Title Page
ABSTRACT
Contents
1. INTRODUCTION 12
1.1. Overview of the trend of lightweight material and 6061-T6 Aluminum alloy 12
1.2. Overview of welding and Friction stir welding. 13
1.3. Overview of Post-weld heat treatment of aluminum alloy. 14
1.4. Objective 16
2. METHOD 17
2.1. Processing 17
2.2. Microstructural characterization 20
2.3. Mechanical testing 21
3. RESULTS AND DISCUSSION 23
3.1. Microstructural analysis 23
3.1.1. Optical microscopy and SEM analysis 23
3.1.2. EBSD analysis 26
3.2. Mechanical properties 30
4. CONCLUSION 37
REFERENCE 38
Table 2.1. Chemical compositions of AA6061-T6 18
Table 2.2. Tool geometry. 19
Table 2.3. Welding process parameters. 19
Table 3.1. Mechanical properties of the BM, FSW, and PWHT joints. 33
Figure 2.1. The experimental setup with a clamping system. 17
Figure 2.2. Schematic illustration of (a) butt FSW process of AA6061-T6 sheets, (b) all-weld, and (c) transverse tensile specimen fabrication. 18
Figure 2.3. Diagrammatic representation of the heat treatment procedure. 20
Figure 3.1. Macrograph of the AA6061-T6 cross-section showing various regions of (a) the FSW and (b) PWHT joints. 23
Figure 3.2. SEM/EDS point scan images showing the precipitate in (a, b) the BM and SZ of the FSW and (c) the SZ of the PWHT joints 24
Figure 3.3. EBSD analysis: (a) IPF map, (b) KAM map, (c) GBCD map in the BM of the FSW joint. 26
Figure 3.4. EBSD analysis: (a) IPF map, (b) KAM map, (c) GBCD map in the SZ of the FSW joint. 27
Figure 3.5. EBSD analysis: (a) IPF map, (b) KAM map, (c) GBCD map in the SZ of the PWHT joint. 28
Figure 3.6. Stress-strain curves of the base metal, FSW, and PWHT joints. 33
Figure 3.7. Microhardness mapping of (a) the FSW joint and (b) PWHT; (c) microhardness profile of weld cross-section 34
Figure 3.8. The broke tensile specimens fractured visual position in (a) the FSW and (b) the PWHT joints; (c, d) magnified views of the rupture area of (a, b). 35
Figure 3.9. (a, b) SEM fractography of the fractured tensile specimens in the FSW and the PWHT joints; (c, d) magnified views of the areas in (a) and (b) that are indicated by black rectangles. 36