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

Year 2024, Volume: 12 Issue: 1, 324 - 331, 25.03.2024

Gözde Altuntaş Bulent Bostan

https://doi.org/10.29109/gujsc.1446429

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

Supporting Institution

gazi üniversitesi BAP

Project Number

This study was supported by Gazi University scientific research projects number FGA-2024-9104. We would like to thank our university BAP coordinatorship.

Thanks

This study was supported by Gazi University scientific research projects number FGA-2024-9104. We would like to thank our university BAP coordinatorship.

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