High-strain-rate superplasticity in bulk cryomilled ultra-fine-grained 5083 Al

Chauhan, Manish; Roy, Indranil; Mohamed, Farghalli A.

doi:10.1007/bf02586105

Cited by 17 publications

(16 citation statements)

References 35 publications

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“…These two characteristics were also reported for several alloys processed by ECAP and HPT [16]. Equally important are the substructural features observed in the alloy [19] following deformation. These features are typical of those reported for micrograin superplasticity in Zn-22 % Al that contained dispersion particles (introduced via cryomilling) [9,10].…”

Section: Superplasticity In Ultrafine-grained Materialssupporting

confidence: 64%

“…Consideration of the mechanical characteristics of 5083 Al led to two main findings [19]. First, the creep characteristics of 5083 Al were consistent with those associated with HSR superplasticity.…”

Section: Superplasticity In Ultrafine-grained Materialsmentioning

confidence: 70%

“…4. The presence of cavity stringers in UFG 5083 Al along the tensile axis (vertical) [19]. line, demonstrating the presence of good correspondence between the rate-equation representing this deformation process and the experimental data for nc Ni and nc Cu, which were obtained under different conditions of temperature, grain size, and strain rates [27].…”

Section: Superplasticity In Nanocrystalline Materialsmentioning

confidence: 93%

“…Several examples for HSR in ultrafine-grained alloys that were prepared by ECAP, HPT, and SF were extensively discussed elsewhere [16][17][18]. Accordingly, it seems appropriate to provide an example for HSR superplasticity in an Al alloy [19] that was processed via cryomilling [20].…”

Section: Superplasticity In Ultrafine-grained Materialsmentioning

confidence: 99%

“…The microstructure of 5083 Al after cryomilling followed by consolidation and extrusion exhibited an average grain size of about 305 nm [19,20]. After annealing for 30 minutes at 673 K, an examination of the microstructure of the alloy revealed that the grain size was about 440 nm [19,20].…”

Section: Superplasticity In Ultrafine-grained Materialsmentioning

confidence: 99%

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Effect of grain refinement on superplasticity in micrograined materials

Mohamed¹

2015

LoM

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Under superplasticity conditions, micrograined materials (grain sizes in the range 1 µm -10 µm) exhibit extensive neck-free elongations during tensile deformation at elevated temperatures (T>0.5T m , where T m is the melting point). The deformation mechanism responsible for such behavior is based on grain boundary sliding accommodated by the generation and movement of lattice dislocations in the grains blocking sliding. Such a mechanism is characterized by a stress exponent of 2, an activation energy that is close to that for boundary diffusion, and a grain size sensitivity of 2. When the grain size of the material is refined to the ultrafine-grained range (300 nm-900 nm), there is no change either in the characteristics of superplasticity or in the details of its deformation mechanism. By contrast, when the grain size of the material is refined to the nanoscale range (grain size ≤100 nm), superplasticity is lost due to the emergence of a new deformation mechanism. This new deformation mechanism is also based on grain boundary sliding accommodated by lattice dislocations. It is characterized by a stress exponent that is high and variable, an activation energy that is close to the activation energy for boundary diffusion but decreases with increasing applied stress, and a grain size sensitivity of 3.Keywords: boundary sliding, deformation mechanisms, nanocrystalline materials, ultrafine grained materials Влияние измельчения зерен на сверхпластичность в мелкозернистых материалах В условиях сверхпластичности мелкозернистые материалы (размер зерен в интервале 1-10 мкм) демонстрируют большие удлинения без шейки при деформации растяжением при высоких температурах (T>0.5T m , где T m -тем-пература плавления). Механизм деформации, ответственный за такое поведение, основан на зернограничном про-скальзывании, аккомодируемом генерацией и движением решеточных дислокаций в зернах, блокирующих про-скальзывание. Этот механизм характеризуется показателем напряжения 2, активационной энергией, которая близка к активационной энергии диффузии по границам, и чувствительностью к размеру зерен 2. Когда размер зерен ма-териала измельчается до интервала, соответствующего ультрамелкозернистым материалам (300-900 нм), ни в ха-рактеристиках сверхпластичности, ни в деталях деформационных механизмов не происходит никаких изменений. Однако когда зерна измельчаются до наноразмерного уровня (размер зерен менее 100 нм), сверхпластичность теря-ется из-за появления нового деформационного механизма. Этот новый деформационный механизм также основан на зернограничном проскальзывании, аккомодируемом решеточными дислокациями. Он характеризуется показате-лем напряжения, который имеет высокое изменяющееся значение, активационную энергию, которая близка к акти-вационной энергии диффузии по границам, но уменьшается с увеличением приложенного напряжения, и чувстви-тельностью к размеру зерен 3.

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Section: Superplasticity In Ultrafine-grained Materialssupporting

confidence: 64%

Section: Superplasticity In Ultrafine-grained Materialsmentioning

confidence: 70%

Section: Superplasticity In Nanocrystalline Materialsmentioning

confidence: 93%

Section: Superplasticity In Ultrafine-grained Materialsmentioning

confidence: 99%

Section: Superplasticity In Ultrafine-grained Materialsmentioning

confidence: 99%

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Effect of grain refinement on superplasticity in micrograined materials

Mohamed¹

2015

LoM

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Creep and Superplasticity: Evolution and Rationalization

Mohamed

2020

Adv Eng Mater

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Detailed studies on the creep behavior of materials are of scientific and practical significance. From a scientific point of view, data obtained from such studies are critical to the characterization of creep behavior in terms of deformation mechanisms. From a practical point of view, information inferred from such studies is useful because of its relevance to many design considerations. Over the past several decades, much progress has been made in rationalizing the creep behavior of metals and solid‐solution alloys. Such progress is extended to understanding the creep behavior of new classes of materials such as powder metallurgy (PM) Al alloys, discontinuous SiC composites, superplastic alloys, and high‐entropy alloys (HEAs). Progress in micrograin superplasticity (1 μm < d < 10 μm, where d is the grain size) has been applied to the emergence of high strain rate (HSR) superplasticity using ultrafine‐grained alloys (0.3 μm < d < 1 μm). The concept of creep is utilized to develop a deformation mechanism for nanocrystalline (nc) materials (d < 100 nm). Using the details of this mechanism, it is possible (1) to explain why the behavior of nc material is not superplastic and 2) to predict a transition from superplastic behavior to nc behavior.

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