An atomistic-to-microscale computational analysis of the dislocation pileup-induced local stresses near an interface in plastically deformed two-phase materials

Peng, Yipeng; Ji, Rigelesaiyin; Phan, Thanh; Gao, Wei; Levitas, Valery I.; Xiong, Liming

doi:10.1016/j.actamat.2022.117663

Cited by 36 publications

(8 citation statements)

References 76 publications

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“…As designed, the interface under consideration here indeed blocks the motion of dislocations without allowing any transmission. Also, as shown in [102], the dislocation configuration behind the pileup tip in Fig. 3 actually matches an analytical solution from Hirth and Lothe very well.…”

Section: A Dislocation Pileup Processsupporting

confidence: 74%

“…Here we have carefully chosen the crystallographic orientation of both the hexagonal and square lattices to construct the incoherent interface (Fig. 2b) such that: (a) the initially introduced dislocation slip is perpendicular to the interface, and (b) a dislocation transmission across the interface is suppressed, which has been justified through a detailed Schmid factor analysis and geometric compatibility factor analysis in [102]. In this way, a large number of dislocations can be piled up at the in-terface and a high internal stress is generated ahead of the slip-interface intersection, whose contributions to the subsequent PTs can be then well quantified without the need of considering transmission, cross-slip, and among several other complexities.…”

Section: B the Computer Model Setupmentioning

confidence: 99%

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Effect of a Micro-scale Dislocation Pileup on the Atomic-Scale Multi-variant Phase Transformation and Twinning

Peng¹,

Ji²,

Phan³

et al. 2022

Preprint

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In this paper, we perform concurrent atomistic-continuum (CAC) simulations to: (i) characterize the internal stress induced by the microscale dislocation pileup at an atomically structured interface; (ii) decompose this stress into two parts, one of which is from the dislocations behind the pileup tip according to the Eshelby model and the other is from the dislocations at the pileup tip according to a super-dislocation model; and (iii) assess how such internal stresses contribute to the atomicscale phase transformations (PTs), reverse PTs, and twinning. The main novelty of this work is to unify the atomistic description of the interface and the coarse-grained (CG) description of the lagging dislocations away from the interface within one single framework. Our major findings are: (a) the interface dynamically responds to a pileup by forming steps/ledges, the height of which is proportional to the number of dislocations arriving at the interface; (b) the stress intensity factors are linearly proportional to the number of the dislocations in a nanoscale pileup, but upper bends to a high level when tens of dislocations are involved in a microscale pileup; (c) when the presheared sample is compressed, a direct square-to-hexagonal PT occurs ahead of the pileup tip and eventually grows into a wedge shape. The two variants of the hexagonal phases form a twin with respect to each other; (d) upon a further increase of the loading, part of the newly formed hexagonal phase transforms back to the square phase. The square product phase resulting from this reverse PT forms a twin with respect to the initial square phase. All phase boundaries (PBs) and twin boundaries (TBs) are stationary and correspond to zero thermodynamic Eshelby driving forces; and (e) the stress intensity induced by a pileup consisting of 16 dislocations reduces the stress required for initiating a PT by a factor of 5.5, comparing with that in the sample containing no dislocations. This work is a first characterization of the behavior of PTs/twinning resulting from the reaction between a microscale dislocation slip and an atomically structured interface. The gained knowledge will advance our understanding on how the multi-phase material behaves in many complex physical processes, such as the synthesis of multi-phase high-entropy alloys or superhard ceramics under high pressure torsion, deep mantle earthquakes in geophysics, and so on, which all involve dislocation slip, PTs, twinning, and their interactions across from the atomistic to the microscale and beyond.

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Section: A Dislocation Pileup Processsupporting

confidence: 74%

Section: B the Computer Model Setupmentioning

confidence: 99%

Effect of a Micro-scale Dislocation Pileup on the Atomic-Scale Multi-variant Phase Transformation and Twinning

Peng¹,

Ji²,

Phan³

et al. 2022

Preprint

Self Cite

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“…14,16). It follows from our phasefield, 101103) molecular dynamics, 118) and concurrent atomistic-continuum simulations 121,122) that most dislocations are located at the grain or phase boundary for large shear stress, making a step (superdislocation) (Fig. 7).…”

Section: Revisiting Grain-size Dependence Of the Minimummentioning

confidence: 69%

“…Coupled atomistic-continuum approaches to determine stress concentrators at the tip of dislocation pileup 121) and following martensitic PT 122) utilize atomistic resolution at the tip of the pileup and an obstacle (grain or phase boundary) and FEM solutions elsewhere. This allows for a significantly increased sample size while resolving critical atomistic processes.…”

Section: Atomistic and Phase-field Studies Of The Mechanism Of Plasti...mentioning

confidence: 99%

Recent <i>In Situ</i> Experimental and Theoretical Advances in Severe Plastic Deformations, Strain-Induced Phase Transformations, and Microstructure Evolution under High Pressure

Levitas

2023

Mater. Trans.

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Severe plastic deformations (SPD) under high pressure, mostly by high-pressure torsion, are employed for producing nanostructured materials and stable or metastable high-pressure phases. However, they were studied postmortem after pressure release. Here, we review recent in situ experimental and theoretical studies of coupled SPD, strain-induced phase transformations (PTs), and microstructure evolution under high pressure obtained under compression in diamond anvil cell or compression and torsion in rotational diamond anvil cell. The utilization of x-ray diffraction with synchrotron radiation allows one to determine the radial distribution of volume fraction of phases, pressure, dislocation density, and crystallite size in each phase and find the main laws of their evolution and interaction. Coupling with the finite element simulations of the sample behavior allows the determination of fields of all components of the stress and plastic strain tensors and volume fraction of high-pressure phase and provides a better understanding of ways to control occurring processes. Atomistic, nanoscale and scale-free phase-field simulations allow elucidation of the main physical mechanisms of the plastic strain-induced drastic reduction in phase transformation pressure (by one to two orders of magnitude), the appearance of new phases, and strain-controlled PT kinetics in comparison with hydrostatic loading. Combining in situ experiments with multiscale theory potentially leads to the formulation of methods to control strain-induced PT and microstructure evolution and designing economic synthetic paths for the defect-induced synthesis of desired high-pressure phases, nanostructures, and nanocomposites.

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“…The interaction between a pileup and a disclination was studied by Rybin et al (2018) and Perevezentsev et al (2020). These simplified models incorporate the strain-induced GB-deformation which was studied with an advanced multiscale model by Peng et al (2022). Liu et al (2022a) studied the effect of DPUs at grain boundaries with varying strength in a study of the Bauschinger effect.…”

Section: Theoretical Analysis Of Dpusmentioning

confidence: 99%

Dislocation pileups in small grains

Schouwenaars

Kestens

2023

International Journal of Plasticity

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An atomistic-to-microscale computational analysis of the dislocation pileup-induced local stresses near an interface in plastically deformed two-phase materials

Cited by 36 publications

References 76 publications

Effect of a Micro-scale Dislocation Pileup on the Atomic-Scale Multi-variant Phase Transformation and Twinning

Effect of a Micro-scale Dislocation Pileup on the Atomic-Scale Multi-variant Phase Transformation and Twinning

Recent <i>In Situ</i> Experimental and Theoretical Advances in Severe Plastic Deformations, Strain-Induced Phase Transformations, and Microstructure Evolution under High Pressure

Dislocation pileups in small grains

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