Metals and alloys,including stainless steel,titanium and its alloys,cobalt alloys,and other metals and alloys have been widely used clinically as implant materials,but implant-related infection or inflammation is stil...Metals and alloys,including stainless steel,titanium and its alloys,cobalt alloys,and other metals and alloys have been widely used clinically as implant materials,but implant-related infection or inflammation is still one of the main causes of implantation failure.The bacterial infection or inflammation that seriously threatens human health has already become a worldwide complaint.Antibacterial metals and alloys recently have attracted wide attention for their long-term stable antibacterial ability,good mechanical properties and good biocompatibility in vitro and in vivo.In this review,common antibacterial alloying elements,antibacterial standards and testing methods were introduced.Recent developments in the design and manufacturing of antibacterial metal alloys containing various antibacterial agents were described in detail,including antibacterial stainless steel,antibacterial titanium alloy,antibacterial zinc and alloy,antibacterial magnesium and alloy,antibacterial cobalt alloy,and other antibacterial metals and alloys.Researches on the antibacterial properties,mechanical properties,corrosion resistance and biocompatibility of antibacterial metals and alloys have been summarized in detail for the first time.It is hoped that this review could help researchers understand the development of antibacterial alloys in a timely manner,thereby could promote the development of antibacterial metal alloys and the clinical application.展开更多
As compared to permanent orthopedic implants for load-bearing applications, biodegradable orthopedic implants have the advantage of no need for removing after healing, but they suffer from the ＂trilemma＂ problem of ...As compared to permanent orthopedic implants for load-bearing applications, biodegradable orthopedic implants have the advantage of no need for removing after healing, but they suffer from the ＂trilemma＂ problem of compromising among sufficiently high mechanical properties, good biocompatibility and proper degradation rate conforming to the growth rate of new bones. In the present work, in vitro and in vivo studies of a Zn-0.05 wt%Mg alloy（namely, Zn-0.05 Mg alloy） were conducted with pure Zn as a control. The Zn-0.05 Mg alloy is composed of a small amount of Mg2 Zn11 phase embedded in the refined Zn matrix with an average grain size of ～20 μm. The addition of 0.05 wt% Mg into Zn significantly increases the ultimate tensile strength up to 225 MPa and the elongation to fracture to 26%, but has little influence on the in vitro degradation rate. Both Zn and Zn-0.05 Mg alloy exhibit homogeneous in vitro degradation with a rate of about 0.15 mm/year. Based on the cytotoxicity evaluation, Zn and Zn-0.05 Mg alloy do not induce toxicity to L-929 cells, indicating that they have little toxicity to the general functions of the animal. An in vivo biocompatibility study of Zn and Zn-0.05 Mg alloy samples by placing them in a rabbit model for 4.12 and 24 weeks, respectively did not show any inflammatory cells, and demonstrated that new bone tissue formed at the bone/implant interface, suggesting that Zn and Zn-0.05 Mg alloy promote the formation of new bone tissue. The in vivo degradation of Zn and Zn-0.05 Mg alloy does not bring harm to the important organs and their cell structures. More interestingly, Zn and Zn-0.05 Mg alloy exhibit strong antibacterial activity against Escherichia coli and Staphylococcus aureus. The above results clearly demonstrate that the Zn-0.05 Mg alloy could be a potential biodegradable orthopedic implant material.展开更多
To expand the application of wire-arc additive manufacturing(WAAM)in aluminum alloy forming com-ponents,it is vitally important to reduce the porosity,refine microstructure,and thereby improve the mechanical propertie...To expand the application of wire-arc additive manufacturing(WAAM)in aluminum alloy forming com-ponents,it is vitally important to reduce the porosity,refine microstructure,and thereby improve the mechanical properties of the components.In this study,the interlayer friction stir processing(FSP)tech-nique was employed to assist the WAAM of 4043 Al-Si alloy,and the related effects on the microstruc-ture evolutions and mechanical properties of the fabricated builds were systematacially investigated.As compared to the conventional WAAM processing of Al-Si alloy,it was found that the introduction of in-terlayer FSP can effectively eliminate the pores,and both theα-Al dendrites and Si-rich eutectic network were severely broken up,leading to a remarkable enhancement in ductility and fatigue performance.The average yield strength(YS)and ultimate tensile strength(UTS)of the Al-based components produced by the combination of WAAM and interlayer FSP methods were 88 and 148 MPa,respectively.Meanwhile,the elongation(EL)of 37.5%and 28.8%can be achieved in the horizontal and vertical directions,respec-tively.Such anisotropy of EL was attributed to the inhomogeneous microstructure in the stir zone(SZ).Notably,the stress concentration can be effectively reduced by the elimination of porosity and Si-rich eu-tectic network fragmentation by the interlayer FSP,and thus the fatigue behavior was improved with the fatigue strength and elongation increased by∼28%and∼108.7%,respectively.It is anticipated that this study will provide a powerful strategy and theoretical guidance for the WAAM fabrication of Al-based alloy components with high ductility and fatigue performance.展开更多
This work reported the effect of extrusion speeds on the microstructures and mechanical properties of Mg-Ca binary alloy.The results showed that yield strength of the as-extruded Mg-1.2wt.%Ca alloys decrease from∼360...This work reported the effect of extrusion speeds on the microstructures and mechanical properties of Mg-Ca binary alloy.The results showed that yield strength of the as-extruded Mg-1.2wt.%Ca alloys decrease from∼360MPa to∼258MPa as the ram speed increases from 0.4mm/s to 2.4 mm/s,and the elongation increases from∼3.9%to∼12.2%.The microstructure changes from bimodal grain feature to the complete dynamical recrystallization(DRX)with increase of the extrusion speed.The ultrafine DRXed grains in size of∼0.85μm,the numerous nano-Mg_(2)Ca particles dispersing along the grain boundaries and interiors,as well as the high density of residual dislocations,should account for the high strength.It is believed that the high degree of dynamic recrystallization and the resulting texture randomization play the critical roles in the ductility enhancement of the high-speed extruded Mg alloys.展开更多
Previous study has shown that Ti-3Cu alloy shows good antibacterial properties(>90%antibacterial rate),but the mechanical properties still need to be improved.In this paper,a series of heat-treatment processes were...Previous study has shown that Ti-3Cu alloy shows good antibacterial properties(>90%antibacterial rate),but the mechanical properties still need to be improved.In this paper,a series of heat-treatment processes were selected to adjust the microstructure in order to optimize the properties of Ti-3Cu alloy.Microstructure,mechanical properties,biocorrosion properties and antibacterial properties of wrought Ti-3Cu alloy at different conditions was systematically investigated by X-ray diffraction,optical microscope,scanning electron microscope,transmission electron microscopy,electrochemical measurements,tensile test,fatigue test and antibacterial test.Heat treatment could significantly improve the mechanical properties,corrosion resistance and antibacterial rate due to the redistribution of copper elements and precipitation of Ti2Cu phase.Solid solution treatment increased the yield strength from 400 to 740MPa and improved the antibacterial rate from 33%to 65.2%while aging treatment enhanced the yield strength to 800e850MPa and antibacterial rate(>91.32%).It was demonstrated that homogeneous distribution and fine Ti2Cu phase plays a very important role in mechanical properties,corrosion resistance and antibacterial properties.展开更多
Antibacterial Ti-5Cu alloy is a promising substitute material for Ti-made cardiovascular implants,so its surface engineering is crucial to expediting clinical implementation.Given the antibacterial and cardiovas-cular...Antibacterial Ti-5Cu alloy is a promising substitute material for Ti-made cardiovascular implants,so its surface engineering is crucial to expediting clinical implementation.Given the antibacterial and cardiovas-cular biological benefits of Cu^(2+)and titanium-nitride-oxide(TiN x O y)coatings,a Cu_(2)O/CuO-TiN x O y coating with upregulated Cu^(2+)release was successfully deposited on Ti-5Cu alloy for the first time using oxygen and nitrogen plasma-based surface modification.The superhydrophilic and nanostructured Cu_(2)O/CuO-TiN x O y coating had a dense structure and was well bonded to the substrate,resulting in enhanced cor-rosion resistance,while CuO/Cu_(2)O in the coating released Cu^(2+)faster than Ti_(2)Cu phase in the matrix.More gratifying,the coating demonstrated perfect antibacterial properties(R>99.9%against S.aureus),owing primarily to direct contact sterilization of Cu_(2)O/CuO.The most encouraging phenomenon was that the coating dramatically accelerated HUVEC adhesion(1.4 times),proliferation(RGR:106%-116%),and particularly migration(RMR:158%-247%)compared with the control Ti.The coating extract also signifi-cantly stimulated in vitro angiogenesis capacity.The rapid endothelialization for Cu_(2)O/CuO-TiN x O y coating was attributed to the surface nanostructure and Cu^(2+)/NO_(2)−release,which upregulated the angiogenesis-related gene expression of HIF-1α,VEGF,and eNOS to increase VEGF secretion and NO production.All of the findings indicated that the Cu_(2)O/CuO-TiN x O y coating could enhance the corrosion resistance,an-tibacterial properties,and endothelialization potential of Ti-Cu alloy,displaying great clinical potential in cardiovascular applications.展开更多
Precipitation habits plays a decisive role in strengthening materials,especially for Mg alloys the non-basal plane precipitation is necessary but very limited.Generally,the precipitates would nucleate and grow up in a...Precipitation habits plays a decisive role in strengthening materials,especially for Mg alloys the non-basal plane precipitation is necessary but very limited.Generally,the precipitates would nucleate and grow up in a specific habit plane owing to the constraint of free-energy minimization of the system.Herein,in an aged ultralight Mg-Li-Zn alloy,we confirmed that the precipitates dominated by C15 Laves structure could form in a variety of habit planes,to generate three forms of strengthening-phases,i.e.,precipitate-rod,precipitate-lath,and precipitate-plate.Among which,the precipitate-plates are on basal plane as usually but precipitate-rods/laths are on non-basal plane,and such non-basal precipitates would transform into the basal(Mg,Li)Zn_(2)Laves structure with prolonged aging.These findings are interesting to understand the precipitation behaviors of multi-domain Laves structures in hexagonal close-packed crystals,and expected to provide a guidance for designing ultralight high-strength Mg-Li based alloys via precipitation hardening on the non-basal planes.展开更多
High-entropy alloys(HEAs)provide an ideal platform for developing highly active electrocatalysts and investigating the synergy of mixed elements.Far-from-equilibrium synthesis holds great potential for fabricating HEA...High-entropy alloys(HEAs)provide an ideal platform for developing highly active electrocatalysts and investigating the synergy of mixed elements.Far-from-equilibrium synthesis holds great potential for fabricating HEAs at the nanoscale by rapidly shifting the thermodynamic conditions and manipulat-ing the growth kinetics.While far-from-equilibrium synthesis of nanomaterials has been successful un-der thermochemical conditions,it is markedly challenging under electrochemical environments,as the use of an electrolyte limits the accessible temperature window and the temporal tunability of tem-perature.Herein,we demonstrate that applying a large electrochemical overpotential would create a far-from-equilibrium condition as changing the temperature of the system by considering the equation △G=△H−T△S+nF△ψ.An electrochemical far-from-equilibrium approach is thus setup for construct-ing hierarchical and self-supporting high-entropy alloy nanostructures.The large overpotential drives the simultaneous reduction of multiple cations and the subsequent formation of a single-phase alloy.As a proof-of-concept,hierarchical Fe_(0.22)Co_(0.18)Ni_(0.18)Cr_(0.14)Cu_(0.28)was fabricated and used as an electrocatalyst for the hydrogen evolution reaction in alkaline media.The noble-metal-free HEA exhibits an overpoten-tial of 84 mV at a current density of 10 mA cm^(-2),which is among the lowest even compared to noble metal-based electrocatalysts.This work opens a new avenue for building a variety of HEAs for energy and catalysis applications.展开更多
A novel low-cost Mg-Al-Ca-Zn-Mn-based alloy was developed to simultaneously improve its strength and ductility.The high yield strength of 411 MPa and the high elongation to failure of~8.9%have been achieved in the as-...A novel low-cost Mg-Al-Ca-Zn-Mn-based alloy was developed to simultaneously improve its strength and ductility.The high yield strength of 411 MPa and the high elongation to failure of~8.9%have been achieved in the as-extruded Mg-1.3Al-1.2Ca-0.5Zn-0.6Mn(wt%)sample.Microstructure characterizations showed that the high strength is mainly associated with the ultra-fined dynamically recrystallized(DRXed)grains.Moreover,high-density dislocations in the un-DRXed region and nano-precipitates are distributed among theα-Mg matrix.The high ductility property can be ascribed to the high volume fraction of DRXed grains with a much randomized texture,as well as the formations of high-density subgrains in the un-DRXed grain regions.展开更多
In this work,the microstructure and mechanical properties of large cross-sectioned Mg-9Gd-3Y-1.2Zn-0.5Zr(VWZ931)samples produced by the small extrusion ratio has been investigated.The as-extruded VWZ931 sample with di...In this work,the microstructure and mechanical properties of large cross-sectioned Mg-9Gd-3Y-1.2Zn-0.5Zr(VWZ931)samples produced by the small extrusion ratio has been investigated.The as-extruded VWZ931 sample with diameter of~30 mm can exhibit the high yield strength(YS)of 339 MPa,ultimate tensile strength(UTS)of 387 MPa and elongation of 8.2%,respectively.After peak-aged,the YS and UTS of the Mg samples were significantly increased to 435 MPa and 467 MPa.The small extrusion ratio leads to the low fraction of dynamic recrystallized(DRX)grains in VWZ931 sample,and the texture hardening effect can be fully utilized to achieve high strength.The combined effect of precipitation strengthening due to the long-period stacking ordered phases and theβ′phase,grain boundary strengthening due to the fine DRX grains,heterogeneous deformation-induced strengthening caused by bimodal microstructure,can together contribute to the high strength of present Mg alloy.The findings can shed light on designing other large-sized Mg wrought alloys with high mechanical performance.展开更多
β-type titanium alloys have attracted much attention as implant materials because of their low elastic modulus and high strength,which is closer to human bones and can avoid the problem of stress fielding and extend ...β-type titanium alloys have attracted much attention as implant materials because of their low elastic modulus and high strength,which is closer to human bones and can avoid the problem of stress fielding and extend the lifetime of prosthetics.However,other issues,such as the infection or inflammation postimplantation,still trouble the titanium alloy's clinical application.In this paper,we developed a novel nearβ-titanium alloy(Ti-13Nb-13Zr-13Ag,TNZA)with low elastic modulus and strong antibacterial ability by the addition of Ag element followed by proper microstructure controlling,which could reduce the stress shielding and bacterial infections simultaneously.The microstructure,mechanical properties,corrosion resistance,antibacterial properties and cell toxicity were studied using SEM,electrochemical testing,mechanical test and cell tests.The results have demonstrated that TNZA alloy exhibited an elastic modulus of 75-87 GPa and a strong antibacterial ability(up to 98%reduction)and good biocompatibility.Moreover,it was also shown that this alloy's corrosion resistance was better than that of Ti-13Nb-13Zr.All the results suggested that Ti-13Nb-13Zr-13Ag might be a competitive biomedical titanium alloy.展开更多
This work demonstrates a two-step method to produce oxide-derived Cu nanowires on Cu mesh surface to offer a monolithic catalyst that outstandingly improves the hydrogen production from reforming formaldehyde and wate...This work demonstrates a two-step method to produce oxide-derived Cu nanowires on Cu mesh surface to offer a monolithic catalyst that outstandingly improves the hydrogen production from reforming formaldehyde and water under ambient conditions.Our results not only reveal that the special oxidederived nanostructure can significantly improve the formaldehyde reforming performance of Cu,but also display that the hydrogen production has a linear relationship with oxygen pressure.Specially,a maximum of 36 times increment in hydrogen generation rate is observed than that without oxygen during the reaction.Density functional theory calculations show that the formaldehyde molecule is adsorbed on Cu surface only when the adsorbed oxygen is in adjacency,and hydrogen release process is the ratedetermining step.This work highlights that the activity of deliberately synthesized catalyst can further be promoted by dynamic chemical modulation of surface states during working.展开更多
Segregation of solutes/impurities in the interfaces plays a decisive role in material performances.However,the segregation of solutes/impurities remains elusive due to the diversity of interfacial structures.Here,in a...Segregation of solutes/impurities in the interfaces plays a decisive role in material performances.However,the segregation of solutes/impurities remains elusive due to the diversity of interfacial structures.Here,in a Mg-Nd-Mn ternary model system,two ordered novel two-dimensional(2D)interfacial superstructures formed by periodic segregation of solute atoms in special symmetric and asymmetric tilt grain boundaries(GBs)have been systematically investigated.Z-Contrast high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)observations provided the atomic-level details on how solute atoms were arranged on these special partially coherent tilt GBs.The strained conditions of each atomic site at the tilt GBs were accurately reproduced by molecular dynamics(MD)simulations plus Voronoi analysis,and the rationality of solute segregation in each atomic-site was evaluated carefully based on the first-principles calculations.These findings expand our knowledge of solute/impurity segregation behaviors in the interfaces,especially the co-segregation behaviors in multi-component materials.展开更多
Low absolute strength becomes one major obstacle for the wider applications of low/no rare-earth(RE) containing Mg alloys. This review firstly demonstrates the importance of grain refinement in improving strength of M...Low absolute strength becomes one major obstacle for the wider applications of low/no rare-earth(RE) containing Mg alloys. This review firstly demonstrates the importance of grain refinement in improving strength of Mg alloys by comprehensively comparing with other strategy, e.g., precipitation strengthening. Dynamic recrystallization(DRX) plays a crucial role in refining grain size of Mg wrought alloys.Therefore, secondly, the DRX models, grain nucleation mechanisms and the related grain refinement abilities in Mg alloys are summarized,including phase boundary, twin boundary and general boundary induced recrystallization. Thirdly, the newly developed low-RE containing Mg alloy, e.g., Mg-Ce, Mg-Nd and Mg-Sm based alloys, and the RE-free Mg alloys, e.g., Mg-Al, Mg-Zn, Mg-Sn and Mg-Ca based alloy,are reviewed, with the focus on enhancing the mechanical properties mainly via the grain refinement strategy. At the last section, the perspectives and outstanding issues concerning high-performance Mg wrought alloys are also proposed. This review is meant to promote the deep understanding on the critical role of grain refinement in Mg alloys and provide reference for the development of other high strength and low-cost Mg alloys which are fabricated by the conventional extrusion/rolling processing.展开更多
Radial forging(RF)is an economical manufacturing forging process,in which four dies arranged radially around the workpiece simultaneously act on the workpiece with high-frequency radial movement.In this study,a ZK60 m...Radial forging(RF)is an economical manufacturing forging process,in which four dies arranged radially around the workpiece simultaneously act on the workpiece with high-frequency radial movement.In this study,a ZK60 magnesium alloy step-shaft bar was processed under different accumulated strains by RF at350℃.The deformation behavior,microstructure evolution,and mechanical responses of this bar were systematically investigated via numerical simulations and experiments.At the early deformation stage of forging,the material undergoes pronounced grain refinement but an inhomogeneous grain structure is formed due to the strain gradient along the radial direction.The grains in different radial parts were gradually refined by increasing the RF pass,resulting in a bimodal grained structure comprising coarse(~14.1μm)and fine(~2.3μm)grains.With the RF pass increased,the initial micro-sizeβ-phases were gradually crushed and dissolved into the matrix mostly,eventually evolving to form a higher area fraction of nano-sized Zn2 Zr spheroidal particles uniformly distributed through the grain interior.The texture changed as the RF strain increased,with the c-axes of most of the deformed grains rotating in the RD.Additionally,excellent mechanical properties including higher values of tensile strengths and ductility were attained after the three RFed passes,compared to the as-received sample.展开更多
The martensite transformation of Co-29Cr-6Mo-xCu(Co-xCu,x=0,1.5,2,4,wt%)alloys was investigated in order to explore ductile Co-based alloy without Ni for biomedical application.The effect of Cu on martensite transform...The martensite transformation of Co-29Cr-6Mo-xCu(Co-xCu,x=0,1.5,2,4,wt%)alloys was investigated in order to explore ductile Co-based alloy without Ni for biomedical application.The effect of Cu on martensite transformation of Co-29 Cr-6 Mo alloy was investigated using scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-Ray diffraction(XRD)and electron backscatter diffraction(EBSD)analysis.EBSD results revealed that the fraction ofγ-phase was increasing with increasing of copper content.In detail,the fraction ofγ-phase of aged Co-1.5 Cu alloy was 4.72%and noγ-phase was found in aged Co-0Cu alloy.Furthermore,the fraction ofγ-phase of aged Co-2Cu alloy and Co-4Cu alloy was 51.68%and 46.17%,respectively.This demonstrated that the minimum Cu content which could inhibit martensite transformation in this alloy system was 2 wt%.Calculated phase diagram revealed that increasing the copper content of this alloy system could enlargeγ-phase zone,which means Cu could inhibit the formation ofγ-phase and consequently stabilizeγ-phase.Randomly distributed Cu-rich phase was identified in aged Co-4Cu alloy.The possible reason for the inhibition of martensite transformation by Cu addition is that alloying with Cu atom might decrease charge accumulations and increase atomic bonds,which increase the stacking fault energy ultimately.展开更多
Room-temperature electrocatalytic nitrogen reduction reaction(NRR)is of paramount significance for the fertilizer industry and fundamental catalysis science.However,many NRR catalysts were based on the use of metals.H...Room-temperature electrocatalytic nitrogen reduction reaction(NRR)is of paramount significance for the fertilizer industry and fundamental catalysis science.However,many NRR catalysts were based on the use of metals.Herein,we focus on exploring boron-based,metal-free,efficient catalysts for NRR by den-sity functional theory calculations with van der Waals corrections(DFT+D3).Our results show that the NRR performance of the boron active site can be improved by tuning the N-coordination environment in a graphene sheet,and the B-N-C structures show excellent stability.By considering the correlation be-tween the Bader charges of the boron dopant over N-decorated graphene and their NRR activities,the ra-tional design principle of a boron-based catalyst for NRR is developed.The boron-site with one pyridinic nitrogen in a double-vacancy structure is found to be a highly active center,with low reaction energy(0.53 eV)and kinetic barrier(0.84 eV)through the distal mechanism.We also found that the charge loss of boron considerably hampers hydrogen adsorption,which in turn promotes the NRR efficiency by hin-dering the competing hydrogen evolution.This work offers new insights into developing low-cost,highly effective boron-based materials as promising electrocatalysts for green ammonia synthesis.展开更多
In order to optimize the deformation processing, the hot deformation behavior of Co-Cr-Mo-Cu （here- after named as Co-Cu） alloy was studied in this paper at a deformation temperature range of 950-1150 ℃ and a strai...In order to optimize the deformation processing, the hot deformation behavior of Co-Cr-Mo-Cu （here- after named as Co-Cu） alloy was studied in this paper at a deformation temperature range of 950-1150 ℃ and a strain rate range of 0.008-5 s^-1. Based on the true stress-true strain curves, a constitutive equation in hyperbolic sin function was established and a hot processing map was drawn. It was found that the flow stress of the Co-Cu alloy increased with the increase of the strain rate and decreased with the increase of the deforming temperature. The hot processing map indicated that there were two unstable regions and one well-processing region. The microstructure, the hardness distribution and the electro- chemical properties of the hot deformed sample were investigated in order to reveal the influence of the hot deformation. Microstructure observation indicated that the grain size increased with the increase of the deformation temperature but decreased with the increase of the strain rate. High temperature and low strain rate promoted the crystallization process but increased the grain size, which results in a reduction in the hardness. The hot deformation at high temperature （1100-1150 ℃） would reduce the corrosion resistance slightly. The final optimized deformation process was： a deformation temperature from 1050to 1100 ℃, and a strain rate from 0.008 to 0.2 s^-1, where a completely recrystallized and homogeneously distributed microstructure would be obtained.展开更多
The interface between metal nanoparticles(NPs)and support plays a vital role in catalysis because both electron and atom exchanges occur across the metal-support interface.However,the rational design of interfacial st...The interface between metal nanoparticles(NPs)and support plays a vital role in catalysis because both electron and atom exchanges occur across the metal-support interface.However,the rational design of interfacial structure facilitating the charge transfer between the neighboring parts remains a challenge.Herein,a guided nucleation strategy based on redox reaction between noble metal precursor and supportsurface is introduced to construct epitaxial interfaces between Pt NPs and CeO2 support.The Pt/CeO2 catalyst exhibits near room temperature catalytic activity for CO oxidation that is benefited from the well-defined interface structure facilitating charge transfer from CeO2 support to Pt NPs.Meanwhile,this general approach based on support-surface-induced-nucleation was successfully extended to synthesize Pd and Cu nanocatalysts on CeO2,demonstrating its universal and feasible characteristics.This work is an important step towards developing highly active supported metal catalysts by engineering their interfaces.展开更多
基金support from National Natural Science Foundation of China(no.31971253/C1002).
文摘Metals and alloys,including stainless steel,titanium and its alloys,cobalt alloys,and other metals and alloys have been widely used clinically as implant materials,but implant-related infection or inflammation is still one of the main causes of implantation failure.The bacterial infection or inflammation that seriously threatens human health has already become a worldwide complaint.Antibacterial metals and alloys recently have attracted wide attention for their long-term stable antibacterial ability,good mechanical properties and good biocompatibility in vitro and in vivo.In this review,common antibacterial alloying elements,antibacterial standards and testing methods were introduced.Recent developments in the design and manufacturing of antibacterial metal alloys containing various antibacterial agents were described in detail,including antibacterial stainless steel,antibacterial titanium alloy,antibacterial zinc and alloy,antibacterial magnesium and alloy,antibacterial cobalt alloy,and other antibacterial metals and alloys.Researches on the antibacterial properties,mechanical properties,corrosion resistance and biocompatibility of antibacterial metals and alloys have been summarized in detail for the first time.It is hoped that this review could help researchers understand the development of antibacterial alloys in a timely manner,thereby could promote the development of antibacterial metal alloys and the clinical application.
基金financially supported by the National Natural Science Foundation of China (Nos. 51525101 and 81271995)Fundamental Research Funds for the Central Universities (No. N141008001)
文摘As compared to permanent orthopedic implants for load-bearing applications, biodegradable orthopedic implants have the advantage of no need for removing after healing, but they suffer from the ＂trilemma＂ problem of compromising among sufficiently high mechanical properties, good biocompatibility and proper degradation rate conforming to the growth rate of new bones. In the present work, in vitro and in vivo studies of a Zn-0.05 wt%Mg alloy（namely, Zn-0.05 Mg alloy） were conducted with pure Zn as a control. The Zn-0.05 Mg alloy is composed of a small amount of Mg2 Zn11 phase embedded in the refined Zn matrix with an average grain size of ～20 μm. The addition of 0.05 wt% Mg into Zn significantly increases the ultimate tensile strength up to 225 MPa and the elongation to fracture to 26%, but has little influence on the in vitro degradation rate. Both Zn and Zn-0.05 Mg alloy exhibit homogeneous in vitro degradation with a rate of about 0.15 mm/year. Based on the cytotoxicity evaluation, Zn and Zn-0.05 Mg alloy do not induce toxicity to L-929 cells, indicating that they have little toxicity to the general functions of the animal. An in vivo biocompatibility study of Zn and Zn-0.05 Mg alloy samples by placing them in a rabbit model for 4.12 and 24 weeks, respectively did not show any inflammatory cells, and demonstrated that new bone tissue formed at the bone/implant interface, suggesting that Zn and Zn-0.05 Mg alloy promote the formation of new bone tissue. The in vivo degradation of Zn and Zn-0.05 Mg alloy does not bring harm to the important organs and their cell structures. More interestingly, Zn and Zn-0.05 Mg alloy exhibit strong antibacterial activity against Escherichia coli and Staphylococcus aureus. The above results clearly demonstrate that the Zn-0.05 Mg alloy could be a potential biodegradable orthopedic implant material.
文摘To expand the application of wire-arc additive manufacturing(WAAM)in aluminum alloy forming com-ponents,it is vitally important to reduce the porosity,refine microstructure,and thereby improve the mechanical properties of the components.In this study,the interlayer friction stir processing(FSP)tech-nique was employed to assist the WAAM of 4043 Al-Si alloy,and the related effects on the microstruc-ture evolutions and mechanical properties of the fabricated builds were systematacially investigated.As compared to the conventional WAAM processing of Al-Si alloy,it was found that the introduction of in-terlayer FSP can effectively eliminate the pores,and both theα-Al dendrites and Si-rich eutectic network were severely broken up,leading to a remarkable enhancement in ductility and fatigue performance.The average yield strength(YS)and ultimate tensile strength(UTS)of the Al-based components produced by the combination of WAAM and interlayer FSP methods were 88 and 148 MPa,respectively.Meanwhile,the elongation(EL)of 37.5%and 28.8%can be achieved in the horizontal and vertical directions,respec-tively.Such anisotropy of EL was attributed to the inhomogeneous microstructure in the stir zone(SZ).Notably,the stress concentration can be effectively reduced by the elimination of porosity and Si-rich eu-tectic network fragmentation by the interlayer FSP,and thus the fatigue behavior was improved with the fatigue strength and elongation increased by∼28%and∼108.7%,respectively.It is anticipated that this study will provide a powerful strategy and theoretical guidance for the WAAM fabrication of Al-based alloy components with high ductility and fatigue performance.
基金This work is supported by National Natural Science Foundation of China(Nos.51525101,U1610253,51701211,and 51971053)funded by the Project of Promoting Talents in Liaoning province(No.XLYC1808038)+2 种基金H.C.Pan acknowledges the financial assistance from the State Key Laboratory of Solidification Processing in NPU(No.SKLSP201920)the Fundamental Research Funds for the Central Universities(No.N2002011)joint R&D fund of Liaoning-Shenyang National Research Center for Materials Science(No.2019JH3/30100040).
文摘This work reported the effect of extrusion speeds on the microstructures and mechanical properties of Mg-Ca binary alloy.The results showed that yield strength of the as-extruded Mg-1.2wt.%Ca alloys decrease from∼360MPa to∼258MPa as the ram speed increases from 0.4mm/s to 2.4 mm/s,and the elongation increases from∼3.9%to∼12.2%.The microstructure changes from bimodal grain feature to the complete dynamical recrystallization(DRX)with increase of the extrusion speed.The ultrafine DRXed grains in size of∼0.85μm,the numerous nano-Mg_(2)Ca particles dispersing along the grain boundaries and interiors,as well as the high density of residual dislocations,should account for the high strength.It is believed that the high degree of dynamic recrystallization and the resulting texture randomization play the critical roles in the ductility enhancement of the high-speed extruded Mg alloys.
基金support from National Natural Science Foundation(no.81071262,no.31271024)Funding from North University of China(985 program,N141008001,LZ2014018).
文摘Previous study has shown that Ti-3Cu alloy shows good antibacterial properties(>90%antibacterial rate),but the mechanical properties still need to be improved.In this paper,a series of heat-treatment processes were selected to adjust the microstructure in order to optimize the properties of Ti-3Cu alloy.Microstructure,mechanical properties,biocorrosion properties and antibacterial properties of wrought Ti-3Cu alloy at different conditions was systematically investigated by X-ray diffraction,optical microscope,scanning electron microscope,transmission electron microscopy,electrochemical measurements,tensile test,fatigue test and antibacterial test.Heat treatment could significantly improve the mechanical properties,corrosion resistance and antibacterial rate due to the redistribution of copper elements and precipitation of Ti2Cu phase.Solid solution treatment increased the yield strength from 400 to 740MPa and improved the antibacterial rate from 33%to 65.2%while aging treatment enhanced the yield strength to 800e850MPa and antibacterial rate(>91.32%).It was demonstrated that homogeneous distribution and fine Ti2Cu phase plays a very important role in mechanical properties,corrosion resistance and antibacterial properties.
基金supported by the National Key R&D Program of China(No.2022YFB3804400)and(No.2022YFE0122800)Research Program(No.62602010113)+1 种基金Na-tional Natural Science Foundation of China(No.31971253/C1002)Beijing Municipal Health Commission(Nos.BMHC-2021-6,BMHC-2019-9,PXM 2020_026275_000002).
文摘Antibacterial Ti-5Cu alloy is a promising substitute material for Ti-made cardiovascular implants,so its surface engineering is crucial to expediting clinical implementation.Given the antibacterial and cardiovas-cular biological benefits of Cu^(2+)and titanium-nitride-oxide(TiN x O y)coatings,a Cu_(2)O/CuO-TiN x O y coating with upregulated Cu^(2+)release was successfully deposited on Ti-5Cu alloy for the first time using oxygen and nitrogen plasma-based surface modification.The superhydrophilic and nanostructured Cu_(2)O/CuO-TiN x O y coating had a dense structure and was well bonded to the substrate,resulting in enhanced cor-rosion resistance,while CuO/Cu_(2)O in the coating released Cu^(2+)faster than Ti_(2)Cu phase in the matrix.More gratifying,the coating demonstrated perfect antibacterial properties(R>99.9%against S.aureus),owing primarily to direct contact sterilization of Cu_(2)O/CuO.The most encouraging phenomenon was that the coating dramatically accelerated HUVEC adhesion(1.4 times),proliferation(RGR:106%-116%),and particularly migration(RMR:158%-247%)compared with the control Ti.The coating extract also signifi-cantly stimulated in vitro angiogenesis capacity.The rapid endothelialization for Cu_(2)O/CuO-TiN x O y coating was attributed to the surface nanostructure and Cu^(2+)/NO_(2)−release,which upregulated the angiogenesis-related gene expression of HIF-1α,VEGF,and eNOS to increase VEGF secretion and NO production.All of the findings indicated that the Cu_(2)O/CuO-TiN x O y coating could enhance the corrosion resistance,an-tibacterial properties,and endothelialization potential of Ti-Cu alloy,displaying great clinical potential in cardiovascular applications.
基金the National Natural Science Foundation of China(Grant No.51525101,No.51971053,No.52101129)the Project of Promoting Talents in Liaoning Province(No.XLYC1808038)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.N2002018)the Project funded by China Postdoctoral Science Foundation(2020M670774)。
文摘Precipitation habits plays a decisive role in strengthening materials,especially for Mg alloys the non-basal plane precipitation is necessary but very limited.Generally,the precipitates would nucleate and grow up in a specific habit plane owing to the constraint of free-energy minimization of the system.Herein,in an aged ultralight Mg-Li-Zn alloy,we confirmed that the precipitates dominated by C15 Laves structure could form in a variety of habit planes,to generate three forms of strengthening-phases,i.e.,precipitate-rod,precipitate-lath,and precipitate-plate.Among which,the precipitate-plates are on basal plane as usually but precipitate-rods/laths are on non-basal plane,and such non-basal precipitates would transform into the basal(Mg,Li)Zn_(2)Laves structure with prolonged aging.These findings are interesting to understand the precipitation behaviors of multi-domain Laves structures in hexagonal close-packed crystals,and expected to provide a guidance for designing ultralight high-strength Mg-Li based alloys via precipitation hardening on the non-basal planes.
基金This work is supported by the China BaoWu Low Carbon Metallurgical Innovation Foundation-BWLCF202113The authors acknowledge the National Science Foundation of China(Nos.51971059,21903058,22173066,and 22103054)+1 种基金the Fundamen-tal Research Funds for the Central Universities(No.N2202012).T.C.thanks the support from Suzhou Key Laboratory of Functional Nano&Soft Materials,the Collaborative Innovation Center of Suzhou Nano Science&Technology,the Priority Academic Program Devel-opment of Jiangsu Higher Education Institutions(PAPD)the 111 Project.
文摘High-entropy alloys(HEAs)provide an ideal platform for developing highly active electrocatalysts and investigating the synergy of mixed elements.Far-from-equilibrium synthesis holds great potential for fabricating HEAs at the nanoscale by rapidly shifting the thermodynamic conditions and manipulat-ing the growth kinetics.While far-from-equilibrium synthesis of nanomaterials has been successful un-der thermochemical conditions,it is markedly challenging under electrochemical environments,as the use of an electrolyte limits the accessible temperature window and the temporal tunability of tem-perature.Herein,we demonstrate that applying a large electrochemical overpotential would create a far-from-equilibrium condition as changing the temperature of the system by considering the equation △G=△H−T△S+nF△ψ.An electrochemical far-from-equilibrium approach is thus setup for construct-ing hierarchical and self-supporting high-entropy alloy nanostructures.The large overpotential drives the simultaneous reduction of multiple cations and the subsequent formation of a single-phase alloy.As a proof-of-concept,hierarchical Fe_(0.22)Co_(0.18)Ni_(0.18)Cr_(0.14)Cu_(0.28)was fabricated and used as an electrocatalyst for the hydrogen evolution reaction in alkaline media.The noble-metal-free HEA exhibits an overpoten-tial of 84 mV at a current density of 10 mA cm^(-2),which is among the lowest even compared to noble metal-based electrocatalysts.This work opens a new avenue for building a variety of HEAs for energy and catalysis applications.
基金supported by National Key Research and Development Program of China (No. 2021 YFB3701000)the National Natural Science Foundation of China (Nos. U2167213 and 51971053)+1 种基金the Young Elite Scientists Sponsorship Program by China Association for Science and Technology (Nos. 2019-2021QNRC001, 20192021QNRC002, and 2019-2021QNRC003)and the Fundamental Research Funds for the Central Universities (No. N2202020)
文摘A novel low-cost Mg-Al-Ca-Zn-Mn-based alloy was developed to simultaneously improve its strength and ductility.The high yield strength of 411 MPa and the high elongation to failure of~8.9%have been achieved in the as-extruded Mg-1.3Al-1.2Ca-0.5Zn-0.6Mn(wt%)sample.Microstructure characterizations showed that the high strength is mainly associated with the ultra-fined dynamically recrystallized(DRXed)grains.Moreover,high-density dislocations in the un-DRXed region and nano-precipitates are distributed among theα-Mg matrix.The high ductility property can be ascribed to the high volume fraction of DRXed grains with a much randomized texture,as well as the formations of high-density subgrains in the un-DRXed grain regions.
基金supported by the National Key Research and Development Program of China(No.2021YFB3701000)the National Natural Science Foundation of China(Nos.U2167213,51971053)+1 种基金H.C.Pan acknowledges the financial assistance from the Young Elite Scientists Sponsorship Program by China Association for Science and Technology(2019-2021QNRC001-003)the fund from the Fundamental Research Funds for the Central Universities(N2202020).
文摘In this work,the microstructure and mechanical properties of large cross-sectioned Mg-9Gd-3Y-1.2Zn-0.5Zr(VWZ931)samples produced by the small extrusion ratio has been investigated.The as-extruded VWZ931 sample with diameter of~30 mm can exhibit the high yield strength(YS)of 339 MPa,ultimate tensile strength(UTS)of 387 MPa and elongation of 8.2%,respectively.After peak-aged,the YS and UTS of the Mg samples were significantly increased to 435 MPa and 467 MPa.The small extrusion ratio leads to the low fraction of dynamic recrystallized(DRX)grains in VWZ931 sample,and the texture hardening effect can be fully utilized to achieve high strength.The combined effect of precipitation strengthening due to the long-period stacking ordered phases and theβ′phase,grain boundary strengthening due to the fine DRX grains,heterogeneous deformation-induced strengthening caused by bimodal microstructure,can together contribute to the high strength of present Mg alloy.The findings can shed light on designing other large-sized Mg wrought alloys with high mechanical performance.
基金The authors would like to acknowledge the financial support from the National Natural Science Foundation of China(Nos.31971253)the Beijing Municipal Health Commission(Nos.BMHC-2019-9,BMHC-2018-4 and PXM2020_026275_000002)。
文摘β-type titanium alloys have attracted much attention as implant materials because of their low elastic modulus and high strength,which is closer to human bones and can avoid the problem of stress fielding and extend the lifetime of prosthetics.However,other issues,such as the infection or inflammation postimplantation,still trouble the titanium alloy's clinical application.In this paper,we developed a novel nearβ-titanium alloy(Ti-13Nb-13Zr-13Ag,TNZA)with low elastic modulus and strong antibacterial ability by the addition of Ag element followed by proper microstructure controlling,which could reduce the stress shielding and bacterial infections simultaneously.The microstructure,mechanical properties,corrosion resistance,antibacterial properties and cell toxicity were studied using SEM,electrochemical testing,mechanical test and cell tests.The results have demonstrated that TNZA alloy exhibited an elastic modulus of 75-87 GPa and a strong antibacterial ability(up to 98%reduction)and good biocompatibility.Moreover,it was also shown that this alloy's corrosion resistance was better than that of Ti-13Nb-13Zr.All the results suggested that Ti-13Nb-13Zr-13Ag might be a competitive biomedical titanium alloy.
基金supported by the China Bao Wu Low Carbon Metallurgical Innovation Foundation(No.BWLCF202113)the Fundamental Research Funds for the Central Universities(Nos.N2202012,N180206004)the National Natural Science Foundation of China(No.51971059)。
文摘This work demonstrates a two-step method to produce oxide-derived Cu nanowires on Cu mesh surface to offer a monolithic catalyst that outstandingly improves the hydrogen production from reforming formaldehyde and water under ambient conditions.Our results not only reveal that the special oxidederived nanostructure can significantly improve the formaldehyde reforming performance of Cu,but also display that the hydrogen production has a linear relationship with oxygen pressure.Specially,a maximum of 36 times increment in hydrogen generation rate is observed than that without oxygen during the reaction.Density functional theory calculations show that the formaldehyde molecule is adsorbed on Cu surface only when the adsorbed oxygen is in adjacency,and hydrogen release process is the ratedetermining step.This work highlights that the activity of deliberately synthesized catalyst can further be promoted by dynamic chemical modulation of surface states during working.
基金financially supported by the National Key Research and Development Program of China(No.2021YFB3701002)the National Natural Science Foundation of China(No.52101129)the Fundamental Research Funds for the Central Universities(Nos.N2202013 and N2007011).
文摘Segregation of solutes/impurities in the interfaces plays a decisive role in material performances.However,the segregation of solutes/impurities remains elusive due to the diversity of interfacial structures.Here,in a Mg-Nd-Mn ternary model system,two ordered novel two-dimensional(2D)interfacial superstructures formed by periodic segregation of solute atoms in special symmetric and asymmetric tilt grain boundaries(GBs)have been systematically investigated.Z-Contrast high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)observations provided the atomic-level details on how solute atoms were arranged on these special partially coherent tilt GBs.The strained conditions of each atomic site at the tilt GBs were accurately reproduced by molecular dynamics(MD)simulations plus Voronoi analysis,and the rationality of solute segregation in each atomic-site was evaluated carefully based on the first-principles calculations.These findings expand our knowledge of solute/impurity segregation behaviors in the interfaces,especially the co-segregation behaviors in multi-component materials.
基金supported by National Key Research and Development Program of China (No.2023YFB3710900)National Natural Science Foundation of China (Nos.U2241235,U2167213,51971053)+2 种基金funded by the Project of Promoting Talents in Liaoning province (No.XLYC2203202)the financial assistance from Young Elite Scientists Sponsorship Program by CAST (2019-2021QNRC001,2019-2021QNRC002,2019-2021QNRC003)the fund from the Fundamental Research Funds for the Central Universities (N2202020)。
文摘Low absolute strength becomes one major obstacle for the wider applications of low/no rare-earth(RE) containing Mg alloys. This review firstly demonstrates the importance of grain refinement in improving strength of Mg alloys by comprehensively comparing with other strategy, e.g., precipitation strengthening. Dynamic recrystallization(DRX) plays a crucial role in refining grain size of Mg wrought alloys.Therefore, secondly, the DRX models, grain nucleation mechanisms and the related grain refinement abilities in Mg alloys are summarized,including phase boundary, twin boundary and general boundary induced recrystallization. Thirdly, the newly developed low-RE containing Mg alloy, e.g., Mg-Ce, Mg-Nd and Mg-Sm based alloys, and the RE-free Mg alloys, e.g., Mg-Al, Mg-Zn, Mg-Sn and Mg-Ca based alloy,are reviewed, with the focus on enhancing the mechanical properties mainly via the grain refinement strategy. At the last section, the perspectives and outstanding issues concerning high-performance Mg wrought alloys are also proposed. This review is meant to promote the deep understanding on the critical role of grain refinement in Mg alloys and provide reference for the development of other high strength and low-cost Mg alloys which are fabricated by the conventional extrusion/rolling processing.
基金the financial support of the National Natural Science Foundation of China(Nos.U1910213 and U1610253)the Key Research and Development Program of Shanxi Province(Nos.201603D111004,201803D121026 and 201903D121088)+1 种基金the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(No.2019L0614)the Taiyuan University of Science and Technology Scientific Research Initial Funding(TYUST SRIF)(No.20192002)。
文摘Radial forging(RF)is an economical manufacturing forging process,in which four dies arranged radially around the workpiece simultaneously act on the workpiece with high-frequency radial movement.In this study,a ZK60 magnesium alloy step-shaft bar was processed under different accumulated strains by RF at350℃.The deformation behavior,microstructure evolution,and mechanical responses of this bar were systematically investigated via numerical simulations and experiments.At the early deformation stage of forging,the material undergoes pronounced grain refinement but an inhomogeneous grain structure is formed due to the strain gradient along the radial direction.The grains in different radial parts were gradually refined by increasing the RF pass,resulting in a bimodal grained structure comprising coarse(~14.1μm)and fine(~2.3μm)grains.With the RF pass increased,the initial micro-sizeβ-phases were gradually crushed and dissolved into the matrix mostly,eventually evolving to form a higher area fraction of nano-sized Zn2 Zr spheroidal particles uniformly distributed through the grain interior.The texture changed as the RF strain increased,with the c-axes of most of the deformed grains rotating in the RD.Additionally,excellent mechanical properties including higher values of tensile strengths and ductility were attained after the three RFed passes,compared to the as-received sample.
基金financial support from National Natural Science Foundation(No.31271024 and No.31470930)。
文摘The martensite transformation of Co-29Cr-6Mo-xCu(Co-xCu,x=0,1.5,2,4,wt%)alloys was investigated in order to explore ductile Co-based alloy without Ni for biomedical application.The effect of Cu on martensite transformation of Co-29 Cr-6 Mo alloy was investigated using scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-Ray diffraction(XRD)and electron backscatter diffraction(EBSD)analysis.EBSD results revealed that the fraction ofγ-phase was increasing with increasing of copper content.In detail,the fraction ofγ-phase of aged Co-1.5 Cu alloy was 4.72%and noγ-phase was found in aged Co-0Cu alloy.Furthermore,the fraction ofγ-phase of aged Co-2Cu alloy and Co-4Cu alloy was 51.68%and 46.17%,respectively.This demonstrated that the minimum Cu content which could inhibit martensite transformation in this alloy system was 2 wt%.Calculated phase diagram revealed that increasing the copper content of this alloy system could enlargeγ-phase zone,which means Cu could inhibit the formation ofγ-phase and consequently stabilizeγ-phase.Randomly distributed Cu-rich phase was identified in aged Co-4Cu alloy.The possible reason for the inhibition of martensite transformation by Cu addition is that alloying with Cu atom might decrease charge accumulations and increase atomic bonds,which increase the stacking fault energy ultimately.
基金H.L.acknowledges the Center for Computational Materials Sci-ence,Institute for Materials Research,Tohoku University for the use of MASAMUNE-IMR(No.202212-SCKXX-0204)the In-stitute for Solid State Physics(ISSP)at the University of Tokyo for the use of their supercomputers+2 种基金the China BaoWu Low Carbon Metallurgical Innovation Foundation(No.BWLCF202113)the Fundamental Research Funds for the Cen-tral Universities(No.N2202012),JSPS KAKENHI(No.JP23K13703)the Iwatani Naoji Foundation.The authors thank the Beijing PARATERA Tech Co.,Ltd.for providing HPC resources.
文摘Room-temperature electrocatalytic nitrogen reduction reaction(NRR)is of paramount significance for the fertilizer industry and fundamental catalysis science.However,many NRR catalysts were based on the use of metals.Herein,we focus on exploring boron-based,metal-free,efficient catalysts for NRR by den-sity functional theory calculations with van der Waals corrections(DFT+D3).Our results show that the NRR performance of the boron active site can be improved by tuning the N-coordination environment in a graphene sheet,and the B-N-C structures show excellent stability.By considering the correlation be-tween the Bader charges of the boron dopant over N-decorated graphene and their NRR activities,the ra-tional design principle of a boron-based catalyst for NRR is developed.The boron-site with one pyridinic nitrogen in a double-vacancy structure is found to be a highly active center,with low reaction energy(0.53 eV)and kinetic barrier(0.84 eV)through the distal mechanism.We also found that the charge loss of boron considerably hampers hydrogen adsorption,which in turn promotes the NRR efficiency by hin-dering the competing hydrogen evolution.This work offers new insights into developing low-cost,highly effective boron-based materials as promising electrocatalysts for green ammonia synthesis.
基金financially supported by the National Natural Science Foundation of China (Nos. 81071262, 31271024 and 31470930)the Funding from Northeastern University ("985 program", Nos. N141008001 and LZ2014018), China
文摘In order to optimize the deformation processing, the hot deformation behavior of Co-Cr-Mo-Cu （here- after named as Co-Cu） alloy was studied in this paper at a deformation temperature range of 950-1150 ℃ and a strain rate range of 0.008-5 s^-1. Based on the true stress-true strain curves, a constitutive equation in hyperbolic sin function was established and a hot processing map was drawn. It was found that the flow stress of the Co-Cu alloy increased with the increase of the strain rate and decreased with the increase of the deforming temperature. The hot processing map indicated that there were two unstable regions and one well-processing region. The microstructure, the hardness distribution and the electro- chemical properties of the hot deformed sample were investigated in order to reveal the influence of the hot deformation. Microstructure observation indicated that the grain size increased with the increase of the deformation temperature but decreased with the increase of the strain rate. High temperature and low strain rate promoted the crystallization process but increased the grain size, which results in a reduction in the hardness. The hot deformation at high temperature （1100-1150 ℃） would reduce the corrosion resistance slightly. The final optimized deformation process was： a deformation temperature from 1050to 1100 ℃, and a strain rate from 0.008 to 0.2 s^-1, where a completely recrystallized and homogeneously distributed microstructure would be obtained.
基金supported by the National Natural Science Foundation of China(Nos.51771047,51525101,U1602275,51601119)the Fundamental Research Funds for the Central Universities(N180204014)+1 种基金the Key Lab for ATM of Northeastern University(China)the Natural Science Foundation of Shenzhen University(No.2019006).
文摘The interface between metal nanoparticles(NPs)and support plays a vital role in catalysis because both electron and atom exchanges occur across the metal-support interface.However,the rational design of interfacial structure facilitating the charge transfer between the neighboring parts remains a challenge.Herein,a guided nucleation strategy based on redox reaction between noble metal precursor and supportsurface is introduced to construct epitaxial interfaces between Pt NPs and CeO2 support.The Pt/CeO2 catalyst exhibits near room temperature catalytic activity for CO oxidation that is benefited from the well-defined interface structure facilitating charge transfer from CeO2 support to Pt NPs.Meanwhile,this general approach based on support-surface-induced-nucleation was successfully extended to synthesize Pd and Cu nanocatalysts on CeO2,demonstrating its universal and feasible characteristics.This work is an important step towards developing highly active supported metal catalysts by engineering their interfaces.
