Dongsheng Xu
Chinese Academy of Sciences
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Featured researches published by Dongsheng Xu.
Acta Materialia | 1999
Yulin Hao; Dongsheng Xu; Y. Y. Cui; Rui Yang; Dongdong Li
The site occupancies of V, Cr, Mn, Fe, Ni, Zr, Nb, Mo, Ta, Ga and Sn (1-5 at.%) in TiAl alloys with different compositions, and in Ti3Al with the compositions of Ti-26 at.%Al-(1-2 at.%)X, were measured by the atom location channelling enhanced microanalysis (ALCHEMI) method. For TiAl alloys, the results show that Zr, Nb and Ta atoms invariably occupy Ti sites, while Fe, Ni, Ga and Sn atoms occupy Al sites, the alloy composition having no significant influence on their site preference. By contrast, the site preference of V, Cr, and Mn changes considerably with alloy composition (the Ti/Al ratio in particular), the probability of these elements substituting for Ti decreasing in the above order. For quaternary Ti-Al-V-Cr alloys, the site occupancies of V and Cr do not show much mutual influence. In general, with increasing atomic number, elements in the same period show increasing tendency to substitute for Al, as is the tendency to substitute for Ti for elements in the same group of the periodic table. For Ti3Al alloys, Ga and Sn atoms occupy Al sites, while V, Cr, Mn, Zr, Nb, Mo and Ta atoms occupy Ti sites, the site preference of V, Cr, Mn and Mo in TiAl alloys being different from that in Ti3Al. The experimental results are interpreted in terms of a Bragg-Williams-type model and bond-order data obtained from electronic structure calculation. Qualitative agreement between the model and measurements is reached
Modelling and Simulation in Materials Science and Engineering | 2006
F.Y. Meng; San-Qiang Shi; Dongsheng Xu; Che Ting Chan
Using a bond order potential, molecular dynamics simulations have been performed to study the mechanical properties of ultrathin single-walled carbon nanotubes with or without junction under uniaxial tensile loading. The ( 3, 3) armchair and ( 5, 0) zigzag nanotubes have been studied. Topological defects in the junction region influence the mechanical properties of junctions.
Philosophical Magazine | 2001
Qing-Miao Hu; Dongsheng Xu; Di Li
Abstract The solute–vacancy interaction energy in α-Ti is investigated systematically by making a supercell total energy calculation using the linear muffin-tin orbital within the atomic sphere approximation. The solutes studied cover most of the elements from the third to the fifth row in the periodic table. The results show that most of the transition-metal elements in the fourth row are repulsive to the vacancy. The simple metal elements and all the transition-metal elements in the fifth row are attractive to the vacancy. The interaction energy between the transition metal solute and vacancy in α-Ti does not exhibit a parabolic behaviour as expected by the d-band-filling mode that has been used to explain the trend of the interaction energy in Cu, Ag, etc. We consider that this deviation is related to the structural instability of some of the solutes in the hcp lattice. Based on the solute–vacancy interaction energy, the effects of the solutes on the creep properties of α-Ti alloys are discussed. On comparison of the calculation results and experimental information, a simple relationship between the solute-vacancy interaction and high-temperature creep properties of Ti alloys is found, that is those solutes attractive to the vacancy can improve the creep resistance, while those repulsive to the vacancy have no beneficial effect on the creep resistance. These results indicate that solute–vacancy interaction may be one of the important factors related to the creep properties of the α-Ti alloys.
Journal of Chemical Physics | 2006
F.Y. Meng; San-Qiang Shi; Dongsheng Xu; Che Ting Chan
A complete surface reconstruction takes place after a local connection between two crossed tubes is established, leading to the creation of an extended X-shaped junction constituted by topological defects with smooth negative curvature. Molecular-dynamics simulations show that the surface reconstructions occur through (1) generalized Stone-Wales transformation and (2) the movement of sp and sp3 atoms and their transformation to sp2 atoms by bond rearrangement. Based on both the principle of energy minimization and a generalized Eulers rule, it is demonstrated that the most stable structure for X junctions contains only 12 heptagons. The annealing temperature influences the topological structure and stability of junctions.
Journal of Physics: Conference Series | 2006
Dongsheng Xu; Qing-Miao Hu; Jianmin Lu; Yulin Hao; Rui Yang; S. E. Kulkova; D. I. Bazhanov
First principles calculations were carried out to investigate the energetics of point defects, including solute atoms, vacancies, and antisite defects, in titanium solid solution and intermetallics. Their influence on the mechanical behavior of titanium alloys and intermetallic compounds were discussed. The self consistent procedure proposed by the authors was applied to TiAl intermetallic compounds. The ordering parameter was redefined to include the contribution of vacancies to the disordering of intermetallic compounds, so that the new approach can be applied to both strongly and weakly ordered compounds. Concentrations of point defects of various kinds can be estimated for intermetallics of different composition at different temperature. The solid solution strengthening of alloying elements through short range ordering was studied for titanium alloys and the solid solution hardening rate was estimated for various alloying elements. The solute-vacancy interaction in titanium alloys was calculated and its influence on the diffusion and creep behavior was discussed. These calculations provided some useful information for the selection of alloying elements in designing new titanium alloys.
Materials Science Forum | 2005
C.G. Bai; Dong Liu; Dongsheng Xu; Yu You Cui; Yulin Hao; Rui Yang
Finite element method (FEM) simulation is carried out to analyze temperature distribution of the workpiece for the controlled-dwell extrusion of gamma-TiAl. We focused on the selection of can and insulating materials and concluded that silica fabric is a better insulating material than ZrO2 powders. 304SS, Ti6Al4V, 1Cr18Ni9Ti and pure Ti can be selected as can material if the dwell time and in-container time are well controlled. Thermo-mechanical coupled analysis is performed to investigate flow uniformity and temperature homogeneity for different can and insulating materials. Extrusion experiment was conducted and the results basically agree well with those of the simulation.
Modelling and Simulation in Materials Science and Engineering | 2010
Xiaolu Gu; Dongsheng Xu; H. Wang; R. Yang
Molecular dynamics simulations are carried out to investigate the influence of edge dislocations on the lattice strength in iron single crystals under tension perpendicular to the dislocation slip plane. Simulations are performed at different temperatures and with different densities of edge dislocations on the [1 1 1] slip system. It is found that cracks nucleate at dislocation cores in dislocation-containing systems at lower critical stresses compared with a perfect lattice, indicating a weakening caused by edge dislocations. Lattice thermal vibration plays an important role during the tensile deformation, resulting in a monotonic decrease in the yield strength as the temperature increases. There exists a critical temperature above which the lattice transforms from brittle to ductile, where dislocation nucleation and glide are favored instead of crack nucleation, and the critical temperature for the dislocated system is lower than that for the perfect lattice. The present simulation shows that higher dislocation density results in lower fracture strength, suggesting that the accumulation of dislocations during cyclic deformation may be the cause of lower strength under fatigue.
Physical Review B | 2007
F.Y. Meng; Shigenobu Ogata; Dongsheng Xu; Yoji Shibutani; San-Qiang Shi
Physical Review B | 2004
F.Y. Meng; San-Qiang Shi; Dongsheng Xu; Ruiqin Yang
Acta Materialia | 2009
G. Wang; Dongsheng Xu; N. Ma; N. Zhou; E.J. Payton; R. Yang; M.J. Mills; Y. Wang