Twin nucleation and variant selection in Mg alloys: An integrated crystal plasticity modelling and experimental approach

Paramatmuni, Chaitanya; Zheng, Zebang; Rainforth, W. M.; Dunne, Fionn P.E.

doi:10.1016/j.ijplas.2020.102778

Cited by 28 publications

(7 citation statements)

References 77 publications

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“…The simulations show crack nucleation near twin tips and there is no strong correlation with slip, which is a more uniform plastic deformation mode in the simulated grains. The stored dislocation energy density has been identified as an important factor to explain the locations of the observed twins (Paramatmuni et al 2020), but in the present simulations the dislocation density does not affect the critical stress for twin nucleation. Including slip bands in the present model would be necessary to describe metals in which twin-induced microcracks are observed, while the actual failure is slip-induced (Reid 1981).…”

Section: Discussioncontrasting

confidence: 53%

Coupling a discrete twin model with cohesive elements to understand twin-induced fracture

2021

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The interplay between twinning and fracture in metals under deformation is an open question. The plastic strain concentration created by twin bands can induce large stresses on the grain boundaries. We present simulations in which a continuum model describing discrete twins is coupled with a crystal plasticity finite element model and a cohesive zone model for intergranular fracture. The discrete twin model can predict twin nucleation, propagation, growth and the correct twin thickness. Therefore, the plastic strain concentration in the twin band can be modelled. The cohesive zone model is based on a bilinear traction-separation law in which the damage is caused by the normal stress on the grain boundary. An algorithm is developed to generate interface elements at the grain boundaries that satisfy the traction-separation law. The model is calibrated by comparing polycrystal simulations with the experimentally observed strain to failure and maximum stress. The dynamics of twin and crack nucleation have been investigated. First, twins nucleate and propagate in a grain, then, microcracks form near the intersection between twin tips and grain boundaries. Microcracks appear at multiple locations before merging. A propagating crack can nucleate additional twins starting from the grain boundary, a few micrometres away from the original crack nucleation site. This model can be used to understand which type of texture is more resistant against crack nucleation and propagation in cast metals in which twinning is a deformation mechanism. The code is available online at https://github.com/TarletonGroup/CrystalPlasticity. Graphic Abstract

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Section: Discussioncontrasting

confidence: 53%

Coupling a discrete twin model with cohesive elements to understand twin-induced fracture

2021

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“…The motion of these dislocations, called twinning dislocations, leads to the propagation of the twin tip along the twin direction s β (Mahajan and Chin 1973). However, the motion of twinning dislocations is hindered by twin boundaries belonging to a different twin system (Zhao et al 2018) because of the energy required for dislocations to enter the twinned region and to reorient the crystal lattice (Paramatmuni et al 2020). This is modelled by a local interaction term:…”

Section: Crystal Plasticity Finite Element Framework and Discrete Twi...mentioning

confidence: 99%

Modelling the nucleation and propagation of cracks at twin boundaries

Grilli

Cocks

2021

Int J Fract

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Fracture arising from cracks nucleating and propagating along twin boundaries is commonly observed in metals that exhibit twinning as a plastic deformation mechanism. This phenomenon affects the failure of macroscopic mechanical components, but it is not fully understood. We present simulations in which a continuum model for discrete twins and a cohesive zone model are coupled to aid the understanding of fracture at twin boundaries. The interaction between different twin systems is modelled using a local term that depends on the continuum twin variables. Simulations reveal that the resolved shear stress necessary for an incident twin to propagate through a barrier twin can be up to eight times the resolved shear stress for twin nucleation. Interface elements are used at the interfaces between all bulk elements to simulate arbitrary intragranular cracks. An algorithm to detect twin interfaces is developed and their strength has been calibrated to give good agreement with the experimentally observed fracture path. The elasto-plastic deformation induced by discrete twins is modelled using the crystal plasticity finite element method and the stress induced by twin tips is captured. The tensile stress caused by the tip of an incident twin on a barrier twin is sufficient to nucleate a crack. A typical staircase fracture path, with cracks propagating along the twin interfaces, is reproduced only if the strength of the twin interfaces is decreased to about one-third of the strength of the bulk material. This model can be used to help understand fracture caused by the activation of multiple twin systems in different materials.

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“…There are arguments for the insufficiency of an elastic field-based criterion (i.e. energy release rate) for twin nucleation and growth, and criteria for stored (dislocation structure) energy have been recently proposed [108], [109].…”

Section: Discussionmentioning

confidence: 99%

J-integral analysis of the elastic strain fields of ferrite deformation twins using electron backscatter diffraction

et al. 2021

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Twin nucleation and variant selection in Mg alloys: An integrated crystal plasticity modelling and experimental approach

Cited by 28 publications

References 77 publications

Coupling a discrete twin model with cohesive elements to understand twin-induced fracture

Coupling a discrete twin model with cohesive elements to understand twin-induced fracture

Modelling the nucleation and propagation of cracks at twin boundaries

J-integral analysis of the elastic strain fields of ferrite deformation twins using electron backscatter diffraction

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