Spark Plasma Sintering As a Solid-State Recycling Technique: The Case of Aluminum Alloy Scrap Consolidation
Abstract
:1. Introduction
1.1. Energy and Material Efficiency Challenges in Aluminum (Al) Recycling
1.2. Solid-State Recycling Techniques
1.3. SPS Description and Advantages
1.4. Research Motivation and Objectives
2. Materials
Sample | Measured density (g/cm3) | Oxide content (%) |
---|---|---|
S1–ΑΑ6061 | 2.807 | 8.48 |
S2–ΑΑ6061 | 2.806 | 8.49 |
Al6061-T0 reference | 2.686 | - |
S3–ΑΑ6082 | 2.83 | 10.42 |
S4–ΑΑ6082 | 2.832 | 10.52 |
AA6082 T-651 reference | 2.701 | - |
3. Experimental Section
3.1. Process and Tool Set-Up
3.2. Sintering Cycle and Precipitation Hardening
3.3. Material Characterization Measurements
3.3.1. Microstructural Characterization
3.3.2. Hardness and Density Measurements
3.3.3. X-ray Industrial Computed Tomography (CT)
3.3.4. Impulse Excitation Technique (IET)
3.3.5. Compression Testing
4. Results and Discussion
4.1. Microstructural Investigations
4.1.1. Factors that Contribute to Oxide Layer Breakage and to Scrap Consolidation Process
4.1.2. Material Texture
4.1.3. Intermetallic and Grain Boundaries
Peaks | Spot 1 | Spot 2 | Selected area |
---|---|---|---|
O K | 3.83/(15.47) | 9.91/(9.48) | - |
Fe L | 1.51/(62.38) | - | - |
Al K | 2.66/(9.9) | 86.47/(2.38) | 95.98/(1.9) |
Bi M | 89.52/(1.46) | - | - |
Cu K | 2.49/(14.42) | 3.63/(9.16) | 4.02/(6.8) |
4.2. Densification, Oxide Content and Impurities
X-ray Industrial CT Analysis
4.3. Mechanical Properties
4.3.1. Hardness
Sample | Hardness after artificial aging (MPa) | Standard deviation σ |
---|---|---|
S1 top surface | 780 | 14.7 |
S1 cross-section | 779 | 14.7 |
S2 top surface | 777 | 17.6 |
S2 cross-section | 802 | 4.9 |
Al6061-T0 reference | 709 | 20.6 |
S3 top surface | 758 | 27.5 |
S3 cross-section | 803 | 36.3 |
S4 top surface | 839 | 19.6 |
S4 cross-section | 740 | 39.2 |
AA6082 T-651 reference | 1106 | 23.5 |
4.3.2. Elastic Properties
Sample | E-modulus (GPa) | G-modulus (GPa) | Poisson’s ratio | Bulk modulus ** (GPa) |
---|---|---|---|---|
S2 (AA6061 chips) | 77.97 ± 0.93 | 28.98 ± 0.34 | 0.345 | 83.84 ** |
AA6061-T0 reference | 69.08 ± 2.48/68–78 * | 25–27 * | 0.325–0.335 * | 65–72 ** |
S3 (AA6082 chips) | 77.34 ± 0.87 | 28.42 ± 0.32 | 0.36 | 92.07 ** |
S4 (AA6082 chips) | 78.95 ± 5.28 | 29.13 ± 1.95 | 0.355 | 90.74 ** |
AA6082-T651 reference | 69.69 ± 0.86/70–74 * | 25–27 * | 0.325–0.335 * | 65–72 ** |
4.3.3. Compression Testing
Sample | Strain hardening exponent (n) | Compressive strength | ||
---|---|---|---|---|
8% strain | 9% strain | 10% strain | ||
S1-Al6061 (top) | 0.46 ± 0.07 | 320 ± 5.9 | 337 ± 6.1 | 350 ± 5.9 |
S2-Al6061 (cross-section) | 0.40 ± 0.03 | 336 ± 9.3 | 348 ± 9.5 | 360 ± 9.2 |
Al6061-T0 reference | 0.49 | 240 | 256 | 270 |
S3-Al6082 (top) | 0.55 ± 0.05 | 329 ± 8 | 351 ± 7 | 371 ± 6 |
S4-Al6082 (cross-section) | 0.46 ± 0.08 | 304 ± 16 | 329 ± 1 | 342 ± 1 |
Al6082-T651 reference | 0.24 | 368 | 376 | 386 |
5. Conclusions and Discussion
6. Future Research
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Paraskevas, D.; Vanmeensel, K.; Vleugels, J.; Dewulf, W.; Deng, Y.; Duflou, J.R. Spark Plasma Sintering As a Solid-State Recycling Technique: The Case of Aluminum Alloy Scrap Consolidation. Materials 2014, 7, 5664-5687. https://doi.org/10.3390/ma7085664
Paraskevas D, Vanmeensel K, Vleugels J, Dewulf W, Deng Y, Duflou JR. Spark Plasma Sintering As a Solid-State Recycling Technique: The Case of Aluminum Alloy Scrap Consolidation. Materials. 2014; 7(8):5664-5687. https://doi.org/10.3390/ma7085664
Chicago/Turabian StyleParaskevas, Dimos, Kim Vanmeensel, Jef Vleugels, Wim Dewulf, Yelin Deng, and Joost R. Duflou. 2014. "Spark Plasma Sintering As a Solid-State Recycling Technique: The Case of Aluminum Alloy Scrap Consolidation" Materials 7, no. 8: 5664-5687. https://doi.org/10.3390/ma7085664