孪晶界对TiAl合金超音速微粒轰击影响的分子动力学模拟

TiAl合金因具有低密度、高比强度、高温抗氧化性等性能成为航空航天等领域最具潜力的高温轻质结构材料之一,但其具有本质脆性,在成型过程中易引入微裂纹、孔洞等缺陷,严重影响了其力学性能。超音速微粒轰击是新型表面改性技术之一,利用该技术研究了不同孪晶界数量和位置对TiAl合金力学性能和变形行为的影响。结果表明：不同孪晶界数量模型的屈服强度随孪晶界数量的增大而降低;孪晶界位置距模型上表面越近,材料屈服强度越低;随着孪晶界数量的增加,孪晶对位错运动的阻碍越明显,模型轰击后表面的塑性变形程度也越大,材料更易发生断裂;孪晶距离材料上表面越近,孪晶对位错生长的抑制越明显,进而影响材料强度;模型变形失效是位错与位错、位错与孪晶及其它缺陷共同作用的结果。

Effect of Twin Boundaries on Supersonic Fine Particle Bombardment of TiAl Alloys via Molecular Dynamics

TiAl alloys have become one of the most promising high-temperature lightweight structural materials in aerospace and other fields because of low density, high specific strength, high-temperature oxidation resistance and other properties. However, due to the brittleness of them, it is easy to introduce micro-cracks, holes and other defects in the forming process, which seriously affect the mechanical properties. For this reason, supersonic fine particle bombardment (SFPB), one of the surface modification techniques, was used to investigate the effect of twin boundaries (TBs) on the mechanical properties and deformation behaviour of TiAl alloys. The findings demonstrate that when the number of TBs increases, the yield strength of models with various numbers of TBs falls. The closer the location of TB to the upper surface of model, the lower the yield strength of the material. As the number of TBs increases, the obstruction of dislocation movement by TBs becomes more evident and the degree of plastic deformation of the surface of the model after bombardment becomes greater, making the material more susceptible to fracture. The closer the TB to the upper surface of the material, the more evident the inhibition of dislocation growth by the twin, which in turn affects the strength of the material. Deformation failure of the model is the combination result between dislocations and dislocations, dislocations and twins and other defects.