Precipitation-strengthened medium/high-entropy alloys(MEAs/HEAs)have great potential for high-temperature applications.In this study,we designed a novel Ni_(45.9)Fe_(23)Cr_(23)V_(4)Nb_(3)Mo_(1)B_(0.1)(at.%)MEA alloy,h...Precipitation-strengthened medium/high-entropy alloys(MEAs/HEAs)have great potential for high-temperature applications.In this study,we designed a novel Ni_(45.9)Fe_(23)Cr_(23)V_(4)Nb_(3)Mo_(1)B_(0.1)(at.%)MEA alloy,hardened by the D0_(22)(Ni,Fe,Cr)_(3)(Nb,V)-type nanoprecipitates,with an excellent strength-ductility com-bination from room to elevated temperatures.Specifically,the tensile strengths,at 700 and 800℃,could be maintained as high as 845 and 589 MPa,respectively;meanwhile,elongations at all testing temper-atures exceeded 25%without any intermediate-temperature embrittlement.The temperature-dependent deformation mechanisms were unraveled using multi-scale characterizations,which involved profound slip planarities,such as stacking fault(SF)networks and deformation twins(DTs).Furthermore,the crit-ical resolved shear stress(CRSS)to initiate SFs in both face-centered cubic(FCC)and D0_(22)phases was evaluated,and the possible reasons for the origin of anomalous DTs at 800℃were discussed in de-tail.The main findings demonstrate that the shearable D0_(22)nanoparticles can provide the FCC matrix with considerable dislocation storage capacity,reinforcing strain hardening at ambient and intermedi-ate temperatures.This work provides fundamental insights into the controllable design and deformation mechanisms of high-performance D0_(22)-strengthened MEAs/HEAs.展开更多
The microstructures and mechanical properties of the directionally solidified Cu-15Ni-8Sn alloy were investigated at solidification rates ranging from 100 to 3000μm/s.The results showed that the solidification rate s...The microstructures and mechanical properties of the directionally solidified Cu-15Ni-8Sn alloy were investigated at solidification rates ranging from 100 to 3000μm/s.The results showed that the solidification rate significantly affects the phase distribution of the as-cast Cu-15Ni-8Sn alloy.The primary and secondary dendritic spacing reduces and eventually becomes stable as the solidification rate increases.Meanwhile,the size of the primary phase decreases,and its distribution becomes more uniform.The most severe segregation problem of this alloy has been greatly improved.Upon solidification at 100μm/s,the as-cast Cu-15Ni-8Sn alloy consists of the α-Cu matrix,γ-CuNi_(2)Sn phase,discontinuous precipitation structure,modulated structure,and DO_(22) ordered phases.However,as the solidification rate increases,the discontinuous precipitation structure,modulated structures,and DO_(22) ordered phases decrease and even disappear,reducing hardness.As the solidification rate increases,after homogenization treatment,the composition and microhardness distributions of Cu-15Ni-8Sn alloy become more uniform.The time for homogenization is also shortened.It reduces production energy usage and facilitates further mechanical processing.展开更多
基金the City University of Hong Kong acknowl-edge the financial support from the Shenzhen Science and Tech-nology Program(Grant No.SGDX20210823104002016)the Hong Kong Research Grant Council(RGC)(Grant Nos.CityU 21205621 and C1020-21G)the National Natural Science Foundation of China(Grant No.52301174).
文摘Precipitation-strengthened medium/high-entropy alloys(MEAs/HEAs)have great potential for high-temperature applications.In this study,we designed a novel Ni_(45.9)Fe_(23)Cr_(23)V_(4)Nb_(3)Mo_(1)B_(0.1)(at.%)MEA alloy,hardened by the D0_(22)(Ni,Fe,Cr)_(3)(Nb,V)-type nanoprecipitates,with an excellent strength-ductility com-bination from room to elevated temperatures.Specifically,the tensile strengths,at 700 and 800℃,could be maintained as high as 845 and 589 MPa,respectively;meanwhile,elongations at all testing temper-atures exceeded 25%without any intermediate-temperature embrittlement.The temperature-dependent deformation mechanisms were unraveled using multi-scale characterizations,which involved profound slip planarities,such as stacking fault(SF)networks and deformation twins(DTs).Furthermore,the crit-ical resolved shear stress(CRSS)to initiate SFs in both face-centered cubic(FCC)and D0_(22)phases was evaluated,and the possible reasons for the origin of anomalous DTs at 800℃were discussed in de-tail.The main findings demonstrate that the shearable D0_(22)nanoparticles can provide the FCC matrix with considerable dislocation storage capacity,reinforcing strain hardening at ambient and intermedi-ate temperatures.This work provides fundamental insights into the controllable design and deformation mechanisms of high-performance D0_(22)-strengthened MEAs/HEAs.
基金supported by the National Key Research and Development Program of China(Grant No.2020YFA0714400)Science and Technology Projects of Jiangxi Provincial Department of Education(Grant Nos.GJ210843 and GJJ200873)+2 种基金Scientific Research Starting Foundation for Advanced Talents of Jiangxi University of Science and Technology(Grant No.205200100570)the Project of the Key Scientific and Technological of Jiangxi Province(Grant No.20181BCB19003)Ningbo Enterprise Innovation Consortium Special Project(Grant No.2021H003).
文摘The microstructures and mechanical properties of the directionally solidified Cu-15Ni-8Sn alloy were investigated at solidification rates ranging from 100 to 3000μm/s.The results showed that the solidification rate significantly affects the phase distribution of the as-cast Cu-15Ni-8Sn alloy.The primary and secondary dendritic spacing reduces and eventually becomes stable as the solidification rate increases.Meanwhile,the size of the primary phase decreases,and its distribution becomes more uniform.The most severe segregation problem of this alloy has been greatly improved.Upon solidification at 100μm/s,the as-cast Cu-15Ni-8Sn alloy consists of the α-Cu matrix,γ-CuNi_(2)Sn phase,discontinuous precipitation structure,modulated structure,and DO_(22) ordered phases.However,as the solidification rate increases,the discontinuous precipitation structure,modulated structures,and DO_(22) ordered phases decrease and even disappear,reducing hardness.As the solidification rate increases,after homogenization treatment,the composition and microhardness distributions of Cu-15Ni-8Sn alloy become more uniform.The time for homogenization is also shortened.It reduces production energy usage and facilitates further mechanical processing.
