Evolution of Microstructure, Hardness, and Wear Behavior of Medium-Entropy CuNiSiCrCoTiNbx Alloy
Abstract
1. Introduction
1.1. General Considerations
1.2. Literature Review
1.3. Motivation and Contributions
- Evolution of configurational entropy as a function of Nb content and its influence on phase stability and solid solution formation of BCC and FCC structures.
- The microstructure of the alloys was characterized by XRD and SEM-EDS to identify the crystalline phases and evaluate the effect of Nb on the lattice parameters.
- To analyze how Nb and different heat treatments influence the refinement and distribution of the precipitated phases and the evolution of the hardness of the alloys in the cast and aged states.
- To determine the wear behavior of the MEA under different heat treatment conditions, they were compared with the CuBe C17510 alloy to establish their viability in applications where wear resistance is a key factor.
2. Materials and Methods
3. Considerations of Thermodynamic Properties in the Formation of Phases in MEAs
4. Results and Discussion
4.1. The XRD Patterns Prior to Heat Treatment
4.2. Microstructural Characterization Before Heat Treatments
4.3. XRD Patterns Following Heat Treatments
4.4. Microstructure Analysis by SEM
4.5. Elemental Distribution Analysis by SEM-EDS
4.6. Hardness Rockwell B Results
4.7. Vickers Hardness Results
4.8. Friction and Wear Behaviors of the MEAs
5. Conclusions
- (1)
- Nb additions were found to favor the gradual increase in configurational entropy values of 8.17 J/mol-K for M1, 8.38 J/mol-K for M2 and 8.61 J/mol-K for M3, which favors the formation of solid solutions and crystalline structures of BCC and FCC types.
- (2)
- The XRD and SEM-EDS spectra showed that the medium-entropy alloys were mainly composed of the FCC phase (αCu) and the precipitated phases Co2Nb, Ni2Si and Cr3Si. In addition, the XRD spectra revealed that the (111) peak undergoes an important variation in the diffraction angle, with a slight shift to larger angles of 50.64°, 50.65°, and 50.69° with an increase in Nb content, which causes at the decrease in lattice parameters in M1, M2, and M3, respectively.
- (3)
- Nb addition and heat treatments strengthened the microstructure through the refinement and distribution of the precipitated phases.
- (4)
- The high hardness values of the as-cast samples manifested a gradual increase of 86 ± 1.21, 87 ± 1.70 and 92 ± 0.11 HRB for M1, M2, and M3, respectively. This increase in hardness is attributed to the microstructural evolution caused by the addition of Nb. In addition, the hardness values of the aged samples were higher than those of the as-cast and commercial CuBe C17510 alloy.
- (5)
- The wear behavior analysis revealed that the E1 samples in as-cast condition obtained satisfactory wear resistance results as the Nb content increased, resulting in a stepwise lost volume behavior of 2.22 mm3, 1.95 mm3 and 1.67 mm3 for the M1, M2, and M3 alloys. On the other hand, wear values for the E4 samples in TTE-60 aged condition reflected a reduction in material loss of 1.77 mm3, 1.53 mm3, and 1.29 mm3 for M1, M2, and M3. For the CuBe alloy C17510, the material loss was 3.34 mm3.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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C | Elemental Constituents (wt%) | |||||||
---|---|---|---|---|---|---|---|---|
Alloy | Cu | Ni | Si | Cr | Co | Ti | Fe | Nb |
M1 | 79.90 | 5.50 | 5.50 | 5.50 | 1.00 | 2.00 | 0.60 | 0.00 |
M2 | 79.13 | 5.50 | 5.50 | 5.50 | 1.00 | 2.00 | 0.87 | 0.50 |
M3 | 78.39 | 5.50 | 5.50 | 5.50 | 1.00 | 2.00 | 1.11 | 1.00 |
Alloy | Phase | ∆HMix (k·J/mol) | ∆SConf (J/mol·K) | δ (%) | ∆χ (%) | VEC | Ω | Tm (K) |
---|---|---|---|---|---|---|---|---|
M1 | FCC/BCC | −7.14 | 8.11 | 5.44 | 0.110 | 8.93 | 1.68 | 1483.15 |
M2 | FCC/BCC | −7.16 | 8.38 | 4.05 | 0.080 | 9.61 | 1.69 | 1488.15 |
M3 | FCC/BCC | −7.17 | 8.61 | 4.11 | 0.082 | 9.58 | 1.79 | 1494.15 |
Alloy | Phase | Elemental Constituents (at%) | |||||||
---|---|---|---|---|---|---|---|---|---|
Cu | Ni | Si | Cr | Co | Ti | Fe | Nb | ||
Nominal | 73.00 | 5.50 | 6.10 | 11.40 | 1.00 | 2.40 | 0.60 | 0.00 | |
A | 90.86 | 3.59 | 5.55 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | |
M1 | B | 32.08 | 24.12 | 23.35 | 4.71 | 2.94 | 5.43 | 7.37 | 0.00 |
C | 1.96 | 0.88 | 22.40 | 70.08 | 0.00 | 0.30 | 4.38 | 0.00 | |
Nominal | 72.40 | 5.50 | 6.10 | 11.40 | 1.00 | 2.40 | 0.90 | 0.30 | |
A | 95.45 | 2.87 | 5.68 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | |
M2 | B | 19.22 | 18.97 | 24.71 | 12.35 | 4.99 | 10.80 | 7.32 | 1.63 |
C | 2.37 | 0.78 | 22.82 | 69.74 | 0.69 | 0.71 | 2.88 | 0.00 | |
Nominal | 71.80 | 5.50 | 6.10 | 11.40 | 1.00 | 2.40 | 1.20 | 0.60 | |
A | 90.92 | 2.50 | 6.58 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | |
M3 | B | 4.59 | 9.79 | 25.55 | 19.29 | 7.20 | 5.67 | 8.83 | 19.08 |
C | 1.45 | 0.16 | 23.65 | 72.12 | 0.11 | 0.41 | 2.10 | 0.00 |
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Avila-Salgado, D.A.; Juárez-Hernández, A.; Izaguirre-Bonilla, N.J.; Muñoz Tabora, J.; Camacho-Martínez, J.L. Evolution of Microstructure, Hardness, and Wear Behavior of Medium-Entropy CuNiSiCrCoTiNbx Alloy. Lubricants 2025, 13, 164. https://doi.org/10.3390/lubricants13040164
Avila-Salgado DA, Juárez-Hernández A, Izaguirre-Bonilla NJ, Muñoz Tabora J, Camacho-Martínez JL. Evolution of Microstructure, Hardness, and Wear Behavior of Medium-Entropy CuNiSiCrCoTiNbx Alloy. Lubricants. 2025; 13(4):164. https://doi.org/10.3390/lubricants13040164
Chicago/Turabian StyleAvila-Salgado, Denis Ariel, Arturo Juárez-Hernández, Nelson Javier Izaguirre-Bonilla, Jonathan Muñoz Tabora, and José Luis Camacho-Martínez. 2025. "Evolution of Microstructure, Hardness, and Wear Behavior of Medium-Entropy CuNiSiCrCoTiNbx Alloy" Lubricants 13, no. 4: 164. https://doi.org/10.3390/lubricants13040164
APA StyleAvila-Salgado, D. A., Juárez-Hernández, A., Izaguirre-Bonilla, N. J., Muñoz Tabora, J., & Camacho-Martínez, J. L. (2025). Evolution of Microstructure, Hardness, and Wear Behavior of Medium-Entropy CuNiSiCrCoTiNbx Alloy. Lubricants, 13(4), 164. https://doi.org/10.3390/lubricants13040164