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Superplasticity, flow and fracture mechanism in an Al-12.7SI-0.7Mg alloy

Superplasticity, flow and fracture mechanism in an Al-12.7SI-0.7Mg alloy
Superplasticity, flow and fracture mechanism in an Al-12.7SI-0.7Mg alloy
The superplastic behavior of an Al–12.7mass%Si–0.7mass%Mg alloy was investigated under different conditions. Reasonable superplastic elongations were achieved in the fine-grained (9.1 ?m) Al–Si–Mg alloy at temperatures ranging from 733 to 793 K at initial strain rates ranging from 1.67×10–4 to 1.67×10–3 s?1. A maximum elongation to failure of 379% was demonstrated with a strain rate sensitivity, m, of 0.52 and an activation energy for flow, Q, of 156.7 KJ/mol at 793 K at an initial strain rate of 1.67×10–4 s?1, which is close to the lattice diffusion activation energy of aluminum. The dislocation activity within Al grains indicated that intragranular slip is the accommodation mechanism of grain boundary sliding. EBSD (Electron Backscatter Diffraction) results revealed that most grain boundaries were high angle boundaries and therefore indicated that boundary sliding and grain rotation occurred during deformation. A deformation mechanism map was plotted for the Al–Si–Mg alloy at 793 K and it is shown that the experimental datum points are in excellent agreement with the predictions of the map. Most cavities were formed around silicon particles and the cavity formation mechanism was proposed. The observation on the fracture surface revealed the presence of filaments. The filament quantity or density increased with increasing testing temperature, which can be interpreted by the transition of dislocation viscous glide creep to grain boundary sliding mechanism at elevated temperatures. The formation of filaments was related to the deformation mechanisms and the lattice diffusion at elevated temperatures. The superplastic fracture in the Al–Si–Mg alloy exhibited a diffuse necking and was a pseudo-brittle fracture. The fracture mechanism was intergranular fracture.
Al-Si-Mg alloy, superplasticity, strain rate sensitivity, activation energy, cavity, fracture
0921-5093
167-183
Cao, Furong
bbd187f4-ce5a-4dd2-8bd0-5079e19aebe7
Li, Zhuoliang
b6ada3da-d8ab-4802-9bfc-3df92c27864d
Zhang, Nianxian
1f72e293-27fe-41d4-956c-7e8c8a40b3b0
Ding, Hua
09d48669-e6db-4d29-87d1-fd53d9adb24c
Yu, Fuxiao
977bd430-8aeb-4745-a188-6558bd8bfe75
Zuo, Liang
8adbf571-a0ac-4404-a356-269eed4c573c
Cao, Furong
bbd187f4-ce5a-4dd2-8bd0-5079e19aebe7
Li, Zhuoliang
b6ada3da-d8ab-4802-9bfc-3df92c27864d
Zhang, Nianxian
1f72e293-27fe-41d4-956c-7e8c8a40b3b0
Ding, Hua
09d48669-e6db-4d29-87d1-fd53d9adb24c
Yu, Fuxiao
977bd430-8aeb-4745-a188-6558bd8bfe75
Zuo, Liang
8adbf571-a0ac-4404-a356-269eed4c573c

Cao, Furong, Li, Zhuoliang, Zhang, Nianxian, Ding, Hua, Yu, Fuxiao and Zuo, Liang (2013) Superplasticity, flow and fracture mechanism in an Al-12.7SI-0.7Mg alloy. Materials Science and Engineering: A, 571, 167-183. (doi:10.1016/j.msea.2013.02.010).

Record type: Article

Abstract

The superplastic behavior of an Al–12.7mass%Si–0.7mass%Mg alloy was investigated under different conditions. Reasonable superplastic elongations were achieved in the fine-grained (9.1 ?m) Al–Si–Mg alloy at temperatures ranging from 733 to 793 K at initial strain rates ranging from 1.67×10–4 to 1.67×10–3 s?1. A maximum elongation to failure of 379% was demonstrated with a strain rate sensitivity, m, of 0.52 and an activation energy for flow, Q, of 156.7 KJ/mol at 793 K at an initial strain rate of 1.67×10–4 s?1, which is close to the lattice diffusion activation energy of aluminum. The dislocation activity within Al grains indicated that intragranular slip is the accommodation mechanism of grain boundary sliding. EBSD (Electron Backscatter Diffraction) results revealed that most grain boundaries were high angle boundaries and therefore indicated that boundary sliding and grain rotation occurred during deformation. A deformation mechanism map was plotted for the Al–Si–Mg alloy at 793 K and it is shown that the experimental datum points are in excellent agreement with the predictions of the map. Most cavities were formed around silicon particles and the cavity formation mechanism was proposed. The observation on the fracture surface revealed the presence of filaments. The filament quantity or density increased with increasing testing temperature, which can be interpreted by the transition of dislocation viscous glide creep to grain boundary sliding mechanism at elevated temperatures. The formation of filaments was related to the deformation mechanisms and the lattice diffusion at elevated temperatures. The superplastic fracture in the Al–Si–Mg alloy exhibited a diffuse necking and was a pseudo-brittle fracture. The fracture mechanism was intergranular fracture.

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More information

Published date: June 2013
Keywords: Al-Si-Mg alloy, superplasticity, strain rate sensitivity, activation energy, cavity, fracture
Organisations: Engineering Mats & Surface Engineerg Gp

Identifiers

Local EPrints ID: 366993
URI: http://eprints.soton.ac.uk/id/eprint/366993
ISSN: 0921-5093
PURE UUID: c029006a-bfb2-47a2-a713-d82428ebb9df

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Date deposited: 21 Jul 2014 10:47
Last modified: 14 Mar 2024 17:21

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Contributors

Author: Furong Cao
Author: Zhuoliang Li
Author: Nianxian Zhang
Author: Hua Ding
Author: Fuxiao Yu
Author: Liang Zuo

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