Twinning mechanism asymmetry in body-centered cubic tantalum under 001 uniaxial compression/tension

GB Wei and HX Xie and FX Yin and GH Lu, PHYSICAL REVIEW MATERIALS, 5, 123604 (2021).

DOI: 10.1103/PhysRevMaterials.5.123604

Plasticity of body-centered cubic tantalum with preexisting dislocations is investigated under 001 uniaxial compression/tension loading using a molecular dynamic simulation method. At low temperature or high strain rate, twinning is the main deformation mechanism under both 001 compression and tension. However, the twinning mechanism under compression is different from the conventional twinning mechanism under tension, which is formed by 1/61 (1) over bar1 twinning dislocations moving on adjacent ((1) over bar 12) planes along the twinning direction. The twin nucleates from six-layer dissociation of a 1/2111 screw dislocation and grows by the glide of disconnections that step the twin boundary by two ((1) over bar 12) planes. Further study shows that this type of twinning mode generates a finite antitwinning shear strain, the magnitude of which is one-half of that generated by the conventional deformation twinning. Finally, the two twinning mechanisms are discussed in terms of the energy landscape.

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