A new rhombohedral phase(termed R′)in a solution-aging-treated titanium alloy(Ti-4.5Al-6.5Mo-2Cr-2Nb-1V-1Sn-1Zr,wt.%)was identified.Its accurate Bravais lattice parameters were determined by a novel unit cell reconst...A new rhombohedral phase(termed R′)in a solution-aging-treated titanium alloy(Ti-4.5Al-6.5Mo-2Cr-2Nb-1V-1Sn-1Zr,wt.%)was identified.Its accurate Bravais lattice parameters were determined by a novel unit cell reconstruction method based on conventional selected-area electron diffraction(SAED)technique.The orientation relationship between R'phase and BCC phase was revealed.The results show that the R′phase is found to have 48crystallographically equivalent variants,resulting in rather complicated SAED patterns with high-order reflections.A series of in-situ SAED patterns were taken along both low-and high-index zone axes,and all weak and strong reflections arising from the 48 variants were properly explained and directly assigned with self-consistent Miller indices,confirming the presence of the rhombohedral phase.Additionally,some criteria were also proposed for evaluating the indexed results,which together with the Bravais lattice reconstruction method shed light on the microstructure characterization of even unknown phases in other alloys.展开更多
From the crystal chemistry and icosahedral phase, two kinds of coordinational polyhedron with 8-fold rotational symmetry——hexakaicahedra and bicapped antiprism were possibly suggested and their one- and two-dimensio...From the crystal chemistry and icosahedral phase, two kinds of coordinational polyhedron with 8-fold rotational symmetry——hexakaicahedra and bicapped antiprism were possibly suggested and their one- and two-dimensional quasilattices were deducted. According to the principle of Bravais in conventional crystallography, four kinds of two-dimensional unit cell have been defined in 5, 8, 10, 12-fold rotational symmetry quasicrystal. The authors considered that quasicrystal is a kind of crystal which possesses an incommensurable translational period. This kind of translation is carried out by inflation or deflation symmetry operation.展开更多
基金financial supports from the National Natural Science Foundation of China(No.51071125)the Major Project of Department of Education of Jiangxi Province,China(No.GJJ210605)。
文摘A new rhombohedral phase(termed R′)in a solution-aging-treated titanium alloy(Ti-4.5Al-6.5Mo-2Cr-2Nb-1V-1Sn-1Zr,wt.%)was identified.Its accurate Bravais lattice parameters were determined by a novel unit cell reconstruction method based on conventional selected-area electron diffraction(SAED)technique.The orientation relationship between R'phase and BCC phase was revealed.The results show that the R′phase is found to have 48crystallographically equivalent variants,resulting in rather complicated SAED patterns with high-order reflections.A series of in-situ SAED patterns were taken along both low-and high-index zone axes,and all weak and strong reflections arising from the 48 variants were properly explained and directly assigned with self-consistent Miller indices,confirming the presence of the rhombohedral phase.Additionally,some criteria were also proposed for evaluating the indexed results,which together with the Bravais lattice reconstruction method shed light on the microstructure characterization of even unknown phases in other alloys.
基金Project supported by the National Natural Science Foundation of China.
文摘From the crystal chemistry and icosahedral phase, two kinds of coordinational polyhedron with 8-fold rotational symmetry——hexakaicahedra and bicapped antiprism were possibly suggested and their one- and two-dimensional quasilattices were deducted. According to the principle of Bravais in conventional crystallography, four kinds of two-dimensional unit cell have been defined in 5, 8, 10, 12-fold rotational symmetry quasicrystal. The authors considered that quasicrystal is a kind of crystal which possesses an incommensurable translational period. This kind of translation is carried out by inflation or deflation symmetry operation.
