Metallic alloys with high strength and large ductility are required for extreme structural applications.However,the achievement of ultrahigh strength often results in a substantially decreased ductility.Here,we report...Metallic alloys with high strength and large ductility are required for extreme structural applications.However,the achievement of ultrahigh strength often results in a substantially decreased ductility.Here,we report a strategy to achieve the strength-ductility synergy by tailoring the alloy composition to control the local stacking fault energy(SFE)of the face-centered-cubic(fcc)matrix in an L1_(2)-strengthened superlattice alloy.As a proof of concept,based on the thermodynamic calculations,we developed a non-equiatomic CoCrNi_(2)(Al_(0.2)Nb_(0.2))alloy using phase separation to create a near-equiatomic low SFE disordered CoCrNi medium-entropy alloy matrix with in situ formed high-content coherent Ni_(3)(Al,Nb)-type ordered nanoprecipitates(∼12 nm).The alloy achieves a high tensile strength up to 1.6 GPa and a uniform ductility of 33%.The low SFE of the fcc matrix promotes the formation of nanotwins and parallel microbands during plastic deformation which could remarkably enhance the strain hardening capacity.This work provides a strategy for developing ultrahigh-strength alloys with large uniform ductility.展开更多
The biocompatible metallic implants with strong osteointegration often lack the ability of anti-infection.The biocompatible niobium(Nb)containing the antibacterial copper(Cu),the obtained Nb-Cu alloy,could be a potent...The biocompatible metallic implants with strong osteointegration often lack the ability of anti-infection.The biocompatible niobium(Nb)containing the antibacterial copper(Cu),the obtained Nb-Cu alloy,could be a potential candidate to solve this issue.To test this hypothesis,ultrafine-grained Nb-Cu immiscible alloys were fabricated via mechanical alloying and spark plasma sintering.The aim of this study was to investigate the microstructure,mechanical properties,magnetic susceptibility,corrosion behavior,ion release,and the bactericidal activity,biocompatibility and osteogenic potential of the Nb-Cu alloys in vitro and their osteogenesis and osteointegration ability in vivo with a comparison with pure Nb.The rat cranial defect model and the bone screws insertion in rabbit femoral bone were used to evaluate the osteogenesis and osteointegration ability,respectively.The results showed that after the addition of 3 wt.%of Cu,the compressive strength was significantly improved from 1.57 GPa to 2.21 GPa and the magnetic susceptibility slightly decreased.The Nb-3 wt.%Cu(Nb-3Cu)alloy exhibited higher corrosion resistance than pure Nb in Hank’s solution and strong bactericidal activity against both E.coli and S.aureus.In vitro,the Nb-3Cu alloy showed comparable biocompatibility with pure Nb.The addition of 3 wt.%Cu also significantly enhanced the expression of osteogenesis-related genes(RUNX2,ALP,COLA1 and OCN)of pre-osteoblasts.In vivo,the Nb-3Cu alloy promoted bone regeneration at the defect sites and showed enhanced osteointegration after 12 weeks of implantation.Such a good combination of high mechanical strength and corrosion resistance,strong antibacterial activity and improved osteogenesis and osseointegration ability enables the present Nb-3Cu alloy a promising candidate for heavy load-bearing hard tissue repair.展开更多
Refractory metal niobium(Nb) incorporated with a small amount of silver(Ag),the resulting Nb-Ag twophase alloys,were fabricated by mechanical alloying and spark plasma sintering.The microstructure,mechanical propertie...Refractory metal niobium(Nb) incorporated with a small amount of silver(Ag),the resulting Nb-Ag twophase alloys,were fabricated by mechanical alloying and spark plasma sintering.The microstructure,mechanical properties,wear resistance,corrosion behavior,in vitro and in vivo antibacterial properties and biocompatibility of the Nb-Ag alloys were systematically investigated.The results show that the mechanical properties,wear resistance,corrosion resistance and antibacterial ability were significantly enhanced after addition of 5 at.% Ag.The fabricated Nb-5 at.% Ag alloy demonstrates high yield strength of up to ~1486 MPa and fracture strain of ~35 %.The precipitated Ag particles could reduce friction and wear.The enhanced corrosion resistance was attributed to the higher relative density of the sintered alloys and the formation of a stable and dense passive film of niobium and silver oxides.In vitro and in vivo evaluations show that the Nb-5 at.% Ag alloy also has strong antibacterial activity and good biocompatibility and osteointegration ability.These results demonstrate great potential of the nanostructured Nb-Ag alloys for dental and orthopedic implants.展开更多
基金The authors also thank the Microscope and Imaging Center at Southern University of Science and Technology,China.This work was financially supported by the National Natural Science Foundation of China(52122102)Guangdong Innovative&Entrepreneurial Research Team Program(2016ZT06C279)APT research was conducted at the Inter-University 3D APT Unit of City University of Hong Kong(CityU),which is supported by the CityU grant(9360161).
文摘Metallic alloys with high strength and large ductility are required for extreme structural applications.However,the achievement of ultrahigh strength often results in a substantially decreased ductility.Here,we report a strategy to achieve the strength-ductility synergy by tailoring the alloy composition to control the local stacking fault energy(SFE)of the face-centered-cubic(fcc)matrix in an L1_(2)-strengthened superlattice alloy.As a proof of concept,based on the thermodynamic calculations,we developed a non-equiatomic CoCrNi_(2)(Al_(0.2)Nb_(0.2))alloy using phase separation to create a near-equiatomic low SFE disordered CoCrNi medium-entropy alloy matrix with in situ formed high-content coherent Ni_(3)(Al,Nb)-type ordered nanoprecipitates(∼12 nm).The alloy achieves a high tensile strength up to 1.6 GPa and a uniform ductility of 33%.The low SFE of the fcc matrix promotes the formation of nanotwins and parallel microbands during plastic deformation which could remarkably enhance the strain hardening capacity.This work provides a strategy for developing ultrahigh-strength alloys with large uniform ductility.
基金the National Natural Science Foundation of China(No.52122102)the Natural Science Foundation of Guangdong(No.2019A1515011755)the Shenzhen Fundamental Research Project(No.JCYJ20190809153205492)。
文摘The biocompatible metallic implants with strong osteointegration often lack the ability of anti-infection.The biocompatible niobium(Nb)containing the antibacterial copper(Cu),the obtained Nb-Cu alloy,could be a potential candidate to solve this issue.To test this hypothesis,ultrafine-grained Nb-Cu immiscible alloys were fabricated via mechanical alloying and spark plasma sintering.The aim of this study was to investigate the microstructure,mechanical properties,magnetic susceptibility,corrosion behavior,ion release,and the bactericidal activity,biocompatibility and osteogenic potential of the Nb-Cu alloys in vitro and their osteogenesis and osteointegration ability in vivo with a comparison with pure Nb.The rat cranial defect model and the bone screws insertion in rabbit femoral bone were used to evaluate the osteogenesis and osteointegration ability,respectively.The results showed that after the addition of 3 wt.%of Cu,the compressive strength was significantly improved from 1.57 GPa to 2.21 GPa and the magnetic susceptibility slightly decreased.The Nb-3 wt.%Cu(Nb-3Cu)alloy exhibited higher corrosion resistance than pure Nb in Hank’s solution and strong bactericidal activity against both E.coli and S.aureus.In vitro,the Nb-3Cu alloy showed comparable biocompatibility with pure Nb.The addition of 3 wt.%Cu also significantly enhanced the expression of osteogenesis-related genes(RUNX2,ALP,COLA1 and OCN)of pre-osteoblasts.In vivo,the Nb-3Cu alloy promoted bone regeneration at the defect sites and showed enhanced osteointegration after 12 weeks of implantation.Such a good combination of high mechanical strength and corrosion resistance,strong antibacterial activity and improved osteogenesis and osseointegration ability enables the present Nb-3Cu alloy a promising candidate for heavy load-bearing hard tissue repair.
基金financially supported by the Natural Science Foundation of Guangdong(Grant No.2019A1515011755)the Fundamental Research Program of Shenzhen(Grant Nos.JCYJ20170412153039309 and JCYJ20170307110418960)the Natural Science Foundation of Tianjin(General Program,No.18JCYBJC19500),China。
文摘Refractory metal niobium(Nb) incorporated with a small amount of silver(Ag),the resulting Nb-Ag twophase alloys,were fabricated by mechanical alloying and spark plasma sintering.The microstructure,mechanical properties,wear resistance,corrosion behavior,in vitro and in vivo antibacterial properties and biocompatibility of the Nb-Ag alloys were systematically investigated.The results show that the mechanical properties,wear resistance,corrosion resistance and antibacterial ability were significantly enhanced after addition of 5 at.% Ag.The fabricated Nb-5 at.% Ag alloy demonstrates high yield strength of up to ~1486 MPa and fracture strain of ~35 %.The precipitated Ag particles could reduce friction and wear.The enhanced corrosion resistance was attributed to the higher relative density of the sintered alloys and the formation of a stable and dense passive film of niobium and silver oxides.In vitro and in vivo evaluations show that the Nb-5 at.% Ag alloy also has strong antibacterial activity and good biocompatibility and osteointegration ability.These results demonstrate great potential of the nanostructured Nb-Ag alloys for dental and orthopedic implants.
