Anisotropic deformation behavior of [11(2)over-bar0], [10(1)over-bar0] and [0001]-textured nanocrystalline titanium

Molecular dynamics (MD) simulation is employed to investigate tensile deformation of [11(2)over bar0] , [10(1)over bar0] and [0001]-textured nanocrystalline titanium with average grain size ranging from 4 nm to 48 nm. The grain size and orientation dependent mechanical properties are determined. Average flow stress of [11(2)over bar0] texture is much higher than that of other textures, which may be induced by the complex twinning-dislocation and dislocation-dislocation interactions involving {10(1)over bar2}(10(1)over bar1) twinning (TW), basal (a) and pyramidal (c +a) slip within this texture. In contrast to this, the easier prismatic (a) slip acts as the dominant slip mode for the [0001]-textured samples. Plastic deformation of the [10(1)over bar0]-textured samples is mainly controlled by {11(2)over bar1}(11(2)over bar6) TW. Grain boundary mediated plasticity (GBMP) is more pronounced in the [10(1)over bar0]-textured structures, while it is restricted by dislocation pile-ups in the [11(2)over bar0]-textured structures. Further discussions about effects of grain size on different deformation mechanisms including GBMP, dislocation slip and deformation TW are made. In particular, the variation of twin variant number, twin fraction and dislocation number with grain size are quantitatively counted. The detailed analysis of TW nucleation mechanism reveals the emergence of multiple TW nucleation sources with increasing grain size. The current study sheds light on the deformation anisotropy of nanocrystalline titanium, facilitating the optimization design of Ti-based nanostructures.

Automated summary

Molecular dynamics simulation is used to investigate the tensile deformation of nanocrystalline titanium with different textures and grain sizes. The study reveals that the mechanical properties vary with different textures, with complex twinning-dislocation and dislocation-dislocation interactions being the main factors in [11(2)bar0] texture, and easier prismatic slip dominantly occurring in [0001]-textured samples. Plastic deformation in [10(1)bar0]-textured samples is mainly controlled by twinning. Grain boundary mediated plasticity is more pronounced in [10(1)bar0]-textured structures, while it is restricted by dislocation pile-ups in [11(2)bar0]-textured structures. The study also quantitatively analyzes the effects of grain size on twin variant number, twin fraction, and dislocation number.