Quasti-Static and Dynamic Response, and Texture Evolution of Two Overaged Al 7056 Alloy Plates in T761 and T721 Tempers: Experiments and Modeling

Published

January 1, 2020

Author(s)

Angela Y. Ku, Akhtar S. Khan, Thomas H. Gnaupel-Herold

Abstract

The thermo-mechanical behavior and texture evolution of two overaged Al 7056 alloy plates, in near peak strength (T761) and near peak aged (T721) tempers, are measured over a wide range of strain rates (10^-4 – 3 x 10₃ s^-1) and temperatures (22 – 300°C) under uniaxial tension and compression along the thickness direction, i.e. normal to the plate surface. A detailed study of the initial microstructure reveals an increase in grain size and decrease in density of precipitates, as the alloy is aged from the T761 to T721 temper; which in turn affects the flow stress and strain hardening behavior. Differences in flow strength and strain hardening rate, as well as tension-compression asymmetry in the two tempers, are apparent at the lower temperatures (22°C & 100°C) and decrease significantly at the higher temperatures (200°C & 300°C). Furthermore, initial texture measurements show a strong texture gradient along the normal direction (ND) of the plate. This texture gradient affects the ultimate stress insignificantly. However, it does have a considerable effect on the failure strains of specimens taken from different locations through the thickness. A transition from shear fracture at and below 200°C to cup and cone fracture mode above 200°C is observed in tension. Both tempers exhibit a positive strain rate sensitivity (SRS) that is dependent on temperature and strain rate. A sharp decrease in flow stress is found at 300°C. The Khan-Liu (KL) model is modified to correlate with the measured thermo-mechanical responses of the two tempers over the studied, wide range of strain rates and temperatures. There is a close correlation between simulated and observed results.

Citation

International Journal of Plasticity

Volume

130

Pub Type

Journals

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Keywords

7XXX series aluminum alloys, Precipitation hardening, Strain rate sensitivity, Texture evolution, Constitutive modeling

Citation

Ku, A. , Khan, A. and Gnaupel-Herold, T. (2020), Quasti-Static and Dynamic Response, and Texture Evolution of Two Overaged Al 7056 Alloy Plates in T761 and T721 Tempers: Experiments and Modeling, International Journal of Plasticity, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=928826 (Accessed December 9, 2024)