Mitigating Intergranular Stress Corrosion Cracking in Age-Hardenable Al-Zn-Mg-Cu Alloys
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This article reports an attempt to develop high-strength aluminum alloys of 7xxx series resistant to intergranular stress corrosion cracking (SCC). A novel aging technique reported in this work exhibited improved strength levels (as high as ~ 100 MPa to that of conventional overaged temper for AA 7050) with significant resistance to SCC measured even at a low strain rate (10−7 s−1) in 3.5 wt pct NaCl. The novel aging heat treatment produced a microstructure that is finer and dense enough in the matrix to impart strength, whereas it is enriched with Cu on the grain boundaries to impart SCC resistance. A detailed explanation for the enhanced strength and SCC resistance is discussed.
One of the authors (MAK) acknowledges the financial support and other facilities provided by M/s Godrej Aerospace, the Science and Engineering Research Board (SERB), and the Confederation of Indian Industries (CII) under the Prime Minister’s fellowship scheme. MAK is thankful to Mr. Ankit Kothari for his help and support in the specimen fabrication. The authors thankfully acknowledge Dr. James Moran and Mr. Peter Vanderburgh, ALCOA, for providing the AA 7085 alloy, and CRNTS, IIT Bombay, for providing the microscopy facilities.
Competing Financial Interests
The authors declare that there is a competing financial interest. The proposed work is from a pending patent with International Application No. PCT/IN2016/000280(2016) filed by Godrej Aerospace and the Indian Institute of Technology Bombay. The authors AJK, VSR, and SMV are inventors in the patent.
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