{112̄2}〈23〉 Slip system in magnesium

Obara, Takashi; Yoshinga, H.; Morozümi, Shotaro

doi:10.1016/0001-6160(73)90141-7

Cited by 616 publications

(267 citation statements)

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“…Nature 526, 62-67 (2015). The final publication is available at http://dx.doi.org/10.1038/nature15364 the exceptionally high measured work hardening is accompanied by the observation of a rapid increase of straight c + a dislocations and also loops (density of ∼10 20 m −3 at 1% plastic strain 14 ).In fact, when c + a dislocations are observed in TEM 8,9,11,19,21 , they often exist as uniform arrays or pile-ups of long, straight dislocation segments. In contrast, at low temperatures, the c + a transitions cannot occur fast enough, leading to more normal evolution of dislocation densities, strengthening, and strain hardening, although now limited simply by the low temperature.…”

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confidence: 95%

“…Due to its critical importance and promise, observing and understanding c + a slip has been extensively studied over five decades [7][8][9][10] , and is accelerating recently [11][12][13][14] . In Mg single crystals, c+a slip occurs predominantly on the pyramidal II (Pyr.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the Pyr. II c + a dislocation transformations are responsible for the anomalous temperature dependence of the strengthening observed in the range of ∼130-293K 16,17 , for the high hardening rate observed at 300K 9,14,18,19 , and for the associated low ductility. …”

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confidence: 98%

“…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 promise, observing and understanding c + a slip has been extensively studied over five decades [7][8][9][10] , and is accelerating recently [11][12][13][14] . In Mg single crystals, c+a slip occurs predominantly on the pyramidal II (Pyr.…”

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confidence: 99%

“…Under c-axis compression, single crystal Mg also exhibits a rapid increase in stress with increasing strain, i.e. high work hardening 9,15,18,19 , and fractures at low strains at temperatures up to 500 K 9,15,19 . New work shows the formation of a very high density of c + a dislocation loops also dissociated on, and lying on, the basal planes 14 , with similar observations dating back fifty years 7,8,20 .…”

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The origins of high hardening and low ductility in magnesium

Curtin

2015

Nature

569

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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confidence: 95%