Strain rate dependence of internal and effective stresses in superplastic deformation

Furushiro, Norio; Toyoda, Masao; Hori, Shigenori

doi:10.1016/0001-6160(88)90084-3

Cited by 13 publications

(14 citation statements)

References 32 publications

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“…The most widely used technique in the superplasticity community to measure strain rate sensitivity is the strain-rate change test (1,2,4,6,7,8,9). It is used to explore the upper region of the strain-rate history (approximately greater than 10 Ϫ5 s Ϫ1 ).…”

Section: Theoretical Backgroundmentioning

confidence: 99%

On the application of load relaxation in characterizing superplastic Al-Li 8090

Booeshaghi

Garmestani

1999

Scripta Materialia

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Section: Theoretical Backgroundmentioning

confidence: 99%

On the application of load relaxation in characterizing superplastic Al-Li 8090

Booeshaghi

Garmestani

1999

Scripta Materialia

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“…Classical example of a superplastic material is the Zn-Al eutectoid alloy (Zn-22Al) [1,2]. The maximum strain attainable during tensile deformation of this alloy depends critically on the strain rate, testing temperature, and the initial grain size [1][2][3][4][5][6][7][8][9][10]. Strains up to 3,000 % have been observed in a region where the relationship between flow stress and strain rate exhibits a maximum slope (region II) [1][2][3][4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Superplastic behavior of Zn–Al eutectoid alloy with 2 % Cu

2012

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The effects of deformation temperature and strain rate on the superplastic behavior of the Zn-21Al-2Cu alloy (Zinalco alloy) were investigated by uniaxial tensile tests. Results were compared with those of the Zn22Al eutectoid alloy without Cu. It was observed that additions of 2 % Cu leads to a decrease of the maximum strain attainable from 2600 % to 1000 %. The maximum strain in Zinalco alloy is obtained at lower strain rates. The presence of Cu increases the values of flow stress up to 600 % compared with those reported in the Zn-22Al alloy. Grain size sensitivity (p), true activation energy (Q t ), and constant A of the constitutive equation were not affected by presence of Cu unlike the stress exponent (n) which increased from 2.5 to 3.9. The main effect of Cu was to decrease the plastic flow stability of the Zn-22Al alloy.The results indicate that presence of Cu in the Zinalco alloy causes a hardening effect at low strain rates leading to a decrease in the strain rate sensitivity which promotes the formation and growth of sharp necks. Microstructural characterization suggests that the large deformations at necking could possibly be due to the substantial elongation capability of the Zn-rich phase (g).

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“…It is generally accepted that grain boundary sliding (GBS) and dislocation creep are the rate-controlling processes in regions II and III of superplastic metals, respectively, in relation to strain rate sensitivity, activation energy for deformation and microstructural changes during deformation in each region [3][4][5][6][7]. However, the deformation mechanism in region I has not clearly been revealed yet because of low m-value and high activation energy in low stress region.…”

Section: Introductionmentioning

confidence: 99%

“…However, the deformation mechanism in region I has not clearly been revealed yet because of low m-value and high activation energy in low stress region. Several models have so far been proposed to provide an explanation for the presennce of region I [1,2,[7][8][9][10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

A threshold stress for high-temperature plastic flow in WC-CO cemented carbides

Lee

1995

Metals and Materials

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The logarithmic relationship between flow stress and strain rate in WC-Co cemented carbides is represented by a signoidal curve at a constant temperature and is divided into three regions, as in superplastic metals. The flow stress in region I has no dependence on both carbide grain size and binder content, indicative of the presence of a threshold stress for high-temperature plastic flow in cemented carbides. The threshold stress estimated by extrapolating the plot of k ~ against cr to zero strain rate has a strong dependence on temperature. The logarithmic plot of the effective stress compensated by the threshold stress against strain rate shows a single straight line for region I and region II at a constant temperature, which suggests that the regions I and II are controlled by the same deformation process i.e. the grain boundary sliding in WC/WC boundaries. A small addition of Cr3C2 and VC gives rise to the outstanding increase in flow stress in region I and subsequently results in the marked increase in the threshold stress. The origin of the threshold stress in WC-Co cemented carbides is closely related to the impurity elements or the intensional additives such as Cr3Ca and VC.

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Strain rate dependence of internal and effective stresses in superplastic deformation

Cited by 13 publications

References 32 publications

On the application of load relaxation in characterizing superplastic Al-Li 8090

On the application of load relaxation in characterizing superplastic Al-Li 8090

Superplastic behavior of Zn–Al eutectoid alloy with 2 % Cu

A threshold stress for high-temperature plastic flow in WC-CO cemented carbides

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