Molecular Dynamics Study On Tension Deformation Of Nano-single Crystal γ-TiAl Intermetallics

The mechanical properties and deformation mechanism of nano-single crystal rodγ-TiAl intermetallics were studied by Molecular Dynamics(MD) simulation in this thesis. And the mechanical properties and deformation mechanism of different orientations, different sections, and different temperatures were compared.At the temperature of 300K, the values of the yield stress and the yield strain of the [001] direction are higher than those of the [100] direction. When the direction is [100], it shows that the 1/ 6[112] partial dislocation takes place firstly to form stacking fault. And then the 1/ 2[110] ordinary dislocation is formed by the reaction of the 1/ 6[211] partial dislocation and the 1/ 6[121] partial dislocation.When the direction is [001], the 1/ 6[121] partial dislocation emits firstly, the other three partial dislocations( 1/ 6[112] , 1/ 6[121] , 1/ 6[112] ) happen gradually and the four partial dislocations form [011] super dislocation finally. Because the energy of the < 121]{111} slip system is higher than the result of the < 112]{111} slip system, the value of the yield stress is higher.The value of the yield stress is higher when the larger section area is larger. Since the proportion of surface atoms decrease with the section area increasing, and this induces the surface effect weakening, so that the larger stress is needed for the dislocation starting. Different deformation mechanisms are not detected for different sections.The values of the yield stress and the corresponding yield strain at the temperature of 300K are higher than those of 500K. The reason is that the value of the kinetic energies of the atoms is higher at a higher temperature, so that the energy needed to override the energy barrier is lower, which leads a lower yield stress. The deformation mechanisms are the same at the two temperatures.