Molecular Dynamics Simulation Of Mechanical Properties Of Nanocrystalline γ-TiAl Intermetallics

The mechanical properties of single crystal γ-TiAl intermetallics such as elasticity, plastic deformation and fracture were studied by using Molecular Dynamics (MD) simulation in this thesis.The energy changes were calculated when a specimen deformed elastically in the isothermal condition. Based on the results calculated, the values of six isothermalelastic constants (c₁₁,c₁₂,c₁₃,c₃₃,c₄₄ and c₆₆) were obtained, and elastic moduli can be also gained. Then stack fault energies in various slip systems and twinning fault energies in (1/6) <11(?)]{111} twinning system were calculated at 0.01K. The resultsshowed that γ-TiAl had less mobile slip systems than an FCC crystal. Based on the results obtained, the deformation mechanisms of γ-TiAl intermetallics were also discussed according to the competition between slip and twinning in plastic deformation and two ductile-brittle criteria proposed by Rice and Zhou respectively.Deformation twinning (1/6) < 11(?)] {111} was concluded to be the principal deformation mode while ordinary dislocation slip (1/2) < 1(?)0] {111} andsupperdislocation slip (1/2) < 0(?)1] {111} were the complementary mode todeformation twinning, which were in good agreement with experimental results. Stack fault energies and twinning fault energies were also calculated at different temperatures. Based on the results, the temperature dependent mechanisms of plastic deformation and fracture were analyzed. With this analysis, γ-TiAl intermetallics was predicted as ductile at elevated temperatures and ordinary dislocation slip(1/2) < 1(?)0] {111} was the major deformation mode.The strain-stress curves were gained through MD simulation on isothermal loading of...