γ/α 2 相界面对TiAl合金超音速微粒轰击影响的分子动力学模拟

Effect of γ/α 2 Phase Interface on Supersonic Fine Particle Bombardment of TiAl Alloy by Molecular Dynamics Simulation

摘要:

为探究γ/α₂相界面对TiAl合金在轰击过程中的变形机制和轰击后力学性能的影响，通过分子动力学来模拟超音速微粒轰击双相TiAl合金的过程。结果表明：γ/α₂不同厚度比模型的冲击变形机制不同，变形主要集中在γ相和界面处。随着γ相厚度的减小，与相界面接触的位错首先被界面处的失配位错网络吸收，然后在相界面处成核，最终穿过相界面进入α₂相。冲击过程中产生的位错以Shockley位错为主，试样中形成了不完全层错四面体。冲击之后分别使用单轴拉伸模拟和纳米压痕模拟，测定了试样的强度和表面硬度。拉伸过程中相变、孪晶和层错是不同厚度比试样的主要变形机制。与其他试样相比，厚度比为1:3的双相TiAl合金在冲击后具有最高的屈服强度、硬度和弹性模量。

Abstract:

In order to investigate the effect of γ/α₂ phase interface on the deformation mechanism and mechanical properties of TiAl alloy during bombardment process, the supersonic fine particle bombardment of dual-phase TiAl alloy was simulated by molecular dynamics. Results show that the impact deformation mechanisms of γ/α₂ models with different thickness ratios are different, and the deformation is mainly concentrated at the γ phase and interface. With decreasing the γ phase thickness, the dislocations in contact with the phase interface are firstly absorbed by the mismatched dislocation network, then they are nucleated at the phase interface, and eventually the dislocations pass through the phase interface, entering the α₂ phase. Shockley dislocation is the main dislocation type in the impact process, and incomplete stacking fault tetrahedron forms in the specimen. After impact, uniaxial tensile simulation and nano-indentation simulation were conducted to measure the strength and surface hardness of the specimens. The main deformation mechanisms of specimens with different thickness ratios are the phase transformation, twins, and stacking faults during tensile process. Compared with other specimens, TiAl alloy with thickness ratio of 1:3 has the highest yield strength, the highest hardness, and the highest elastic modulus after impact.