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Laser compression of nanocrystalline tantalum

Laser compression of nanocrystalline tantalum
Laser compression of nanocrystalline tantalum
Nanocrystalline tantalum (grain size ?70 nm) prepared by severe plastic deformation (high-pressure torsion) from monocrystalline [1 0 0] stock was subjected to shock compression generated by high-energy laser (?350–850 J), creating pressure pulses with initial duration of ?3 ns and amplitudes of up to ?145 GPa. The laser beam, with a spot radius of ?1 mm, created a crater of significant depth (?135 ?m). Transmission electron microscopy revealed few dislocations within the grains and an absence of twins at the highest shock pressure, in contrast with monocrystalline tantalum. Hardness measurements were conducted and show a rise as the energy deposition surface is approached, evidence of shock-induced defects. The grain size was found to increase at a distance of 100 ?m from the energy deposition surface as a result of thermally induced grain growth. The experimentally measured dislocation densities are compared with predictions using analyses based on physically based constitutive models, and the similarities and differences are discussed in terms of the mechanisms of defect generation. A constitutive model for the onset of twinning, based on a critical shear stress level, is applied to the shock compression configuration. The predicted threshold pressure at which the deviatoric component of stress for slip exceeds the one for twinning is calculated and it is shown that it is increased from ?24 GPa for the monocrystalline to ?150 GPa for the nanocrystalline tantalum (above the range of the present experiments). Calculations using the Hu–Rath analysis show that grain growth induced by the post shock-induced temperature rise is consistent with the experimental results: grains grow from 70 to 800 nm within the post-shock cooling regime when subjected to a laser pulse with energy of 684 J.
dislocations, high-pressure torsion, laser treatment, tantalum, shock compression
1359-6454
7767-7780
Lu, C.H.
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Remington, B.A.
2cbfec39-2562-48a1-aba6-92552c1eddff
Maddox, B.R.
4489920f-d512-4f18-a72c-affa86764917
Kad, B.
c0ce60a1-5bad-44c7-84fa-426c3e0d8b6f
Park, H.S.
37395c90-bc75-4c48-9d46-daac0107844b
Kawasaki, M.
d0ce18b9-8403-4db2-9cb2-3a6165f288a6
Langdon, T.G.
86e69b4f-e16d-4830-bf8a-5a9c11f0de86
Meyers, M.A.
1c87f689-ba29-4c2b-aa58-da8462a7abc2
Lu, C.H.
1fb156b6-feaf-46a6-b6a7-ee4e554728d3
Remington, B.A.
2cbfec39-2562-48a1-aba6-92552c1eddff
Maddox, B.R.
4489920f-d512-4f18-a72c-affa86764917
Kad, B.
c0ce60a1-5bad-44c7-84fa-426c3e0d8b6f
Park, H.S.
37395c90-bc75-4c48-9d46-daac0107844b
Kawasaki, M.
d0ce18b9-8403-4db2-9cb2-3a6165f288a6
Langdon, T.G.
86e69b4f-e16d-4830-bf8a-5a9c11f0de86
Meyers, M.A.
1c87f689-ba29-4c2b-aa58-da8462a7abc2

Lu, C.H., Remington, B.A., Maddox, B.R., Kad, B., Park, H.S., Kawasaki, M., Langdon, T.G. and Meyers, M.A. (2013) Laser compression of nanocrystalline tantalum. Acta Materialia, 61 (20), 7767-7780. (doi:10.1016/j.actamat.2013.09.016).

Record type: Article

Abstract

Nanocrystalline tantalum (grain size ?70 nm) prepared by severe plastic deformation (high-pressure torsion) from monocrystalline [1 0 0] stock was subjected to shock compression generated by high-energy laser (?350–850 J), creating pressure pulses with initial duration of ?3 ns and amplitudes of up to ?145 GPa. The laser beam, with a spot radius of ?1 mm, created a crater of significant depth (?135 ?m). Transmission electron microscopy revealed few dislocations within the grains and an absence of twins at the highest shock pressure, in contrast with monocrystalline tantalum. Hardness measurements were conducted and show a rise as the energy deposition surface is approached, evidence of shock-induced defects. The grain size was found to increase at a distance of 100 ?m from the energy deposition surface as a result of thermally induced grain growth. The experimentally measured dislocation densities are compared with predictions using analyses based on physically based constitutive models, and the similarities and differences are discussed in terms of the mechanisms of defect generation. A constitutive model for the onset of twinning, based on a critical shear stress level, is applied to the shock compression configuration. The predicted threshold pressure at which the deviatoric component of stress for slip exceeds the one for twinning is calculated and it is shown that it is increased from ?24 GPa for the monocrystalline to ?150 GPa for the nanocrystalline tantalum (above the range of the present experiments). Calculations using the Hu–Rath analysis show that grain growth induced by the post shock-induced temperature rise is consistent with the experimental results: grains grow from 70 to 800 nm within the post-shock cooling regime when subjected to a laser pulse with energy of 684 J.

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More information

e-pub ahead of print date: 5 October 2013
Published date: December 2013
Keywords: dislocations, high-pressure torsion, laser treatment, tantalum, shock compression
Organisations: Engineering Mats & Surface Engineerg Gp

Identifiers

Local EPrints ID: 359498
URI: http://eprints.soton.ac.uk/id/eprint/359498
ISSN: 1359-6454
PURE UUID: 9f6883db-d21d-4106-a8b3-e8771edc3884
ORCID for T.G. Langdon: ORCID iD orcid.org/0000-0003-3541-9250

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Date deposited: 05 Nov 2013 11:14
Last modified: 15 Mar 2024 03:13

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Contributors

Author: C.H. Lu
Author: B.A. Remington
Author: B.R. Maddox
Author: B. Kad
Author: H.S. Park
Author: M. Kawasaki
Author: T.G. Langdon ORCID iD
Author: M.A. Meyers

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