Influence of prior mechanical and thermal treatments on shock-induced substructures in molybdenum

Mahajan, S.; Bartlett, A.F.

doi:10.1016/0001-6160(71)90043-5

Cited by 24 publications

(13 citation statements)

References 7 publications

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“…In this study, we examine the effect of pre-strain on the twining behavior of polycrystalline Ta across a wide range of initial conditions. While this work shows trends similar to previous studies of other bcc materials, 10,12,13 the focus is to examine the effect of both the global stress and the initial dislocation density on the formation and growth of twins.…”

Section: Introductionmentioning

confidence: 56%

“…6 There have been studies, however, that show that a critical twinning stress alone cannot fully describe all of the twinning behavior observed. 9 Mahajan and Boucher, [10][11][12] have shown that small amounts of pre-strain can suppress twinning in shocked Mo, where the imposed normal stresses are nominally equivalent. These results imply that the dislocation density plays a critical role in determining whether a material twins.…”

Section: Introductionmentioning

confidence: 99%

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Effect of strain rate and dislocation density on the twinning behavior in tantalum

et al. 2016

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The conditions which affect twinning in tantalum have been investigated across a range of strain rates and initial dislocation densities. Tantalum samples were subjected to a range of strain rates, from 10−4/s to 103/s under uniaxial stress conditions, and under laser-induced shock-loading conditions. In this study, twinning was observed at 77K at strain rates from 1/s to 103/s, and during laser-induced shock experiments. The effect of the initial dislocation density, which was imparted by deforming the material to different amounts of pre-strain, was also studied, and it was shown that twinning is suppressed after a given amount of pre-strain, even as the global stress continues to increase. These results indicate that the conditions for twinning cannot be represented solely by a critical global stress value, but are also dependent on the evolution of the dislocation density. In addition, the analysis shows that if twinning is initiated, the nucleated twins may continue to grow as a function of strain, even as the dislocation density continues to increase.

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Section: Introductionmentioning

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Effect of strain rate and dislocation density on the twinning behavior in tantalum

et al. 2016

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“…Previous studies have shown that there is a competition between dislocation slip and twinning 2,3,25,26 , and many models account for this with a critical stress, where twinning is initiated once the local stress reaches a critical value 7,14 . The main limitation with such a model is that there is an inherent assumption that changes in the dislocation density do not affect the driving force required for twinning.…”

Section: Resultsmentioning

confidence: 99%

“…Materials with tetragonal or orthorhombic symmetry are more likely to deform via twinning than cubic symmetry materials, due to a) Electronic mail: florando1@llnl.gov relatively few easily activated slip systems and geometric considerations. Twinning has also been generally observed in the regime of very low temperatures, where the dislocation mobility is low, or high deformation rates, as for example, shock loading, where the applied stress rate outpaces the plastic relaxation from dislocation nucleation and multiplication 2,3 . Tantalum is one of the materials with cubic crystal symmetry for which twinning has been observed experimentally, and studies have shown that both polycrystalline and single crystal Ta deformed at liquid He (4.2 Kelvin) temperatures twin under quasi-static loading conditions [4][5][6] .…”

Section: Introductionmentioning

confidence: 99%

Analysis of deformation twinning in tantalum single crystals under shock loading conditions

Florando

Barton

El-Dasher

et al. 2013

Journal of Applied Physics

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The competition between dislocation slip and twinning in tantalum single crystals has been investigated utilizing a crystal level twinning model and the results from gas gun recovery experiments conducted at peak normal stresses of 25 and 55 GPa. The recovered samples were characterized using electron back scattered diffraction, and the observed twining fractions were compared with the model. The experimental results show very low twin fractions in all orientations at 25 GPa; and that among (100), (110), (111), and (123) crystals the (110) crystals had the largest amount of twinning at 55GPa. The analysis shows that the general trends observed in the experimental data can be reproduced by the model when an orientation dependent dislocation evolution is used. This analysis gives insight into the possible influence of the dislocation density and its evolution on the observed twinning behavior.

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“…Copper and aluminium, as moderate to high stacking fault energy fcc metals, display a high degree of dislocation motion and generation during shock loading [38,39]. The deformation mechanisms of the second group are more varied, but iron, molybdenum and uranium have been shown to deform under shock loading conditions via twinning [40][41][42][43] whilst beryllium (hcp) and uranium (orthorhombic) both possess low symmetry unit cells, which will also reduce the ability of these materials to deform by simple dislocation generation.…”

Section: Discussionmentioning

confidence: 99%

The Behaviour of 2169 Steel Under Uniaxial Stress and Uniaxial Strain Loading

Whiteman

Keightley

Millett

2016

J. dynamic behavior mater.

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A series of plate impact and uniaxial stress compression experiments have been undertaken on 2169 steel, a nitrogen strengthened austenitic stainless steel. The shock experiments ranged from impact stresses of 3.7-17.8 GPa, recording the wave profiles of the shock and spall behaviour observed at the rear target surfaces. Target and impactor configurations were varied to observe the effects of tensile strain-rates achieved at spall planes. Spall strength was observed to vary linearly with impact stress and tensile strain-rate although was less rate sensitive than 300 series steels suggestive of an influence of the shock induced microstructure on void nucleation. A fourth power relationship between strain-rate in the shock front and shock stress was observed similar to many other materials. The linear coefficient A relating the two is discussed in terms of dislocation mobility. Uniaxial stress compression experiments were undertaken on two grain sizes of the same material at a range of strain-rates from *10 -4 to 10 3 s -1 . The data is consistent with other published data on 2169 steel showing a clear grain-size dependence on flow stress and higher flow stresses than other common austenitic steels.

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Influence of prior mechanical and thermal treatments on shock-induced substructures in molybdenum

Cited by 24 publications

References 7 publications

Effect of strain rate and dislocation density on the twinning behavior in tantalum

Effect of strain rate and dislocation density on the twinning behavior in tantalum

Analysis of deformation twinning in tantalum single crystals under shock loading conditions

The Behaviour of 2169 Steel Under Uniaxial Stress and Uniaxial Strain Loading

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