Effect of Process Parameters on Fatigue and Fracture Behavior of Al-Cu-Mg Alloy after Creep Aging
Abstract
:1. Introduction
2. Experimental
2.1. Samples and Heat Treatment
2.2. Tensile and Fatigue Testing
2.3. Microstructural Analysis
3. Results and Discussion
3.1. Creep Behavior of Alloy
3.2. Mechanical Properties of Alloy
3.3. Effect of Aging Temperature on Fatigue Fracture of Alloy
3.4. Effect of Stress on Fatigue Fracture of Alloy
3.5. Relationship between Microstructure and Fatigue Fracture Behavior of Alloy
3.5.1. Effect of Aging Temperature
3.5.2. Effect of Stress
- (1)
- During the creep aging process, the strengthening phases in the grain interior can precipitate under the combined impact of stress and temperature. These precipitation phases in the matrix impede the dislocations movement and improve the strength and anti-plastic deformation of alloy until they eventually reduce the deformation damage during the fatigue process and prolong fatigue life.
- (2)
- The precipitation phases in the grain interior are semi-coherent or incoherent with the matrix, causing dislocations passing round the precipitation phases and leaving a dislocations loop. It makes dislocations unable to slip repeatedly in grains, which leads to the dislocations easily slipping to the grain boundary. The precipitation phase is not conducive to the crack growth and the reduction of deformation damage.
- (3)
- The precipitation-free zone (PFZ) and coarse particles along the grain boundaries will reduce the strength of grain boundaries, so that the dislocations are more likely to slip at the grain boundary. These can increase the stress concentration of grain boundaries, forming cracks easily along the grain boundaries.
4. Conclusions
- (1)
- With the increase of temperature and stress, the creep strain of the alloy is improved. As the temperature rises, the tensile strength and yield strength first increase, and then decrease. The mechanical properties of alloy are improved after creep aging, but stress has a weak effect on the mechanical properties.
- (2)
- The process parameters can obviously impact the fatigue life of the alloy. The fatigue life first increases, and then decreases with the rise of both temperature and stress. Both overhigh temperature and stress can shorten the fatigue life. The best fatigue life is 90971 cycles at 180 °C under 180 MPa in this study.
- (3)
- The precipitation characteristics of alloy are the main reason for the fatigue life change of the alloy. When the precipitation phases are fine and dispersed, the strength and anti-plastic deformation of the alloy are improved, and fatigue life increases. However, when the precipitation phases become coarse, the precipitation phases cannot be cut by dislocation, so the fatigue life dropped. Besides, the PFZ at the grain boundary is a weak part of alloy, where the fatigue life decreases with a wide PFZ.
Author Contributions
Acknowledgments
Conflicts of Interest
References
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Cu | Mg | Mn | Fe | Zn | Ti | Cr | Si | Al |
---|---|---|---|---|---|---|---|---|
4.26 | 1.36 | 0.57 | 0.037 | 0.024 | 0.01 | 0.002 | 0.089 | Bal. |
Temperature/°C | Stress/MPa | Creep Strain/% | Steady-State Creep/s−1 |
---|---|---|---|
160 | 180 | 0.068 | 3.3 × 10−3 |
210 | 0.082 | 4.02 × 10−3 | |
180 | 180 | 0.145 | 7.58 × 10−3 |
210 | 0.169 | 8.42 × 10−3 | |
200 | 180 | 0.235 | 1.033 × 10−2 |
210 | 0.315 | 1.46 × 10−2 |
Temperature/°C | Stress/MPa | Tensile Strength/MPa | Yield Strength/MPa | Elongation/% |
---|---|---|---|---|
160 | 0 | 482.6 ± 2.5 | 331.6 ± 3.4 | 19.9 ± 0.3 |
160 | 180 | 497.5 ± 4.1 | 362.4 ± 5.6 | 21.6 ± 0.5 |
160 | 210 | 496.6 ± 3.0 | 358.6 ± 3.6 | 21.6 ± 0.4 |
180 | 0 | 495.6 ± 2.7 | 443.4 ± 3.4 | 10.1 ± 0.4 |
180 | 180 | 504.2 ± 4.5 | 463.2 ± 4.8 | 10.1 ± 0.3 |
180 | 210 | 501.4 ± 2.8 | 461.1 ± 3.1 | 10.4 ± 0.3 |
200 | 0 | 465.6 ± 3.6 | 372.6 ± 4.2 | 8.8 ± 0.5 |
200 | 180 | 472.7 ± 3.5 | 417.3 ± 4.6 | 8.9 ± 0.4 |
200 | 210 | 475.2 ± 2.1 | 419.9 ± 2.6 | 8.9 ± 0.3 |
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Zhan, L.; Wu, X.; Wang, X.; Yang, Y.; Liu, G.; Xu, Y. Effect of Process Parameters on Fatigue and Fracture Behavior of Al-Cu-Mg Alloy after Creep Aging. Metals 2018, 8, 298. https://doi.org/10.3390/met8050298
Zhan L, Wu X, Wang X, Yang Y, Liu G, Xu Y. Effect of Process Parameters on Fatigue and Fracture Behavior of Al-Cu-Mg Alloy after Creep Aging. Metals. 2018; 8(5):298. https://doi.org/10.3390/met8050298
Chicago/Turabian StyleZhan, Lihua, Xintong Wu, Xun Wang, Youliang Yang, Guiming Liu, and Yongqian Xu. 2018. "Effect of Process Parameters on Fatigue and Fracture Behavior of Al-Cu-Mg Alloy after Creep Aging" Metals 8, no. 5: 298. https://doi.org/10.3390/met8050298