孪晶密度和温度对纳米孪晶钛力学性能的影响

The mechanical behavior of nano-twinned titanium under uniaxial tension was simulated by molecular dynamics at different twin densities and temperatures. The simulation results show that with the decrease of twin density, the yield strength of nano-twinned titanium first increases and then decreases at room temperature, and there is a critical twin density in the material. When the twin density is less than the critical twin density, the grain refinement effect of twins leads to the increase of the strength of the material. When the twin density is larger than the critical twin density, the nucleation and increment of dislocations at twin boundary, grain boundary and their intersection become the dominant factors of material deformation, which affect the mechanical properties of nano-twinned titanium. When the twin density is far away from the critical value, the twin spacing becomes smaller, the nucleation and proliferation of dislocations become more intense, and the strength of the material decreases. The change of temperature can affect the activity of atoms and the deformation mechanism of lattice. With the increase of temperature, the bonding force between atoms decreases, the disorder of atomic structure near the grain boundary and the degree of HCP-BCC phase transformation increase, resulting in the decrease of elastic modulus and yield strength, and the increase of dislocation nucleation and movement affects the plastic deformation of the material.