Environment-Induced Cracking of High-Strength Al-Zn-Mg-Cu Aluminum Alloys - Past, Present and Future

Timothy Burnett, Nigel Holroyd, G.M. Scamans, JJ Lewandowski

Research output: Contribution to journalArticlepeer-review


Environment induced cracking (EIC) during commercial use of aluminum alloys started over 125 years
ago (mid-1890’s), some 45 years earlier than previously documented, with earliest failures for Al-Zn-MgCu, 7xxx series alloys occurring a decade later. Needs for lighter, thicker and stronger alloy products,
firstly driven by WW1 and WW2 militaristic requirements and subsequently by relentless demands from
modern aircraft industry designers, resulted in major in-service EIC in commercial high strength Al-ZnMg-Cu alloys in the US and UK during the 1950’s, 1960’s and 1970’s. These were avoidable had research
findings from France, Germany and Japan from the 1930’s and 1940’s been implemented.
Unprecedented US Government R&D funding during the late 1960’s, 1970’s and early 1980’s led to
AA7050 and similar alloys, that essentially eliminated EIC issues during commercial usage for several
decades. EIC assessment for the following ‘new-generation’ high-strength alloys relied totally on
standard ASTM Test Methods, incapable of providing data directly relatable to the service conditions.
Although EIC service issues for the latest generation of 7xxx series alloys remains manageable, the
premature appearance of EIC requires a quantitative understanding of EIC initiation under
environmental and mechanical conditions directly relatable to intended use, to prevent un-expected
failures for future alloys. Directions for future high-strength 7xxx series aluminum alloy development
and EIC assessment to provide quantitative date relatable to service conditions and input for structural
design and for service life prediction are discussed.
Original languageEnglish
Pages (from-to)48-71
Early online date27 Oct 2022
Publication statusPublished - 1 Jan 2023


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