氢在γ-TiAl晶体中作用的第一性原理研究
发布时间：2018-09-09 10:24
【摘要】：本文采用基于第一性原理赝势法的CASTEP软件构建了γ-TiAl和γ-TiAl(H)的晶体模型,计算研究了氢对γ-TiAl晶体的能量、电子结构和弹性性质的影响;研究了γ-TiAl(H)晶体中氢原子的间隙扩散;计算了γ-TiAl和γ-TiAl(H)晶体中Ti、Al原子的单空位形成能和自扩散激活能,研究氢对γ-TiAl晶体中Ti、Al原子自扩散性质的影响;计算了γ-TiAl和γ-TiAl(H)晶体层错能,研究氢对γ-TiAl晶体层错能的影响。γ-TiAl晶体中有富Ti八面体间隙(O1)、富Al八面体间隙(O2)和四面体间隙(T),氢倾向于占据O1间隙位置。γ-TiAl和γ-TiAl(H)晶体的态密度、Mulliken布居数、电荷密度和差分电荷密度计算结果表明,氢原子存在会引起γ-TiAl(H)晶体中Ti-Ti键和Ti-Al键作用减弱,而Al-Al键的作用增强。γ-TiAl和γ-TiAl(H)晶体的弹性常数结果表明,氢会使得γ-TiAl(H)晶体的G/B值增大,脆性增大。氢原子在γ-TiAl(H)晶体中的间隙扩散路径为O1→T→O1,氢含量为0.917at.%、1.54at.%和2.04at.%的γ-TiAl(H)晶体中氢原子的间隙扩散激活能分别为0.5052e V、0.4713e V、0.4628e V,γ-TiAl(H)晶体中氢扩散系数与实验值吻合。γ-TiAl晶体的Ti单空位形成能、Al单空位形成能、Ti反位形成能和Al反位形成能分别为1.4018eV、2.2226e V、0.8629e V和0.1302e V;γ-TiAl(H)晶体中氢的最近邻四个点缺陷形成能分别变为1.1931e V、1.6598eV、0.3092eV和0.2291e V。γ-TiAl晶体中Ti自扩散激活能值是2.4899e V,和实验值(2.59e V)相吻合,而Al自扩散激活能为3.3646e V,较实验值(3.71e V)低;γ-TiAl(H)晶体中氢最近邻Ti、Al原子自扩散激活能分别为2.3793e V和2.9718e V。计算结果表明氢的加入会降低Ti、Al原子自扩散激活能,提高γ-TiAl晶体的塑性。随氢含量增加,Ti自扩散激活能降低量变化很小,而Al自扩散激活能降低量增大。γ-TiAl晶体的不稳定层错能和稳定层错能的计算值分别为333.82eV和209.45e V,与其他计算值相符。随着氢含量的增加,γ-TiAl(H)晶体的不稳定层错能和稳定层错能逐渐降低,这将提高γ-TiAl(H)晶体发生孪晶的可能性。差分电荷密度计算结果表明,氢原子的加入导致Ti-Ti键强度减弱,引起γ-TiAl晶体层错能减小。
[Abstract]:In this paper, the crystal models of 纬 -TiAl and 纬 -TiAl (H) are constructed by using CASTEP software based on the first-principle pseudopotential method, the effects of hydrogen on the energy, electronic structure and elastic properties of 纬 -TiAl crystals are calculated, and the gap diffusion of hydrogen atoms in 纬 -TiAl (H) crystals is studied. The single vacancy formation energy and self-diffusion activation energy of Ti,Al atoms in 纬 -tial and 纬 -tial (H) crystals are calculated, and the effects of hydrogen on the self-diffusion properties of Ti,Al atoms in 纬 -TiAl crystals are studied, and the stacking dislocation energies of 纬 -TiAl and 纬 -tial (H) crystals are calculated. The effect of hydrogen on the stacking fault energy of 纬 -TiAl crystals is studied. There are rich Ti octahedron gaps (O1), Al octahedron gaps (O2) and tetrahedron gaps (T), hydrogen tend to occupy the O 1 gap positions in 纬 -TiAl and 纬 -TiAl (H) crystals, and the density of states of 纬 -TiAl and 纬 -TiAl (H) crystals is Mulliken population. The calculated results of charge density and differential charge density show that the existence of hydrogen atoms will lead to the decrease of the interaction between Ti-Ti bond and Ti-Al bond in 纬 -TiAl (H) crystal, while the effect of Al-Al bond will be enhanced. The elastic constants of 纬 -TiAl and 纬 -TiAl (H) crystal show that hydrogen can increase the GB value of 纬 -TiAl (H) crystal. Brittleness increases. The gap diffusion path of hydrogen atom in 纬 -TiAl (H) crystal is O _ 1 / T _ 2O _ 1. The gap diffusion activation energy of hydrogen atom in 纬 -TiAl (H) crystal with hydrogen content of 0.917at.0.54at.% and 2.04at.% is 0.5052e V ~ 0.4713e V 0.4628e, respectively. The hydrogen diffusion coefficient of 纬 -TiAl (H) crystal is in agreement with the experimental value. The formation energies of Ti and Al are 1.4018eV ~ 2.2226e V _ (0.8629e) V and 0.1302e V respectively, and the formation energies of the nearest four defects of hydrogen in 纬 -TiAl (H) crystals are 1.1931 e V 1.6598eV 0.3092eV and 0.2291e V respectively. The self-diffusion activation energy of Ti in 纬 -TiAl crystal is 0.2291e. The value is 2.4899e V, which is consistent with the experimental value (2.59e V). The self-diffusion activation energy of Al is 3.3646 EV, which is lower than the experimental value (3.71 EV), and the self-diffusion activation energy of nearest neighbor Ti,Al atom in 纬 -TiAl (H) crystal is 2.3793 EV and 2.9718 EV, respectively. The results show that the addition of hydrogen can decrease the self-diffusion activation energy of Ti,Al atoms and improve the plasticity of 纬 -TiAl crystal. With the increase of hydrogen content, the decrease of self-diffusion activation energy of Ti is small, while that of Al increases. The calculated values of unstable stacking fault energy and stable layer fault energy of 纬 -TiAl crystal are 333.82eV and 209.45e V, respectively, which are in agreement with other calculated values. With the increase of hydrogen content, the unstable stacking fault energy and stable stacking fault energy of 纬 -TiAl (H) crystal decrease gradually, which will increase the possibility of twins in 纬 -TiAl (H) crystal. The results of differential charge density calculation show that the addition of hydrogen atoms leads to the decrease of Ti-Ti bond strength and the decrease of laminated fault energy of 纬 -TiAl crystal.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG111
，
本文编号：2232113
[Abstract]:In this paper, the crystal models of 纬 -TiAl and 纬 -TiAl (H) are constructed by using CASTEP software based on the first-principle pseudopotential method, the effects of hydrogen on the energy, electronic structure and elastic properties of 纬 -TiAl crystals are calculated, and the gap diffusion of hydrogen atoms in 纬 -TiAl (H) crystals is studied. The single vacancy formation energy and self-diffusion activation energy of Ti,Al atoms in 纬 -tial and 纬 -tial (H) crystals are calculated, and the effects of hydrogen on the self-diffusion properties of Ti,Al atoms in 纬 -TiAl crystals are studied, and the stacking dislocation energies of 纬 -TiAl and 纬 -tial (H) crystals are calculated. The effect of hydrogen on the stacking fault energy of 纬 -TiAl crystals is studied. There are rich Ti octahedron gaps (O1), Al octahedron gaps (O2) and tetrahedron gaps (T), hydrogen tend to occupy the O 1 gap positions in 纬 -TiAl and 纬 -TiAl (H) crystals, and the density of states of 纬 -TiAl and 纬 -TiAl (H) crystals is Mulliken population. The calculated results of charge density and differential charge density show that the existence of hydrogen atoms will lead to the decrease of the interaction between Ti-Ti bond and Ti-Al bond in 纬 -TiAl (H) crystal, while the effect of Al-Al bond will be enhanced. The elastic constants of 纬 -TiAl and 纬 -TiAl (H) crystal show that hydrogen can increase the GB value of 纬 -TiAl (H) crystal. Brittleness increases. The gap diffusion path of hydrogen atom in 纬 -TiAl (H) crystal is O _ 1 / T _ 2O _ 1. The gap diffusion activation energy of hydrogen atom in 纬 -TiAl (H) crystal with hydrogen content of 0.917at.0.54at.% and 2.04at.% is 0.5052e V ~ 0.4713e V 0.4628e, respectively. The hydrogen diffusion coefficient of 纬 -TiAl (H) crystal is in agreement with the experimental value. The formation energies of Ti and Al are 1.4018eV ~ 2.2226e V _ (0.8629e) V and 0.1302e V respectively, and the formation energies of the nearest four defects of hydrogen in 纬 -TiAl (H) crystals are 1.1931 e V 1.6598eV 0.3092eV and 0.2291e V respectively. The self-diffusion activation energy of Ti in 纬 -TiAl crystal is 0.2291e. The value is 2.4899e V, which is consistent with the experimental value (2.59e V). The self-diffusion activation energy of Al is 3.3646 EV, which is lower than the experimental value (3.71 EV), and the self-diffusion activation energy of nearest neighbor Ti,Al atom in 纬 -TiAl (H) crystal is 2.3793 EV and 2.9718 EV, respectively. The results show that the addition of hydrogen can decrease the self-diffusion activation energy of Ti,Al atoms and improve the plasticity of 纬 -TiAl crystal. With the increase of hydrogen content, the decrease of self-diffusion activation energy of Ti is small, while that of Al increases. The calculated values of unstable stacking fault energy and stable layer fault energy of 纬 -TiAl crystal are 333.82eV and 209.45e V, respectively, which are in agreement with other calculated values. With the increase of hydrogen content, the unstable stacking fault energy and stable stacking fault energy of 纬 -TiAl (H) crystal decrease gradually, which will increase the possibility of twins in 纬 -TiAl (H) crystal. The results of differential charge density calculation show that the addition of hydrogen atoms leads to the decrease of Ti-Ti bond strength and the decrease of laminated fault energy of 纬 -TiAl crystal.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG111
，
本文编号：2232113
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