Molecular Dynamics Simulations Of Void Growth And Closing In γ-TiAl Single Crystal

This γ-TiAl intermetallic compound has many special physical and chemical properties and mechanical properties, such as high melting point, low density, high elastic modulus, low diffusion coefficient, good structural stability and excellent oxidation resistance and corrosion resistance. Therefore, it becomes an alternative material in aerospace field, especially supersonic aircraft in the future, causing many researchers’attention and study. In the present work, molecular dynamics simulation was performed to study the growth and closing of spherical nano-voids, and the fracture properties of y-TiAl single crystal. It is found that the emission of shear loops is the primary mechanism of the void growth:continued production of dislocation cores and the propagation of shear loops make the void grow, and they are also the primary mechanisms of the formation of materials’defects. Cracks originate from the deformed area between the void surface and the sample boundaries. As the cracks propagate to the void surface and to the crystal boundaries, they connect the void and y-TiAl single crystal finally fractures. The dependence of the void growth on the specimen size, strain rate, and void volume fraction were also investigated. The incipient yield strength decreases as the specimen size or void volume fraction increases, but increases with the increase of the strain rate. Young’s modulus is not sensitive to the specimen size and strain rate, only affected by the void volume fraction. In order to more systematically study the mechanical behavior of the voided y-TiAl single crystal, we simulated the closing process of spherical and conical voids in samples. We know that the void closing is mainly depending on the mechanism of the expansion of the fault structure under the compressive stress, and the degree of defects’ closing is associated with the shape and size of the defects.