Mechanical behavior and dynamic failure of high-strength ultrafine grained tungsten under uniaxial compression

Wei, Q.; Jiao, Tifeng; Ramesh, K.T.; Ma, E.; Kecskes, Laszlo J.; Magness, Lee S.; Dowding, Robert J.; Kazykhanov, Vil U.; Valiev, Ruslan Z.

doi:10.1016/j.actamat.2005.08.031

Cited by 80 publications

(98 citation statements)

References 37 publications

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“…Due to recent improvements in tool design, special technical solutions were evolved, which enabled the processing of difficult-to-work materials and the "scaling up" for a significant increase in production efficiency [2,4]. Recent papers report the application of SPD on titanium alloys [5], low and medium carbon steels [6][7][8], tungsten composites [9] or even pure tungsten [10][11][12][13]. Within a various number of different SPD-techniques [2] the most utilized are Equal Channel Angular Extrusion (ECAE) and High Pressure Torsion (HPT).…”

Section: Introductionmentioning

confidence: 99%

Ultimate Strength of a Tungsten Heavy Alloy after Severe Plastic Deformation at Quasi-Static and Dynamic Loading

Meyer

Hockauf

Hohenwarter

et al. 2008

MSF

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Abstract. A tungsten heavy alloy (92%W, Ni-Co matrix) is subjected to severe plastic deformation (SPD) by high pressure torsion (HPT) at room temperature up to equivalent strains of 0.7, 5.3, 10.7 and 14.3. The microstructure and the mechanical properties are investigated by cylindrical compression samples at quasi-static and dynamic loading. The harder spherical W particles are homogeneously deformed within the softer matrix, becoming ellipsoidal at medium strains and banded at high strains without shear localization or fracture. Results of quasi-static loading show that the strength is approaching a limiting value at strains of ~10. At this strain for the matrix a grain size of ~80 nm and for W a cell size of ~250 nm was observed, suggesting strain concentration on the matrix. The initial yield stress of 945 MPa for the coarse-grained condition is increased thereby to an ultimate value of 3500 MPa, while a peak stress of ~3600 MPa is reached. Such remarkably strength has never been reported before for pure W or W-based composites. The strain hardening capacity as well as the strain rate sensitivity is reduced drastically, promoting the early formation of (adiabatic) shear bands.

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Section: Introductionmentioning

confidence: 99%

Ultimate Strength of a Tungsten Heavy Alloy after Severe Plastic Deformation at Quasi-Static and Dynamic Loading

Meyer

Hockauf

Hohenwarter

et al. 2008

MSF

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“…For example, if one considers a boundary comprising a sequence of dislocations of spacing h and Burgers vector b, the misorientation at the boundary can be computed as b/h [98], on the order of 4 • for 10-nm-spaced dislocations in tungsten. For subgrain boundaries produced in tungsten crystals deformed through SPD processes [99,100], misorientations of such magnitude have been documented. Furthermore, strain gradient-based continuum defect theories are designed to address such phenomena in the context of crystal plasticity [51][52][53][54][55], so results presented here may be applied to motivate continuum energy dependencies, at least in a qualitative sense, on defect densities that serve an important role in such theories.…”

Section: International Journal For Multiscale Computational Engineeringmentioning

confidence: 99%

“…Furthermore, strain gradient-based continuum defect theories are designed to address such phenomena in the context of crystal plasticity [51][52][53][54][55], so results presented here may be applied to motivate continuum energy dependencies, at least in a qualitative sense, on defect densities that serve an important role in such theories. The thermodynamics of stored energy of cold working may also influence shear localization processes in ultra fine grained tungsten [100,101], a material that can exhibit dislocation densities of the magnitudes studied here.…”

Section: International Journal For Multiscale Computational Engineeringmentioning

confidence: 99%

“…The formulation accounts for large deformations of nominally hyperelastic, monocrystalline solids. Unit cell calculations are performed to determine minimum energy configurations of ensembles of atoms of body-centered cubic tungsten in the presence of periodic arrays of vacancies and screw dislocations of line orientations [111] or [100]. Results of the theory and numerical implementation are verified versus molecular statics calculations based on conjugate gradient minimization (CGM) and are also compared with predictions from the local Cauchy-Born rule.…”

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Multiscale Modeling of Point and Line Defects in Cubic Lattices

Chung

Clayton

2007

Int J Mult Comp Eng

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) March 2008 REPORT TYPE Reprint DATES COVERED (From SPONSOR/MONITOR'S ACRONYM(S) 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTESA reprint from the International Journal for Multiscale Computational Engineering, vol. 5, nos. 3 and 4, pp. 203-226, 2007. 14. ABSTRACT A multilength scale method based on asymptotic expansion homogenization (AEH) is developed to compute minimum energy configurations of ensembles of atoms at the fine length scale and the corresponding mechanical response of the material at the coarse length scale. This multiscale theory explicitly captures heterogeneity in microscopic atomic motion in crystalline materials, attributed, for example, to the presence of various point and line lattice defects. The formulation accounts for large deformations of nominally hyperelastic, monocrystalline solids. Unit cell calculations are performed to determine minimum energy configurations of ensembles of atoms of body-centered cubic tungsten in the presence of periodic arrays of vacancies and screw dislocations of line orientations [111] or [100]. Results of the theory and numerical implementation are verified versus molecular statics calculations based on conjugate gradient minimization (CGM) and are also compared with predictions from the local Cauchy-Born rule. For vacancy defects, the AEH method predicts the lowest system energy among the three methods, while computed energies are comparable between AEH and CGM for screw dislocations. Computed strain energies and defect energies (e.g., energies arising from local internal stresses and strains near defects) are used to construct and evaluate continuum energy functions for defective crystals parameterized via the vacancy density, the dislocation density tensor, and the generally incompatible lattice deformation gradient. For crystals with vacancies, a defect energy increasing linearly with vacancy density and applied elastic deformation is suggested, while for crystals with screw d...

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“…However, the strain-rate sensitivity of BCC metals was found to decrease with the reduction in grain size, especially in the ultrafine-grained and nanocrystalline regimes. [1,[11][12][13] To understand this trend, Wei et al [11,12] used the m ∼ 1/ √ τ scaling relation to explain the grain size effect on m based on the HallPetch-type elevation of the flow stress (τ ) at small grain sizes. More recently, Cheng et al [2] proposed an alternative explanation.…”

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confidence: 99%

Flow Stress in Submicron BCC Iron Single Crystals: Sample-size-dependent Strain-rate Sensitivity and Rate-dependent Size Strengthening

Huang

Wang

et al. 2015

Materials Research Letters

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Mechanical behavior and dynamic failure of high-strength ultrafine grained tungsten under uniaxial compression

Cited by 80 publications

References 37 publications

Ultimate Strength of a Tungsten Heavy Alloy after Severe Plastic Deformation at Quasi-Static and Dynamic Loading

Ultimate Strength of a Tungsten Heavy Alloy after Severe Plastic Deformation at Quasi-Static and Dynamic Loading

Multiscale Modeling of Point and Line Defects in Cubic Lattices

Flow Stress in Submicron BCC Iron Single Crystals: Sample-size-dependent Strain-rate Sensitivity and Rate-dependent Size Strengthening

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