Molecular Dynamics Simulations Of The Influence Of Intracrystalline Nano Void On Tensile Deformation Of γ-TiAl Polycrystalline

γ-TiAl alloys are widely used in aerospace as high-temperature structural materials, based on its’ low density, high melting point and excellent high temperature oxidation resistance and corrosion resistance. But its brittle at room temperature and low fracture toughness has not been effectively improved. During the production and using process of γ-TiAl alloys, the microvoids often generated in weak places inside the alloy because of hot and cold processing, load and temperature viariation and other factors. Growth and coalescence of microvoids is one of the main causes of alloy failure. Thus, it’s necessary to study the influence of nano voids on the mechanical behaviors of γ-TiAl alloys. It’s conducive to explore improvement approach of brittle at room temperature and low fracture toughness of γ-TiAl alloys. For nanomaterials, experimental observations are hard to obtain explicit microstructural evolution. As a representative of atomic simulation method, the dynamic tracking of material microstructure can be realized via molecular dynamics(MD) method by solving the Newton’s motion equations of each particle. MD is an effective means of computer-aided materials research.Employing MD method, the present discusses the influence of intracrystalline nano void on tensile deformation of γ-TiAl polycrystalline with single void, double voids and the different locations and number of voids. The mechanisms of plastic deformation and fracture of γ-TiAl polycrystalline were studied through analysis of microstructural evolution during low temperature tensile deformation with various distributuion of inner voids from atomic scale. The main contents are as follows:(1) The plastic deformation mechanisms of γ-Ti Al polycrystalline with intracrystalline voids were the dislocation nucleation at grain boundaries, and the dislocations first nucleate at the triple grain boundaries. Emission of dislocations was getting ahead with the increase of void radius(R) and the number of voids, which indicated that the presence of voids accelaerated the dislocation nucleation.(2) In the tensile deformation simulations of γ-TiAl polycrystalline with single void of different sizes, two kind of void location was considered as in the center position(within grain 1) and boeder position(within grain 2) of the peferct cell. Voids at the specific locations has a significant impact on the plasticity and fracture behaviors of γ-TiAl polycrystalline. For the polycrystalline with a single void inner grain 1, the peak stress was less than the perfect polycrystalline when R was small. However, the fracture toughness was improved, which indicated the properly increasing of the plasticity with existence of microvoid, and when R=0.2nm is best. When R<1nm, the fracture mechanism of the polycrystalline was intergranular fracture.When R≥1nm, the fracture mechanism was voids growth and rupture. For the polycrystalline with void inner grain 2, the peak stress of polycrystalline gradually increased with R increasing, and the strain corresponding to the peak stress gradually increases, which also suggested that the plasticity was improved. When R<1.5nm, fracture mechanism was the intergranular fracture. When R increases to 1.5nm, fracture mechanism was voids growth and rupture.(3) On the basis of polycrystalline cells with single void, the simulation cells were build as a model with two void inner one grain and another model with single void inner different grains. Then the tensile deformation of these polycrystalline cells was simulated. The results indicated that the peak stress further decrease and the strain corresponding to the peak stress further increase with the existence of the multiple voids. It was an effective way to improve the plasticity and fracture toughness of γ-TiAl alloys by microstructure control of dispersive distribution of nano-voids.