The development of high-performance structural and functional materials is vital in many industrial fields.High-and medium-entropy alloys(H/MEAs)with superior comprehensive properties owing to their specific microstru...The development of high-performance structural and functional materials is vital in many industrial fields.High-and medium-entropy alloys(H/MEAs)with superior comprehensive properties owing to their specific microstructures are promising candidates for structural materials.More importantly,multitudinous efforts have been made to regulate the microstructures and the properties of H/MEAs to further expand their industrial applications.The various heterostructures have enormous potential for the development of H/MEAs with outstanding performance.Herein,multiple heterogeneous structures with single and hierarchical heterogeneities were discussed in detail.Moreover,preparation methods for compositional inhomogeneity,bimodal structures,dualphase structures,lamella/layered structures,harmonic structures(core-shell),multiscale precipitates and heterostructures coupled with specific microstructures in H/MEAs were also systematically reviewed.The deformation mechanisms induced by the different heterostructures were thoroughly discussed to explore the relationship between the heterostructures and the optimized properties of H/MEAs.The contributions of the heterostructures and advanced microstructures to the H/MEAs were comprehensively elucidated to further improve the properties of the alloys.Finally,this review discussed the future challenges of high-performance H/MEAs for industrial applications and provides feasible methods for optimizing heterostructures to enhance the comprehensive properties of H/MEAs.展开更多
Titanium(Ti)and its alloys are frequently utilized as critical components in a variety of engineering ap-plications because of their high specific strength and excellent corrosion resistance.Compared to conven-tional ...Titanium(Ti)and its alloys are frequently utilized as critical components in a variety of engineering ap-plications because of their high specific strength and excellent corrosion resistance.Compared to conven-tional surface strengthening technologies,laser shock peening(LSP)has increasingly attracted attention from researchers and industries,since it significantly improves the surface strength,biocompatibility,fa-tigue resistance,and anti-corrosion ability of Ti and its alloys.Despite numerous studies that have been carried out to elucidate the effects of LSP on microstructural evolution and mechanical properties of Ti and its alloys in recent years,a comprehensive review of recent advancements in the field of Ti and its alloys subjected to LSP is still lacking.In this review,the standard LSP and the novel process designs of LSP assisted by thermal,cryogenic,electropulsing and magnetic fields are discussed and compared.Microstructural evolution,with focuses on the dislocation dynamics,deformation twinning,grain refine-ment and surface amorphization,during LSP processing of Ti alloys is reviewed.Furthermore,the en-hanced engineering performance of the L SP-processed(L SPed)Ti alloys,including surface hardness,wear resistance,fatigue life and corrosion resistance are summarized.Finally,this review concludes by present-ing an overview of the current challenges encountered in this field and offering insights into anticipated future trends.展开更多
The waterproof performance,mechanical properties,chemical composition,microstructure,and pore structure of hydrophobically-modified geopolymer concrete are investigated before and after dry-wet cycles,to determine the...The waterproof performance,mechanical properties,chemical composition,microstructure,and pore structure of hydrophobically-modified geopolymer concrete are investigated before and after dry-wet cycles,to determine the long-term feasibility of using hydrophobically-modified geopolymer concrete in wet environments.We use two types of organic modifying agents:polydimethylsiloxane(PDMS)and sodium methyl siliconate(SMS).The experimental results show that incorporating 2%–6%PDMS or 5%–15%SMS can make the concrete hydrophobic,with water absorption and chloride transport rates decreasing by up to 94.3%.We also analyze the bonding modes of organic molecules and geopolymer gels,as well as their evolution mechanisms during dry-wet cycles.PDMS-modified geopolymer concrete is found to exhibit long-term waterproof performance that is not weakened by dry-wet cycles.This is attributed to the robust combination of organic components and the geopolymer gel skeleton formed through phase cross-linking.Meanwhile,PDMS-modified geopolymer concrete’s hydrophobicity,strength,and microstructure are essentially unaffected.In contrast,SMS-modified geopolymer concrete shows higher water sensitivity,although it does maintain efficient waterproof performance.Due to relatively low binding energy,the dry-wet cycles may lead to the detachment of some SMS molecules from the gel network,which results in a decrease of 18.6%in compressive strength and an increase of 37.6%in total porosity.This work confirms the utility of hydrophobically-modified geopolymer concrete as a building material for long-term service in wet environments,for instance,areas with frequent precipitation,or splash and tidal zones.展开更多
The effect of high welding heat inputs in the range of 50–200 kJ/cm on the microstructural evolution,MX(M=Ti,Nb and V;X=N and C)precipitation and mechanical properties was investigated in the coarse-grained heat-affe...The effect of high welding heat inputs in the range of 50–200 kJ/cm on the microstructural evolution,MX(M=Ti,Nb and V;X=N and C)precipitation and mechanical properties was investigated in the coarse-grained heat-affected zone(CGHAZ)of a high-Nb(0.10 wt.%)structural steel.The results showed that the primary microconstituents varied from lath bainite(LB)to intragranular acicular ferrite(IAF)+intragranular polygonal ferrite(IPF),and the most content of IAF was acquired at 100 kJ/cm.Moreover,the submicron Ti-and Nb-rich MX precipitates not only pinned prior austenite grain boundaries but also facilitated IAF and IPF nucleation with the Kurdjumov–Sachs orientation relationship of[011]_(MX)//[111]_(Ferrite);the nanoscale V-rich MX precipitates hindered dislocation movement and followed the Baker–Nutting orientation relationship of[001]_(MX)//[001]_(Ferrite)with ferrite matrix,synergistically strengthening and toughening the CGHAZ.In addition,the−20℃impact absorbed energy firstly elevated from 93±5.2 J at 50 kJ/cm to 131±5.4 J at 100 kJ/cm and finally decreased to 59±3.0 J at 200 kJ/cm,being related to the IAF content,while the microhardness decreased from 312±26.1 to 269±12.9 HV0.1,because of the coarsened microstructure and the decreased content of LB and martensite.Compared to the CGHAZ properties with 0.05 wt.%Nb,a higher Nb content produced better low-temperature toughness,as more solid dissolved Nb atoms and precipitated Nb-rich MX particles in austenite limited prior austenite grain growth and promoted IAF formation.Furthermore,the welding process at 100 kJ/cm was most applicable for the high-Nb steel.展开更多
ZrCoRE(RE denotes rare earth elements)non-evaporable getter films have significant applications in vacuum packaging of micro-electro mechanical system devices because of their excellent gas adsorption performance,low ...ZrCoRE(RE denotes rare earth elements)non-evaporable getter films have significant applications in vacuum packaging of micro-electro mechanical system devices because of their excellent gas adsorption performance,low activation temperature and environmental friendliness.The films were deposited using DC magnetron sputtering with argon and krypton gases under various deposition pressures.The effects of sputtering gas type and pressure on the morphology and hydrogen adsorption performance of ZrCoRE films were investigated.Results show that the films prepared in Ar exhibit a relatively dense structure with fewer grain boundaries.The increase in Ar pressure results in more grain boundaries and gap structures in the films.In contrast,films deposited in Kr display a higher density of grain boundaries and cluster structures,and the films have an obvious columnar crystal structure,with numerous interfaces and gaps distributed between the columnar structures,providing more paths for gas diffusion.As Kr pressure increases,the film demonstrates more pronounced continuous columnar structure growth,accompanied by deeper and wider grain boundaries.This structural configuration provides a larger specific surface area,which significantly improves the hydrogen adsorption speed and capacity.Consequently,high Ar and Kr pressures are beneficial to improve the adsorption performance.展开更多
This study investigates the crystal structure,microstructure,electronic,thermal transport properties,and thermoelectric performance ofα-MgAgSb synthesized through various ball milling techniques.Variations in synthes...This study investigates the crystal structure,microstructure,electronic,thermal transport properties,and thermoelectric performance ofα-MgAgSb synthesized through various ball milling techniques.Variations in synthesis methods can significantly impact thermoelectric performance.Our findings indicate that impurity phases,particularly the secondary phase Ag_(3)Sb,hinder grain growth and decrease carrier mobility.By systematically adjusting milling conditions,the increased grain size resulting from the suppression of impurity formation improves charge carrier mobility and enhances the power factor.Low-temperature resistivity analysis reveals distinct scattering mechanisms influenced by impurity levels.α-MgAgSb with a tiny content of Sb primarily exhibits electron-electron scattering,whereas higher impurity levels introduce both electron-electron and electron-phonon scattering.Additionally,thermal conductivity analysis using three Effective Medium Theory(EMT)methods shows that the distribution of Ag_(3)Sb increases interfacial resistance.The maximum zT value of 1.36 was achieved in a compound with anα-MgAgSb to Sb ratio of 99%:1%.展开更多
The growing demand for high-efficiency and low-loss energy conversion and transportation techniques urges the development of advanced Fe-Si based soft magnet alloys.Simultaneous achievement of low coercivity(Hc)and la...The growing demand for high-efficiency and low-loss energy conversion and transportation techniques urges the development of advanced Fe-Si based soft magnet alloys.Simultaneous achievement of low coercivity(Hc)and large saturation magnetization(Ms)however,remains challenging.In this study,soft magnetic alloys with the composition Fe82-xSi18Cox(x=0 at.%,4 at.%,8 at.%,12 at.%,16 at.%,and 20 at.%)have been designed followed by microstructural tuning.The Co incorporation results in initially decreased Hc followed by increment due to reduced magnetocrystalline anisotropy and increased saturation mag-netostriction from negative to positive values of the alloys.Meanwhile,the Ms raises with subsequent reduction,which origins from competitive mechanisms of increased average moment of Fe atoms and decreased average moment of Co atoms according to first principles calculations.Microstructural evolu-tion during annealing of the Fe70Si18C012 with synergistically optimized Hc and Ms has been revealed that after elevated-temperature annealing,the DO3 phase is predominately transformed from the B2 phase ac-companied by an increase in the degree of ordering.The growth of the DO3 phase deteriorates the Hc due to the aggravating pinning effect on the domain wall movement,which arises from the inhomogeneous magnetization distribution caused by increasing antiphase boundaries.展开更多
This research focused on the influences of Cr element doping on the microstructure,thermal stability,microhardness,soft magnetic,and anti-corrosion properties of FeCoNiSiB multi-principal element alloys.The as-receive...This research focused on the influences of Cr element doping on the microstructure,thermal stability,microhardness,soft magnetic,and anti-corrosion properties of FeCoNiSiB multi-principal element alloys.The as-received Fe-Co-Ni-Si-B-Cr alloy ribbons made by melt-spinning technique could maintain amorphous nature.The glass-transition temperature and onset crystallization temperature become lower with the addition of Cr,and the highest values are 782.0 K and 821.5 K,respectively.When the Cr content reaches 3at.%,the alloy owns the best soft magnetic performance with the saturation magnetic flux density of~0.578 T and coercivity of~5.5 A·m^(-1)among the studied melt-spun ribbon samples.The microhardness of all alloy ribbons reduces with an increasing Cr content on the whole,and the values are 810 HV_(0.5) or above.The corrosion behavior of these multi-principal element amorphous alloys containing Cr was also investigated in detail.As the Cr content increases,the corrosion resistance becomes superior and the specimens present the obvious passive regions in 3.5wt.%NaCl solution.The glassy ribbons with 8at.%Cr have the highest self-corrosion potential of-0.340 V and pitting potential of 0.288 V as well as the widest passive region of 0.628 V.Besides,the corroded micrographs of alloy ribbons immersed in corrosive environment lasting 100 h are also presented,which further confirms the above-mentioned experimental results.This research deepens the understanding about the role of Cr element in the microstructure and a series of physical and chemical properties of Fe-Co-Ni-Si-B-Cr multi-principal element amorphous alloys.展开更多
A series of as-cast Si_(x)Al_(0.43)CoCrFeNi_(2.1)(x=0,0.1,0.2,and 0.3)high-entropy alloys(HEAs)was successfully fabricated by va-cuum-assisted melting.The phase constituents,microstructural features,and mechanical pro...A series of as-cast Si_(x)Al_(0.43)CoCrFeNi_(2.1)(x=0,0.1,0.2,and 0.3)high-entropy alloys(HEAs)was successfully fabricated by va-cuum-assisted melting.The phase constituents,microstructural features,and mechanical properties(including hardness,tensile behavior,and wear behavior)of alloys with various Si contents were evaluated.The results revealed that the addition of Si promoted the precipita-tion of a body-centered cubic 1(BCC1)phase enriched in Al,Ni,and Si with a B2-ordered structure.Furthermore,the secondary BCC2 phase was enriched with Cr,Fe,and Si precipitates within the BCC1 matrix.Ultimately,a multiphase face-centered cubic(FCC)/(BCC1/BCC2)structure was formed.The microstructural evolution driven by Si addition significantly enhanced the mechanical properties of the Si_(x)Al_(0.43)CoCrFeNi_(2.1) HEAs.As the Si content increased,the microhardness and tensile strength improved by approxim-ately 42%and 55%,reaching 2.359 GPa and 785 MPa,respectively.The quantitative evaluation of the various strengthening mechanisms indicated that the intrinsic hardness of the FCC matrix and hardening due to BCC1/BCC2 precipitation dominated the overall microhard-ness.The comparison of the energy barriers indicates that BCC2 primarily strengthens the alloy through a shear mechanism rather than an Orowan bypass mechanism.Furthermore,with increasing Si content,reduced friction and wear,together with smoother worn surfaces,re-flect a greatly enhanced wear resistance.After the optimal cold-rolling and 1 h annealing at 800℃,the Si_(0.3)Al_(0.43)CoCrFeNi_(2.1) alloy showed 56%and 62%increases in microhardness and tensile strength,respectively,compared to the as-cast state,reaching 3.68 GPa and 1270 MPa.The enhanced mechanical properties are attributed to the synergistic effects of residual strain hardening by FCC ordering and L1_(2)/BCC precipitation strengthening.展开更多
With the laser remelting of cast alloys combined with non-equilibrium liquidus projection thermodynamic calculations,a high-strength and heat-resistant Al-3Fe-2Mn alloy was designed.Incorporating Mn atoms into the met...With the laser remelting of cast alloys combined with non-equilibrium liquidus projection thermodynamic calculations,a high-strength and heat-resistant Al-3Fe-2Mn alloy was designed.Incorporating Mn atoms into the metastable nanoscale Al_(6)Fe phase,occupying some lattice sites,enhances its thermal stability.Additionally,during rapid solidification of laser powder bed fusion(L-PBF),the solubility of Fe and Mn elements in the aluminum alloy increases significantly,forming a supersaturated solid solution with improved strength.This alloy demonstrates excellent processability,achieving a relative density of over 99%,and tensile strengths of 295 MPa at 200℃ and 230 MPa at 300℃.The Al-3Fe-2Mn alloy holds great potential for wide applications due to its high strength at high temperature.展开更多
In this work,a small amount of Al_(2)O_(3)powders(≤0.3 wt%)were incorporated into the Sm_(2)Co_(17)-type sin-tered magnets,obtaining both high mechanical and magnetic properties.It is found that 0.1%weight percentage...In this work,a small amount of Al_(2)O_(3)powders(≤0.3 wt%)were incorporated into the Sm_(2)Co_(17)-type sin-tered magnets,obtaining both high mechanical and magnetic properties.It is found that 0.1%weight percentage of Al_(2)O_(3)doping is enough to enhance the flexural strength by about 20%(∼180 MPa for the case of the c-axis parallel to height).Meanwhile,the(BH)max remains around 219 kJ/m^(3),and Hcj is 2052 kA/m,which is over 95%of that of the original magnets without doping.The promising improvement in flexural strength is mainly attributed to the grain size effective refinement caused by Sm_(2)O_(3)particles including newly-formed ones from the reaction of the Al_(2)O_(3)powder and Sm in the matrix.Furthermore,the grain size of the magnets decreases significantly with increasing of Al_(2)O_(3)doping up to 0.3 wt%.Espe-cially,the grain size of 0.3 wt%Al_(2)O_(3)doped magnets is refined by 37%.However,the flexural strengths(for the c-axis parallel to height and the c-axis parallel to width cases)of the magnets decrease sequen-tially and are even lower than that of the original magnet.The microstructure investigations indicate that the decrease in flexural strength may closely be correlated to the larger cell size and the incomplete cell boundaries phase.The obtained results infer that the flexural strength is susceptible to not only grain size but also the cellular structure of the magnets.展开更多
Aluminum alloys that are additively manufactured using the laser powder bed fusion(LPBF)suffer from relatively poor high cycle fatigue(HCF)resistance.In an effort to alleviate this,a high-strength Al alloy,Al-Mn-Mg-Sc...Aluminum alloys that are additively manufactured using the laser powder bed fusion(LPBF)suffer from relatively poor high cycle fatigue(HCF)resistance.In an effort to alleviate this,a high-strength Al alloy,Al-Mn-Mg-Sc-Zr,with columnar,equiaxed,and bi-modal microstructures was produced by varying the scanning velocity and the substrate temperature during the LPBF process.The tensile strength of LPBF Al-Mn-Mg-Sc-Zr alloy is 475±5–516±6 MPa with favorable elongation of approximately 11%,higher than that of most of the other Al alloys,including conventional high-strength rolled/ECAP Al alloys and AM Al-Mg-Sc-Zr alloys.Specimens with bimodal microstructure and specimens with fully equiaxed microstructure both show a fatigue strength of 230 MPa(at 107 loading cycles),which is the highest among those reported for the LPBF Al alloys.The deformation synergy in the bimodal microstructure also improves the fatigue resistance in the strain-controlled low cycle fatigue(LCF)regime.The equiaxed microstructure restricts the to-and-fro dislocation motion during cyclic loading,which,in turn,minimizes the strain localization.At the later stages of strain accumulation,microcracks form at the grain boundaries,limiting the further improvement of the alloy's fatigue strength.This study demonstrates microstructural tailoring through AM enables improvement of the fatigue resistance of aluminum alloys.展开更多
The effect of rare earth addition on the microstructure and mechanical performances of as-cast and wrought Al alloys has been attracting increasing attention recently.Rare earth addition has great potential in modifyi...The effect of rare earth addition on the microstructure and mechanical performances of as-cast and wrought Al alloys has been attracting increasing attention recently.Rare earth addition has great potential in modifying the structure and improving the properties of materials.However,there are currently few reports about the effect of rare earth addition on the microstructure and performances of Al alloys prepared via selective laser melting.Here,AlSi10Mg alloys were manufactured using selective laser melting,and the effect of Er addition was investigated.The results indicate that Er addition leads toα-Al refinement and modifies the minority Si phase.The formation of the Al_(3)Er phase induced by Er addition enhances the stren gth of the material.Modification of the Si phase also increases ductility.This strategy can help improve the mechanical performance of alum inum alloys prepared via selective laser melting.展开更多
The microstructure and mechanical performance of the unidirectionally and cross-directionally rolled Mg-8Li-6Zn-1Y(in wt.%)sheets have been investigated and compared.It reveals that after the unidirectional rolling(UR...The microstructure and mechanical performance of the unidirectionally and cross-directionally rolled Mg-8Li-6Zn-1Y(in wt.%)sheets have been investigated and compared.It reveals that after the unidirectional rolling(UR),the broken I-phase particles are aggregated at theα-Mg/β-Li phase interfaces.However,the cross-rolling(CR)process can not only severely break the bulk I-phase,but also cause the obviously uniform distribution of I-phase particles in the matrix phases.Moreover,the average grain size of the CR samples is 3.61μm and about 50%that of the UR samples.The maximum texture intensities ofα-Mg andβ-Li phases in the CR samples are slightly stronger than those in the UR samples.Tensile results demonstrate that the CR process can effectively enhance the tensile properties and remarkably reduce the mechanical anisotropy of the alloy.For the UR samples,the yield strength,ultimate tensile strength,and elongation ratio along the rolling direction(RD)are 164 MPa,198 MPa,and 16.4%,whereas those along the transverse direction(TD)are 157 MPa,185 MPa,and 22.0%,respectively.For the CR samples,their mechanical properties are basically the same and the mechanical anisotropy is almost eliminated.The yield strength,ultimate tensile strength,and elongation ratio along the cross-rolling direction 1(CRD1)and 2(CRD2)are respectively measured to be 181 MPa and 182 MPa,220 MPa and 218 MPa,20.6%and 20.7%.Failure analysis indicates that for the UR samples being tensile tested along the RD and TD,microcracks are preferentially initiated in the region of aggregated I-phase particles.For the CR samples being tensile tested along both two cross-rolling directions,the initiation of micro-cracks mainly occurs at the I-phase/matrix phase interfaces and in the interior of matrix phases.展开更多
Soil-bentonite(SB)backfills in vertical cutoff walls are used extensively to contain contaminated groundwater.Previous studies show that the hydraulic conductivity of backfill can exceed the typically recommended maxi...Soil-bentonite(SB)backfills in vertical cutoff walls are used extensively to contain contaminated groundwater.Previous studies show that the hydraulic conductivity of backfill can exceed the typically recommended maximum value(k=1×10^(−9) m/s)if exposed to groundwater impacted by organic acids commonly released from uncontrolled landfills and municipal solid waste dumps.Polymer amended backfills exhibit excellent chemical compatibility to metal-laden groundwater.However,few studies to date have explored the effect of organic acid contaminated groundwater on hydraulic performance of polymer amended backfills.This study presents an experimental investigation on the hydraulic performance and microstructural properties of a composite polymer amended backfill used to contain flow of acetic acid-laden groundwater.A series of laboratory experiments were performed to evaluate free-swell indices of the composite polymer amended bentonites,liquid limits of the composite polymer amended and unamended bentonites,and slump heights and hydraulic conductivity(k)values of the amended backfills to acetic acid solutions with varying concentrations.The results were compared with those of the unamended bentonites and unamended backfills reported in a previous study.The results showed that the free-swell index and liquid limit of the amended bentonites were higher than those of the unamended bentonites.Permeation with acetic acid solutions with concentrations ranging from 40 mmol/L to 320 mmol/L conducted on the amended backfill only resulted in an increase in k of less than a factor of about 10 related to that based on permeation with tap water(4.41×10^(−11)-1.68×10^(−10) m/s to acetic acid solution versus 1.65×10^(−11) m/s to tap water).Mechanisms contributing to enhanced chemical compatibility of amended backfill were ascertained based on scanning electron microscopy,mercury intrusion porosimetry,and zeta potential analyses.展开更多
Oxide ceramic coatings were fabricated on tantalum alloys by micro-arc oxidation (MAO) to improve their hardness and tribological properties. The MAO coatings were manufactured in a mixed silicatephosphate electrolyte...Oxide ceramic coatings were fabricated on tantalum alloys by micro-arc oxidation (MAO) to improve their hardness and tribological properties. The MAO coatings were manufactured in a mixed silicatephosphate electrolyte containing NaF and/or EDTA (ethylene diamine tetraacetic acid). The surface morphology,cross-sectional view, chemical composition, hardness, and wear performance of the coatings were analysed. As revealed by the scanning electron microscopy, silica-rich nodules appear on the MAO coating obtained in the silicate-phosphate electrolyte, but the formation of nodules is inhibited with NaF and/or EDTA in the electrolyte.Also, they reduce the roughness and improve the compactness of the coatings, which are composed of Ta_(2)O_(5),(Ta, O), and TaO. A thick and hard coating is obtained in the NaF-containing electrolyte, and the tribology performance is effectively improved. With additives, the nodule structure is detached from the coating surface and dissolved in the electrolyte. By using NaF as an electrolyte additive, the abrasion performance of the MAO coating is enhanced by decreasing the nodule structure, increasing the size of micropores, and improving the coating hardness.展开更多
In this work,a high-strength crack-free TiN/Al-Mn-Mg-Sc-Zr composite was fabricated by laser powder bed fusion(L-PBF).A large amount of uniformly distributed L1_(2)-Al_(3)(Ti,Sc,Zr)nanoparticles were formed during the...In this work,a high-strength crack-free TiN/Al-Mn-Mg-Sc-Zr composite was fabricated by laser powder bed fusion(L-PBF).A large amount of uniformly distributed L1_(2)-Al_(3)(Ti,Sc,Zr)nanoparticles were formed during the L-PBF process due to the partial melting and decomposition of TiN nanoparticles under a high temperature.These L1_(2)-Al_(3)(Ti,Sc,Zr)nanoparticles exhibited a highly coherent lattice relationship with the Al matrix.All the prepared TiN/Al-Mn-Mg-Sc-Zr composite samples exhibit ultrafine grain mi-crostructure.In addition,the as-built composite containing 1.5 wt%TiN shows an excellent tensile prop-erty with a yield strength of over 580 MPa and an elongation of over 8%,which were much higher than those of wrought 7xxx alloys.The effects of various strengthening mechanisms were quantitatively estimated and the high strength of the alloy was mainly attributed to the refined microstructure,solid solution strengthening,and precipitation strengthening contributed by L1_(2)-Al_(3)(Ti,Sc,Zr)nanoparticles.展开更多
A series of Zn-xAl(x=0-35 wt.%)alloy filler metals were designed to join AZ31 Mg alloy to 6061 Al alloy by laser-TIG hybrid welding.The effect of Al content on the wettability of filler metals,microstructure evolution...A series of Zn-xAl(x=0-35 wt.%)alloy filler metals were designed to join AZ31 Mg alloy to 6061 Al alloy by laser-TIG hybrid welding.The effect of Al content on the wettability of filler metals,microstructure evolution and strength of joint was investigated.The results indicated that the strength of joints was improved with the increase of Al content in filler metals.When Zn-15Al filler was used,the ultimate fracture load reached the maximum of 1475.3 N/cm,which was increased by 28%than that with pure Zn filler.The reason is that the Al element acts as a"reaction depressant"in filler metal,which contributes to inhibiting the dissolution of Mg base metal and the Mg-Zn reaction.The addition of appropriate quantity of Al element promoted the precipitation of Al-rich solid solution instead of Zn solid solution.The MgZn_(2) IMCs have lower lattice mismatch with Al solid solution than Zn solid solution,thus the strength of joints is improved.However,the excessive addition of Al caused the formation of brittle Mg32(Al,Zn)49 ternary compounds,leading to the deterioration of joint performance.展开更多
We developed ultra-high performance concrete(UHPC)incorporating mullite sand and brown corundum sand(BCS),and the quartz sand UHPC was utilized to prepare for comparison.The properties of compressive strength,elastic ...We developed ultra-high performance concrete(UHPC)incorporating mullite sand and brown corundum sand(BCS),and the quartz sand UHPC was utilized to prepare for comparison.The properties of compressive strength,elastic modulus,ultrasonic pulse velocity,flexural strength,and toughness were investigated.Scanning electron microscopy and nanoindentation were also conducted to reveal the underlying mechanisms affecting macroscopic performance.Due to the superior interface bonding properties between mullite sand and matrix,the compressive strength and flexural toughness of UHPC have been significantly improved.Mullite sand and BCS aggregates have higher stiffness than quartz sand,contributing to the excellent elastic modulus exhibited by UHPC.The stiffness and volume of aggregates have a more significant impact on the elastic modulus of UHPC than interface performance,and the latter contributes more to the strength of UHPC.This study will provide a reference for developing UHPC with superior elastic modulus for structural engineering.展开更多
In this work,poly(3-hexylthiophene)(P3HT)ultrathin films(P3HT-T)were prepared by spin-coating a dilute P3HT solution(in a toluene:o-dichlorobenzene(Tol:ODCB)blend with a volume ratio of 80:20)with ultrasonication and ...In this work,poly(3-hexylthiophene)(P3HT)ultrathin films(P3HT-T)were prepared by spin-coating a dilute P3HT solution(in a toluene:o-dichlorobenzene(Tol:ODCB)blend with a volume ratio of 80:20)with ultrasonication and the addition of the nucleating agent bicycle[2.2.1]heptane-2,3-dicarboxylic acid disodium salt(HPN-68L)on glass,Si wafers and indium tin oxide(ITO)substrates.The electrical and mechanical properties of the P3HT-T ultrathin films were investigated,and it was found that the conductivity and crack onset strain(COS)were simultaneously improved in comparison with those of the corresponding pristine P3HT film(P3HT-0,without ultrasonication and nucleating agent)on the same substrate,regardless of what substrate was used.Moreover,the conductivity of P3HT-T ultrathin films on different substrates was similar(varying from 3.7 S·cm^(-1)to 4.4 S·cm^(-1)),yet the COS increased from 97%to 138%by varying the substrate from a Si wafer to ITO.Combining grazing-incidence wide-angle X-ray diffraction(GIXRD),UV-visible(UV-Vis)spectroscopy and atomic force microscopy(AFM),we found that the solid order and crystallinity of the P3HT-T ultrathin film on the Si wafer are highest,followed by those on glass,and much lower on ITO.Finally,the surface energy and roughness of three substrates were investigated,and it was found that the polar component of the surface energyγp plays a critical role in determining the crystalline microstructures of P3HT ultrathin films on different substrates.Our work indicates that the P3HT ultrathin film can obviously improve the stretchability and simultaneously retain similar electrical performance when a suitable substrate is chosen.These findings offer a new direction for research on stretchable CP ultrathin films to facilitate future practical applications.展开更多
基金National Natural Science Foundation of China(52261032,51861021,51661016)Science and Technology Plan of Gansu Province(21YF5GA074)+2 种基金Public Welfare Project of Zhejiang Natural Science Foundation(LGG22E010008)Wenzhou Basic Public Welfare Scientific Research Project(G2023020)Incubation Program of Excellent Doctoral Dissertation-Lanzhou University of Technology。
文摘The development of high-performance structural and functional materials is vital in many industrial fields.High-and medium-entropy alloys(H/MEAs)with superior comprehensive properties owing to their specific microstructures are promising candidates for structural materials.More importantly,multitudinous efforts have been made to regulate the microstructures and the properties of H/MEAs to further expand their industrial applications.The various heterostructures have enormous potential for the development of H/MEAs with outstanding performance.Herein,multiple heterogeneous structures with single and hierarchical heterogeneities were discussed in detail.Moreover,preparation methods for compositional inhomogeneity,bimodal structures,dualphase structures,lamella/layered structures,harmonic structures(core-shell),multiscale precipitates and heterostructures coupled with specific microstructures in H/MEAs were also systematically reviewed.The deformation mechanisms induced by the different heterostructures were thoroughly discussed to explore the relationship between the heterostructures and the optimized properties of H/MEAs.The contributions of the heterostructures and advanced microstructures to the H/MEAs were comprehensively elucidated to further improve the properties of the alloys.Finally,this review discussed the future challenges of high-performance H/MEAs for industrial applications and provides feasible methods for optimizing heterostructures to enhance the comprehensive properties of H/MEAs.
基金supported by the National Key R&D Plan of China(No.2022YFB3705603)the National Natural Science Foundation of China(No.52101046)+1 种基金the Excellent Youth Overseas Project of National Science and Natural Foundation of China,the Baowu Special Metallurgy Cooperation Limited(No.22H010101336)the Medicine-Engineering Interdisciplinary Project of Shanghai Jiao Tong University(No.YG2022QN076).
文摘Titanium(Ti)and its alloys are frequently utilized as critical components in a variety of engineering ap-plications because of their high specific strength and excellent corrosion resistance.Compared to conven-tional surface strengthening technologies,laser shock peening(LSP)has increasingly attracted attention from researchers and industries,since it significantly improves the surface strength,biocompatibility,fa-tigue resistance,and anti-corrosion ability of Ti and its alloys.Despite numerous studies that have been carried out to elucidate the effects of LSP on microstructural evolution and mechanical properties of Ti and its alloys in recent years,a comprehensive review of recent advancements in the field of Ti and its alloys subjected to LSP is still lacking.In this review,the standard LSP and the novel process designs of LSP assisted by thermal,cryogenic,electropulsing and magnetic fields are discussed and compared.Microstructural evolution,with focuses on the dislocation dynamics,deformation twinning,grain refine-ment and surface amorphization,during LSP processing of Ti alloys is reviewed.Furthermore,the en-hanced engineering performance of the L SP-processed(L SPed)Ti alloys,including surface hardness,wear resistance,fatigue life and corrosion resistance are summarized.Finally,this review concludes by present-ing an overview of the current challenges encountered in this field and offering insights into anticipated future trends.
基金supported by the National Natural Science Foundation of China(Nos.52101328 and 52171277)the National Key Research and Development Program of China(No.2022YFE0109200)+1 种基金the Foundation of the Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(No.2022SZ-TD006)the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(CPSF)(No.GZB20230653)。
文摘The waterproof performance,mechanical properties,chemical composition,microstructure,and pore structure of hydrophobically-modified geopolymer concrete are investigated before and after dry-wet cycles,to determine the long-term feasibility of using hydrophobically-modified geopolymer concrete in wet environments.We use two types of organic modifying agents:polydimethylsiloxane(PDMS)and sodium methyl siliconate(SMS).The experimental results show that incorporating 2%–6%PDMS or 5%–15%SMS can make the concrete hydrophobic,with water absorption and chloride transport rates decreasing by up to 94.3%.We also analyze the bonding modes of organic molecules and geopolymer gels,as well as their evolution mechanisms during dry-wet cycles.PDMS-modified geopolymer concrete is found to exhibit long-term waterproof performance that is not weakened by dry-wet cycles.This is attributed to the robust combination of organic components and the geopolymer gel skeleton formed through phase cross-linking.Meanwhile,PDMS-modified geopolymer concrete’s hydrophobicity,strength,and microstructure are essentially unaffected.In contrast,SMS-modified geopolymer concrete shows higher water sensitivity,although it does maintain efficient waterproof performance.Due to relatively low binding energy,the dry-wet cycles may lead to the detachment of some SMS molecules from the gel network,which results in a decrease of 18.6%in compressive strength and an increase of 37.6%in total porosity.This work confirms the utility of hydrophobically-modified geopolymer concrete as a building material for long-term service in wet environments,for instance,areas with frequent precipitation,or splash and tidal zones.
基金financially supported by the National Natural Science Foundation of China(Grant No.52104333)the Natural Science Foundation of Inner Mongolia(Grant No.2024MS05029)+1 种基金the Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region(Grant No.NJYT24070)the Research Project of Carbon Peak and Carbon Neutrality in Universities of Inner Mongolia Autonomous Region(Grant No.STZX202316).
文摘The effect of high welding heat inputs in the range of 50–200 kJ/cm on the microstructural evolution,MX(M=Ti,Nb and V;X=N and C)precipitation and mechanical properties was investigated in the coarse-grained heat-affected zone(CGHAZ)of a high-Nb(0.10 wt.%)structural steel.The results showed that the primary microconstituents varied from lath bainite(LB)to intragranular acicular ferrite(IAF)+intragranular polygonal ferrite(IPF),and the most content of IAF was acquired at 100 kJ/cm.Moreover,the submicron Ti-and Nb-rich MX precipitates not only pinned prior austenite grain boundaries but also facilitated IAF and IPF nucleation with the Kurdjumov–Sachs orientation relationship of[011]_(MX)//[111]_(Ferrite);the nanoscale V-rich MX precipitates hindered dislocation movement and followed the Baker–Nutting orientation relationship of[001]_(MX)//[001]_(Ferrite)with ferrite matrix,synergistically strengthening and toughening the CGHAZ.In addition,the−20℃impact absorbed energy firstly elevated from 93±5.2 J at 50 kJ/cm to 131±5.4 J at 100 kJ/cm and finally decreased to 59±3.0 J at 200 kJ/cm,being related to the IAF content,while the microhardness decreased from 312±26.1 to 269±12.9 HV0.1,because of the coarsened microstructure and the decreased content of LB and martensite.Compared to the CGHAZ properties with 0.05 wt.%Nb,a higher Nb content produced better low-temperature toughness,as more solid dissolved Nb atoms and precipitated Nb-rich MX particles in austenite limited prior austenite grain growth and promoted IAF formation.Furthermore,the welding process at 100 kJ/cm was most applicable for the high-Nb steel.
基金National Natural Science Foundation of China(62171208)Natural Science Foundation of Gansu Province(23JRRA1355)。
文摘ZrCoRE(RE denotes rare earth elements)non-evaporable getter films have significant applications in vacuum packaging of micro-electro mechanical system devices because of their excellent gas adsorption performance,low activation temperature and environmental friendliness.The films were deposited using DC magnetron sputtering with argon and krypton gases under various deposition pressures.The effects of sputtering gas type and pressure on the morphology and hydrogen adsorption performance of ZrCoRE films were investigated.Results show that the films prepared in Ar exhibit a relatively dense structure with fewer grain boundaries.The increase in Ar pressure results in more grain boundaries and gap structures in the films.In contrast,films deposited in Kr display a higher density of grain boundaries and cluster structures,and the films have an obvious columnar crystal structure,with numerous interfaces and gaps distributed between the columnar structures,providing more paths for gas diffusion.As Kr pressure increases,the film demonstrates more pronounced continuous columnar structure growth,accompanied by deeper and wider grain boundaries.This structural configuration provides a larger specific surface area,which significantly improves the hydrogen adsorption speed and capacity.Consequently,high Ar and Kr pressures are beneficial to improve the adsorption performance.
基金financially supported by JST Mirai Program(No.JPMJMI19A1).
文摘This study investigates the crystal structure,microstructure,electronic,thermal transport properties,and thermoelectric performance ofα-MgAgSb synthesized through various ball milling techniques.Variations in synthesis methods can significantly impact thermoelectric performance.Our findings indicate that impurity phases,particularly the secondary phase Ag_(3)Sb,hinder grain growth and decrease carrier mobility.By systematically adjusting milling conditions,the increased grain size resulting from the suppression of impurity formation improves charge carrier mobility and enhances the power factor.Low-temperature resistivity analysis reveals distinct scattering mechanisms influenced by impurity levels.α-MgAgSb with a tiny content of Sb primarily exhibits electron-electron scattering,whereas higher impurity levels introduce both electron-electron and electron-phonon scattering.Additionally,thermal conductivity analysis using three Effective Medium Theory(EMT)methods shows that the distribution of Ag_(3)Sb increases interfacial resistance.The maximum zT value of 1.36 was achieved in a compound with anα-MgAgSb to Sb ratio of 99%:1%.
基金supported by the National Key R&D Program of China(No.2021YFB3501303)the National Natural Science Foundation of China(No.52122106)+3 种基金the"Pioneer"R&D Program of Zhejiang Province(No.2022C01230)"Leading Goose"R&D Program of Zhejiang Province(No.2022C01110)Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(No.2021SZ-FR005)the Space Application System of China Manned Space Program(No.KJZ-YY-NCL03).
文摘The growing demand for high-efficiency and low-loss energy conversion and transportation techniques urges the development of advanced Fe-Si based soft magnet alloys.Simultaneous achievement of low coercivity(Hc)and large saturation magnetization(Ms)however,remains challenging.In this study,soft magnetic alloys with the composition Fe82-xSi18Cox(x=0 at.%,4 at.%,8 at.%,12 at.%,16 at.%,and 20 at.%)have been designed followed by microstructural tuning.The Co incorporation results in initially decreased Hc followed by increment due to reduced magnetocrystalline anisotropy and increased saturation mag-netostriction from negative to positive values of the alloys.Meanwhile,the Ms raises with subsequent reduction,which origins from competitive mechanisms of increased average moment of Fe atoms and decreased average moment of Co atoms according to first principles calculations.Microstructural evolu-tion during annealing of the Fe70Si18C012 with synergistically optimized Hc and Ms has been revealed that after elevated-temperature annealing,the DO3 phase is predominately transformed from the B2 phase ac-companied by an increase in the degree of ordering.The growth of the DO3 phase deteriorates the Hc due to the aggravating pinning effect on the domain wall movement,which arises from the inhomogeneous magnetization distribution caused by increasing antiphase boundaries.
基金supported by the National Natural Science Foundation of China(Grant Nos.52401202,62203028,52275225).
文摘This research focused on the influences of Cr element doping on the microstructure,thermal stability,microhardness,soft magnetic,and anti-corrosion properties of FeCoNiSiB multi-principal element alloys.The as-received Fe-Co-Ni-Si-B-Cr alloy ribbons made by melt-spinning technique could maintain amorphous nature.The glass-transition temperature and onset crystallization temperature become lower with the addition of Cr,and the highest values are 782.0 K and 821.5 K,respectively.When the Cr content reaches 3at.%,the alloy owns the best soft magnetic performance with the saturation magnetic flux density of~0.578 T and coercivity of~5.5 A·m^(-1)among the studied melt-spun ribbon samples.The microhardness of all alloy ribbons reduces with an increasing Cr content on the whole,and the values are 810 HV_(0.5) or above.The corrosion behavior of these multi-principal element amorphous alloys containing Cr was also investigated in detail.As the Cr content increases,the corrosion resistance becomes superior and the specimens present the obvious passive regions in 3.5wt.%NaCl solution.The glassy ribbons with 8at.%Cr have the highest self-corrosion potential of-0.340 V and pitting potential of 0.288 V as well as the widest passive region of 0.628 V.Besides,the corroded micrographs of alloy ribbons immersed in corrosive environment lasting 100 h are also presented,which further confirms the above-mentioned experimental results.This research deepens the understanding about the role of Cr element in the microstructure and a series of physical and chemical properties of Fe-Co-Ni-Si-B-Cr multi-principal element amorphous alloys.
基金supported by the National Natural Science Foundation of China(No.52071012)Open Research Fund of the National Key Laboratory of Advanced Casting Technologies(No.CAT2023-004)+2 种基金Key Research and Development Program of Shandong Province,China(No.2022JMRH0209)Hebei Province Innovation Capability Enhancement Plan Project,China(No.244A7607D)the Open Foundation of the State Key Laboratory for Advanced Metals and Materials(No.2022-Z01).
文摘A series of as-cast Si_(x)Al_(0.43)CoCrFeNi_(2.1)(x=0,0.1,0.2,and 0.3)high-entropy alloys(HEAs)was successfully fabricated by va-cuum-assisted melting.The phase constituents,microstructural features,and mechanical properties(including hardness,tensile behavior,and wear behavior)of alloys with various Si contents were evaluated.The results revealed that the addition of Si promoted the precipita-tion of a body-centered cubic 1(BCC1)phase enriched in Al,Ni,and Si with a B2-ordered structure.Furthermore,the secondary BCC2 phase was enriched with Cr,Fe,and Si precipitates within the BCC1 matrix.Ultimately,a multiphase face-centered cubic(FCC)/(BCC1/BCC2)structure was formed.The microstructural evolution driven by Si addition significantly enhanced the mechanical properties of the Si_(x)Al_(0.43)CoCrFeNi_(2.1) HEAs.As the Si content increased,the microhardness and tensile strength improved by approxim-ately 42%and 55%,reaching 2.359 GPa and 785 MPa,respectively.The quantitative evaluation of the various strengthening mechanisms indicated that the intrinsic hardness of the FCC matrix and hardening due to BCC1/BCC2 precipitation dominated the overall microhard-ness.The comparison of the energy barriers indicates that BCC2 primarily strengthens the alloy through a shear mechanism rather than an Orowan bypass mechanism.Furthermore,with increasing Si content,reduced friction and wear,together with smoother worn surfaces,re-flect a greatly enhanced wear resistance.After the optimal cold-rolling and 1 h annealing at 800℃,the Si_(0.3)Al_(0.43)CoCrFeNi_(2.1) alloy showed 56%and 62%increases in microhardness and tensile strength,respectively,compared to the as-cast state,reaching 3.68 GPa and 1270 MPa.The enhanced mechanical properties are attributed to the synergistic effects of residual strain hardening by FCC ordering and L1_(2)/BCC precipitation strengthening.
基金supported by the National Natural Science Foundation of China(No.U21B2073)the Science and Technology Project of the Science and Technology Department of Hubei Province,China(No.2022EHB020)。
文摘With the laser remelting of cast alloys combined with non-equilibrium liquidus projection thermodynamic calculations,a high-strength and heat-resistant Al-3Fe-2Mn alloy was designed.Incorporating Mn atoms into the metastable nanoscale Al_(6)Fe phase,occupying some lattice sites,enhances its thermal stability.Additionally,during rapid solidification of laser powder bed fusion(L-PBF),the solubility of Fe and Mn elements in the aluminum alloy increases significantly,forming a supersaturated solid solution with improved strength.This alloy demonstrates excellent processability,achieving a relative density of over 99%,and tensile strengths of 295 MPa at 200℃ and 230 MPa at 300℃.The Al-3Fe-2Mn alloy holds great potential for wide applications due to its high strength at high temperature.
基金supported by the National Key Research and Development Program of China(Nos.2021YFB3503100,2022YFB3505303,2021YFB3501500)the Major Projects in the Inner Mongolia Autonomous Region of China.
文摘In this work,a small amount of Al_(2)O_(3)powders(≤0.3 wt%)were incorporated into the Sm_(2)Co_(17)-type sin-tered magnets,obtaining both high mechanical and magnetic properties.It is found that 0.1%weight percentage of Al_(2)O_(3)doping is enough to enhance the flexural strength by about 20%(∼180 MPa for the case of the c-axis parallel to height).Meanwhile,the(BH)max remains around 219 kJ/m^(3),and Hcj is 2052 kA/m,which is over 95%of that of the original magnets without doping.The promising improvement in flexural strength is mainly attributed to the grain size effective refinement caused by Sm_(2)O_(3)particles including newly-formed ones from the reaction of the Al_(2)O_(3)powder and Sm in the matrix.Furthermore,the grain size of the magnets decreases significantly with increasing of Al_(2)O_(3)doping up to 0.3 wt%.Espe-cially,the grain size of 0.3 wt%Al_(2)O_(3)doped magnets is refined by 37%.However,the flexural strengths(for the c-axis parallel to height and the c-axis parallel to width cases)of the magnets decrease sequen-tially and are even lower than that of the original magnet.The microstructure investigations indicate that the decrease in flexural strength may closely be correlated to the larger cell size and the incomplete cell boundaries phase.The obtained results infer that the flexural strength is susceptible to not only grain size but also the cellular structure of the magnets.
基金the National Natural Science Foundation of China(No.52171026)the Equipment Pre-Research Field Foundation(No.80923010304).
文摘Aluminum alloys that are additively manufactured using the laser powder bed fusion(LPBF)suffer from relatively poor high cycle fatigue(HCF)resistance.In an effort to alleviate this,a high-strength Al alloy,Al-Mn-Mg-Sc-Zr,with columnar,equiaxed,and bi-modal microstructures was produced by varying the scanning velocity and the substrate temperature during the LPBF process.The tensile strength of LPBF Al-Mn-Mg-Sc-Zr alloy is 475±5–516±6 MPa with favorable elongation of approximately 11%,higher than that of most of the other Al alloys,including conventional high-strength rolled/ECAP Al alloys and AM Al-Mg-Sc-Zr alloys.Specimens with bimodal microstructure and specimens with fully equiaxed microstructure both show a fatigue strength of 230 MPa(at 107 loading cycles),which is the highest among those reported for the LPBF Al alloys.The deformation synergy in the bimodal microstructure also improves the fatigue resistance in the strain-controlled low cycle fatigue(LCF)regime.The equiaxed microstructure restricts the to-and-fro dislocation motion during cyclic loading,which,in turn,minimizes the strain localization.At the later stages of strain accumulation,microcracks form at the grain boundaries,limiting the further improvement of the alloy's fatigue strength.This study demonstrates microstructural tailoring through AM enables improvement of the fatigue resistance of aluminum alloys.
基金Project supported by the National Natural Science Foundation of China(51974092,U21A2043)Guangdong Basic and Applied Basic Research Foundation(2020A1515110136,2020B1515120065,2022B1515120066)Dongguan Science and Technology Special Agent Project(20221800500212)。
文摘The effect of rare earth addition on the microstructure and mechanical performances of as-cast and wrought Al alloys has been attracting increasing attention recently.Rare earth addition has great potential in modifying the structure and improving the properties of materials.However,there are currently few reports about the effect of rare earth addition on the microstructure and performances of Al alloys prepared via selective laser melting.Here,AlSi10Mg alloys were manufactured using selective laser melting,and the effect of Er addition was investigated.The results indicate that Er addition leads toα-Al refinement and modifies the minority Si phase.The formation of the Al_(3)Er phase induced by Er addition enhances the stren gth of the material.Modification of the Si phase also increases ductility.This strategy can help improve the mechanical performance of alum inum alloys prepared via selective laser melting.
基金supported by the National Natural Science Foundation of China Projects under Grant(Nos.52071220,U21A2049,51871211,51701129,and 51971054)China Postdoctoral Science Foundation(No.2023M733572)+7 种基金Liaoning Province’s project of“Revitalizing Liaoning Talents”(No.XLYC1907062)the Doctor Startup Fund of Natural Science Foundation Program of Liaoning Province(No.2019-BS-200)High level achievement construction project of Shenyang Ligong University(No.SYLUXM202105)Liaoning BaiQianWan Talents Program,the Domain Foundation of Equipment Advance Research of 13th Five-year Plan(No.61409220118)National Key Research and Development Program of China under Grant(Nos.2017YFB0702001 and 2016YFB0301105)the Innovation Fund of Institute of Metal Research(IMR),Chinese Academy of Sciences(CAS),the National Basic Research Program of China(973 Program)project under Grant No.2013CB632205the Fundamental Research Fund for the Central Universities under Grant(No.N2009006)Bintech-IMR R&D Program(No.GYY-JSBU-2022–009).
文摘The microstructure and mechanical performance of the unidirectionally and cross-directionally rolled Mg-8Li-6Zn-1Y(in wt.%)sheets have been investigated and compared.It reveals that after the unidirectional rolling(UR),the broken I-phase particles are aggregated at theα-Mg/β-Li phase interfaces.However,the cross-rolling(CR)process can not only severely break the bulk I-phase,but also cause the obviously uniform distribution of I-phase particles in the matrix phases.Moreover,the average grain size of the CR samples is 3.61μm and about 50%that of the UR samples.The maximum texture intensities ofα-Mg andβ-Li phases in the CR samples are slightly stronger than those in the UR samples.Tensile results demonstrate that the CR process can effectively enhance the tensile properties and remarkably reduce the mechanical anisotropy of the alloy.For the UR samples,the yield strength,ultimate tensile strength,and elongation ratio along the rolling direction(RD)are 164 MPa,198 MPa,and 16.4%,whereas those along the transverse direction(TD)are 157 MPa,185 MPa,and 22.0%,respectively.For the CR samples,their mechanical properties are basically the same and the mechanical anisotropy is almost eliminated.The yield strength,ultimate tensile strength,and elongation ratio along the cross-rolling direction 1(CRD1)and 2(CRD2)are respectively measured to be 181 MPa and 182 MPa,220 MPa and 218 MPa,20.6%and 20.7%.Failure analysis indicates that for the UR samples being tensile tested along the RD and TD,microcracks are preferentially initiated in the region of aggregated I-phase particles.For the CR samples being tensile tested along both two cross-rolling directions,the initiation of micro-cracks mainly occurs at the I-phase/matrix phase interfaces and in the interior of matrix phases.
基金National Natural Science Foundation of China (Grant No.42177133)Primary R&D Plan of Jiangsu Province (Grant No.BE2022830)Primary R&D Plan of Anhui Province (Grant No.2023t07020018).
文摘Soil-bentonite(SB)backfills in vertical cutoff walls are used extensively to contain contaminated groundwater.Previous studies show that the hydraulic conductivity of backfill can exceed the typically recommended maximum value(k=1×10^(−9) m/s)if exposed to groundwater impacted by organic acids commonly released from uncontrolled landfills and municipal solid waste dumps.Polymer amended backfills exhibit excellent chemical compatibility to metal-laden groundwater.However,few studies to date have explored the effect of organic acid contaminated groundwater on hydraulic performance of polymer amended backfills.This study presents an experimental investigation on the hydraulic performance and microstructural properties of a composite polymer amended backfill used to contain flow of acetic acid-laden groundwater.A series of laboratory experiments were performed to evaluate free-swell indices of the composite polymer amended bentonites,liquid limits of the composite polymer amended and unamended bentonites,and slump heights and hydraulic conductivity(k)values of the amended backfills to acetic acid solutions with varying concentrations.The results were compared with those of the unamended bentonites and unamended backfills reported in a previous study.The results showed that the free-swell index and liquid limit of the amended bentonites were higher than those of the unamended bentonites.Permeation with acetic acid solutions with concentrations ranging from 40 mmol/L to 320 mmol/L conducted on the amended backfill only resulted in an increase in k of less than a factor of about 10 related to that based on permeation with tap water(4.41×10^(−11)-1.68×10^(−10) m/s to acetic acid solution versus 1.65×10^(−11) m/s to tap water).Mechanisms contributing to enhanced chemical compatibility of amended backfill were ascertained based on scanning electron microscopy,mercury intrusion porosimetry,and zeta potential analyses.
基金Funded by the National Natural Science Foundation of China (No. 51905506)。
文摘Oxide ceramic coatings were fabricated on tantalum alloys by micro-arc oxidation (MAO) to improve their hardness and tribological properties. The MAO coatings were manufactured in a mixed silicatephosphate electrolyte containing NaF and/or EDTA (ethylene diamine tetraacetic acid). The surface morphology,cross-sectional view, chemical composition, hardness, and wear performance of the coatings were analysed. As revealed by the scanning electron microscopy, silica-rich nodules appear on the MAO coating obtained in the silicate-phosphate electrolyte, but the formation of nodules is inhibited with NaF and/or EDTA in the electrolyte.Also, they reduce the roughness and improve the compactness of the coatings, which are composed of Ta_(2)O_(5),(Ta, O), and TaO. A thick and hard coating is obtained in the NaF-containing electrolyte, and the tribology performance is effectively improved. With additives, the nodule structure is detached from the coating surface and dissolved in the electrolyte. By using NaF as an electrolyte additive, the abrasion performance of the MAO coating is enhanced by decreasing the nodule structure, increasing the size of micropores, and improving the coating hardness.
基金Zhiyu Xiao acknowledges the financial support from the National Natural Science Foundation of China(No.52274363)the Guangdong Basic Applied Basic Research Foundation,China(No.2022A1515010558)+2 种基金Chaofeng Gao acknowledges the financial support by the Guangdong Basic Applied Basic Research Founda-tion,China(No.2022A1515011597)J.T.Zhang acknowledges the financial support by the Guangdong Basic Applied Basic Research Foundation,China(No.2022A1515240065)the Natural Science Foundation Project of Guangzhou,China(No.202201010526).
文摘In this work,a high-strength crack-free TiN/Al-Mn-Mg-Sc-Zr composite was fabricated by laser powder bed fusion(L-PBF).A large amount of uniformly distributed L1_(2)-Al_(3)(Ti,Sc,Zr)nanoparticles were formed during the L-PBF process due to the partial melting and decomposition of TiN nanoparticles under a high temperature.These L1_(2)-Al_(3)(Ti,Sc,Zr)nanoparticles exhibited a highly coherent lattice relationship with the Al matrix.All the prepared TiN/Al-Mn-Mg-Sc-Zr composite samples exhibit ultrafine grain mi-crostructure.In addition,the as-built composite containing 1.5 wt%TiN shows an excellent tensile prop-erty with a yield strength of over 580 MPa and an elongation of over 8%,which were much higher than those of wrought 7xxx alloys.The effects of various strengthening mechanisms were quantitatively estimated and the high strength of the alloy was mainly attributed to the refined microstructure,solid solution strengthening,and precipitation strengthening contributed by L1_(2)-Al_(3)(Ti,Sc,Zr)nanoparticles.
基金supported by the National Natural Science Funds of China(No.52175290 and No.51975090).
文摘A series of Zn-xAl(x=0-35 wt.%)alloy filler metals were designed to join AZ31 Mg alloy to 6061 Al alloy by laser-TIG hybrid welding.The effect of Al content on the wettability of filler metals,microstructure evolution and strength of joint was investigated.The results indicated that the strength of joints was improved with the increase of Al content in filler metals.When Zn-15Al filler was used,the ultimate fracture load reached the maximum of 1475.3 N/cm,which was increased by 28%than that with pure Zn filler.The reason is that the Al element acts as a"reaction depressant"in filler metal,which contributes to inhibiting the dissolution of Mg base metal and the Mg-Zn reaction.The addition of appropriate quantity of Al element promoted the precipitation of Al-rich solid solution instead of Zn solid solution.The MgZn_(2) IMCs have lower lattice mismatch with Al solid solution than Zn solid solution,thus the strength of joints is improved.However,the excessive addition of Al caused the formation of brittle Mg32(Al,Zn)49 ternary compounds,leading to the deterioration of joint performance.
基金Funed by the National Natural Science Foundation of China(No.U21A20149)the Ecological Environment Scientific Research Project of Anhui Province(No.2023hb0014)+2 种基金the Research Reserve of Anhui Jianzhu University(No.2022XMK01)the Excellent Scientific Research and Innovation Team in Colleges and Universities of Anhui Province(No.2022AH010017)Research on the preparation technology of self compacting concrete with strength grade C100.
文摘We developed ultra-high performance concrete(UHPC)incorporating mullite sand and brown corundum sand(BCS),and the quartz sand UHPC was utilized to prepare for comparison.The properties of compressive strength,elastic modulus,ultrasonic pulse velocity,flexural strength,and toughness were investigated.Scanning electron microscopy and nanoindentation were also conducted to reveal the underlying mechanisms affecting macroscopic performance.Due to the superior interface bonding properties between mullite sand and matrix,the compressive strength and flexural toughness of UHPC have been significantly improved.Mullite sand and BCS aggregates have higher stiffness than quartz sand,contributing to the excellent elastic modulus exhibited by UHPC.The stiffness and volume of aggregates have a more significant impact on the elastic modulus of UHPC than interface performance,and the latter contributes more to the strength of UHPC.This study will provide a reference for developing UHPC with superior elastic modulus for structural engineering.
基金supported by the National Natural Science Foundation of China(No.21975029)。
文摘In this work,poly(3-hexylthiophene)(P3HT)ultrathin films(P3HT-T)were prepared by spin-coating a dilute P3HT solution(in a toluene:o-dichlorobenzene(Tol:ODCB)blend with a volume ratio of 80:20)with ultrasonication and the addition of the nucleating agent bicycle[2.2.1]heptane-2,3-dicarboxylic acid disodium salt(HPN-68L)on glass,Si wafers and indium tin oxide(ITO)substrates.The electrical and mechanical properties of the P3HT-T ultrathin films were investigated,and it was found that the conductivity and crack onset strain(COS)were simultaneously improved in comparison with those of the corresponding pristine P3HT film(P3HT-0,without ultrasonication and nucleating agent)on the same substrate,regardless of what substrate was used.Moreover,the conductivity of P3HT-T ultrathin films on different substrates was similar(varying from 3.7 S·cm^(-1)to 4.4 S·cm^(-1)),yet the COS increased from 97%to 138%by varying the substrate from a Si wafer to ITO.Combining grazing-incidence wide-angle X-ray diffraction(GIXRD),UV-visible(UV-Vis)spectroscopy and atomic force microscopy(AFM),we found that the solid order and crystallinity of the P3HT-T ultrathin film on the Si wafer are highest,followed by those on glass,and much lower on ITO.Finally,the surface energy and roughness of three substrates were investigated,and it was found that the polar component of the surface energyγp plays a critical role in determining the crystalline microstructures of P3HT ultrathin films on different substrates.Our work indicates that the P3HT ultrathin film can obviously improve the stretchability and simultaneously retain similar electrical performance when a suitable substrate is chosen.These findings offer a new direction for research on stretchable CP ultrathin films to facilitate future practical applications.
