Microstructure and mechanical properties of a recycled aluminum alloy fabricated by consolidation of small pieces

Figures & data

Figure 1. Images of experimental materials at different steps: (a) small pieces cut from the four scrap AA6063 profiles, (b) blend of the small pieces from different scrap profiles, (c) a small piece compact, (d) a forging compact, (e) 9:1 rod, (f) 25:1 rod.

Table 1. Compositions of four scrap AA6063 aluminum alloy profiles (wt.%).

Profile	Si	Mg	Fe	Al
1	0.40	0.54	0.14	Bal
2	0.41	0.52	0.13	Bal
3	0.44	0.54	0.15	Bal
4	0.45	0.58	0.54	Bal

Table 2. Composition of the 9:1 rod (wt.%).

Element	Si	Mg	Fe	Cu	Al
Content	0.42	0.53	0.21	0.03	Bal

Table 3. Relative densities of the small piece compact, forging compact and as-extruded rod.

Sample	Relative density /%
Small piece compact	98.5
Forging compact	99.5
As-extruded rod	99.8

Figure 2. SEM images of the microstructure of small pieces from the four scrap profiles: (a) 1, (b) 2, (c) 3, (d) 4.

Figure 3. Optical microscopy images of the microstructure of small pieces from the four scrap profiles: (a) 1, (b) 2, (c) 3, (d) 4.

Figure 4. SEM images and EDS spectra of the second phase particles in the microstructure of small pieces form the four scrap profiles: (a) and (b) 1, (c) and (d) 2, (e) and (f) 3, and (g) and (h) 4.

Figure 5. XRD patterns of the as-extruded and heat-treated samples.

Figure 6. Optical microscopy images of the microstructure of the four samples: (a) 9:1, (b) 25:1, (c) 9-T6, (d) 25-T6.

Figure 7. SEM image and EDS elemental maps of the microstructure of two samples: (a) 9:1, (b) 25:1.

Figure 8. SEM images of the microstructure of I and II regions in the as-extruded samples: (a) 9:1, (b) 25:1.

Table 4. Compositions of different types of regions in the 9:1 sample (wt.%), determined by EDS area analysis.

Region	Si	Mg	Fe	Al
I	0.31	0.63	0.45	Bal
II	0.33	0.63	<0.20	Bal

Note: The minimum value of EDS surface scanning element content statistics is 0.20%.

Table 5. Compositions of different types of regions in the 25:1 sample (wt.%), determined by EDS area analysis.

Region	Si	Mg	Fe	Al
I	0.36	0.71	0.44	Bal
II	0.36	0.66	<0.20	Bal

Note: The minimum value of EDS surface scanning element content statistics is 0.20%.

Figure 9. EBSD band contrast and IPF contrast images of the microstructure of as-extruded samples: (a) and (b) 9:1, (c) and (d) 25:1.

Figure 10. EBSD band contrast and IPF contrast images of T6 heat-treated samples: (a) and (b) 9-T6, (c) and (d) 25-T6.

Figure 11. The distributions of aspect ratios of the Al grains of T6 heat-treated samples: (a) 9-T6, (b) 25-T6.

Figure 12. Recrystallization distribution of grains in the four samples: (a) 9:1, (b) 25:1, (c) 9-T6, (d) 25-T6, (e) histograms showing the fractions of different types of grains in the samples.

Figure 13. SEM images of the microstructure of different types of regions of T6 heat-treated samples: (a) 9-T6, (b) 25-T6.

Table 6. Compositions of different types of regions in the 9-T6 sample (wt.%), determined by EDS area analysis.

Region	Si	Mg	Fe	Al
Fe-R	0.37	0.67	0.42	Bal
Fe-L	0.32	0.63	<0.20	Bal

Note: The minimum value of EDS surface scanning element content statistics is 0.20%.

Table 7. Compositions of different types of regions in the 25-T6 sample (wt.%), determined by EDS area analysis.

Region	Si	Mg	Fe	Al
Fe-R	0.31	0.63	0.50	Bal
Fe-L	0.31	0.62	<0.20	Bal

Note: The minimum value of EDS surface scanning element content statistics is 0.20%.

Figure 14. Microhardness values of the samples.

Figure 15. Engineering stress-engineering strain curves of the samples.

Table 8. Tensile properties of the samples.

Sample	YS/MPa	UTS/MPa	EL/%
9:1	67 ± 0.5	118 ± 4.0	11.4 ± 0.1
25:1	75 ± 9.3	139 ± 4.0	24.3 ± 4.0
9-T6	174 ± 10.2	221 ± 7.9	22.1 ± 3.7
25-T6	213 ± 2.7	237 ± 2.9	15.4 ± 1.2

Figure 16. SEM images of the fracture surfaces of the tensile test specimens cut from the samples: (a) and (b) 9:1, (c) and (d) 25:1, (e) and (f) 9-T6, (g) and (h) 25-T6.

Figure 17. Longitudinal sections below the fracture surfaces of the tensile test specimens cut from the samples: (a) 9:1, (b) 25:1, (c) 9-T6, (d) 25-T6.