Atomistic study of edge and screw 〈c+a〉 dislocations in magnesium

Nogaret, T.; Curtin, W.A.; Yasi, Joseph A.; Hector, Louis G.; Trinkle, Dallas R.

doi:10.1016/j.actamat.2010.04.022

Cited by 120 publications

(66 citation statements)

References 31 publications

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“…The MEP on the pyramidal II plane follows the c + a direction while on the pyramidal I plane, the MEP is more complex. Overall, these GSF energy surfaces are consistent with available DFT results [13,14,45]. Figure 4 shows the GSF energy curves along specific directions for the basal, prismatic, pyramidal I, and pyramidal II planes.…”

Section: Generalized Stacking Fault Energysupporting

confidence: 73%

“…The previous sections show that both the MEAM and Kim potentials reproduce the physical properties and GSF energies of Mg in quite good agreement with experimental/ab initio [43], [13], [45], and [15], respectively. In sub figure (a), the generalized stacking fault energy curve is identical for shifts along the leading and trailing partial dislocation Burgers vectors and is drawn only for the leading partial.…”

Section: Dislocation Propertiessupporting

confidence: 50%

“…[50,51]) that have been fit to its bulk properties and some GSF energies, but these have not been tested for dislocations. Furthermore, our current and previous results [45] show that GSF energy alone is not sufficient to get good dislocation properties and therefore, their validity remains unclear in study focusing on dislocations and plasticity.…”

Section: Discussionmentioning

confidence: 88%

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Magnesium interatomic potential for simulating plasticity and fracture phenomena

Francis

Curtin

2014

Modelling Simul. Mater. Sci. Eng.

136

104

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Abstract.Magnesium has multiple dislocation and twinning systems with starkly different properties, which make its plastic deformation strongly anisotropic and highly complex. Existing empirical interatomic potentials fail to capture the full scope of these properties, making current molecular statics and dynamics simulation results of limited quantitative and predictive use. Here, based on the work by Kim et al, a new modified embedded-atom method potential for magnesium is introduced and rigorously validated against existing ab initio, continuum theory and experimental results. The new potential satisfactorily reproduces all the necessary mechanical properties for plastic deformation, including the various generalized stacking fault energy surfaces, dislocations core structures, Peierls stresses, surface energies, and basal plane cohesive strength. The capability of this potential to accurately describe all the important slip systems and fracture behavior makes it valuable for future realistic atomistic studies of general magnesium deformation and failure problems.

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Section: Generalized Stacking Fault Energysupporting

confidence: 73%

Section: Dislocation Propertiessupporting

confidence: 50%

Section: Discussionmentioning

confidence: 88%

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Magnesium interatomic potential for simulating plasticity and fracture phenomena

Francis

Curtin

2014

Modelling Simul. Mater. Sci. Eng.

136

104

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“…II plane 6,44 . In the current work, we use a newly developed MEAM-type interatomic potential 26 which has been validated to predict all observed glide dislocation cores in Mg in agreement with all available DFT computations and experiments.…”

Section: Meam Potentialmentioning

confidence: 99%

The origins of high hardening and low ductility in magnesium

Curtin

2015

Nature

546

170

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Magnesium is the ultimate lightweight structural metal but exhibits low ductility connected to unusual, mechanistically-unexplained, dislocation/plasticity phenomena, which make it difficult to form and use in energy-saving lightweight structures. Here, long-time molecular dynamics simulations using a DFT-validated interatomic potential reveal the fundamental origins of the previouslyunexplained phenomena and show a clear path toward design of new ductile magnesium alloys. The key c + a dislocation is metastable on easy-glide pyramidal II planes and undergoes a thermallyactivated, stress-dependent transition to one of three lower-energy, basal-dissociated immobile dislocation structures, which (i) cannot contribute to plastic straining and (ii) serve as strong obstacles to the motion of all other dislocations. The transition is intrinsic to magnesium, driven by reduction in dislocation energy and predicted to occur at very high frequency at room temperature, thus eliminating all major dislocation slip systems able to contribute to c-axis strain and leading to its low ductility.Enhancing ductility can thus be achieved by delaying, in time and temperature, the transition from the easy-glide metastable dislocation to the immobile basal-dissociated structures, and our results provide the underlying insights needed to guide the design of ductile magnesium alloys. * Corresponding author: william.curtin@epfl.ch 1 This is a post-print of the following article: Wu, Z. & Curtin, W. A. The origins of high hardening and low ductility in magnesium. Nature 526, 62-67 (2015). The final publication is available at http://dx.doi.org/10.1038/nature15364Developing lightweight structural metal is a crucial step on the path toward reduced energy consumption in many industries, especially automotive 1,2 and aerospace 3 . Magnesium (Mg) is the ultimate lightweight metal, with a density 23% that of steel and 66% that of aluminum, and so has tremendous potential to achieve energy efficiency 4 . In spite of this tantalizing property, Mg generally exhibits low ductility, insufficient for the forming and performance of structural components. The low ductility is associated with the inability of hexagonally-close-packed (hcp) Mg to deform plastically in the crystallographic c direction, which is accomplished primarily by dislocation glide on the pyramidal II plane with the c + a Burgers vector 5 (see Fig. 1).Experiments reveal a range of unusual, confounding, conflicting, and mechanistically-unexplained phenomena connected to c+a dislocations that coincide with the inability of Mg to achieve high plastic strains 6 . Uncovering and controlling the fundamental behavior of c + a dislocations is thus the key issue in Mg, and any solution would catapult Mg science, technology, and applications forward. Success would enable, for instance, lightweight automobiles that would consume less energy, independent of the energy source, and thus act as a multiplier for many other energyreduction strategies.Due to its critical importance and pro...

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“…Very recently, it has been reported atomistic study of edge and screw <c+a> dislocations in magnesium (Nogaret et al 2010). They concluded that at 300 K both screw and edge <c+a> dislocations may glide at stresses smaller than the experimentally observed.…”

Section: Wwwintechopencommentioning

confidence: 92%