Measurements of electrical resistivity, X-ray diffraction, and tensile test at room temperature and ?196°C were performed to investigate the effects of Al addition substituting Ni on the phase transformation beh...Measurements of electrical resistivity, X-ray diffraction, and tensile test at room temperature and ?196°C were performed to investigate the effects of Al addition substituting Ni on the phase transformation behaviors, the mechanical properties, and the shape memory effects of Ti50Ni47Fe2Al1 and Ti50Ni46.5Fe2.5Al1 alloys. It is found that 1at% Al addition dramatically decreases the martensitic start transformation temperature and expands the transformation temperature range of R-phase for TiNiFeAl alloys. The results of tensile test indicate that 1at% Al improves the yield strength of Ti50Ni47Fe2Al1 and Ti50Ni46.5Fe2.5Al1 alloys by 40% and 64%, but de- creases the plasticity to 11% and 12% from 26% and 27% respectively. Moreover, excellent shape memory effect of 6.6% and 7.5% were found in Ti50Ni47Fe2Al1 and Ti50Ni46.5Fe2.5Al1 alloys, which results from the stress-induced martensite transformation from the R-phase.展开更多
High-resolution transmission electron microscope (HRTEM) was employed to investigate the deformation-induced α2→γ phase transformation phenomenon in a hot deformed Ti-45Al-10Nb alloy. Such a tronsformation can be n...High-resolution transmission electron microscope (HRTEM) was employed to investigate the deformation-induced α2→γ phase transformation phenomenon in a hot deformed Ti-45Al-10Nb alloy. Such a tronsformation can be nucleated either at α2/γ interfaces or at stacking faults on the basal planes of the α2 phase. The growth of deformation-induced γplate is accomplished by the motion of α/6<100> Shockley partials on alternate basal planes (0001)α2, and the α/6<100> Shockley partials move in coordination rather than sweep on (0001)α2 plane one by one. It appears that no atom transportation is involved in this stress-induced α2→γ transfromation.展开更多
The face-centered cubic structure(fcc)and its deformation behaviors,as well as the distinctive role of fcc-Ti in nanocrystallization in TC17 subjected to high energy shot peening(HESP),were investigated by using compr...The face-centered cubic structure(fcc)and its deformation behaviors,as well as the distinctive role of fcc-Ti in nanocrystallization in TC17 subjected to high energy shot peening(HESP),were investigated by using comprehensive high-resolution transmission electron microscopy(HRTEM).The results showed that there was a stress-induced fcc-Ti in TC17 with a lattice constant of 0.420–0.433 nm and the B-type orientation relationship between the hcp-Ti and the fcc-Ti as[2-1-10]_(hcp)//[-110]_(fcc)and(0001)_(hcp)//(111)_(fcc),which was accomplished by the gliding of Shockley partial dislocations with Burgers vector of 1/3[01-10]on the basal plane.The deformation twinning dominated the subsequent deformation of fcc-Ti,producing two types of{111}<11-2>twins with different characteristics.Among them,the I-type twin with complete structure was generated by successive gliding of Shockley partial dislocations with the same Burgers vector of 1/6[11-2].In contrast,the cooperative slip of three Shockley partials,whose sum of Burgers vectors was equal to zero,produced the II-type twin with zero net macroscopic strain.And then,the emission of Shockley partial with the Burgers vector of 1/6[11-2]on every three(111)fccplanes resulted in the formation of a 9R structure.Due to the dissociation effect of lamellar fcc-Ti and the superior deformation ability of fcc structure,the occurrence of fcc-Ti effectively promoted surface nanocrystallization of TC17.展开更多
文摘Measurements of electrical resistivity, X-ray diffraction, and tensile test at room temperature and ?196°C were performed to investigate the effects of Al addition substituting Ni on the phase transformation behaviors, the mechanical properties, and the shape memory effects of Ti50Ni47Fe2Al1 and Ti50Ni46.5Fe2.5Al1 alloys. It is found that 1at% Al addition dramatically decreases the martensitic start transformation temperature and expands the transformation temperature range of R-phase for TiNiFeAl alloys. The results of tensile test indicate that 1at% Al improves the yield strength of Ti50Ni47Fe2Al1 and Ti50Ni46.5Fe2.5Al1 alloys by 40% and 64%, but de- creases the plasticity to 11% and 12% from 26% and 27% respectively. Moreover, excellent shape memory effect of 6.6% and 7.5% were found in Ti50Ni47Fe2Al1 and Ti50Ni46.5Fe2.5Al1 alloys, which results from the stress-induced martensite transformation from the R-phase.
文摘High-resolution transmission electron microscope (HRTEM) was employed to investigate the deformation-induced α2→γ phase transformation phenomenon in a hot deformed Ti-45Al-10Nb alloy. Such a tronsformation can be nucleated either at α2/γ interfaces or at stacking faults on the basal planes of the α2 phase. The growth of deformation-induced γplate is accomplished by the motion of α/6<100> Shockley partials on alternate basal planes (0001)α2, and the α/6<100> Shockley partials move in coordination rather than sweep on (0001)α2 plane one by one. It appears that no atom transportation is involved in this stress-induced α2→γ transfromation.
基金the financial support of the National Natural Science Foundation of China(Grants Nos.51475375 and 51705425)Shaanxi Province Postdoctoral Science Foundation(Grant No.2017BSHEDII06)。
文摘The face-centered cubic structure(fcc)and its deformation behaviors,as well as the distinctive role of fcc-Ti in nanocrystallization in TC17 subjected to high energy shot peening(HESP),were investigated by using comprehensive high-resolution transmission electron microscopy(HRTEM).The results showed that there was a stress-induced fcc-Ti in TC17 with a lattice constant of 0.420–0.433 nm and the B-type orientation relationship between the hcp-Ti and the fcc-Ti as[2-1-10]_(hcp)//[-110]_(fcc)and(0001)_(hcp)//(111)_(fcc),which was accomplished by the gliding of Shockley partial dislocations with Burgers vector of 1/3[01-10]on the basal plane.The deformation twinning dominated the subsequent deformation of fcc-Ti,producing two types of{111}<11-2>twins with different characteristics.Among them,the I-type twin with complete structure was generated by successive gliding of Shockley partial dislocations with the same Burgers vector of 1/6[11-2].In contrast,the cooperative slip of three Shockley partials,whose sum of Burgers vectors was equal to zero,produced the II-type twin with zero net macroscopic strain.And then,the emission of Shockley partial with the Burgers vector of 1/6[11-2]on every three(111)fccplanes resulted in the formation of a 9R structure.Due to the dissociation effect of lamellar fcc-Ti and the superior deformation ability of fcc structure,the occurrence of fcc-Ti effectively promoted surface nanocrystallization of TC17.