Effect of Retrogression Medium to the Mechanical Properties of Aluminum Alloy 7075

Abstract:

Aluminum alloy 7075 is a useful material in industry due to its light weight, high strength, and resistance to general corrosion properties. The drawback of this alloy is its susceptibility to stress corrosion cracking (SCC). From the previous research, it was found that retrogression and re-aging (RRA) heat treatment is able to improve the SCC resistance of this alloy. In this study, the mechanical properties and microstructure alteration due to RRA was studied. First, the tensile specimens are heat treated to T6 and then retrogressed at 165/185/205°C for 10/30 minutes followed by re-aging at 120°C for 24 hours. The retrogression methods are categorized as standard retrogression and oil retrogression. Next, the specimens were gone through tensile test, hardness test, and microstructure characterization by using SEM. From the mechanical test result, the tensile strength and hardness of the alloy decreased upon the increment of retrogression temperature and time. The highest tensile strength of 638.48 MPa was observed at oil retrogress sample at 165°C for 10 minutes which is slight higher than T6 sample. Besides, different phases of precipitation were reviewed by the Kellers etching process. Also, the volume fraction of η phase is increased upon increasing the retrogression temperature and time.

• Periodical: Applied Mechanics and Materials (Volume 165)
• Pages: 6-11
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.165.6
• Online since: April 2012
• Authors: Ng Guan Yao, Mohd Warikh Abdul Rashid, Buang Zolkepli, N. Nadiah, S.C. Leng
• Keywords: 7075 Series Aluminium Alloy, Air, Hardness, Heat Treatment, Keller’s Etch, Mechanical Property, Microstructure, Oil, Re-Aging, Retrogression, SEM, Tensile Strength

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