Molecular Dynamics Simulation of Nano Single Crystal Gamma-TiAl Alloy Strain Rate Effect

The propagation form of the preset edge crack in the nano single crystal gamma-TiAl at different strain rates were simulated by molecular dynamics. Dynamic uniaxial tension for preset edge cracks was carried out by velocity loading in the single crystal gamma-TiAl within 5.0 x 10(7) similar to 7.5 x 10(9) s(-1). The results show that the crack propagation form varies with the range of strain rate. In the non-sensitive region ((epsilon)over dot <= 4 x 10(8) s(-1)), the crack propagates in a brittle cleavage manner. In the sensitive region (4.0 x 10(8) s(-1) < (epsilon)over dot <= 1.0 x 10(9) s(-1)), it exhibits cleavage extension feature early; in the latter stage, the slip dislocation is emitted from the crack tip, and the void defect initiates the place where dislocation pile up and then grow to the child crack, the child crack links the main crack when it bias 45 degrees when (epsilon)over dot <= 5.0 x 10(8) s(-1), but it connects the main crack at the same direction under 5.0 x 10(8) s(-1) < (epsilon)over dot <= 1.0 x 10(9) s(-1), thus leading to the fracture finally. In the sharp-change region ((epsilon)over dot >= 1.0x10(9) s(-1)), the crack does not craze at the maximum stress for the reinforcement of strain, and the stress decreases after it continues to increase for some time. The non-crystallizing of the atom structure occurs near the crack tip because of high strain rate, and then the micro crack initiates in the area of structure disordered, the micro crack growth causes fracture of the "test specimen" eventually.