Deformation and stored energy of polycrystalline bismuth

Das, G. C.; Bever, M. B.

doi:10.1007/bf02663422

Cited by 8 publications

(7 citation statements)

References 15 publications

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“…It has been observed that the yield strength is often proportional to the hardness and that, in the absence of strain hardening, the constant of proportionality is~1/3. [49] Clearly, comparison of the measured H V at f W = 0 with the yield strengths reported for compression testing of Bi discussed earlier [24] implies that this relation is not met for the current system. However, Bi is known to exhibit extensive work hardening, [24] and the powder compaction process probably leaves the Bi in a highly cold-worked condition.…”

Section: ½30mentioning

confidence: 99%

“…[49] Clearly, comparison of the measured H V at f W = 0 with the yield strengths reported for compression testing of Bi discussed earlier [24] implies that this relation is not met for the current system. However, Bi is known to exhibit extensive work hardening, [24] and the powder compaction process probably leaves the Bi in a highly cold-worked condition. Thus, the differences in the specimen fabrication methods may make direct comparison of the hardness with the prior compression data questionable.…”

Section: ½30mentioning

confidence: 99%

“…7-Anisotropy parameters given by Eqs. [23] and [24] are plotted vs f W . Complete isotropy corresponds to a value of 1.00, and is indicated by the solid line for reference purposes.…”

Section: ½30mentioning

confidence: 99%

“…However, the calculated r o values compare favorably with the yield strengths determined from the compression testing of polycrystalline Bi at different temperatures and strain rates. [24] In Reference 24, room-temperature yield occurred between~13 and 24 MPa, depending on the strain rate (2 9 10 À4 to 2 9 10 À2 , respectively). Thus, the calculated r o for Bi appears to be in an appropriate range to provide a representative estimate of the yield strength.…”

Section: A Compaction Behaviormentioning

confidence: 99%

“…[23] and Eq. [24] provide a measure of the longitudinal (compressive) and shear anisotropy, with C 33 = C 11 and 2C 44 = (C 11 À C 12 ) indicating isotropy. These parameters are plotted vs f W in Figure 7, in which values of ''1.00'' correspond to complete isotropy.…”

Section: B Postcompaction Characterizationmentioning

confidence: 99%

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Compaction Behavior and Mechanical Properties of Uniaxially Pressed Bi-W Composites

Martin

Hodge

Campbell

2009

Metall Mater Trans A

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Powder metallurgy is a useful route to forming particulate composite materials; however, the densification of hard and soft powder mixtures is usually inhibited by the more refractory phase. The Bi-W powder compacts were uniaxially pressed at room temperature and the compaction behavior and mechanical properties were evaluated. Pressing was performed in incremental steps from~1 to 540 MPa. After each step, the pressure was relieved and the thickness and sound-wave transit time were measured in situ (in the die), in order to determine the density and sound-wave velocity in the compact. The data show that the unreinforced Bi powder compacts to~98 pct density at 540 MPa. The W reinforcement inhibits the densification process, resulting in increased levels of residual porosity. The compaction behavior was evaluated using a modified Heckel equation, while the porosity dependence of the ultrasonically determined elastic modulus was described by a site percolation approach. Postcompaction sound-wave velocity and Vicker's hardness measurements show <5 pct anisotropy between the axial (pressing) and radial directions. The mechanical characterization illustrates the competing effects of the W reinforcement and the associated residual porosity.

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Section: ½30mentioning

confidence: 99%

Section: ½30mentioning

confidence: 99%

“…7-Anisotropy parameters given by Eqs. [23] and [24] are plotted vs f W . Complete isotropy corresponds to a value of 1.00, and is indicated by the solid line for reference purposes.…”

Section: ½30mentioning

confidence: 99%

Section: A Compaction Behaviormentioning

confidence: 99%

Section: B Postcompaction Characterizationmentioning

confidence: 99%

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