Magnesium interatomic potential for simulating plasticity and fracture phenomena

Wu, Zhaoxuan; Francis, Michael F; Curtin, W.A.

doi:10.1088/0965-0393/23/1/015004

Cited by 136 publications

(123 citation statements)

References 48 publications

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“…An initial c + a edge dislocation core starts on the Pyr. II glide plane and dissociates into 1/2 c + a +1/2 c + a on this plane, a structure in good agreement with DFT 26 (see Methods and Ref 5 for all the Burgers vector notations). We then execute long-time MD at elevated temperatures T = 500, 600, 700 K to accelerate any thermally activated processes, and under various applied stresses normal to the glide plane.…”

Section: Mechanisms Of C + a Dislocation Transitionsupporting

confidence: 69%

“…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. Extend Data Fig.…”

Section: Meam Potentialmentioning

confidence: 93%

“…Extend Data Fig. 1 shows the c + a edge and screw dislocation core structures on pyramidal II planes as predicted by the MEAM potential 26 and DFT 45 . Dislocation core structures are visualized using both the component of the Nye tensor plot 46 and differential displacement plot 47 .…”

Section: Meam Potentialmentioning

confidence: 99%

“…II planes with the partial dislocations having primarily pure edge or pure screw character and different partial core structures. For further details, see Ref 26 .…”

Section: Meam Potentialmentioning

confidence: 99%

“…5 and the attractive configurational force γ I 1 due to the basal I 1 stacking fault. Using the calculated elastic constants and γ I 1 = 11.3 mJ/m 2 of the MEAM potential 26 , the equilibrium separation is d = 37 nm. This suggests there is a thermodynamic driving force to increase the partial separation beyond the separation observed in the simulations.…”

Section: Meam Potentialmentioning

confidence: 99%

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The origins of high hardening and low ductility in magnesium

Curtin

2015

Nature

538

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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Section: Mechanisms Of C + a Dislocation Transitionsupporting

confidence: 69%

Section: Meam Potentialmentioning

confidence: 93%

Section: Meam Potentialmentioning

confidence: 99%

“…II planes with the partial dislocations having primarily pure edge or pure screw character and different partial core structures. For further details, see Ref 26 .…”

Section: Meam Potentialmentioning

confidence: 99%

Section: Meam Potentialmentioning

confidence: 99%

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The origins of high hardening and low ductility in magnesium

Curtin

2015

Nature

538

170

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Modified Embedded‐Atom Method Potentials for the Plasticity and Fracture Behaviors of Unary HCP Metals

Chen

Aitken

Sorkin

et al. 2021

Advcd Theory and Sims

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Modified embedded‐atom method (MEAM) potentials have been widely used in molecular dynamics (MD) simulations to describe the interatomic interactions in metallic systems. However, conventional MEAM potentials are almost exclusively fit to a limited number of key single‐value properties, limiting the predictability of MD simulations, especially for complex hexagonal‐close‐packed (HCP) metals with multiple slip systems. Here, three MEAM potentials for unary HCP metals (Mg, Co, and Ti) are fit to conventional target properties, as well as continuous‐energy curves and their gradients obtained from density‐functional theory calculations. These targets include the lattice parameters, cohesive energy, elastic constants, and surface energies as well as the cohesive energy curve, basal plane decohesion energy curve, and generalized stacking fault energy curves for basal, prismatic, pyramidal I, and pyramidal II planes. These interatomic potentials demonstrate excellent reproduction of relevant properties and enable accurate MD simulations of volumetric and plastic deformations, as well as fracture in Mg, Co, and Ti HCP metals. Importantly, the interatomic potentials demonstrate better performance than all existing EAM/MEAM potentials readily available from the literature.

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The Effect of the Orientation of Second-Order Pyramidal <c + a > Dislocations on Plastic Flow in Magnesium

Srivastava

El‐Awady

2019

The Minerals, Metals &Amp; Materials Series

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Magnesium interatomic potential for simulating plasticity and fracture phenomena

Cited by 136 publications

References 48 publications

The origins of high hardening and low ductility in magnesium

The origins of high hardening and low ductility in magnesium

Modified Embedded‐Atom Method Potentials for the Plasticity and Fracture Behaviors of Unary HCP Metals

The Effect of the Orientation of Second-Order Pyramidal <c + a > Dislocations on Plastic Flow in Magnesium

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