Viscoplastic lattice strain during repeated relaxation of age-hardened Al alloy

Hyongjoon Lee; Hobyung Chae; You Sub Kim; Min Ji Song; Sangyeob Lim; Kali Prasad; Hariharan Krishnaswamy; Jayant Jain; Ke An; Soo Yeol Lee

doi:10.1016/j.mechmat.2021.103899

Viscoplastic lattice strain during repeated relaxation of age-hardened Al alloy

Hyongjoon Lee, Hobyung Chae, You Sub Kim, Min Ji Song, Sangyeob Lim, Kali Prasad, Hariharan Krishnaswamy, Jayant Jain, Ke An, Soo Yeol Lee

Research output: Contribution to journal › Article › peer-review

12 Scopus citations

Abstract

We examined the repetitive stress relaxation behavior of extruded AA7075 subjected to different heat-treatments (solid-solutionized (SS), under-aged (UA), peak-aged (PA)). Compared to SS and UA, the PA showed the highest stress drop (Δσ_s), plastic strain change (Δε_p) and re-yielding (Δσ_r), in conjunction with the largest reduction in mobile dislocation density right after stress relaxation. As stress relaxation cycles repeated, the stress drop decreased due to lower activities of mobile dislocations. During stress relaxation, the harder the grain orientation was, the more was the reduction in lattice strain. However, this tendency was not consistent with the order in the magnitude of the shear stresses imposed on the respective grains based on Schmid's law. The current results confirm the grain-orientation dependency on the relative activities of dislocation slip and diffusion-controlled creep during the stress relaxation at room temperature.

Original language	English
Article number	103899
Journal	Mechanics of Materials
Volume	158
DOIs	https://doi.org/10.1016/j.mechmat.2021.103899
State	Published - Jul 2021
Externally published	Yes

Funding

This work was supported by the National Research Foundation (NRF) grant funded by the Korean Government (2020R1I1A2070474). A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. This work was supported by the National Research Foundation (NRF) grant funded by the Korean Government (2020R1I1A2070474). A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory .

Keywords

Aging
Aluminum alloys
Neutron diffraction
Precipitate
Stress relaxation

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title = "Viscoplastic lattice strain during repeated relaxation of age-hardened Al alloy",

abstract = "We examined the repetitive stress relaxation behavior of extruded AA7075 subjected to different heat-treatments (solid-solutionized (SS), under-aged (UA), peak-aged (PA)). Compared to SS and UA, the PA showed the highest stress drop (Δσs), plastic strain change (Δεp) and re-yielding (Δσr), in conjunction with the largest reduction in mobile dislocation density right after stress relaxation. As stress relaxation cycles repeated, the stress drop decreased due to lower activities of mobile dislocations. During stress relaxation, the harder the grain orientation was, the more was the reduction in lattice strain. However, this tendency was not consistent with the order in the magnitude of the shear stresses imposed on the respective grains based on Schmid's law. The current results confirm the grain-orientation dependency on the relative activities of dislocation slip and diffusion-controlled creep during the stress relaxation at room temperature.",

keywords = "Aging, Aluminum alloys, Neutron diffraction, Precipitate, Stress relaxation",

author = "Hyongjoon Lee and Hobyung Chae and Kim, {You Sub} and Song, {Min Ji} and Sangyeob Lim and Kali Prasad and Hariharan Krishnaswamy and Jayant Jain and Ke An and Lee, {Soo Yeol}",

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doi = "10.1016/j.mechmat.2021.103899",

language = "English",

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T1 - Viscoplastic lattice strain during repeated relaxation of age-hardened Al alloy

AU - Lee, Hyongjoon

AU - Chae, Hobyung

AU - Kim, You Sub

AU - Song, Min Ji

AU - Lim, Sangyeob

AU - Prasad, Kali

AU - Krishnaswamy, Hariharan

AU - Jain, Jayant

AU - An, Ke

AU - Lee, Soo Yeol

PY - 2021/7

Y1 - 2021/7

N2 - We examined the repetitive stress relaxation behavior of extruded AA7075 subjected to different heat-treatments (solid-solutionized (SS), under-aged (UA), peak-aged (PA)). Compared to SS and UA, the PA showed the highest stress drop (Δσs), plastic strain change (Δεp) and re-yielding (Δσr), in conjunction with the largest reduction in mobile dislocation density right after stress relaxation. As stress relaxation cycles repeated, the stress drop decreased due to lower activities of mobile dislocations. During stress relaxation, the harder the grain orientation was, the more was the reduction in lattice strain. However, this tendency was not consistent with the order in the magnitude of the shear stresses imposed on the respective grains based on Schmid's law. The current results confirm the grain-orientation dependency on the relative activities of dislocation slip and diffusion-controlled creep during the stress relaxation at room temperature.

AB - We examined the repetitive stress relaxation behavior of extruded AA7075 subjected to different heat-treatments (solid-solutionized (SS), under-aged (UA), peak-aged (PA)). Compared to SS and UA, the PA showed the highest stress drop (Δσs), plastic strain change (Δεp) and re-yielding (Δσr), in conjunction with the largest reduction in mobile dislocation density right after stress relaxation. As stress relaxation cycles repeated, the stress drop decreased due to lower activities of mobile dislocations. During stress relaxation, the harder the grain orientation was, the more was the reduction in lattice strain. However, this tendency was not consistent with the order in the magnitude of the shear stresses imposed on the respective grains based on Schmid's law. The current results confirm the grain-orientation dependency on the relative activities of dislocation slip and diffusion-controlled creep during the stress relaxation at room temperature.

KW - Aging

KW - Aluminum alloys

KW - Neutron diffraction

KW - Precipitate

KW - Stress relaxation

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U2 - 10.1016/j.mechmat.2021.103899

DO - 10.1016/j.mechmat.2021.103899

M3 - Article

AN - SCOPUS:85105300425

SN - 0167-6636

VL - 158

JO - Mechanics of Materials

JF - Mechanics of Materials

M1 - 103899

ER -

Viscoplastic lattice strain during repeated relaxation of age-hardened Al alloy

Abstract

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Keywords

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