Tension–compression asymmetry of bilayer Ni/Ni3Al affected by dislocation formation–decomposition and twinning size

Molecular dynamics simulations were used to study the tensile and compressive properties of bilayer Ni/ Ni3Al. We found that: the tension–compression asymmetry behaviours of bilayer Ni/Ni3Al with different crystal orientations are different. The tension–compression asymmetry of different crystal orientations is result from different origins. For [001] crystal orientation, the formation of face angle dislocation in the γ' phase during tension, and no formation of face angle dislocation when compressed result in asymmetry. The reason for the [011] crystal orientation asymmetry is the twinning, and the twinning region during tension is larger than when it is compressed. [111] crystal orientation asymmetry is due to super dislocation decomposition. When dislocation is formed, the fault dislocation area during tension is smaller than that during compression, which results in the ability of preventing cross-slip when tension less than the compression state. The cross-slip is formed during tension, and the cross-slip does not occur during compression, exhibiting different tension–compression asymmetry behaviours. This study will provide theoretical guidance for the application of Ni-based single crystal alloys and further enhancement of their mechanical properties.