钛－氢合金力学性质及变形过程中位错运动特性的分子动力学模拟研究

Thermohydrogen processing (THP), which is adding appropriate hydrogen content to titanium alloys, can improve their thermo plasticity properties and thermo workability. The current understanding of the mechanism of hydrogen-induced thermoplasticity of titanium alloys is not clear and should be further investigated. The effect of hydrogen-induced thermoplasticity is closely related to the response of titanium alloys to the applied stress, temperature and hydrogen content in the atomic scale and the interaction between hydrogen atoms and dislocation. In the present application, the deformation behavior and the structure evolution and movement of dislocations during deformation process of Ti-H alloys are simulated in atomic scale by the molecular dynamics method, and the effect of hydrogen content, loading conditions, deformation temperature, deformation rate on the mechanical properties of titanium alloy and dislocation movement characteristic is studies, the mechanism of it is also revealed, and the interaction model of hydrogen and dislocation is established; The dislocation configurations and structures in titanium alloys with different hydrogen content before and after deformation are observed by high resolution electron microscopy in order to verify the simulation results. This research work can reveal the mechanism of hydrogen-induced thermoplasticity titanium alloy from atomic scale, clarify its physical essence, and enrich the theory of thermohydrogen processing of titanium alloys, moreover, it can supply the theory basis for the effective control of hydrogen content in titanium alloys and the determination of thermo processing parameters of titanium alloys. In summary, the present research has important theoretical significance and practical value.

采用钛合金氢处理技术，在钛合金中加入适量氢，可使其热塑性提高，热加工性能得到明显改善。目前氢致钛合金热塑性的微观机理尚不明确，需要进一步深入系统研究。氢致钛合金热塑性效应与含氢钛合金在原子尺度上对于外加应力、温度和氢含量的响应以及氢与位错间相互作用密切相关。本项目拟采用分子动力学方法从原子尺度模拟钛-氢合金的变形行为及其形变过程中位错结构演变和位错运动，研究氢含量、加载条件、变形温度、变形速度等对钛-氢合金力学性质和位错运动特性的影响规律和作用机理，建立氢与位错相互作用模型；结合高分辨电镜等测试手段，观察不同氢含量α钛合金和β钛合金变形前后位错组态和结构，验证模拟结果。本课题研究可以从原子角度揭示氢致钛合金热塑性微观机理，阐明其物理本质，丰富钛合金氢处理理论，同时为有效控制钛合金中的氢含量，制定最佳的含氢钛合金热加工工艺参数提供理论依据，具有重要的理论意义和应用价值。

采用钛合金氢处理技术，在钛合金中加入适量氢，可使其热塑性提高，热加工性能得到明显改善。目前氢致钛合金热塑性的微观机理尚不明确，需要深入系统研究。本项目采用分子动力学方法从原子尺度研究了钛-氢合金的变形行为及其形变过程中位错结构演变和位错运动。基于EAM原模型，结合Johnson的分析型EAM模型，建立了Ti-H体系的EAM作用势模型。基于此模型，采用分子动力学方法模拟计算了Ti-H晶体的结构和能量性质，模拟结果验证了所建模型的合理性和可靠性。基于此模型的分子动力学模拟结果表明，氢的加入降低了 α-Ti 晶体的理论断裂强度和理论屈服强度，促进了位错运动。氢提高了β 钛的理论断裂强度和理论屈服强度，阻碍了位错运动。结合微观分析，观察不同氢含量α 钛合金和β 钛合金变形前后位错组态和结构。发现氢的加入显著降低了钛合金中位错密度。热变形温度升高，Ti-H 晶体热变形后位错密度降低。氢促进了 Ti-H 晶体的位错运动。本研究原子尺度揭示了氢在钛中的作用机理和弱键效应的物理本质，充实和完善了钛氢微观作用理论，为有效控制钛合金中的氢含量，制定最佳的氢处理和热加工工艺参数提供理论依据，具有较大的理论和实际意义。