Effect of Zr particles and RRA heat treatment on properties and grain boundary precipitation of 7055 Aluminum alloys

Shakoory, Mehdi; Esmailian, Mohammad; Taheri, Morteza

doi:10.22104/jpst.2026.7865.1287

Effect of Zr particles and RRA heat treatment on properties and grain boundary precipitation of 7055 Aluminum alloys

Document Type : Research Article

Authors

Mehdi Shakoory

Mohammad Esmailian

Morteza Taheri

Advanced Materials and New Technology Department, Iranian Research Organization for Science and Technology (IROST), Tehran, Iran

10.22104/jpst.2026.7865.1287

Abstract

Due to its high strength and corrosion resistance, aluminum alloy 7055 is widely used in aerospace structures. However, its susceptibility to stress corrosion cracking (SCC) limits its performance. In this study, the combined effects of zirconium (Zr) addition and retrogression and re-aging (RRA) heat treatment on the microstructure, grain boundary precipitates, and stress corrosion resistance (SCR) of 7055 aluminum alloy were investigated. For property evaluation, microstructural characterization was carried out using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), while mechanical and stress corrosion tests were conducted according to ASTM standards. The results showed that Zr addition refined the grains and promoted the formation of Al₃Zr particles within the matrix, inhibiting grain growth during heat treatment. RRA treatment accompanied by Zr addition improved the mechanical strength from 528 to 608 MPa and increased the stress corrosion resistance from 68 to 96 %. The combined effect of Zr addition and RRA treatment resulted in a more stable microstructure, with improved strength and resistance to stress-corrosion cracking.

Graphical Abstract

Effect of Zr particles and RRA heat treatment on properties and grain boundary precipitation of 7055 Aluminum alloys

Highlights

Retrogression and re-aging (RRA) heat treatment improves both the mechanical strength and the stress-corrosion resistance of the 7055 aluminum alloy.
After RRA heat treatment, better distribution and composition changes of the precipitates have been achieved.
With the addition of Zr, this element remains within the grains during heat treatment and inhibits grain growth, thereby improving the mechanical properties and corrosion resistance of the aluminum alloy.

Keywords

7055 Al Treatment

Zr in Al Grain boundary

Al 7055 Corrosion

Zr in Al 7055

Subjects

Materials Science

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