Innovative Approaches to the Development of Corrosion Resistant Aircraft Alloys Navy STTR FY2008 Sol No.: Navy STTR FY2008 Topic No.: N08-T010 Topic Title: Innovative Approaches to the Development of Corrosion Resistant Aircraft Alloys Proposal No.: N08A-010-0409 Firm: ATI Inc. 1505 Bull Lea Road Lexington, Kentucky 40511 Contact: Alex Cho Phone: (304) 541-1825 Abstract: Aluminum alloys are known to suffer from Stress Corrosion Cracking(SCC). SCC of high strength alloys can proceed rapidly, and can lead to devastating structural failures. However, a solid understanding of combined interactions of metallurgical, environmental and mechanical factors surrounding the crack tip during SCC is still elusive. Therefore, Al alloy developement for high corrosion resistance has been empirical in nature. The objective of this study is to understand the effect of microstructure in conjuction with the local environment(chemical and electrochemical)on the transition behavior from the incubation regime to high rate crack propagation regime during SCC. A quantitative predictive model will be developed based on the mechanistic underestanding fo SCC. This model will be utilzed in development of a new Al alloy most suitable for Navy aircrafts which normally operates in the most severe environment. Benefits: With a successful completion of this program, a new aluminum alloy will be developed, which would be most suitable for Navy aircraft structures, operating in the severely corrosive salt fog environment. The improved SCC resistance and the improved corrosion fatigue resistance of the new alloy would allow longer active service between the grounding for the planned maintenance, and would save substantial amount of maintenance costs. When the new alloy is ready for commercial scale production, the alloy composition will be optimized for thick gauge plates and forgings initially for bulkhead applications. This is where most structural improvement and weight savings can be realized. Return