Environmental Assisted Cracking in High Strength 7XXX Aluminum – The Path to Understanding (25/10/24)
Speaker and Affliation:
Andrew Rosenberger
Air Force Research Laboratory, Material and Manufacturing Directorate, AFRL/RXNMB, 2230 Tenth St., Wright-Patterson AFB, OH 45433-7817, USA
When?
25th October, 2024 (Friday), 3.00 PM (India Standard Time)
Where
KPA Auditorium, Dept. of Materials Engineering, IISc, Bangalore
Abstract:
Environmentally assisted cracking (EAC) has been a problem with Al-Zn-Mg-Cu 7XXX high-strength alloys for over 125 years. Heat treatment, composition modifications, and limiting the sustained stress has largely kept this problem at bay. Several of the newest 7XXX alloys have shown a susceptibility to EAC in a warm, humid environment that is not detected using the conventional alternate immersion, stress corrosion cracking (SCC) standard, ASTM G47. This new form of EAC appears to be a mechanism depending on hydrogen assisted grain boundary embrittlement. This is different than the classical SCC anodic dissolution with loss of material via corrosive attach of grain boundaries. There is a safety bulletin from the European Union Aviation Safety Agency (EASA SIB 2018-04R2) that proposes a new test method that activates this damage mechanism. It is unclear if this approach is sufficient to screen these new alloys. The problem and future work will be discussed to ensure air worthiness of current USAF systems.
About the Speaker:
Dr. Rosenberger completed his baccalaureate (1986) and master’s (1987) degrees in mechanical engineering at Michigan Technological University. He earned his PhD in 1993, at the University of Rhode Island under the direction of Professor Ghonem. He performed extensive scanning electron microscopic analysis of fracture surfaces and crack tip plastic zones of small cracks at Ecole National Superieure des Mines de Paris (France) during his PhD work. Rosenberger came to the Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, OH in 1993 as a visiting scientist and became a government civilian in 1997. Currently he is a Senior Materials Research Engineer in AFRL. His current research is focused on conducting innovative experiments on high temperature materials for gas turbine engines and developing techniques to better assess the durability of materials in a high temperature environment. He has an extensive knowledge of nickel base superalloys, their fatigue, fracture, and creep behaviors, and their suitability for use in the aggressive gas turbine engine environment. A current research thrust is to place the design of gas turbine engine components on a more physical basis rather than the largely data-driven approach that has been used in the past. This involves taking experimental observations and developing models that predict the behavior under more complex loading conditions.