College - Author 1
College of Engineering
Department - Author 1
Materials Engineering Department
Degree Name - Author 1
BS in Materials Engineering
College - Author 2
College of Engineering
Department - Author 2
Materials Engineering Department
Degree - Author 2
BS in Materials Engineering
Date
6-2021
Primary Advisor
Blair London, College of Engineering, Materials Engineering Department
Abstract/Summary
7175 is a heat-treatable aluminum alloy commonly used in aerospace forgings. This alloy is aged with a multi-step heat treatment. This treatment must balance strength with stress corrosion cracking resistance through a degree of overaging. The team was tasked by Weber Metals to increase the strength of this treatment without sacrificing stress corrosion cracking resistance. Both two-step and retrogression and reaging treatments were tested in experiments to find a heat treatment that could increase the yield and tensile strength by 1-2 ksi while maintaining a minimum electrochemical conductivity equivalence of 38% relative to copper. Two-step aging is the more conventional process for achieving this mixture of properties, while retrogression and reaging has seen promising results in the literature but is not widely used in industry. A two-step aging treatment that aged samples in a 117°C furnace for 6 hours followed by a 185°C step for 13 hours was identified as a suitable candidate. Twelve samples tested over three different runs showed this treatment to have an average yield and tensile strength 1.57 ksi and 1.18 ksi respectively higher than the control group. This was accompanied by an average conductivity of 38.6% relative to copper. None of the retrogression and reaging treatments had suitable properties.
URL: https://digitalcommons.calpoly.edu/matesp/230