Slip, twinning, and fracture in hexagonal close-packed metals

Yoo, M.H.

doi:10.1007/bf02648537

Cited by 1,654 publications

(577 citation statements)

References 64 publications

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“…The simplest approach is based on the consideration of a ductility parameter D = K/G, defined as the ratio of the bulk modulus (K) to the Voigt average of the shear modulus (G). In hcp metals, this parameter has been shown to correlate well with the relative ductility 9,12 , with a higher K/G-ratio indicating a tendency towards enhanced ductility. This correlation can be understood simply from a picture where microcrack initiation and propagation requires bond breaking, which becomes more difficult for high values of the bulk modulus, K, while deformation mechanisms that give rise to plasticity are expected to be more prevalent in materials with comparatively low shear moduli G.…”

Section: Introductionmentioning

confidence: 91%

“…Several approaches have been proposed in the literature to examine the intrinsic ductility of a material from first-principles DFT calculations [9][10][11][12][13][14][15] . The simplest approach is based on the consideration of a ductility parameter D = K/G, defined as the ratio of the bulk modulus (K) to the Voigt average of the shear modulus (G).…”

Section: Introductionmentioning

confidence: 99%

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First-principles study of the structural and elastic properties of rhenium-based transition-metal alloys

et al. 2012

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Structural, energetic and elastic properties of hexagonal-close-packed rhenium-based transitionmetal alloys are computed by density-functional theory. The practical interest in these materials stems from the attractive combination of mechanical properties displayed by rhenium for structural applications requiring the combination of high melting temperature and low-temperature ductility. Single-crystal elastic constants, atomic volumes, axial c/a ratios, and dilute heats of solution for Re-X alloys are computed, considering all possible transition-metal solute species X. Calculated elastic constants are used to compute values of a commonly considered intrinsic-ductility parameter K/G, where K is the bulk modulus and G denotes the Voigt average of the shear modulus, as well as the anisotropies in the Young's modulus and shear modulus. The calculated properties show clear trends as a function of d-band filling, which can be rationalized through tight-binding theory. The results indicate that solutes to the left of rhenium in the periodic table show a tendency to increase the intrinsic ductility parameter, a trend that correlates with an increase of the c/a ratio towards the ideal value associated optimal close packing. The Young's modulus shows a trend towards increasing isotropy with alloying of solutes X to the left of Re, while the shear modulus shows the opposite trend but with an overall weaker dependence on solute additions.

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Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

First-principles study of the structural and elastic properties of rhenium-based transition-metal alloys

et al. 2012

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“…6 and 9 is compared, it may be concluded that much more twins generated near the surface underwent a tensile strain. This may, however, be attributed to the lesser twinning shear component needed for nucleation of the 84.70°twinning system [32].…”

Section: Mechanical Formingmentioning

confidence: 98%

Response of Ti microstructure in mechanical and laser forming processes

et al. 2018

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Microstructural deformation mechanisms present during three different forming processes in commercially pure Ti were analysed. Room temperature mechanical forming, laser beam forming and a combination of these two processes were applied to thick metal plates in order to achieve the same final shape. An electron backscatter diffraction technique was used to study the plate microstructure before and after applying the forming processes. Substantial differences among the main deformation mechanisms were clearly detected. In pure mechanical forming at room temperature, mechanical twinning predominates in both compression and tensile areas. A dislocation slip mechanism inside the compression and tensile area is characteristic of the pure laser forming process. Forming processes which subsequently combine the laser and mechanical approaches result in a combination of twinning and dislocation mechanisms. The Schmid factor at an individual grain level, the local temperature and the strain rate are factors that determine which deformation mechanism will prevail at the microscopic level. The final microstructures obtained after the different forming processes were applied are discussed from the point of view of their influence on the performance of the resulting formed product. The observations suggest that phase transformation in Ti is an additional microstructural factor that has to be considered during laser forming.

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“…The total amount of twinning, hence the anelastic strain, is reduced as the strength of the SRO increases. 2 This explanation, however, is at odds with the reversion of the effect at the largest concentration of Gd. To understand why the reversion happens, the effect of other solutes, Al and Zn, must be compared with that of Gd.…”

Section: Solute Concentrationmentioning

confidence: 99%

“…The activation of twinning at low stress and strains in Mg allows it to play a crucial role, that of indirectly meeting the von-Mises criterion of five independent slip systems, for homogeneous plastic deformation [1][2][3]. These twins are not fully stable in the deformed state [4] and tend to partly revert, once the applied stress is removed [5] or reversed [6,7], leading to hysteresis loops during loading and unloading.…”

Section: Introductionmentioning

confidence: 99%

Anelasticity in cast Mg-Gd alloys

Nagarajan

2017

Materials Science and Engineering: A

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Cyclic loading-unloading tests in tension and compression were carried out on pure Mg and alloys with 0.4, 1.5 and 4.2 at.% Gd, over a range of grain sizes, to quantify the solute and strain dependence of the materials anelasticity in the form of hysteresis loops. For a given grain size, the anelastic effect was more pronounced, i.e., the loops were wider, for pure Mg, and it decreased rapidly with the Gd concentration. The effect was larger for the finer grains in all materials, and in compression for the pure Mg and the 0.4Gd alloy. No difference between tension and compression was observed for the 1.5Gd alloy, whereas the loops were wider in tension than in compression for the 4.2Gd alloy. In comparison with existing studies in Mg-Al and Mg-Zn alloys, for a given solute concentration, Gd was more effective in reducing the magnitude of the effect than either Zn or Al, in that order. The overall behavior is discussed in terms of the hardening effects of short range order of the alloys on {1012} and {1011} twinning.

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Slip, twinning, and fracture in hexagonal close-packed metals

Cited by 1,654 publications

References 64 publications

First-principles study of the structural and elastic properties of rhenium-based transition-metal alloys

First-principles study of the structural and elastic properties of rhenium-based transition-metal alloys

Response of Ti microstructure in mechanical and laser forming processes

Anelasticity in cast Mg-Gd alloys

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