Strength Improvement for 7175 Aluminum Alloy Through Multi-Step Aging Treatments
7175 is a heat-treatable aluminum alloy commonly used in aeronautic 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.