simultaneously.An ingot of AlCrFeNi2Ti0.5 weighing 2.5 kg was firstly fabricated by medium frequency induction melting.Then samples from the same height of the bulk ingot were annealed for 6 h at 600,700,800 and 1000 ℃,respectively.After 1000 ℃ annealing,an optimal microstructure was obtained by using our approach which can make some precipitation particles distribute homogeneously in the dendrite interior while keep the interdendrite structure as a single solid solution phase.The mechanical test on this AlCrFeNi2Ti0.5 alloy sample showed that,the compressive fracture strength σbc was increased by about600 MPa and the plastic strain ep was doubled,compared with those of the as-cast sample.Our approach can be readily adapted to large-scale industrial production of high entropy alloys with high strength and ductility by proper annealing treatment.
基金financial support of National Key Research and Development Program of China (No. 2017YFA0403803)the National Natural Science Foundation of China (Nos.51525401, 51774065, 51601028, 51690163)+1 种基金Dalian Support Plan for Innovation of High-level Talents (Top and Leading Talents, 2015R013)fundamental research funds for the central universities (Nos. DUT18RC(3)042, DUT17RC(3)108)
文摘B4Cp/6061Al composites have become important structural and functional materials and can be fabricated by powder metallurgy and subsequent hot rolling. In this work, the effects of the hot-pressing temperature on microstructures and mechanical behaviors of the B4Cp/6061Al composites were investigated. The results showed that compared with the T4 heat treated B4Cp/6061Al composite hot pressed at 560℃, the yield strength and failure strain of the composites hot pressed at 580℃ were increased to 235 MPa and 18.4%, respectively. This was associated with the interface bonding strength between the B4C particles and the matrix. However, the reaction products, identified to be MgAl2O4 phases, were detected in the composites hot pressed at 600℃. The formation of the MgAl2O4 phases resulted in the Mg depletion, thus reducing the yield strength to 203.5 MPa after the T4 heat treatment due to the effect of the solid solution strengthening being weakened. In addition, the variation of hardness and electrical conductivity was mainly related to the Mg content in the matrix. Based on the as-rolled microstructures observed by SEM, SR-μCT and fracture surfaces, the deformation schematic diagram was depicted to reflect the tensile deformation process of the composites.