A study of dynamic recovery and recrystallisation mechanisms in aluminium alloy AA7050 at different thermomechanical processing conditions
File(s)
Published version
Author(s)
Jiang, Shuai
Lv, Jiaxin
Shi, Zhusheng
Lin, Jianguo
Type
Journal Article
Abstract
The effects of hot deformation strain rates and temperatures on aluminium alloys’ dynamic recovery and
recrystallisation mechanisms have been widely discussed in the literature. However, their influence remains
controversial due to a need for comprehensive and detailed thermomechanical testing and characterisation data
across a wide range of hot deformation conditions. In this study, hot compression tests of AA7050 were conducted at strain rates of 0.0005–5 s
− 1 and temperatures of 380–460 ◦C. The geometrically necessary dislocation
(GND), low-angle grain boundary (LAGB) and high-angle grain boundary (HAGB) were acquired by the latest
high angular resolution, high-speed EBSD detector (OI Symmetry 2), and their underlying mechanisms were
analysed in relation to Zener-Hollomon parameter (Z). It was found that within the tested range of the hot
compression condition (ln (Z) between 20.23 and 29.45), continuous dynamic recrystallisation (CDRX) predominates at lower ln (Z) values with its activity being initially increased and then decreased as ln (Z) rises, while
discontinuous dynamic recrystallisation (DDRX) becomes dominant at higher ln (Z) levels. This transition of the
dominant mechanism is intriguingly reflected in the evolution of HAGB length, which increases, then decreases
and finally increases again. The LAGB length shows a relatively linear relationship with ln (Z), and the average
GND density exhibits a near-linear correlation until reaching a plateau. Based on the obtained results, the
transformation of the dominant microstructural evolution mechanisms with increasing ln (Z) was clarified: from
grain growth, to recovery, to CDRX, and then to DDRX, along with the quantitative trend of HAGB length per unit
area. This transformation mechanism is believed to encompass the full range of material processing window,
providing a basis for justifying the previous controversial proposition in literature and a guide for defining and
fabricating microstructures in manufacturing applications.
recrystallisation mechanisms have been widely discussed in the literature. However, their influence remains
controversial due to a need for comprehensive and detailed thermomechanical testing and characterisation data
across a wide range of hot deformation conditions. In this study, hot compression tests of AA7050 were conducted at strain rates of 0.0005–5 s
− 1 and temperatures of 380–460 ◦C. The geometrically necessary dislocation
(GND), low-angle grain boundary (LAGB) and high-angle grain boundary (HAGB) were acquired by the latest
high angular resolution, high-speed EBSD detector (OI Symmetry 2), and their underlying mechanisms were
analysed in relation to Zener-Hollomon parameter (Z). It was found that within the tested range of the hot
compression condition (ln (Z) between 20.23 and 29.45), continuous dynamic recrystallisation (CDRX) predominates at lower ln (Z) values with its activity being initially increased and then decreased as ln (Z) rises, while
discontinuous dynamic recrystallisation (DDRX) becomes dominant at higher ln (Z) levels. This transition of the
dominant mechanism is intriguingly reflected in the evolution of HAGB length, which increases, then decreases
and finally increases again. The LAGB length shows a relatively linear relationship with ln (Z), and the average
GND density exhibits a near-linear correlation until reaching a plateau. Based on the obtained results, the
transformation of the dominant microstructural evolution mechanisms with increasing ln (Z) was clarified: from
grain growth, to recovery, to CDRX, and then to DDRX, along with the quantitative trend of HAGB length per unit
area. This transformation mechanism is believed to encompass the full range of material processing window,
providing a basis for justifying the previous controversial proposition in literature and a guide for defining and
fabricating microstructures in manufacturing applications.
Date Issued
2024-11
Date Acceptance
2024-08-15
Citation
Materials Science and Engineering A: Structural Materials: Properties, Microstructure and Processing, 2024, 914
ISSN
0921-5093
Publisher
Elsevier
Journal / Book Title
Materials Science and Engineering A: Structural Materials: Properties, Microstructure and Processing
Volume
914
Copyright Statement
© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
License URL
Identifier
http://dx.doi.org/10.1016/j.msea.2024.147117
Publication Status
Published
Article Number
147117
Date Publish Online
2024-08-21