Plastic flow behavior of 7017 and 7055 aluminum alloys under different high strain rate test methods

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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High-Strain-Rate Superplastic Flow Mechanism in ZrO2-30vol% Spinel Two-Phase Composite

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.433.333 ◽

2010 ◽

Vol 433 ◽

pp. 333-338 ◽

Cited By ~ 1

Author(s):

Koji Morita ◽

Keijiro Hiraga ◽

Byung Nam Kim ◽

Hidehiro Yoshida

Keyword(s):

High Strain Rate ◽

Strain Rate ◽

High Strain ◽

Flow Behavior ◽

Recovery Process ◽

Lattice Diffusion ◽

Two Phase ◽

Data Set ◽

Strain And Strain Rate ◽

Accommodation Process

High-strain-rate superplasticity (HSRS) can be attained in tetragonal ZrO2-30vol% MgAl2O4 spinel composite. In order to examine the flow behavior of the two-phase composite, the standard rule of the mixture model was employed. The strain rate of the composite can be explained by the isostrain model that is predicted from the data set of Al2O3 doped ZrO2 and spinel polycrystals. For the isostrain model, since the strain and strain rate are the same for ZrO2 and spinel phases, the harder ZrO2 phase carries more of the stress in the composite. In order to preserve homogeneous deformation and material continuity, a concomitant accommodation process within the harder ZrO2 grains is also necessary. For HSRS in the ZrO2-spinel composite, therefore, the rate of deformation may be controlled by the slower dislocation recovery process limited by the lattice diffusion within harder ZrO2 grains rather than within spinel grains.

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Detormation Characteristics in High-strain-rate Superplastic Aluminum Alloys Produced by Powder Metallurgy.

Journal of the Japan Society of Powder and Powder Metallurgy ◽

10.2497/jjspm.42.725 ◽

1995 ◽

Vol 42 (6) ◽

pp. 725-734

Author(s):

Kenji Higashi

Keyword(s):

Powder Metallurgy ◽

Aluminum Alloys ◽

High Strain Rate ◽

Strain Rate ◽

High Strain

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