Microstructure of superplastic alloys

Johnson, R. H.; Packer, C.M.; Anderson, L. J.; Sherby, O. D.

doi:10.1080/14786436808227761

Cited by 53 publications

(8 citation statements)

References 3 publications

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“…37 (2) Development of curved or bulbous interphase boundaries, 38 as reported in the Zn-Al eutectoid 39 and Al-Cu eutectic alloys. Figure 3 shows the microstructures of the gauge and shoulder sections of the tensile specimens of the Al-Cu eutectic alloy.…”

Section: Grain Boundary Migrationmentioning

confidence: 96%

Interfacial phenomena and microstructural evolution during superplastic deformation

Kashyap

2001

Surface & Interface Analysis

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Certain polycrystalline materials of fine equiaxed grains of size <10 µm exhibit tensile ductility of several hundred to a few thousand per cent, called superplasticity, at intermediate strain rates and high temperatures. Experimental and theoretical results on mechanisms for superplastic deformation and concurrent microstructural evolution are reviewed to understand the role of grain boundary phenomena towards enhancement of grain growth and cavitation, etc. Grain boundary sliding (GBS) dominates superplastic flow, the extent of which varies between the grain and interphase boundaries in twophase alloys. Accommodation to GBS is provided by diffusional and dislocation mechanisms, which are manifested in the form of grain boundary migration (GBM), grain rotation and grain switching events. Although GBS helps in retaining the initial equiaxed grain shape of superplastic materials, the accommodation processes accelerate grain growth. In the lack of other accommodation processes the cavities are formed, being more pronounced at the boundaries of maximum sliding. The ppm-level impurities present in superplastic materials do not influence the sliding and flow characteristics under typical superplastic conditions but they do promote cavitation and limit the ductility. The presence of precipitate or hard particles in quasi-single-phase superplastic materials inhibits GBM but provides sites for cavitation. Such materials exhibit more dislocation activities than anticipated for accommodation of GBS. The nature of microstructural changes noted during superplastic deformation supports the operation of cooperative GBS, in addition to a large variety of combinations between sliding and accommodation processes.

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Section: Grain Boundary Migrationmentioning

confidence: 96%

Interfacial phenomena and microstructural evolution during superplastic deformation

Kashyap

2001

Surface & Interface Analysis

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“…For example, Johnson et al [33] reported that original round tensile bars maintain round cross sections in textureless two-phase superplastic Zn-Al alloy, while they develop elliptical cross sections in textured counterpart alloy. A high degree of shape anisotropy is also observed in textured Cd and the compressive flow stresses differ between longitudinal and transverse directions [5].…”

Section: Anisotropy Of Flow Stress and Macroscopic Specimen Shape Chamentioning

confidence: 98%

Isotropic superplastic flow in textured magnesium alloy

Watanabe

Kurimoto

Uesugi

et al. 2012

Materials Science and Engineering: A

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“…Furthermore, direct evidence has been provided [50,51] that there is considerable diffusion in the boundaries during superplastic deformation and Morrison [17] has shown that alloying elements which enhance diffusion also enhance superplasticbehaviour. On the other hand, it has been pointed out that in the two-phase structures where the phases are structurally and chemically dissimilar, sliding cannot be accommodated without large redistribution of solute [33,43]. However, Alden and Schadler [36] found that interphase boundaries and intercrystalline boundaries are similar in their contribution to superplasticity.…”

Section: Proposed Mechanismsmentioning

confidence: 98%

“…(e) The model of Johnson et al [33,43] involved a combination of intergranular deformation (perhaps by grain boundary sliding) followed by recrystallisation. Three observations cast doubt on this model.…”

Section: Proposed Mechanismsmentioning

confidence: 99%