The phase composition,microstructure and hardening of aluminum-based experimental alloys containing0.3%Sc,0?14%Si and0?10%Ca(mass fraction)were studied.The experimental study(electron microscopy,thermal analysis and h...The phase composition,microstructure and hardening of aluminum-based experimental alloys containing0.3%Sc,0?14%Si and0?10%Ca(mass fraction)were studied.The experimental study(electron microscopy,thermal analysis and hardnessmeasurements)was combined with Thermo-Calc software simulation for the optimization of the alloy composition.It wasdetermined that the maximum hardening corresponded to the annealing at300?350°С,which was due to the precipitation of Al3Scnanoparticles with their further coarsening.The alloys falling into the phase region(Al)+Al4Ca+Al2Si2Ca have demonstrated asignificant hardening effect.The ternary eutectic(Al)+Al4Ca+Al2Si2Ca had a much finer microstructure as compared to the Al?Sieutectic,which suggests a possibility of reaching higher mechanical properties as compared to commercial alloys of the A356type.Unlike commercial alloys of the A356type,the model alloy does not require quenching,as hardening particles are formed in thecourse of annealing of castings.展开更多
Cold-rolled Ti/Al laminated composites were annealed at 525−625℃for 0−128 h,and the interfacial microstructure evolution was investigated.The results indicate that only the TiAl_(3) phase was formed at the Ti/Al inte...Cold-rolled Ti/Al laminated composites were annealed at 525−625℃for 0−128 h,and the interfacial microstructure evolution was investigated.The results indicate that only the TiAl_(3) phase was formed at the Ti/Al interface;most of TiAl_(3) grains were fine equiaxed with average sizes ranging from hundreds of nanometers to several microns and the TiAl_(3) grain size increased with increasing annealing time and/or temperature,but the effect of annealing temperature on the TiAl_(3) grain size was far greater than that of annealing time.The growth of the TiAl_(3) phase consisted of two stages.The initial stage was governed by chemical reaction with a reaction activation energy of 195.75 kJ/mol,and the reaction rate constant of the TiAl_(3) phase was larger as the Ti/Al interface was bonded with fresh surfaces.At the second stage,the growth was governed by diffusion,the diffusion activation energy was 33.69 kJ/mol,and the diffusion growth rate constant of the TiAl_(3) phase was mainly determined by the grain boundary diffusion owing to the smaller TiAl_(3) grain size.展开更多
The texture evaluation of α2 phase in Ti-25Al-10Nb-3V-1Mo sheet during rolling and annealing has been investigated by means of microstructure observation and ODF analysis. From the weak initial {1010} (1210) and {000...The texture evaluation of α2 phase in Ti-25Al-10Nb-3V-1Mo sheet during rolling and annealing has been investigated by means of microstructure observation and ODF analysis. From the weak initial {1010} (1210) and {0001}(1210) textures a {1210}(1010) texture and a {0001}(uvtw)fibre texture are formed after cold rolling. The {0001} (1210) texture is also strengthened simultaneously. The activation process of slip systems is discussed concerning formation of the rolling texture. Because of the disappearance of {0001} (nvtw) fibre texture the primary recrystallization process should occur and the {1210}(1010) texture forms during annealing展开更多
The Zn,Cu,and Sc contents of 7xxx Al alloys were adjusted according to the chemical composition of a 7085 Al alloy,and the effects of Zn and Cu contents and Sc addition on the microstructures,hardness,and quench sensi...The Zn,Cu,and Sc contents of 7xxx Al alloys were adjusted according to the chemical composition of a 7085 Al alloy,and the effects of Zn and Cu contents and Sc addition on the microstructures,hardness,and quench sensitivity of the 7xxx Al alloys were studied.The alloys with high Zn content and Sc addition exhibited higher hardness than the 7085 alloy at the position 3 mm away from the quenching end.The density ofηand T phases increased with the increase in Zn and Cu contents,and the Sc addition led to the formation of the Y phase and moreηphases at the position 120 mm away from the quenching end.Compared with the 7085 alloy,the high Zn−high Cu and Sc-added alloys exhibited higher quench sensitivity,while the simultaneous increase in Zn content and decrease in Cu content could enhance the hardness and reduce the quench sensitivity of the 7085 alloy.展开更多
The differences of grain-refining effect between Sc and Ti additions in aluminum,which cannot be substantially explained by traditional theories,were carefully studied.The empirical electron theory(EET) of solids and ...The differences of grain-refining effect between Sc and Ti additions in aluminum,which cannot be substantially explained by traditional theories,were carefully studied.The empirical electron theory(EET) of solids and molecules was employed to calculate the valence electron structures(VES) of Al3Ti and Al3Sc.The conclusions can be drawn that,in the two alloys Al-Ti and Al-Sc,the different valence electron structures of Al3Ti and Al3Sc and the consequent differences of growth habit of the two particles,and the different interfacial electron density between particles and matrix fundamentally lead to the differences of grain-refining effect between Sc and Ti additions on aluminum and make Sr the better grain-refiner of aluminum.展开更多
A novel technique for fabricating TiB_2/Al composites in molten aluminum was introduced. The formation mechanism of brittleAl,Ti particulates up to 30 m in size produced in the composites was studied and a method of e...A novel technique for fabricating TiB_2/Al composites in molten aluminum was introduced. The formation mechanism of brittleAl,Ti particulates up to 30 m in size produced in the composites was studied and a method of eliminating them was proposed. The resultsshow that (l) the brittle Al,Ti particulates are always present in the composites when the molar ratio of Ti to B 'T,:nB is l:2; and (2) theformation of the brittle Al,Ti phase can be avoided entirely from the final product by using a proper 'T,:nB of l:4 in the Ti-B-Al preforms.In the former case, the tensile elongation of the composite is only 4%, much lower than the value of pure aluminum (20%). In the latercase, the tensile elongation of this composite is 10%, higher than the value of the composite with a lot ofAl,Ti (4%), whereas the ultimatetensile stfength of the former is nearly that of the later.展开更多
The microstructure of alloy Ti 3Al 10Nb 3V 1Mo after heated at 1170℃ for 1 h and cooled to room temperature at different rates was investigated by TEM. The result showed that W.Q. microstructure consisted of sing...The microstructure of alloy Ti 3Al 10Nb 3V 1Mo after heated at 1170℃ for 1 h and cooled to room temperature at different rates was investigated by TEM. The result showed that W.Q. microstructure consisted of single B2 phase, A.C. microstructure consisted of B2 phase matrix and second phase in some regions of the B2 phase crystal grains, and C.C. and F.C. microstructure appeared as a Widmannstatten structure consisting of coarse α 2 phase plates and β phase stripes between the plates. With the decreasing of colling rate, the tension strength was obviously decreased and the plasticity was slightly increased at room temperature.展开更多
Structure transformations in the two-phase (Ti, Nb)3Al alloy, induced by shock-wave loading, were studied. The samples were subjected to an impact of a steel plate. The maximum pressure on the samples’ surfaces was 1...Structure transformations in the two-phase (Ti, Nb)3Al alloy, induced by shock-wave loading, were studied. The samples were subjected to an impact of a steel plate. The maximum pressure on the samples’ surfaces was 100 GPa, while the maximum temperature was 573 K. The β0→α2 phase transformation occurred during strong deformations. High temperature rectilinear dislocations (such types of dislocations usually could arise at 1073 K) with the c-component, which occasionally formed slip bands, were located at the α2-phase grains after the shock. The deformation α2-phase twins were not observed.展开更多
Microstructural evolution and phase transformation of hydrogenated and dehydrogenated TC21 alloys were investigated by optical microscopy （OM）, X-ray diffraction （XRD） and transmission electron microscopy （TEM）....Microstructural evolution and phase transformation of hydrogenated and dehydrogenated TC21 alloys were investigated by optical microscopy （OM）, X-ray diffraction （XRD） and transmission electron microscopy （TEM）. XRD peaks ofαandβphases after hydrogenation shifted to low angle because of lattice expansion with the solution of hydrogen atoms. Microstructure of TC21 alloy after hydrogenation changed apparently. Compared to the as-received one, the contrasts of equiaxedαphase and transformedβphase under optical microscope were reversed. In addition, XRD and TEM analyses revealed that hydrides and α′ martensite precipitated fromαandβphases. Bulk of twins and some Ti3Al particles were observed in hydrogenated TC21 alloy, which means that hydrogen led to the redistribution of alloying elements inαandβphase. After dehydrogenation, the microstructure of TC21 alloy was similar to that of the as-received one, which consisted ofαandβphases.展开更多
基金supported by Russian Science Foundation(Grant No.14-19-00632)
文摘The phase composition,microstructure and hardening of aluminum-based experimental alloys containing0.3%Sc,0?14%Si and0?10%Ca(mass fraction)were studied.The experimental study(electron microscopy,thermal analysis and hardnessmeasurements)was combined with Thermo-Calc software simulation for the optimization of the alloy composition.It wasdetermined that the maximum hardening corresponded to the annealing at300?350°С,which was due to the precipitation of Al3Scnanoparticles with their further coarsening.The alloys falling into the phase region(Al)+Al4Ca+Al2Si2Ca have demonstrated asignificant hardening effect.The ternary eutectic(Al)+Al4Ca+Al2Si2Ca had a much finer microstructure as compared to the Al?Sieutectic,which suggests a possibility of reaching higher mechanical properties as compared to commercial alloys of the A356type.Unlike commercial alloys of the A356type,the model alloy does not require quenching,as hardening particles are formed in thecourse of annealing of castings.
基金the financial supports from the S&T Program of Hebei Province,China(No.20373901D)the National Natural Science Foundation of China(Nos.51807047,51804095)+2 种基金the National Science Foundation of Hebei Province,China(No.E2019402433)the Youth Top Talents Science and Technology Research Project of Hebei Province University,China(No.BJ2019003)the Research and Development Project of Science and Technology of Handan City,China(No.19422111008-19).
文摘Cold-rolled Ti/Al laminated composites were annealed at 525−625℃for 0−128 h,and the interfacial microstructure evolution was investigated.The results indicate that only the TiAl_(3) phase was formed at the Ti/Al interface;most of TiAl_(3) grains were fine equiaxed with average sizes ranging from hundreds of nanometers to several microns and the TiAl_(3) grain size increased with increasing annealing time and/or temperature,but the effect of annealing temperature on the TiAl_(3) grain size was far greater than that of annealing time.The growth of the TiAl_(3) phase consisted of two stages.The initial stage was governed by chemical reaction with a reaction activation energy of 195.75 kJ/mol,and the reaction rate constant of the TiAl_(3) phase was larger as the Ti/Al interface was bonded with fresh surfaces.At the second stage,the growth was governed by diffusion,the diffusion activation energy was 33.69 kJ/mol,and the diffusion growth rate constant of the TiAl_(3) phase was mainly determined by the grain boundary diffusion owing to the smaller TiAl_(3) grain size.
文摘The texture evaluation of α2 phase in Ti-25Al-10Nb-3V-1Mo sheet during rolling and annealing has been investigated by means of microstructure observation and ODF analysis. From the weak initial {1010} (1210) and {0001}(1210) textures a {1210}(1010) texture and a {0001}(uvtw)fibre texture are formed after cold rolling. The {0001} (1210) texture is also strengthened simultaneously. The activation process of slip systems is discussed concerning formation of the rolling texture. Because of the disappearance of {0001} (nvtw) fibre texture the primary recrystallization process should occur and the {1210}(1010) texture forms during annealing
基金The authors are grateful for the financial supports from the Science and Technology Major Project of Guangxi,China(GKAA17202007).
文摘The Zn,Cu,and Sc contents of 7xxx Al alloys were adjusted according to the chemical composition of a 7085 Al alloy,and the effects of Zn and Cu contents and Sc addition on the microstructures,hardness,and quench sensitivity of the 7xxx Al alloys were studied.The alloys with high Zn content and Sc addition exhibited higher hardness than the 7085 alloy at the position 3 mm away from the quenching end.The density ofηand T phases increased with the increase in Zn and Cu contents,and the Sc addition led to the formation of the Y phase and moreηphases at the position 120 mm away from the quenching end.Compared with the 7085 alloy,the high Zn−high Cu and Sc-added alloys exhibited higher quench sensitivity,while the simultaneous increase in Zn content and decrease in Cu content could enhance the hardness and reduce the quench sensitivity of the 7085 alloy.
基金Project(20050003042) supported by Research Fund for the Doctoral Program of Higher Education of China
文摘The differences of grain-refining effect between Sc and Ti additions in aluminum,which cannot be substantially explained by traditional theories,were carefully studied.The empirical electron theory(EET) of solids and molecules was employed to calculate the valence electron structures(VES) of Al3Ti and Al3Sc.The conclusions can be drawn that,in the two alloys Al-Ti and Al-Sc,the different valence electron structures of Al3Ti and Al3Sc and the consequent differences of growth habit of the two particles,and the different interfacial electron density between particles and matrix fundamentally lead to the differences of grain-refining effect between Sc and Ti additions on aluminum and make Sr the better grain-refiner of aluminum.
文摘A novel technique for fabricating TiB_2/Al composites in molten aluminum was introduced. The formation mechanism of brittleAl,Ti particulates up to 30 m in size produced in the composites was studied and a method of eliminating them was proposed. The resultsshow that (l) the brittle Al,Ti particulates are always present in the composites when the molar ratio of Ti to B 'T,:nB is l:2; and (2) theformation of the brittle Al,Ti phase can be avoided entirely from the final product by using a proper 'T,:nB of l:4 in the Ti-B-Al preforms.In the former case, the tensile elongation of the composite is only 4%, much lower than the value of pure aluminum (20%). In the latercase, the tensile elongation of this composite is 10%, higher than the value of the composite with a lot ofAl,Ti (4%), whereas the ultimatetensile stfength of the former is nearly that of the later.
文摘The microstructure of alloy Ti 3Al 10Nb 3V 1Mo after heated at 1170℃ for 1 h and cooled to room temperature at different rates was investigated by TEM. The result showed that W.Q. microstructure consisted of single B2 phase, A.C. microstructure consisted of B2 phase matrix and second phase in some regions of the B2 phase crystal grains, and C.C. and F.C. microstructure appeared as a Widmannstatten structure consisting of coarse α 2 phase plates and β phase stripes between the plates. With the decreasing of colling rate, the tension strength was obviously decreased and the plasticity was slightly increased at room temperature.
文摘Structure transformations in the two-phase (Ti, Nb)3Al alloy, induced by shock-wave loading, were studied. The samples were subjected to an impact of a steel plate. The maximum pressure on the samples’ surfaces was 100 GPa, while the maximum temperature was 573 K. The β0→α2 phase transformation occurred during strong deformations. High temperature rectilinear dislocations (such types of dislocations usually could arise at 1073 K) with the c-component, which occasionally formed slip bands, were located at the α2-phase grains after the shock. The deformation α2-phase twins were not observed.
基金Project(Z1120117)supported by the Key Program in Xihua University,ChinaProject(12201453)supported by Department of Education Research Fund in Sichuan Province
文摘Microstructural evolution and phase transformation of hydrogenated and dehydrogenated TC21 alloys were investigated by optical microscopy （OM）, X-ray diffraction （XRD） and transmission electron microscopy （TEM）. XRD peaks ofαandβphases after hydrogenation shifted to low angle because of lattice expansion with the solution of hydrogen atoms. Microstructure of TC21 alloy after hydrogenation changed apparently. Compared to the as-received one, the contrasts of equiaxedαphase and transformedβphase under optical microscope were reversed. In addition, XRD and TEM analyses revealed that hydrides and α′ martensite precipitated fromαandβphases. Bulk of twins and some Ti3Al particles were observed in hydrogenated TC21 alloy, which means that hydrogen led to the redistribution of alloying elements inαandβphase. After dehydrogenation, the microstructure of TC21 alloy was similar to that of the as-received one, which consisted ofαandβphases.
