The effect of Co addition on the formation of Ni-Ti clusters in maraging stainless steel was studied by three dimensional atom probe（3 DAP） and first-principles calculation. The cluster analysis based on the maximum...The effect of Co addition on the formation of Ni-Ti clusters in maraging stainless steel was studied by three dimensional atom probe（3 DAP） and first-principles calculation. The cluster analysis based on the maximum separation approach showed an increase in size but a decrease in density of Ni-Ti clusters with increasing the Co content. The first-principles calculation indicated weaker Co-Ni（Co-Ti） interactions than Co-Ti（Fe-Ti） interactions, which should be the essential reason for the change of distribution characteristics of Ni-Ti clusters in bcc Fe caused by Co addition.展开更多
Fabricated through a newly developed hot-warm rolling process,Zn-0.8 Li(wt%)alloy has ideal strength and ductility far beyond the mechanical benchmark of materials for biodegradable stents.Precipitation of needle-like...Fabricated through a newly developed hot-warm rolling process,Zn-0.8 Li(wt%)alloy has ideal strength and ductility far beyond the mechanical benchmark of materials for biodegradable stents.Precipitation of needle-like Zn in primary p-LiZn4 phase is observed in Zn-Li alloy for the first time.Orientation relationship between them can be described as[1-213]β//[2-1-10](Zn),(10-10)βabout 4.5°from(0002)(Zn).Zn grains with an average size of 640 nm exhibit strong basal texture,detected by transmission electron back-scatter diffraction.Li distribution is determined by three-dimensional atom probe,which reveals the formation of nano-sized metastableα-Li2Zn3 precipitates with a number density of 7.16×10^22 m^-3.The fine lamellar Zn+β-LiZn4 structure,sub-micron grains and the nano-sized precipitates contribute to the superior mechanical properties.展开更多
Excellent comprehensive mechanical properties including good formability,high strength and high ductility are prior demands for Al-Mg-Si-Cu alloys.This study utilizes calculation of phase diagram(CALPHAD)to simplify t...Excellent comprehensive mechanical properties including good formability,high strength and high ductility are prior demands for Al-Mg-Si-Cu alloys.This study utilizes calculation of phase diagram(CALPHAD)to simplify the alloy design and meet these demands.Specifically,CALPHAD was used to finely tune the Mg/Si atomic ratio in solid solution and accurately control the type and content of second phases,especially to avoid the formation of the harmful constituent phaseβ-Al Fe Si.Constituents and dispersoids of only-Al Fe Mn Si phase were found in the alloy prepared.An optimized microstructure with fine grains,micro scale constituents,densely distributed submicron scale dispersoids and extremely dense nano precipitates provides effective impediment to dislocation gliding and induces transgranular fracture.Therefore,the designed alloy has better comprehensive mechanical properties than other 6 xxx series aluminum alloys,including excellent formability,strength and ductility.The low T4P strength of 149 MPa as well as the high elongation of 26.1%implies the alloy’s applicability to automobile body panel forming.The yield strength was rapidly improved from 149 MPa to 277 MPa during the paint bake ageing,because the number density of precipitates is twice as high as that of some other 6xxx alloys.Meanwhile,the elongation was kept at a high level of 20.0%.展开更多
Three-dimensional distribution of solute elements in an Mg–Zn–Gd alloy during ageing process is quantitatively characterized by three-dimensional atom probe(3DAP) tomography. Based on the radius distribution functio...Three-dimensional distribution of solute elements in an Mg–Zn–Gd alloy during ageing process is quantitatively characterized by three-dimensional atom probe(3DAP) tomography. Based on the radius distribution function, it is found that Zn–Gd solute pairs in Mg matrix appear mainly at two peaks at early stage of ageing, and the separation distance between Zn and Gd atoms could be well rationalized by the first-principle calculation. Moreover, the fraction of Zn–Gd solute pairs increases first and then decreases due to the precipitation of long-period stacking ordered(LPSO) structures. Both the composition of the structural unit in LPSO structure and the solute enrichment around it are quantified. It is found that Zn and Gd elements are synchronized in the LPSO structure, and solute segregation of pure Zn or Gd is not observed at the transformation front of the LPSO structure in this alloy. In addition, the crystallography of transformation front is further determined by 3DAP data.展开更多
Three-dimensional atom probe （3DAP） technique has been used to study the nucleation and growth of M23C6 carbide in a supersaturated multi-component Fe-based alloy aged at 800℃. 3D images indicate that the radius of...Three-dimensional atom probe （3DAP） technique has been used to study the nucleation and growth of M23C6 carbide in a supersaturated multi-component Fe-based alloy aged at 800℃. 3D images indicate that the radius of M23C6 carbide after ageing for 10 min is about 9 nm. Concentration profiles of alloy elements in the carbide are also obtained. Combined with PANDAT and Thermo-Calc software, attempts to model the early stages of precipitation are present. The calculated particle size and composition of M23C6 carbide is in good agreement with 3DAP data.展开更多
Manufacturing temperatures of severely cold-drawn hyper-eutectoid steel wires are sufficiently high to influence the mobility of dislocations and alloy elements,thereby affecting the materials’mechanical properties.H...Manufacturing temperatures of severely cold-drawn hyper-eutectoid steel wires are sufficiently high to influence the mobility of dislocations and alloy elements,thereby affecting the materials’mechanical properties.Herein,we describe the evolution of microstructure and tensile strength of the as-drawn 3.45 GPa steel wire during post-deformation annealing for 30 min at 150-450℃.Annealing at 150℃raised the strength to 3.77 GPa by age-hardening through activation of dislocations pinning by carbon,while further temperature rising up to 450℃caused a severe loss of strength.It was proved that annealing at 300 and 450℃destabilizes the lamellar microstructure,promoting the formation of carbon-deficient(Fe,Mn,Cr)3 C-type cementite particles with preferentially rounded and partially faceted hetero-interfaces.Annealing at 450℃yielded the accumulation of Mn and Cr at the ferrite/particle interfaces,and their concentrations at the interfaces were dependent on the interface structure;i.e.,lower concentrations at rounded interfaces(formed through capillarity–driven coarsening of the spheroidized cementite),and higher concentrations at faceted interfaces(that are initially existing in the as-drawn state).Our proof-of-principle observations,supported by thermodynamic calculations and kinetic assessments,provide a pathway for understanding the changes in microstructural and tensile properties during manufacturing of the hyper-eutectoid steel wires.展开更多
基金sponsored by Youth Innovation Promotion Association of Chinese Academy of Sciences (2017233)National Natural Science Foundation of C hina (No. 51472249)+2 种基金Innovation Project of Institute of Metal Research (2015-ZD04)National Natural Science Foundation of China Research Fund for International Young Scientists (No. 51750110515)the Special Program for Applied Research on Super Computation of the NSFCGuangdong Joint Fund (second phase) under Grant No. U1501501
文摘The effect of Co addition on the formation of Ni-Ti clusters in maraging stainless steel was studied by three dimensional atom probe（3 DAP） and first-principles calculation. The cluster analysis based on the maximum separation approach showed an increase in size but a decrease in density of Ni-Ti clusters with increasing the Co content. The first-principles calculation indicated weaker Co-Ni（Co-Ti） interactions than Co-Ti（Fe-Ti） interactions, which should be the essential reason for the change of distribution characteristics of Ni-Ti clusters in bcc Fe caused by Co addition.
基金supported financially by the National Key R&D Program of China (No.2016YFC1102500)the National Natural Science Foundation of China (No.51871020)
文摘Fabricated through a newly developed hot-warm rolling process,Zn-0.8 Li(wt%)alloy has ideal strength and ductility far beyond the mechanical benchmark of materials for biodegradable stents.Precipitation of needle-like Zn in primary p-LiZn4 phase is observed in Zn-Li alloy for the first time.Orientation relationship between them can be described as[1-213]β//[2-1-10](Zn),(10-10)βabout 4.5°from(0002)(Zn).Zn grains with an average size of 640 nm exhibit strong basal texture,detected by transmission electron back-scatter diffraction.Li distribution is determined by three-dimensional atom probe,which reveals the formation of nano-sized metastableα-Li2Zn3 precipitates with a number density of 7.16×10^22 m^-3.The fine lamellar Zn+β-LiZn4 structure,sub-micron grains and the nano-sized precipitates contribute to the superior mechanical properties.
基金financially supported by the National Natural Science Foundation of China(Nos.51531009,51711530713 and 51501230)the Central South University(No.2018gczd033).
文摘Excellent comprehensive mechanical properties including good formability,high strength and high ductility are prior demands for Al-Mg-Si-Cu alloys.This study utilizes calculation of phase diagram(CALPHAD)to simplify the alloy design and meet these demands.Specifically,CALPHAD was used to finely tune the Mg/Si atomic ratio in solid solution and accurately control the type and content of second phases,especially to avoid the formation of the harmful constituent phaseβ-Al Fe Si.Constituents and dispersoids of only-Al Fe Mn Si phase were found in the alloy prepared.An optimized microstructure with fine grains,micro scale constituents,densely distributed submicron scale dispersoids and extremely dense nano precipitates provides effective impediment to dislocation gliding and induces transgranular fracture.Therefore,the designed alloy has better comprehensive mechanical properties than other 6 xxx series aluminum alloys,including excellent formability,strength and ductility.The low T4P strength of 149 MPa as well as the high elongation of 26.1%implies the alloy’s applicability to automobile body panel forming.The yield strength was rapidly improved from 149 MPa to 277 MPa during the paint bake ageing,because the number density of precipitates is twice as high as that of some other 6xxx alloys.Meanwhile,the elongation was kept at a high level of 20.0%.
基金supported by a Grant-in-Aid for Scientific Research on Innovative Areas,‘‘Synchronized Long-Period Stacking Ordered Structure’’,from the Ministry of Education,Culture,Sports,Science and Technology,Japan(No.23109006)Fundamental Research Funds for the Central Universities(No.FRFTP-17-003A1)
文摘Three-dimensional distribution of solute elements in an Mg–Zn–Gd alloy during ageing process is quantitatively characterized by three-dimensional atom probe(3DAP) tomography. Based on the radius distribution function, it is found that Zn–Gd solute pairs in Mg matrix appear mainly at two peaks at early stage of ageing, and the separation distance between Zn and Gd atoms could be well rationalized by the first-principle calculation. Moreover, the fraction of Zn–Gd solute pairs increases first and then decreases due to the precipitation of long-period stacking ordered(LPSO) structures. Both the composition of the structural unit in LPSO structure and the solute enrichment around it are quantified. It is found that Zn and Gd elements are synchronized in the LPSO structure, and solute segregation of pure Zn or Gd is not observed at the transformation front of the LPSO structure in this alloy. In addition, the crystallography of transformation front is further determined by 3DAP data.
基金supported by the National Natural Science Foundation of China (Nos. 50971137 and 50934011)
文摘Three-dimensional atom probe （3DAP） technique has been used to study the nucleation and growth of M23C6 carbide in a supersaturated multi-component Fe-based alloy aged at 800℃. 3D images indicate that the radius of M23C6 carbide after ageing for 10 min is about 9 nm. Concentration profiles of alloy elements in the carbide are also obtained. Combined with PANDAT and Thermo-Calc software, attempts to model the early stages of precipitation are present. The calculated particle size and composition of M23C6 carbide is in good agreement with 3DAP data.
基金financially supported by the Basic Science Research Program through the National Research Foundation(NRF)funded by the Ministry of Science,ICT&Future Planning(MSIP)of Korea(2018R1C1B6008585).
文摘Manufacturing temperatures of severely cold-drawn hyper-eutectoid steel wires are sufficiently high to influence the mobility of dislocations and alloy elements,thereby affecting the materials’mechanical properties.Herein,we describe the evolution of microstructure and tensile strength of the as-drawn 3.45 GPa steel wire during post-deformation annealing for 30 min at 150-450℃.Annealing at 150℃raised the strength to 3.77 GPa by age-hardening through activation of dislocations pinning by carbon,while further temperature rising up to 450℃caused a severe loss of strength.It was proved that annealing at 300 and 450℃destabilizes the lamellar microstructure,promoting the formation of carbon-deficient(Fe,Mn,Cr)3 C-type cementite particles with preferentially rounded and partially faceted hetero-interfaces.Annealing at 450℃yielded the accumulation of Mn and Cr at the ferrite/particle interfaces,and their concentrations at the interfaces were dependent on the interface structure;i.e.,lower concentrations at rounded interfaces(formed through capillarity–driven coarsening of the spheroidized cementite),and higher concentrations at faceted interfaces(that are initially existing in the as-drawn state).Our proof-of-principle observations,supported by thermodynamic calculations and kinetic assessments,provide a pathway for understanding the changes in microstructural and tensile properties during manufacturing of the hyper-eutectoid steel wires.
