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Research Papers

Properties of Friction-Stir Welded Aluminum Alloys 6111 and 5083

[+] Author and Article Information
W. Gan

Minneapolis/St. Paul Office, Simulia, 539 Bielenberg Drive Suite 110, Woodbury, MN 55125

K. Okamoto

R&D Division, Hitachi America, Ltd., 34500 Grand River Avenue, Farmington Hills, MI 48335

S. Hirano

 Hitachi Research Laboratory, Hitachi Ltd. 7-1-1 Omika, Hitachi, Ibaraki 319-1292, Japan

K. Chung

School of Materials Science and Engineering, Seoul National University, 56-1 Shinlim-dong, Kwanak-gu, Seoul 151-742, Korea

C. Kim

 Materials and Processes Laboratories, General Motors R&D Center, 30500 Mound Road, MC 480106224, Warren, MI 48090

R. H. Wagoner

Department of Materials Science and Engineering, The Ohio State University, 2041 College Road, Columbus, OH 43210

J. Eng. Mater. Technol 130(3), 031007 (Jun 10, 2008) (15 pages) doi:10.1115/1.2931143 History: Received July 24, 2006; Revised September 20, 2007; Published June 10, 2008

Friction-stir welding (FSW) promises joints with low porosity, fine microstructures, minimum phase transformation, and low oxidation compared with conventional welding techniques. It is capable of joining combinations of alloys not amenable to conventional welding. Certain combinations of FSW parameters were used to create FSWs of aluminum alloys 5083-H18 and 6111-T4, and the physical weld defects were measured. The mechanical behavior of FSW welds made under the most favorable choice of parameters was determined using tensile tests and hardness measurements and was correlated to the microstructures of the weld and base material. Stir zones (SZs) in the 5083 specimens were much softer than the strain-hardened base materials. SZs in the 6111 material are approximately as hard as the base material. Natural aging of 6111 FSW specimens occurred in some parts of the heat-affected zone and produced hardening for up to 12weeks after welding. Annealing of 5083 FSW specimens produced abnormal grain growth (AGG) for welds produced under certain welding conditions and in certain parts of the weld zone. AGG is more severe for low-heat conditions, i.e., higher tool travel speed but lower rotational speed. The conditions for most favorable FSW are presented, as well as the expected microstructures and mechanical properties, along with the weld conditions that promote AGG.

Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the FSW process and definition of parameters

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Figure 2

Orientation of the pin axis with respect to the plate and weld directions

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Figure 3

Classification of ductile failure mechanisms for forming of TWBs: (a) Type 1 failure-longitudinal loading, stronger/less-ductile weld, (b) Type 2 failure-transverse loading, stronger/less ductile weld, (c) Type 1A failure-longitudinal loading, weaker/more ductile weld, and (d) Type 2A failure-transverse loading, weaker/more ductile weld. (a) and (b) have appeared in literature (2).

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Figure 4

Embedded thermocouple locations (represented by circles). Groups of thermocouples are labeled by A, B, or C and individual thermocouples are designated by their distance from the center of the weld line.

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Figure 5

Summary of welding process development results for 5083 dissimilar gage welds. Most favorable parameters are shown in bold.

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Figure 6

Summary of welding process development results for 5083 same gage welds. Most favorable parameters are shown in bold.

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Figure 7

Summary of welding process development results for 6111 dissimilar gage welds. Most favorable parameters are shown in bold.

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Figure 8

Summary of welding process development results for 6111 same gage welds. Most favorable parameters are shown in bold.

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Figure 9

Temperatures measured during FSW of 5083. Letters A, B, and C refer to thermocouple grouping shown in Fig. 4. Cases: (a) same gage, advancing side, (b) same gage, retreating side, (c) dissimilar gage, advancing side, and (d) dissimilar gage, retreating side

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Figure 10

Temperatures measured during FSW of 6111. Cases: (a) same gage, advancing side, (b) same gage, retreating side, (c) dissimilar gage, advancing side, and (d) dissimilar gage, retreating side

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Figure 11

Comparison of strain hardening of base materials using full-sized and subsized tensile specimens

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Figure 12

Comparison of Vickers hardness profiles across the FSW weld zone for 5083 and 6111

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Figure 13

Comparison of base and FSW zone strain hardening for (a) 5083 and (b) 6111

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Figure 14

Formability analysis: (a) schematic of the tensile analysis model and its relationship to a part of a TWB, (b) calculated tensile response of TD FSW samples made from 5083-H18, and (c) calculated tensile response of TD FSW samples made from 6111-T4

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Figure 15

Weld configuration and microstructures for 5083: (a) weld profile, (b) optical micrograph, base material, (c) optical micrograph, center of weld, (d) TEM micrograph, base material, and (e) TEM micrograph, center of weld

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Figure 16

Weld configuration and microstructures for 6111: (a) weld profile, (b) optical micrograph, base material, (c) optical micrograph, center of weld, (d) TEM micrograph, base material, and (e) TEM micrograph, center of weld

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Figure 17

Detailed weld microstructures for 6111: (a) TEM micrograph, grain structure and (b) TEM micrograph, dislocation structure

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Figure 18

Hardness profiles evolution with time for FSW 6111. The peak temperatures during welding are shown for two locations in the HAZ.

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Figure 19

TEM micrographs for 6111: (a) locations of sections related to weld, (b) base material, (c) HAZ, (d) and weld

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Figure 20

Hardness profiles before and after heat treatment of 5083 welds (465°C for 5min)

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Figure 21

Base material grain structures for 5083: (a) optical micrograph, before heat treatment and (b) optical micrograph, after heat treatment

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Figure 22

Tensile properties of 5083 before and after heat treatment (465°C for 5min)

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Figure 23

Optical micrographs of the microstructures for 5083: (a) weld profile before heat treatment, (b) weld profile after heat treatment, (c) base material before heat treatment, (d) base material after heat treatment, (f) weld before heat treatment, and (f) weld after heat treatment

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Figure 24

Grain morphologies after heat treatment of the 5083 welds

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Figure 25

Temperatures measured during FSW of 5083. Cases: (a) standard, advancing side, (b) standard, retreating side, (c) worst AGG, advancing side, (d) worst AGG, retreating side, (e) least AGG, advancing side, and (f) least AGG, retreating side

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Figure 26

The relationship between peak welding temperatures and occurrence of rapid recrystallization and grain growth

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Figure 27

Grain morphologies of the 5083 welds, heat treated at 465°C from 1minto2h

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