Twinning in lead

Weertman, J.

doi:10.1007/bf00550122

Cited by 26 publications

(23 citation statements)

References 4 publications

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“…This dislocation reaction has a high-energy barrier and might be difficult to activate. Nanocrystalline materials have a much higher strength than their coarse-grained counterparts [38][39][40], and therefore deform under very high stress. This high stress helps overcome the high-energy barrier for the dislocation reactions.…”

Section: Discussionmentioning

confidence: 99%

Formation of single and multiple deformation twins in nanocrystalline fcc metals

Zhu¹,

Narayan²,

Hirth³

et al. 2009

Acta Materialia

172

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Deformation twins are often observed to meet each other to form multi-fold twins in nanostructured face-centered cubic (fcc) metals. Here we propose two types of mechanism for the nucleation and growth of four different single and multiple twins. These mechanisms provide continuous generation of twinning partials for the growth of the twins after nucleation. A relatively high stress or high strain rate is needed to activate these mechanisms, making them more prevalent in nanocrystalline materials than in their coarse-grained counterparts. Experimental observations that support the proposed mechanisms are presented.

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Section: Discussionmentioning

confidence: 99%

Formation of single and multiple deformation twins in nanocrystalline fcc metals

Zhu¹,

Narayan²,

Hirth³

et al. 2009

Acta Materialia

172

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“…[32][33][34] The reverse Hall-Petch effect seems to depend strongly on the sample preparation technique used and on the sample history, perhaps indicating that in most cases the reverse Hall-Petch effect is caused by various kinds of defects in the samples. Surface defects alone have been shown to be able to decrease the strength of nanocrystalline metals by a factor of 5, 58,66 and recent studies have shown that even very small amounts of porosity can have a dramatic effect on the strength. 60,67 Improved inert gas condensation techniques 68 have reduced the porosity resulting in samples with densities above 98% of the fully dense value.…”

Section: B Reverse Hall-petch Effectmentioning

confidence: 99%

Atomic-scale simulations of the mechanical deformation of nanocrystalline metals

et al. 1999

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Nanocrystalline metals, i.e., metals in which the grain size is in the nanometer range, have a range of technologically interesting properties including increased hardness and yield strength. We present atomic-scale simulations of the plastic behavior of nanocrystalline copper. The simulations show that the main deformation mode is sliding in the grain boundaries through a large number of uncorrelated events, where a few atoms ͑or a few tens of atoms͒ slide with respect to each other. Little dislocation activity is seen in the grain interiors. The localization of the deformation to the grain boundaries leads to a hardening as the grain size is increased ͑reverse Hall-Petch effect͒, implying a maximum in hardness for a grain size above the ones studied here. We investigate the effects of varying temperature, strain rate, and porosity, and discuss the relation to recent experiments. At increasing temperatures the material becomes softer in both the plastic and elastic regime. Porosity in the samples result in a softening of the material; this may be a significant effect in many experiments. ͓S0163-1829͑99͒05941-X͔

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“…On the one hand some data are possibly consistent with Eq. (1) although with a lower value of K than for larger grain sizes [30][31][32][33][34] and on the other hand some data exhibit an apparent Fig. 1 The maximum yield strength, r p,max /l, obtained by ECAP versus the absolute melting temperature, T m , for fcc metals Al 120 [14] 122 [22] 119 [22] Au 245 [25] 237 [unpublished] Cu 395 [14] 380 [26] 390 [27] 383 [22] Ni -1138 [unpublished] decrease in yield stress with decreasing grain size indicating a softening effect at very fine grain sizes [32,[34][35][36][37].…”

Section: Introductionmentioning

confidence: 98%

Characteristics of face-centered cubic metals processed by equal-channel angular pressing

2007

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This review surveys the characteristics of face-centered cubic (fcc) metals and alloys processed by equal-channel angular pressing (ECAP). The significance of the Hall-Petch relationship for ultrafine grained structures is examined and the dependence of the saturated stress obtained in ECAP on the absolute melting temperature is described and discussed. In addition, the flow processes at low temperatures in ultrafine-grained materials and the microstructural evolution of the dislocation densities and precipitates in some alloys of practical importance are also considered briefly.

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Twinning in lead

Cited by 26 publications

References 4 publications

Formation of single and multiple deformation twins in nanocrystalline fcc metals

Formation of single and multiple deformation twins in nanocrystalline fcc metals

Atomic-scale simulations of the mechanical deformation of nanocrystalline metals

Characteristics of face-centered cubic metals processed by equal-channel angular pressing

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