镍基合金掺杂W、Mo原子在γ/γ′相界面扩散机理研究

Study on the diffusion mechanism of W and Mo atoms doped inNickel base alloy atγ/γ′interface

运用基于密度泛函理论的第一性原理,研究掺杂W、Mo在镍基高温合金的沉淀强化γ′相分配差异的因素.通过VASP软件,建立γ′-Ni_(3)(Al_(3/8)Ti_(5/8))相的体系模型,选取非等效位置的不同阵点,计算W、Mo原子在不同位置的替代形成能,分析W、Mo在γ′相的占位倾向;计算掺杂W、Mo原子前后,界面的吸附能,研究掺杂W、Mo对相界的影响;计算W、Mo原子从γ向γ′相扩散,获得W、Mo扩散的路径与势垒.结果表明,W、Mo的掺杂优先替代γ′-Ni_(3)(Al_(3/8)Ti_(5/8))相5号Al原子,并提高相界的稳定性;分配的差异是W相比于Mo替代γ′相位置的Al原子更易形成空位,而γ相中的Ni原子较难形成空位,且逆扩散所需能量更多导致的.

Based on the first principles of density functional theory,the factors for the difference of γ′phase distribution in the precipitation strengthening of W and Mo doped nickel base superalloy were studied.The system model of γ′-Ni_(3)(Al_(3/8)Ti_(5/8)) phase was established by VASP software,and the substitution energies of W and Mo atoms in different positions were calculated by selecting different array points in non-equivalent positions,and the occupying tendencies of W and Mo atoms inγ′phase were analyzed.The adsorption energy of the interface before and after doping W and Mo atoms were calculated,and the influences of doping W and Mo on the phase boundary were studied.The diffusion paths and potential barriers of W and Mo atoms fromγtoγ′were also calculated.The results show that the doping of W or Mo preferentially replaces No.5 Al atom inγ′-Ni_(3)(Al_(3/8)Ti_(5/8)) phase and improves the stability of the phase boundary.The difference in allocation is caused by the fact that W replacing Al atom in theγ′phase is more likely to form vacancies than Mo,while Ni atoms in theγphase are more difficult to form vacancies and require more energy for reverse diffusion.