The activity of non-basal slip systems and dynamic recovery at room temperature in fine-grained AZ31B magnesium alloys

Koike, Junichi; Kobayashi, Takuya; Mukai, Toshiji; Watanabe, Hiroyuki; Suzuki, Masato; Maruyama, Kouichi; Higashi, Kenji

doi:10.1016/s1359-6454(03)00005-3

Cited by 1,256 publications

(435 citation statements)

References 31 publications

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“…Indeed, TEM observations in large grain materials show arrays of straight c + a dislocation segments 11,21 inside grains but particularly near grain boundaries 35 , suggesting that the c + a are nucleated near grain boundaries but then only travel a short distance before transforming. In contrast, high ductility is achieved in Mg with micronscale grain sizes 10 . Finally, the mechanism of the c + a transition and its consequent strength anomalies may not be unique to Mg; similar observations are seen in other hcp metals 7,17,20 (Cd, Zn, etc.).…”

Section: Discussionmentioning

confidence: 94%

“…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%

“…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%

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The origins of high hardening and low ductility in magnesium

Curtin

2015

Nature

543

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: Discussionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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The origins of high hardening and low ductility in magnesium

Curtin

2015

Nature

543

170

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“…According to Frank's formula, this change is consistent with the view that prismatic and/or <c + a> dislocations are incorporated into the sub-boundaries as they gradually take on a high angle character. The activation of non-basal dislocations is required in the vicinities of the initial boundaries in order to accommodate the large plastic incompatibility stresses (Koike et al, 2003). The differences between the two distributions therefore arise because the cDRX grains considered here were formed essentially near the initial grain boundaries while the MBs-KBs developed in the grain interiors.…”

Section: Wwwintechopencommentioning

confidence: 97%

Deformation Structures and Recrystallization in Magnesium Alloys

Martin¹,

Mishra²,

Jonas³

2011

Magnesium Alloys - Design, Processing and Properties

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“…The active slip systems were identified using the EBSD data and the SE SEM images acquired after the in-situ creep test. Based on the literatures, [28][29][30] three slip modes were used for deformation analysis: basal <a> ({0001}<-2110>), first-order prismatic <a> ({01-10}<2-1-10>), and second-order pyramidal <c+a> ({11-22}<-1-123>). Fig.…”

Section: Microstructural Evolution During Creep Exposurementioning

confidence: 99%

Creep and Fracture Behavior of Peak-Aged Mg-11Y-5Gd-2Zn-0.5Zr (wt pct)

Yin

Wang

Boehlert

et al. 2012

Metall Mater Trans A

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The tensile-creep and creep-rupture behavior of heat-resistant peak-aged Mg-11Y-5Gd-2Zn-0.5Zr (wt.%) (WGZ1152) was investigated at T=523-598K (0.58-0.66T m ) and stresses between 30MPa to 140MPa. The minimum creep rate of the alloy was almost two orders of magnitude lower than that for WE54-T6, and was comparable to that for HZ32-T5. The creep behavior exhibited an extended tertiary creep stage, which was believed to be associated with precipitate coarsening. The creep stress exponent value was 4.5, suggesting that dislocation creep was the rate-controlling mechanism. The activation energy for creep (221±20kJ/mol) was higher than that for self-diffusion in magnesium, and was believed to be associated with the activation of non-basal slip and cross slip. This was consistent with the surface deformation observations, which revealed a transition from basal slip to non-basal slip and cross slip with increasing temperature. The minimum creep rate and rupture time followed the original and modified Monkman-Grant relationships. The microcracks and cavities preferentially nucleated at grain boundaries and at the interface between Mg matrix and the second phase. In-situ creep experiments highlighted the intergranular cracking evolution.

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The activity of non-basal slip systems and dynamic recovery at room temperature in fine-grained AZ31B magnesium alloys

Cited by 1,256 publications

References 31 publications

The origins of high hardening and low ductility in magnesium

The origins of high hardening and low ductility in magnesium

Deformation Structures and Recrystallization in Magnesium Alloys

Creep and Fracture Behavior of Peak-Aged Mg-11Y-5Gd-2Zn-0.5Zr (wt pct)

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