氫在γ-TiAl晶體中作用的第一性原理研究
發(fā)布時(shí)間：2018-09-09 10:24
【摘要】：本文采用基于第一性原理贗勢(shì)法的CASTEP軟件構(gòu)建了γ-TiAl和γ-TiAl(H)的晶體模型,計(jì)算研究了氫對(duì)γ-TiAl晶體的能量、電子結(jié)構(gòu)和彈性性質(zhì)的影響;研究了γ-TiAl(H)晶體中氫原子的間隙擴(kuò)散;計(jì)算了γ-TiAl和γ-TiAl(H)晶體中Ti、Al原子的單空位形成能和自擴(kuò)散激活能,研究氫對(duì)γ-TiAl晶體中Ti、Al原子自擴(kuò)散性質(zhì)的影響;計(jì)算了γ-TiAl和γ-TiAl(H)晶體層錯(cuò)能,研究氫對(duì)γ-TiAl晶體層錯(cuò)能的影響。γ-TiAl晶體中有富Ti八面體間隙(O1)、富Al八面體間隙(O2)和四面體間隙(T),氫傾向于占據(jù)O1間隙位置。γ-TiAl和γ-TiAl(H)晶體的態(tài)密度、Mulliken布居數(shù)、電荷密度和差分電荷密度計(jì)算結(jié)果表明,氫原子存在會(huì)引起γ-TiAl(H)晶體中Ti-Ti鍵和Ti-Al鍵作用減弱,而Al-Al鍵的作用增強(qiáng)。γ-TiAl和γ-TiAl(H)晶體的彈性常數(shù)結(jié)果表明,氫會(huì)使得γ-TiAl(H)晶體的G/B值增大,脆性增大。氫原子在γ-TiAl(H)晶體中的間隙擴(kuò)散路徑為O1→T→O1,氫含量為0.917at.%、1.54at.%和2.04at.%的γ-TiAl(H)晶體中氫原子的間隙擴(kuò)散激活能分別為0.5052e V、0.4713e V、0.4628e V,γ-TiAl(H)晶體中氫擴(kuò)散系數(shù)與實(shí)驗(yàn)值吻合。γ-TiAl晶體的Ti單空位形成能、Al單空位形成能、Ti反位形成能和Al反位形成能分別為1.4018eV、2.2226e V、0.8629e V和0.1302e V;γ-TiAl(H)晶體中氫的最近鄰四個(gè)點(diǎn)缺陷形成能分別變?yōu)?.1931e V、1.6598eV、0.3092eV和0.2291e V。γ-TiAl晶體中Ti自擴(kuò)散激活能值是2.4899e V,和實(shí)驗(yàn)值(2.59e V)相吻合,而Al自擴(kuò)散激活能為3.3646e V,較實(shí)驗(yàn)值(3.71e V)低;γ-TiAl(H)晶體中氫最近鄰Ti、Al原子自擴(kuò)散激活能分別為2.3793e V和2.9718e V。計(jì)算結(jié)果表明氫的加入會(huì)降低Ti、Al原子自擴(kuò)散激活能,提高γ-TiAl晶體的塑性。隨氫含量增加,Ti自擴(kuò)散激活能降低量變化很小,而Al自擴(kuò)散激活能降低量增大。γ-TiAl晶體的不穩(wěn)定層錯(cuò)能和穩(wěn)定層錯(cuò)能的計(jì)算值分別為333.82eV和209.45e V,與其他計(jì)算值相符。隨著氫含量的增加,γ-TiAl(H)晶體的不穩(wěn)定層錯(cuò)能和穩(wěn)定層錯(cuò)能逐漸降低,這將提高γ-TiAl(H)晶體發(fā)生孿晶的可能性。差分電荷密度計(jì)算結(jié)果表明,氫原子的加入導(dǎo)致Ti-Ti鍵強(qiáng)度減弱,引起γ-TiAl晶體層錯(cuò)能減小。
[Abstract]:In this paper, the crystal models of 緯 -TiAl and 緯 -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 緯 -TiAl crystals are calculated, and the gap diffusion of hydrogen atoms in 緯 -TiAl (H) crystals is studied. The single vacancy formation energy and self-diffusion activation energy of Ti,Al atoms in 緯 -tial and 緯 -tial (H) crystals are calculated, and the effects of hydrogen on the self-diffusion properties of Ti,Al atoms in 緯 -TiAl crystals are studied, and the stacking dislocation energies of 緯 -TiAl and 緯 -tial (H) crystals are calculated. The effect of hydrogen on the stacking fault energy of 緯 -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 緯 -TiAl and 緯 -TiAl (H) crystals, and the density of states of 緯 -TiAl and 緯 -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 緯 -TiAl (H) crystal, while the effect of Al-Al bond will be enhanced. The elastic constants of 緯 -TiAl and 緯 -TiAl (H) crystal show that hydrogen can increase the GB value of 緯 -TiAl (H) crystal. Brittleness increases. The gap diffusion path of hydrogen atom in 緯 -TiAl (H) crystal is O _ 1 / T _ 2O _ 1. The gap diffusion activation energy of hydrogen atom in 緯 -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 緯 -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 緯 -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 緯 -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 緯 -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 緯 -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 緯 -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 緯 -TiAl (H) crystal decrease gradually, which will increase the possibility of twins in 緯 -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 緯 -TiAl crystal.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG111
，
本文編號(hào)：2232113
[Abstract]:In this paper, the crystal models of 緯 -TiAl and 緯 -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 緯 -TiAl crystals are calculated, and the gap diffusion of hydrogen atoms in 緯 -TiAl (H) crystals is studied. The single vacancy formation energy and self-diffusion activation energy of Ti,Al atoms in 緯 -tial and 緯 -tial (H) crystals are calculated, and the effects of hydrogen on the self-diffusion properties of Ti,Al atoms in 緯 -TiAl crystals are studied, and the stacking dislocation energies of 緯 -TiAl and 緯 -tial (H) crystals are calculated. The effect of hydrogen on the stacking fault energy of 緯 -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 緯 -TiAl and 緯 -TiAl (H) crystals, and the density of states of 緯 -TiAl and 緯 -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 緯 -TiAl (H) crystal, while the effect of Al-Al bond will be enhanced. The elastic constants of 緯 -TiAl and 緯 -TiAl (H) crystal show that hydrogen can increase the GB value of 緯 -TiAl (H) crystal. Brittleness increases. The gap diffusion path of hydrogen atom in 緯 -TiAl (H) crystal is O _ 1 / T _ 2O _ 1. The gap diffusion activation energy of hydrogen atom in 緯 -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 緯 -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 緯 -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 緯 -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 緯 -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 緯 -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 緯 -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 緯 -TiAl (H) crystal decrease gradually, which will increase the possibility of twins in 緯 -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 緯 -TiAl crystal.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG111
，
本文編號(hào)：2232113
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