Micrograin Superplasticity: Characteristics and Utilization

Mohamed, Farghalli A.

doi:10.3390/ma4061194

Cited by 28 publications

(16 citation statements)

References 71 publications

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“…The alloy exhibited a stable flow with an elongation of 700-800% at a constant strain rate of 0.02 s −1 in a temperature range of 440 to 520 °C (Figure 2c), and the same elongation values at 440 °C in a constant strain rate range of 0.01 to 0.6 s −1 (Figure 2d). It is notable that the evidence of superplasticity with a mean elongation-to-failure of 402 ± 28% was Figure 2a shows the stress-strain rate logarithmic curves that have a typical superplastic behavior sigmoidal shape that consists of three regions [2,6,8,69]. The second liner region corresponds to superplastic behavior [2,8].…”

Section: Subsectionmentioning

confidence: 99%

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High Strain Rate Superplasticity in Al-Zn-Mg-Based Alloy: Microstructural Design, Deformation Behavior, and Modeling

et al. 2020

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Increasing the strain rate at superplastic forming is a challenging technical and economic task of aluminum forming manufacturing. New aluminum sheets exhibiting high strain rate superplasticity at strain rates above 0.01 s−1 are required. This study describes the microstructure and the superplasticity properties of a new high-strength Al-Zn-Mg-based alloy processed by a simple thermomechanical treatment including hot and cold rolling. The new alloy contains Ni to form Al3Ni coarse particles and minor additions of Zr (0.19 wt.%) and Sc (0.06 wt.%) to form nanoprecipitates of the L12-Al3 (Sc,Zr) phase. The design of chemical and phase compositions of the alloy provides superplasticity with an elongation of 600–800% in a strain rate range of 0.01 to 0.6/s and residual cavitation less than 2%. A mean elongation-to-failure of 400% is observed at an extremely high constant strain rate of 1 s−1. The strain-induced evolution of the grain and dislocation structures as well as the L12 precipitates at superplastic deformation is studied. The dynamic recrystallization at superplastic deformation is confirmed. The superplastic flow behavior of the proposed alloy is modeled via a mathematical Arrhenius-type constitutive model and an artificial neural network model. Both models exhibit good predictability at low and high strain rates of superplastic deformation.

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Section: Subsectionmentioning

confidence: 99%

“…for 30 min, the grain structure consisted of the banded grains of a mean size 2.8 ± 0.2 µm (Figure 1b). Figure 2a shows the stress-strain rate logarithmic curves that have a typical superplastic behavior sigmoidal shape that consists of three regions [2,6,8,69]. The second liner region corresponds to superplastic behavior [2,8].…”

Section: Subsectionmentioning

confidence: 99%

High Strain Rate Superplasticity in Al-Zn-Mg-Based Alloy: Microstructural Design, Deformation Behavior, and Modeling

et al. 2020

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“…It has been suggested that the low m-value obtained at low temperatures is the result of a threshold stress that must be exceeded so that boundary dislocations escape from the impurity atmosphere and contribute to GBS. 14,73,74) It has been stated that threshold stress resulted from the segregation of impurity atoms at grain boundaries and their interaction with boundary dislocations. Thus, threshold stress is directly related to the diffusivity of the impurity atoms, and decreasing the test temperature increases the threshold stress due to the low diffusion coefficient for grain boundary diffusion at low temperatures.…”

Section: Room Temperature Superplasticity In Ufg Materialsmentioning

confidence: 99%

Room Temperature Superplaticity in Fine/Ultrafine Grained Materials Subjected to Severe Plastic Deformation

Demirtas

Pürçek

2019

Mater. Trans.

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Achieving superplasticity at high temperatures and at very low strain rates is considered to be the most important disadvange of superplastic forming processes. Therefore, it is crucial to achieve superplastic behavior at low temperatures and high strain rates. To do so, it is well known that, high amount of grain refinement in the superplastic material is required. Very recent advances in severe plastic deformation (SPD) techniques based on imposing very high strains to the material provide abnormal grain refinement, and ultrafine-grained (UFG) microstructures can be achived in metallic materials by this manner. Formation of UFG microstructures via SPD methods like equal channel angular pressing (ECAP), high pressure torsion (HPT) and friction stir processing (FSP) bring about superplastic behavior in some classes of alloys even at room temperature (RT) as an extreme example of low temperature superplasticity. This paper overviews the studies aiming to investigate the RT superplasticity in some specific metals and alloys after UFG formation by SPD methods. UFG formation or nanostructuring of the materials by SPD to attain RT superplasticity were analyzed in detail. Also, the parameters affecting the RT superplasticity in different classes of materials and superplastic deformation mechanisms operated at RT superplasticity were explained.

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“…Superplasticity is the ability to sustain extensive elongations (more than 200%) without necking and fracture in the fine-grained material [1].The superplastic phenomenon only occurs in a certain range of temperatures and strain rates, which are characterised by low flow stress and high strain rate sensitivity [2]. The mechanism of superplastic deformation includes grain rotation, grain boundary sliding and the fine dispersion of thermally stable particles by pinning the grain boundary within the fine structure.…”

Section: Intoductionmentioning

confidence: 99%

Determination of a Set of Constitutive Equations for an Al-Li Alloy at SPF Conditions

Gao

et al. 2015

Materials Today: Proceedings

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Uniaxial tensile tests of aluminium-lithium alloy AA1420 were conducted at superplastic forming conditions. The mechanical properties of this Al-Li alloy were then modelled by a set of physicallybased constitutive equations. The constitutive equations describe the isotropic work hardening, recovery and damage by dislocation density changes and grain size evolution. Based on a recent upgraded optimisation technique, the material constants for these constitutive equations were determined

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Micrograin Superplasticity: Characteristics and Utilization

Cited by 28 publications

References 71 publications

High Strain Rate Superplasticity in Al-Zn-Mg-Based Alloy: Microstructural Design, Deformation Behavior, and Modeling

High Strain Rate Superplasticity in Al-Zn-Mg-Based Alloy: Microstructural Design, Deformation Behavior, and Modeling

Room Temperature Superplaticity in Fine/Ultrafine Grained Materials Subjected to Severe Plastic Deformation

Determination of a Set of Constitutive Equations for an Al-Li Alloy at SPF Conditions

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