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Research Papers

Postanneal Mechanical Properties of Prestrained AA5182-O Sheets

[+] Author and Article Information
Jingjing Li1

Department of Mechanical Engineering,  The University of Michigan, Ann Arbor, MI 48109lj8@hawaii.edu

S. Jack Hu

Department of Mechanical Engineering,  The University of Michigan, Ann Arbor, MI 48109

John E. Carsley, Theresa M. Lee, Louis G. Hector

 General Motors R&D Center, Warren, MI 48090

Sushil Mishra

 General Motors India Science Lab, Bengaluru, Karnataka, India 560066

1

Corresponding author. Now with Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, HI 96822

J. Manuf. Sci. Eng 133(6), 061007 (Dec 01, 2011) (10 pages) doi:10.1115/1.4004613 History: Received March 28, 2011; Revised July 15, 2011; Published December 01, 2011; Online December 01, 2011

The effects of different prestrain levels, paths, and subsequent annealing on the postannealing mechanical properties of AA5182-O were investigated. Aluminum sheet specimens were prestrained in uniaxial, plane strain, and equibiaxial tension to several equivalent strain levels, annealed at 350 °C for short (10 s) and long (20 min) durations and then tested for postannealing mechanical properties, including tensile properties, anisotropy, and forming limits. The tensile properties, R-values at 0, 45, and 90 deg relative to the sheet rolling direction, and forming limit diagrams (FLDs) exhibited dependencies on prestrain and annealing history. The importance of the process variables and their effects were identified via designed experiments and analysis of variance. Three-dimensional digital image correlation, which captured the onset of local necking, was employed in the FLD development. Texture in the as-received and deformed sheets was investigated with electron backscatter diffraction and provided a means for linking prestrain and static recovery or recrystallization with microstructure. This guided the understanding of the mechanical property changes observed after preforming and annealing. Ultimately, the expanded forming limit curve demonstrated the advantage of annealing in extending the formability of strained AA5182-O.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 2

Specimen design for prestrain in uniaxial tension (unit: mm)

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Figure 4

Main effect plots for postannealing strengths of AA5182-O: (a) prestrain path effect on UTS, (b) prestrain level effect on UTS, (c) annealing effect on UTS, (d) prestrain path effect on YS, (e) prestrain level effect on YS, and (f) annealing effect on YS

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Figure 5

Main effect plots for postannealing strains of AA5182-O: (a) prestrain path effect on strain at UTS, (b) prestrain level effect on strain at UTS, (c) annealing effect on strain at UTS, (d) prestrain path effect on maximum strain at fracture, (e) prestrain level effect on maximum strain at fracture, and (f) annealing effect on maximum strain at fracture

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Figure 6

Inverse pole figure map and pole figure for 0.15 uniaxial prestrain specimens: (a) without annealing, (b) 350 °C for 10 s, (c) 350 °C for 20 min, and (d) average grain size and grain average misorientation versus annealing time for 0.15 uniaxial prestrain specimens

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Figure 7

Prestrain level and annealing effects on total effective maximum engineering strain at fracture

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Figure 8

Postannealing plastic strain ratio: (a) R-values along three directions for unannealed specimens, (b) R-values along three directions for specimens annealed at 350 °C for 10 s, (c) R-values along three directions for specimens annealed at 350 °C for 20min, and (d) R¯ (i.e. Avg. R, calculated from Eq. 2) for these three annealing conditions

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Figure 9

Main effects plot for postannealing directional values of R: (a) prestrain level effect, (b) orientation effect, and (c) annealing effect

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Figure 1

Inverse pole figure, pole figure map, and grain size distribution of AA5182-O as-received: (a) IPF, (b) PF, and (c) grain size distribution

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Figure 3

Postannealing properties of AA5182-O for 0.15 prestrain under different prestrain paths and annealing conditions: (a) UTS, (b) YS, (c) strain at UTS, and (d) max strain at fracture

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Figure 10

FLD of AA5182-O as-received

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Figure 11

Prestrain and annealing effects on postannealing FLDs: (a) annealing effect, (b) prestrain path effect for prestrained specimens w/o annealing (c) prestrain path effect for prestrained specimens annealed for 20min, and (d) prestrain level effect

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Figure 12

Prestrain and annealing effects on total effective FLDs: (a) annealing and prestrain path effects, and (b) prestrain level effects

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