Influence of twist boundary on deformation behaviour of 〈1 0 0〉 BCC Fe nanowires

Journal of Applied Physics

2017

Self Cite

Molecular dynamics simulations have been performed to understand the influence of temperature on the tensile deformation and fracture behavior of <111> BCC Fe nanowires. The simulations have been carried out at different temperatures in the range 10-1000 K employing a constant strain rate of 1× 10 8 s −1 . The results indicate that at low temperatures (10-375 K), the nanowires yield through the nucleation of a sharp crack and fails in brittle manner. On the other hand, nucleation of multiple 1/2<111> dislocations at yielding followed by significant plastic deformation leading to ductile failure has been observed at high temperatures in the range 450-1000 K. At the intermediate temperature of 400 K, the nanowire yields through nucleation of crack associated with many mobile 1/2<111> and immobile <100> dislocations at the crack tip and fails in ductile manner. The ductile-brittle transition observed in <111> BCC Fe nanowires is appropriately reflected in the stress-strain behavior and plastic strain at failure. The ductile-brittle transition increases with increasing nanowire size. The change in fracture behavior has been discussed in terms of the relative variations in yield and fracture stresses and change in slip behavior with respect to temperature. Further, the dislocation multiplication mechanism assisted by the kink nucleation from the nanowire surface observed at high temperatures has been presented.

Section: MD Simulation Detailssupporting

confidence: 80%

Section: Dislocation Multiplication Mechanism and Dissociation Of Imm...mentioning

confidence: 95%

Atomistic simulations on ductile-brittle transition in ⟨111⟩ BCC Fe nanowires

Journal of Applied Physics

2017

Self Cite

“…It has been shown that in samples free of initial defects, the twinning is inherently favoured at low temperatures and high strain rates [25]. However, the presence of initial dislocations may change the deformation mode from twinning to dislocation slip [25,26]. The occurrence of twinning under tensile loading in <100> BCC Fe nanowires is in agreement with earlier MD simulation studies [13,14,17] and experimental obser-vations on BCC W nanowires of size 15 nm [18].…”

Section: Resultssupporting

confidence: 86%

Twinning to slip transition in ultrathin BCC Fe nanowires

2018

Physics Letters A

Self Cite

We report twinning to slip transition with decreasing size and increasing temperature in ultrathin <100> BCC Fe nanowires. Molecular dynamics simulations have been performed on different nanowire size in the range 0.404-3.634 nm at temperatures ranging from 10 to 900 K. The results indicate that slip mode dominates at low sizes and high temperatures, while deformation twinning is promoted at high sizes and low temperatures. The temperature, at which the nanowires show twinning to slip transition, increases with increasing size. The different modes of deformation are also reflected appropriately in the respective stress-strain behaviour of the nanowires.

“…With increasing strain, this reoriented nanowire undergoes deformation by slip, but this has not lead to diffused necking and as a result, the pentagonal atomic chains were not observed. Detailed studies on <100> BCC Fe nanowires have shown that the deformation by twinning followed by reorientation occurs at 10 K [27][28][29] . This result shows that the orientation nanowire also influence the formation of pentagonal atomic chains in BCC Fe nanowires.…”

Section: Resultsmentioning

confidence: 99%

Formation of pentagonal atomic chains in BCC Fe nanowires

2016

Mater. Res. Express

For the first time, we report the formation of pentagonal atomic chains during tensile deformation of ultra thin BCC Fe nanowires. Extensive molecular dynamics simulations have been performed on <100>/{110} BCC Fe nanowires with different cross section width varying from 0.404 to 3.634 nm at temperatures ranging from 10 to 900 K. The results indicate that above certain temperature, long and stable pentagonal atomic chains form in BCC Fe nanowires with cross section width less than 2.83 nm. The temperature, above which the pentagonal chains form, increases with increase in nanowire size. The pentagonal chains have been observed to be highly stable over large plastic strains and contribute to high ductility in Fe nanowires.