氢致TiAl合金増塑共性规律及原子尺度微观机理研究

TiAl alloys show huge potential in the engineering application. However, their intrinsic poor plasticity restricts the application. Thermohydrogen processing technology (hydrogenation→hot processing→dehydrogenation) is a promising method to enhance the plasticity of such alloys. However, the atomic-scale micro-mechanism of hydrogen-enhanced plasticity is not clear, which becomes a bottleneck to restrict the application of thermohydrogen processing technology in the hot processing of TiAl alloys. Therefore, the common regularity and atomic-scale micro-mechanism of hydrogen-enhanced plasticity of TiAl alloys will be investigated by use of the macro tensile test, in-situ TEM tensile test, molecular dynamics simulation and theoretical analysis. The main research topics are as follows: 1) the effect of hydrogen on the precipitation behavior of B2 phase as well as precipitation and dissolution behaviors of ωo phase; 2) the effect of hydrogen on mechanical behavior and microstructure evolution of the beta and two-phase γ-TiAl alloys; 3) atomic-scale mechanism of hydrogen-induced phase transformation, twinning formation and growth, and dislocation multiplication and movement of the beta and two-phase γ-TiAl alloys. The research of this project will establish the theoretical basis for the application of thermohydrogen processing technology in the hot processing of TiAl alloys, which will promote the engineering application of TiAl alloys.

TiAl合金有巨大的工程应用潜力，然而其固有低塑性限制了它的应用。热氢处理技术（置氢→热加工→除氢）是有望提高该合金塑性的方法，但氢致合金増塑原子尺度微观机理尚不明确，成为制约该技术在TiAl合金热加工领域应用的瓶颈。因此，本项目提出利用宏观拉伸和透射电镜原位拉伸实验、分子动力学模拟、理论分析相结合的方法，研究氢致TiAl合金増塑共性规律及原子尺度微观机理。主要研究：1）氢对β型γ-TiAl合金B2相析出行为，以及对ωo相析出和溶解行为的影响规律；2）氢影响β型和双相γ-TiAl合金力学行为和组织演变的共性规律；3）氢致β型和双相γ-TiAl合金相变、孪晶形核和长大、位错增殖和运动的原子机制。本项目的研究将为热氢处理技术在TiAl合金热加工领域的应用奠定理论基础，促进TiAl合金的工程应用。

热氢处理技术是有望提高TiAl合金塑性变形能力的方法，然而氢致该合金増塑共性规律及原子尺度微观机理尚不明确，成为制约该技术在TiAl合金热加工领域应用的瓶颈。针对以上问题，本项目研究了氢对TiAl合金B2、γ、α2相含量和分布的影响，揭示了氢致合金相变转的微观机理，研究了未置氢和置氢TiAl合金在拉伸变形和平面应变压缩变形下的变形规律，构建了置氢合金变形本构方程，提出了氢致位错运动和孪晶变形是氢致TiAl合金塑性变形的共性规律，氢致动态再结晶是氢致TiAl合金软化的共性规律，揭示了位错激发、运动、交互作用等的原子机制，揭示了氢致孪晶变形的微观机理：氢促进机械孪晶变形从而产生真孪晶，真孪晶与120º旋转孪晶结合后反应生成伪孪晶；探明了氢阻碍裂纹扩展的微观机制。最终，揭示了氢致TiAl合金増塑共性规律及微观机理，为热氢处理技术在TiAl合金热加工领域的应用提供了理论支撑。