8 research outputs found
Superplastic Creep of Metal Nanowires from Rate-Dependent Plasticity Transition
Understanding
the time-dependent mechanical behavior of nanomaterials
such as nanowires is essential to predict their reliability in nanomechanical
devices. This understanding is typically obtained using creep tests,
which are the most fundamental loading mechanism by which the time-dependent
deformation of materials is characterized. However, due to existing
challenges facing both experimentalists and theorists, the time-dependent
mechanical response of nanowires is not well-understood. Here, we
use atomistic simulations that can access experimental time scales
to examine the creep of single-crystal face-centered cubic metal (Cu,
Ag, Pt) nanowires. We report that both Cu and Ag nanowires show significantly
increased ductility and superplasticity under low creep stresses,
where the superplasticity is driven by a rate-dependent transition
in defect nucleation from twinning to trailing partial dislocations
at the micro- or millisecond time scale. The transition in the deformation
mechanism also governs a corresponding transition in the stress-dependent
creep time at the microsecond (Ag) and millisecond (Cu) time scales.
Overall, this work demonstrates the necessity of accessing time scales
that far exceed those seen in conventional atomistic modeling for
accurate insights into the time-dependent mechanical behavior and
properties of nanomaterials
Superplastic Creep of Metal Nanowires from Rate-Dependent Plasticity Transition
Understanding
the time-dependent mechanical behavior of nanomaterials
such as nanowires is essential to predict their reliability in nanomechanical
devices. This understanding is typically obtained using creep tests,
which are the most fundamental loading mechanism by which the time-dependent
deformation of materials is characterized. However, due to existing
challenges facing both experimentalists and theorists, the time-dependent
mechanical response of nanowires is not well-understood. Here, we
use atomistic simulations that can access experimental time scales
to examine the creep of single-crystal face-centered cubic metal (Cu,
Ag, Pt) nanowires. We report that both Cu and Ag nanowires show significantly
increased ductility and superplasticity under low creep stresses,
where the superplasticity is driven by a rate-dependent transition
in defect nucleation from twinning to trailing partial dislocations
at the micro- or millisecond time scale. The transition in the deformation
mechanism also governs a corresponding transition in the stress-dependent
creep time at the microsecond (Ag) and millisecond (Cu) time scales.
Overall, this work demonstrates the necessity of accessing time scales
that far exceed those seen in conventional atomistic modeling for
accurate insights into the time-dependent mechanical behavior and
properties of nanomaterials
Superplastic Creep of Metal Nanowires from Rate-Dependent Plasticity Transition
Understanding
the time-dependent mechanical behavior of nanomaterials
such as nanowires is essential to predict their reliability in nanomechanical
devices. This understanding is typically obtained using creep tests,
which are the most fundamental loading mechanism by which the time-dependent
deformation of materials is characterized. However, due to existing
challenges facing both experimentalists and theorists, the time-dependent
mechanical response of nanowires is not well-understood. Here, we
use atomistic simulations that can access experimental time scales
to examine the creep of single-crystal face-centered cubic metal (Cu,
Ag, Pt) nanowires. We report that both Cu and Ag nanowires show significantly
increased ductility and superplasticity under low creep stresses,
where the superplasticity is driven by a rate-dependent transition
in defect nucleation from twinning to trailing partial dislocations
at the micro- or millisecond time scale. The transition in the deformation
mechanism also governs a corresponding transition in the stress-dependent
creep time at the microsecond (Ag) and millisecond (Cu) time scales.
Overall, this work demonstrates the necessity of accessing time scales
that far exceed those seen in conventional atomistic modeling for
accurate insights into the time-dependent mechanical behavior and
properties of nanomaterials
Superplastic Creep of Metal Nanowires from Rate-Dependent Plasticity Transition
Understanding
the time-dependent mechanical behavior of nanomaterials
such as nanowires is essential to predict their reliability in nanomechanical
devices. This understanding is typically obtained using creep tests,
which are the most fundamental loading mechanism by which the time-dependent
deformation of materials is characterized. However, due to existing
challenges facing both experimentalists and theorists, the time-dependent
mechanical response of nanowires is not well-understood. Here, we
use atomistic simulations that can access experimental time scales
to examine the creep of single-crystal face-centered cubic metal (Cu,
Ag, Pt) nanowires. We report that both Cu and Ag nanowires show significantly
increased ductility and superplasticity under low creep stresses,
where the superplasticity is driven by a rate-dependent transition
in defect nucleation from twinning to trailing partial dislocations
at the micro- or millisecond time scale. The transition in the deformation
mechanism also governs a corresponding transition in the stress-dependent
creep time at the microsecond (Ag) and millisecond (Cu) time scales.
Overall, this work demonstrates the necessity of accessing time scales
that far exceed those seen in conventional atomistic modeling for
accurate insights into the time-dependent mechanical behavior and
properties of nanomaterials
Atomistic Simulation of the Rate-Dependent Ductile-to-Brittle Failure Transition in Bicrystalline Metal Nanowires
The
mechanical properties and plastic deformation mechanisms of
metal nanowires have been studied intensely for many years. One of
the important yet unresolved challenges in this field is to bridge
the gap in properties and deformation mechanisms reported for slow
strain rate experiments (∼10<sup>–2</sup> s<sup>–1</sup>), and high strain rate molecular dynamics (MD) simulations (∼10<sup>8</sup> s<sup>–1</sup>) such that a complete understanding
of strain rate effects on mechanical deformation and plasticity can
be obtained. In this work, we use long time scale atomistic modeling
based on potential energy surface exploration to elucidate the atomistic
mechanisms governing a strain-rate-dependent incipient plasticity
and yielding transition for face centered cubic (FCC) copper and silver
nanowires. The transition occurs for both metals with both pristine
and rough surfaces for all computationally accessible diameters (<10
nm). We find that the yield transition is induced by a transition
in the incipient plastic event from Shockley partials nucleated on
primary slip systems at MD strain rates to the nucleation of planar
defects on non-Schmid slip planes at experimental strain rates, where
multiple twin boundaries and planar stacking faults appear in copper
and silver, respectively. Finally, we demonstrate that, at experimental
strain rates, a ductile-to-brittle transition in failure mode similar
to previous experimental studies on bicrystalline silver nanowires
is observed, which is driven by differences in dislocation activity
and grain boundary mobility as compared to the high strain rate case
Superplastic Creep of Metal Nanowires from Rate-Dependent Plasticity Transition
Understanding
the time-dependent mechanical behavior of nanomaterials
such as nanowires is essential to predict their reliability in nanomechanical
devices. This understanding is typically obtained using creep tests,
which are the most fundamental loading mechanism by which the time-dependent
deformation of materials is characterized. However, due to existing
challenges facing both experimentalists and theorists, the time-dependent
mechanical response of nanowires is not well-understood. Here, we
use atomistic simulations that can access experimental time scales
to examine the creep of single-crystal face-centered cubic metal (Cu,
Ag, Pt) nanowires. We report that both Cu and Ag nanowires show significantly
increased ductility and superplasticity under low creep stresses,
where the superplasticity is driven by a rate-dependent transition
in defect nucleation from twinning to trailing partial dislocations
at the micro- or millisecond time scale. The transition in the deformation
mechanism also governs a corresponding transition in the stress-dependent
creep time at the microsecond (Ag) and millisecond (Cu) time scales.
Overall, this work demonstrates the necessity of accessing time scales
that far exceed those seen in conventional atomistic modeling for
accurate insights into the time-dependent mechanical behavior and
properties of nanomaterials
Superplastic Creep of Metal Nanowires from Rate-Dependent Plasticity Transition
Understanding
the time-dependent mechanical behavior of nanomaterials
such as nanowires is essential to predict their reliability in nanomechanical
devices. This understanding is typically obtained using creep tests,
which are the most fundamental loading mechanism by which the time-dependent
deformation of materials is characterized. However, due to existing
challenges facing both experimentalists and theorists, the time-dependent
mechanical response of nanowires is not well-understood. Here, we
use atomistic simulations that can access experimental time scales
to examine the creep of single-crystal face-centered cubic metal (Cu,
Ag, Pt) nanowires. We report that both Cu and Ag nanowires show significantly
increased ductility and superplasticity under low creep stresses,
where the superplasticity is driven by a rate-dependent transition
in defect nucleation from twinning to trailing partial dislocations
at the micro- or millisecond time scale. The transition in the deformation
mechanism also governs a corresponding transition in the stress-dependent
creep time at the microsecond (Ag) and millisecond (Cu) time scales.
Overall, this work demonstrates the necessity of accessing time scales
that far exceed those seen in conventional atomistic modeling for
accurate insights into the time-dependent mechanical behavior and
properties of nanomaterials
Resonant Tunneling in Graphene Pseudomagnetic Quantum Dots
Realistic relaxed configurations
of triaxially strained graphene quantum dots are obtained from unbiased
atomistic mechanical simulations. The local electronic structure and
quantum transport characteristics of y-junctions based on such dots
are studied, revealing that the quasi-uniform pseudomagnetic field
induced by strain restricts transport to Landau level- and edge state-assisted
resonant tunneling. Valley degeneracy is broken in the presence of
an external field, allowing the selective filtering of the valley
and chirality of the states assisting in the resonant tunneling. Asymmetric
strain conditions can be explored to select the exit channel of the
y-junction