Interfacial Characterization and Bonding Properties of Copper/Aluminum Clad Sheets Processed by Horizontal Twin-Roll Casting, Multi-Pass Rolling, and Annealing
Abstract
:1. Introduction
2. Materials and Methods
3. Results and Discussion
3.1. Analysis of the As-Cast Cu/Al Clad Sheet Interface
3.2. Interfacial Microstructure of the Clad Sheets after Multi-Pass Rolling and Annealing
3.3. Peel Strength
3.4. Peeled Surface Morphology
3.5. The Bonding Mechanism of the Cu/Al Clad Sheets
4. Conclusions
- (1)
- The Cu/Al clad sheets were produced with a horizontal twin-roll caster. The interface thickness of the as-cast Cu/Al clad sheet reached 9 μm to 10 μm and the interface was composed of three IMC layers including Al2Cu, AlCu, and Al4Cu9.
- (2)
- During multi-pass rolling, the peel strength first slightly increased and then gradually decreased with the increase of the rolling pass number. The IMC layer was broken and became increasingly separated with the increase of the rolling pass number. Mechanical locking formed in the broken region of the IMC layer. The mechanical locking resisted crack propagation and enhanced the peel strength, but the effect of this locking diminished with the increase of the rolling pass number.
- (3)
- During annealing, the bonding force between the extruded metals and cracking surface of the primary diffusion layer can enhance by thermal diffusion. Therefore, this leads to further increasing of the mechanical locking force. Meanwhile, the integrity of the IMC layer was improved, which propagates more peeling cracks in the Al matrix. The second diffusion layer can form at the Cu/Al direct contact region. All these effects of annealing improved the interfacial microstructure and enhanced the bonding strength of clad sheets. After rolling to 7 mm and annealing at 350 °C for 2 h, the clad sheet had the highest APS of 25 N/mm. This process can be used as the method to improve the peel strength of the Cu/Al clad sheets.
- (4)
- The improvement in the peel strength is mainly based on the following three factors: mechanical locking formed in the Cu/Al direct contact region after rolling, fracture occurred in the Al matrix, and a mechanical biting occurred from the Cu/Al direct contact region. These strengthening mechanisms of the clad sheets with a hard interface layer should be considered during the rolling and annealing processes in future applications.
Author Contributions
Funding
Conflicts of Interest
References
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Rolling Pass Number | Reduction Per Pass (%) | Total Reduction (%) | Clad Sheet Thickness (mm) |
---|---|---|---|
1 | 12.5 | 12.5 | 7 |
2 | 14.3 | 25 | 6 |
3 | 16.7 | 37.5 | 5 |
4 | 20 | 50 | 4 |
5 | 25 | 62.5 | 3 |
Element | 1 (at.%) | 2 (at.%) | 3 (at.%) |
---|---|---|---|
Cu | 62.50 | 43.29 | 31.67 |
Al | 37.50 | 56.71 | 68.33 |
Probable Phase | Al4Cu9 | AlCu | Al2Cu |
Thickness of the Clad Sheets (mm) | Ratio of Cu/Al Direct Contact Region to the Interface Layer (%) | Average Width of Cu/Al Direct Contact Region (μm) | The Number of Cu/Al Direct Contact Region Per Millimeter |
---|---|---|---|
7 | 19.12 | 7.2338 | 26 |
6 | 27.12 | 10.865 | 25 |
5 | 37.68 | 15.10 | 25 |
4 | 51.25 | 26.86 | 19 |
3 | 56.18 | 27.50 | 20 |
Element | 1 (at.%) | 2 (at.%) | 3 (at.%) | 4 (at.%) |
---|---|---|---|---|
Cu | 29.49 | 45.92 | 29.70 | 52.36 |
Al | 70.51 | 54.08 | 70.30 | 47.64 |
Phase | Al2Cu | AlCu | Al2Cu | AlCu |
Phase | Crystal Structure | Hardness/HV0.025 |
---|---|---|
Cu | Cubic (Fm3m, FCC) | 85–92 |
Al | Cubic (Fm3m, FCC) | 45–48 |
Al4Cu9 | Cubic (P43m) | 156 |
AlCu | Monoclinic (C2/m) | 411 |
Al2Cu | Tetragonal (I4/mcm) | 318 |
Element | a1 | a2 | a3 | a4 | b1 | b2 | b3 | b4 |
---|---|---|---|---|---|---|---|---|
Cu | 01.58 | 41.05 | 27.98 | 92.47 | 01.28 | 29.33 | 52.41 | 01.58 |
Al | 98.42 | 58.95 | 72.02 | 07.53 | 98.72 | 70.67 | 47.59 | 98.42 |
Phase | Al | AlCu | Al2Cu | Cu | Al | Al2Cu | AlCu | Al |
c1 | c2 | c3 | c4 | d1 | d2 | d3 | d4 | |
Cu | 54.13 | 30.33 | 89.39 | 01.25 | 02.24 | 29.45 | 46.01 | 01.18 |
Al | 45.87 | 69.67 | 10.61 | 98.75 | 97.76 | 70.55 | 53.99 | 98.82 |
Phase | AlCu | Al2Cu | Cu | Al | Al | Al2Cu | AlCu | Al |
e1 | e2 | e3 | e4 | f1 | f2 | f3 | ||
Cu | 02.20 | 28.51 | 93.76 | 01.77 | 00.68 | 44.59 | 28.43 | |
Al | 97.80 | 71.49 | 06.24 | 98.23 | 99.32 | 55.41 | 71.57 | |
Phase | Al | Al2Cu | Cu | Al | Al | AlCu | Al2Cu |
Element | a1 | a2 | a3 | a4 | b1 | b2 | b3 | b4 |
---|---|---|---|---|---|---|---|---|
Cu | 00.20 | 51.41 | 30.58 | 90.72 | 00.27 | 07.92 | 26.79 | 52.37 |
Al | 99.80 | 48.59 | 69.42 | 09.28 | 99.73 | 92.08 | 73.21 | 47.63 |
Phase | Al | AlCu | Al2Cu | Cu | Al | Al | Al2Cu | AlCu |
c1 | c2 | c3 | d1 | d2 | d3 | |||
Cu | 01.48 | 91.75 | 28.34 | 03.12 | 52.69 | 28.72 | ||
Al | 98.52 | 08.25 | 71.66 | 96.88 | 47.31 | 71.28 | ||
Phase | Al | Cu | Al2Cu | Al | AlCu | Al2Cu | ||
e1 | e2 | e3 | f1 | f2 | f3 | |||
Cu | 00.74 | 29.49 | 23.59 | 30.37 | 29.57 | 00.91 | ||
Al | 99.26 | 70.51 | 76.41 | 69.63 | 70.43 | 99.09 | ||
Phase | Al | Al2Cu | Al2Cu | Al2Cu | Al2Cu | Al |
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Mao, Z.; Xie, J.; Wang, A.; Wang, W.; Ma, D. Interfacial Characterization and Bonding Properties of Copper/Aluminum Clad Sheets Processed by Horizontal Twin-Roll Casting, Multi-Pass Rolling, and Annealing. Metals 2018, 8, 645. https://doi.org/10.3390/met8080645
Mao Z, Xie J, Wang A, Wang W, Ma D. Interfacial Characterization and Bonding Properties of Copper/Aluminum Clad Sheets Processed by Horizontal Twin-Roll Casting, Multi-Pass Rolling, and Annealing. Metals. 2018; 8(8):645. https://doi.org/10.3390/met8080645
Chicago/Turabian StyleMao, Zhiping, Jingpei Xie, Aiqin Wang, Wenyan Wang, and Douqin Ma. 2018. "Interfacial Characterization and Bonding Properties of Copper/Aluminum Clad Sheets Processed by Horizontal Twin-Roll Casting, Multi-Pass Rolling, and Annealing" Metals 8, no. 8: 645. https://doi.org/10.3390/met8080645