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

Document Type : Research Article

Author

Dep. of Advanced Mat. and New Tech., IROST, Tehran, Iran

10.22104/jpst.2026.7865.1287

Abstract

Aluminum alloy 7055, due to its high strength and corrosion resistance, 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 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 MPa 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.

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Articles in Press, Accepted Manuscript
Available Online from 14 February 2026
  • Receive Date: 16 November 2025
  • Revise Date: 09 February 2026
  • Accept Date: 14 February 2026