In order to explore the exact nature of deformation defects previously observed in nanostructured Al-Mg alloys subjected to severe plastic deformation, a more thorough examination of the radiation effect on the format...In order to explore the exact nature of deformation defects previously observed in nanostructured Al-Mg alloys subjected to severe plastic deformation, a more thorough examination of the radiation effect on the formation of the planar defects in the high pressure torsion （HPT） alloys was conducted using high-resolution transmission electron microscopy （HRTEM）. The results show that high density defects in the HRTEM images disappear completely when these images are exposed under the electron beam for some duration of time. At the same time, lattice defects are never observed within no-defect areas even when the beam-exposure increases to the degree that holes appear in the areas. Therefore, it is confirmed that the planar defects observed in the HPT alloys mainly result from the significant plastic deformation and are not due to the radiation effect during HRTEM observation.展开更多
To date,nanostructuring through plastic deformation has rarely been reported in biodegradable zinc(Zn)based alloys that have great potential in load-bearing conditions.Here,typical high-strength Zn-Li-based alloys wer...To date,nanostructuring through plastic deformation has rarely been reported in biodegradable zinc(Zn)based alloys that have great potential in load-bearing conditions.Here,typical high-strength Zn-Li-based alloys were subjected to SPD processes,including equal channel angular pressing(ECAP)and high-pressure torsion(HPT),to achieve nanostructured microstructures.The effects of SPD on the microstructures,mechanical properties,and corrosion behaviors were generally investigated.The two SPD routes resulted in totally different microstructures.ECAPed samples processed at 150℃ exhibited a complicated multilevel structure(nm toμm)with mixed Zn equiaxed grains and lamellar-like eutectoid regions(Zn+α-LiZn_(4)),and HPTed ones(25℃)possessed a fully dynamically recrystallized(DRXed)microstructure with an average grain size below 0.4μm.The tensile strength of the SPD samples could reach 500 MPa.Meanwhile,HPTed samples exhibited extraordinary fracture elongations higher than 100%,because of a different grain boundary sliding deformation mechanism.HPTed samples and ECAPed samples displayed different corrosion patterns,and the former exhibited a much higher corrosion rate in Hank's solution,possibly due to the accelerated corrosion at grain boundaries.In summary,SPD is an efficient way to refine the microstructure of biodegradable Zn-based alloys,possibly improving their performances and clinical applications.展开更多
Deformation twins and stacking faults were observed in nanostructure A1-Mg alloys subjected to high pressure torsion. These observations are surprising because deformation twinnings have never been observed in their c...Deformation twins and stacking faults were observed in nanostructure A1-Mg alloys subjected to high pressure torsion. These observations are surprising because deformation twinnings have never been observed in their coarse-grained counterparts under normal conditions. Experimental evidences are introduced on non-equilibrium grain boundaries, deformation twinnings and partial dislocation emissions from grain boundaries. Some of these features can be explained by the results reported from molecular-dynamics simulations of pure FCC metals. Special emphasis is laid on the recent observations of high density hexagonal and rhombic shaped nanostructures with an average size of 3 nm in the A1-Mg alloys processed by high pressure torsion. A possible formation process of these nanostructures is proposed based on molecular-dynamics simulations.展开更多
基金Project (50971087) supported by the National Natural Science Foundation of ChinaProject (BK2012715) supported by the Basic Research Program (Natural Science Foundation) of Jiangsu Province, China+1 种基金Project (10371800) supported by the Research Council of Norway under the NEW Light (NEWLIGHT) Metals of the Strategic Area (SA) MaterialsProject (11JDG070) supported by the Senior Talent Research Foundation of Jiangsu University, China
文摘In order to explore the exact nature of deformation defects previously observed in nanostructured Al-Mg alloys subjected to severe plastic deformation, a more thorough examination of the radiation effect on the formation of the planar defects in the high pressure torsion （HPT） alloys was conducted using high-resolution transmission electron microscopy （HRTEM）. The results show that high density defects in the HRTEM images disappear completely when these images are exposed under the electron beam for some duration of time. At the same time, lattice defects are never observed within no-defect areas even when the beam-exposure increases to the degree that holes appear in the areas. Therefore, it is confirmed that the planar defects observed in the HPT alloys mainly result from the significant plastic deformation and are not due to the radiation effect during HRTEM observation.
基金supported by the National Natural Science Foundation of China(Nos.U22A20121,52101283 and 52271243)the NSFC-RGC Joint Research Scheme(No.52361165619)+3 种基金The NSFC-RFBR Joint Research Scheme(No.82361138575)the Science and Technology Planning Project of Guangzhou(No.202201011454)the National Key R&D Program of China(Nos.2021YFC2400700 and 2021YFC2400704)the High-level Hospital Construction Project(No.KJ012019520).
文摘To date,nanostructuring through plastic deformation has rarely been reported in biodegradable zinc(Zn)based alloys that have great potential in load-bearing conditions.Here,typical high-strength Zn-Li-based alloys were subjected to SPD processes,including equal channel angular pressing(ECAP)and high-pressure torsion(HPT),to achieve nanostructured microstructures.The effects of SPD on the microstructures,mechanical properties,and corrosion behaviors were generally investigated.The two SPD routes resulted in totally different microstructures.ECAPed samples processed at 150℃ exhibited a complicated multilevel structure(nm toμm)with mixed Zn equiaxed grains and lamellar-like eutectoid regions(Zn+α-LiZn_(4)),and HPTed ones(25℃)possessed a fully dynamically recrystallized(DRXed)microstructure with an average grain size below 0.4μm.The tensile strength of the SPD samples could reach 500 MPa.Meanwhile,HPTed samples exhibited extraordinary fracture elongations higher than 100%,because of a different grain boundary sliding deformation mechanism.HPTed samples and ECAPed samples displayed different corrosion patterns,and the former exhibited a much higher corrosion rate in Hank's solution,possibly due to the accelerated corrosion at grain boundaries.In summary,SPD is an efficient way to refine the microstructure of biodegradable Zn-based alloys,possibly improving their performances and clinical applications.
基金Project(50971087) supported by the National Natural Science Foundation of ChinaProject supported by the Research Council of Norway under the Strategic University Program on Light Metals Technology Projects(67692, 71594) supported by the Hungarian National Science Foundation
文摘Deformation twins and stacking faults were observed in nanostructure A1-Mg alloys subjected to high pressure torsion. These observations are surprising because deformation twinnings have never been observed in their coarse-grained counterparts under normal conditions. Experimental evidences are introduced on non-equilibrium grain boundaries, deformation twinnings and partial dislocation emissions from grain boundaries. Some of these features can be explained by the results reported from molecular-dynamics simulations of pure FCC metals. Special emphasis is laid on the recent observations of high density hexagonal and rhombic shaped nanostructures with an average size of 3 nm in the A1-Mg alloys processed by high pressure torsion. A possible formation process of these nanostructures is proposed based on molecular-dynamics simulations.
