Corrosion and Corrosion-Fatigue Behavior of 7075 Al Alloys

Aluminum alloys are used in a variety of structural applications, such as aircraft wings, fuselage, etc. The relationship between environmental and mechanical effects is not well understood. The driving force at the crack tip is clearly a combination of chemical and mechanical processes operating together. A synergy between these processes is also present. We have been conducting experiments in ultra high vacuum (UHV) and shown that the intrinsic material behavior can be extracted in a UHV environment. We now would like to understand the other end of the spectrum, i.e., the chemical processes driving crack growth under corrosion conditions. Our current vacuum testing system can be used to conduct experiments in moisture environment, but in the 7075 Al alloys we are studying, the effects of moisture environment are modest. Thus, in this DURIP program, we propose to build a new corrosion testing system for conducting experiments in NaCl. We believe that the proposed system and proposed work will provide a huge leap in the fundamental understanding of crack tip processes during combined corrosion and fatigue.