Examining The Phase Formation of Aging and Shallow Cryogenic Process Applied to Aluminum Alloys with Thermal Analysis

Abstract

In this study, cryogenic treatment was applied to the 7*** series alloy, which is one of the aluminum alloys frequently used in the aviation and space industry, after the retrogression and re-aging process, and the phase formations were examined by thermal analysis. First of all, solution heat treatment was applied at 480 °C for 2 hours and water was given. After quenching, artificial aging heat treatment was applied at 120 °C for 24 hours. To start the RRA (retrogression and re-aging) heat treatment, after artificial aging, retrogression was performed at 200 °C for 10 minutes and quenched. Then, re-aging was performed at 120 °C for 24 hours and the aging process was completed. After the RRA heat treatment, cryogenic treatment was applied for 2 hours at -40 °C, -80 °C respectively. The heat treated samples were analyzed with a differential thermal analyzer and the transformations of GP, η′ and η phases were found. Since the η′ phase is known as the strength-increasing phase in the structure, the activation energies of each sample were calculated using the Augis-Bennet and Kissinger equations. The results showed that the activation energy of the sample treated with -40 cryogenic treatment was 50% less than the sample without cryogenic treatment. This situation proved with the Arrhenius equation that the formation of the η′ phase would be easier.

Keywords

• 7075 Al alloy
• thermal analysis
• cryogenic treatment
• retrogression and re-aging

Kaynakça

1. [1] Karakoca, Y. E., & AYTAÇ, A. (2022). Investigation of Drillability of CFRP/Al 7075 Stack. Mechanics, 28(6), 430-438.
2. [2] Altuntaş, G., Altuntaş, O., & Bostan, B. (2021). Characterization of Al-7075/T651 alloy by RRA heat treatment and different pre-deformation effects. Transactions of the Indian Institute of Metals, 74, 3025-3033.
3. [3] Altuntaş, G., & Bostan, B. (2022). Metallurgical characterization of natural aging effects on pre-deformed Al 7075/T651 alloy during retrogression and re-aging heat treatment. Kov. Mater, 60(4), 209-222.
4. [4] Altuntaş, O. (2022). Enhancement of impact toughness properties of Al 7075 alloy via double aging heat treatment. Gazi University Journal of Science Part C: Design and Technology, 10(2), 195-202.
5. [5] Mavi, A., Kaplan, Y., & Aksoz, S. (2021). Effects of aging and deep cryogenic treatment on wear behavior of Al7075 Alloy. Journal of Tribology, 143(12), 121702.
6. [6] Ozer, M., Dalli, K., & Ozer, A. (2023). Effect of ball-burnishing on surface integrity and fatigue behaviour of 7175-T6 AA. Materials Science and Technology, 39(2), 248-257.
7. [7] Ozer, M., Kaplan, Y., Ozer, A., & Aksoz, S. (2023). Influence of different sintering techniques on the wear properties of Al-15Si-2.5 Cu-0.5 Mg/B4C composites. Science of Sintering, (00), 60-60.
8. [8] Cina, B. M., and Gan, R. (1974). Reducing the susceptibility of alloys, particularly aluminium alloys, to stress corrosion cracking. US patent, 3856584.

9. [9] Holt, R. T., Rosario, V., & Durham, K. (1995). RRA Treatment of 7075-T6 Material from a CC130 Hercules Sloping Longeron. NRC/IAR Report LTR-ST-2021.
10. [10] Park, J. K., & Ardell, A. J. (1984). Effect of retrogression and reaging treatments on the microstructure of Ai-7075-T651. Metallurgical and Materials Transactions A, 15, 1531-1543.
11. [11] Danh, N. C., Rajan, K., & Wallace, W. (1983). A TEM study of microstructural changes during retrogression and reaging in 7075 aluminum. Metallurgical Transactions A, 14, 1843-1850.
12. [12] Naeem, H. T., Ahmad, K. R., Mohammad, K. S., & Rahmat, A. (2014). Evolution of the retrogression and reaging treatment on microstructure and properties of aluminum alloy (Al-Zn-Mg-Cu). Advanced materials research, 925, 258-262.
13. [13] Ohnishi, T., Ibaraki, Y., & Ito, T. (1989). Improvement of fracture toughness in 7475 aluminum alloy by the RRA (retrogression and re-aging) process. Materials transactions, JIM, 30(8), 601-607.
14. [14] 57. Xu, X., Zhao, Y., Ma, B., & Zhang, M. (2015). Electropulsing induced evolution of grain-boundary precipitates without loss of strength in the 7075 Al alloy. Materials Characterization, 105, 90-94.
15. [15] Khalfallah, A., Raho, A. A., Amzert, S., & Djemli, A. (2019). Precipitation kinetics of GP zones, metastable η′ phase and equilibrium η phase in Al− 5.46 wt.% Zn− 1.67 wt.% Mg alloy. Transactions of Nonferrous Metals Society of China, 29(2), 233-241.
16. [16] Altuntaş, G., Özdemir, A. T., & Bostan, B. (2023). A survey of the effect of cryogenic treatment and natural ageing on structural changes and second-phase precipitation in Al–Zn–Mg–Cu alloy. Journal of Thermal Analysis and Calorimetry, 1-13.
17. [17] Callister, W. D., and Rethwisch, D. G. (2011). Materials science and engineering (Vol. 5). NY: John Wiley and Sons.
18. [18] Robinson J. S., Cudd R. L., Tanner D. A., Dolan G. P., Quench Sensitivity and Tensile Property Inhomogeneity in 7010 Forgings, Journal of Materials Processing Technology, 2001, 119, 261-267
19. [19] Ferragut, R., Somoza, A., & Tolley, A. (1999). Microstructural evolution of 7012 alloy during the early stages of artificial ageing. Acta Materialia, 47(17), 4355-4364.
20. [20] Berg, L. K., Gjønnes, J., Hansen, V. X., Li, X. Z., Knutson-Wedel, M., Schryvers, D., & Wallenberg, L. R. (2001). GP-zones in Al–Zn–Mg alloys and their role in artificial aging. Acta materialia, 49(17), 3443-3451.
21. [21] Elder, J. P. (1985). The general applicability of the Kissinger equation in thermal analysis. Journal of thermal analysis, 30, 657-669.
22. [22] Augis, J. A., & Bennett, J. E. (1978). Calculation of the Avrami parameters for heterogeneous solid state reactions using a modification of the Kissinger method. Journal of thermal analysis, 13, 283-292.
23. [23] Sha, G., & Cerezo, A. (2004). Early-stage precipitation in Al–Zn–Mg–Cu alloy (7050). Acta materialia, 52(15), 4503-4516.
24. [24] Karabulut, Ş., & Karakoç, H. (2017). Investigation of surface roughness in the milling of Al7075 and open-cell SiC foam composite and optimization of machining parameters. Neural Computing and Applications, 28, 313-327.
25. [25] Khalfallah, A., Raho, A. A., Amzert, S., & Djemli, A. (2019). Precipitation kinetics of GP zones, metastable η′ phase and equilibrium η phase in Al− 5.46 wt.% Zn− 1.67 wt.% Mg alloy. Transactions of Nonferrous Metals Society of China, 29(2), 233-241.