纳米纯Ti对间隙O原子具有强烈的敏感性，O含量可以很大程度上改变其力学性能和变形机制。采用分子动力学方法分别研究了O含量、变形温度、应变速率对纳米多晶α-Ti拉伸性能及变形机制的影响。结果表明，纳米多晶α-Ti的屈服应力随间隙O含量增加而升高。在O含量小于0.3% (原子分数)时，观察到变形孪晶{10\overline{\mathrm{1}}0}<10\overline{\mathrm{1}}2>，该孪晶通过孪晶面上的“带状位错”协调长大；O含量大于等于0.3%时，被激活的滑移系类型向多元化转变，柱面、基面和锥面<c + a>滑移系被激活，位错类型转变为以刃型位错为主。在含O纳米多晶α-Ti中，位错机制和晶界机制辅助塑性变形。晶界迁移率随变形温度和应变速率的增加明显增大。新晶粒形成过程伴随着不稳定的Ti_hcp→Ti_bcc→Ti_hcp相变，这种相变由晶粒的相对旋转所致，且生成新晶粒的数量随着应变速率的增大而增多。通过探索间隙O原子强化的本质，为优化纳米尺度纯Ti力学性能，拓展纯Ti应用范围提供理论依据。

Titanium (Ti) has a strong sensitivity to oxygen atoms. Adding interstitial oxygen to pure Ti can greatly alter its mechanical behavior. Oxygen atoms increase strength and hardness while making Ti brittle. Therefore, controlling the oxygen content in Ti is extremely important. To better understand the influence of oxygen on the mechanical behavior of pure Ti, the plastic deformation behavior of nano-polycrystalline α-Ti with different interstitial oxygen content was studied. Molecular dynamic simulations were performed using the second nearest-neighbor modified embedded atom method and the charge equilibration (Q_eq) method to investigate the effect of O content, tensile temperature, and strain rate on the tensile mechanical properties and deformation mechanism of nano-polycrystalline α-Ti. Results indicate that the yield stress of nano-polycrystalline α-Ti increases with the increase of interstitial O content. {10\overline{\mathrm{1}}0}<10\overline{\mathrm{1}}2> deformation twin was observed when the O content is less than 0.3%, and twin growth was mediated by well-defined “zonal dislocations” at the twin boundary. Different activated slip systems were transformed and diversified when the O content is larger than 0.3%, that is, the prismatic, basal, and pyramidal <c + a> slip systems were simultaneously activated, and the dislocation type changed to edge dislocations. The plastic deformation of nano-polycrystalline α-Ti was mediated by dislocation and grain boundary. In addition, the mobility of the grain boundary increased significantly with the increase of tensile temperature and strain rate. The formation of new grains was accompanied by Ti_hcp→Ti_bcc→Ti_hcp phase transformation, which was due to the relative rotation of the grains. The number of new grains increased with the increase of strain rate. The current work reveals the mechanical properties and deformation mechanism of nano-polycrystalline α-Ti, which promotes the design, and development of Ti-based nano-structured alloys with superior mechanical properties.