The Effects of Aging Treatment On The Exfoliation Corrosion of 2024 Aircraft Aluminum Alloys

Abstract

One significant problems being faced in industries such as the car manufacturing industry, aircraft industry, and the naval industry is that of the aged alloy. Aged alloys are alloys which, starting from a super saturated solid solution state undergo a phase coherency change to eventually experience phase precipitation. In all industries mentioned, this naturally occurs with long operation time. Developing cars, ships and aircraft is expensive and time consuming. As such, one of the key factors all these industries rely upon is long term reliability of their manufactured machines. The focus of this thesis is to establish a connection between aging of the Al2024 alloy, commonly used in the aircraft industry, and corrosion. The methodology followed to establish this connection was to age Al2024 samples at different aging temperatures and times, subject them to accelerated corrosion tests which were the EXCO accelerated corrosion test and the potentiodynamic electrochemical corrosion test, and analyze the results through optical microscopy of metallographic sections and optical and SEM of corroded samples. From the experiments, it was determined that aging time decreases corrosion resistance due to the grain boundary depletion which occurs on the precipitate/matrix boundaries. Furthermore, it was determined that Al2024 samples aged at higher temperature reveal a higher corrosion resistance than samples aged at a lower temperature. This was justified through the lack of GBP zone formation in the alloys aged at a higher temperature, which affects precipitation. These results will provide important insight which will contribute to the goal of the startup project to study, identify and analyze hydrogen trapping sites and establish a relation between corrosion attack, hydrogen trapping, and microstructure and define their link to Hydrogen Embrittlement. Furthermore, the findings have a further impact in understanding the effect intermetallic compounds have on the corrosion behavior of aged Al2024.

Date of Award	Dec 2020
Original language	American English