BS in Materials Engineering
Materials Engineering Department
The aging response of open-die-forged 7050 aluminum was studied at various temperatures. This is of interest because the alloy can potentially crack during stress relief if it ages after its heat treatment. Natural aging limits the ductility enough to potentially cause cracking and is combatted by placing the forgings in freezers. This experiment shows which temperatures successfully inhibit aging in the forgings. The goal was to develop a maximum time that a sample can be stored at certain temperatures before the forgings have naturally aged. The samples were first solution heat treated then water-quenched. Next, the samples were stored at four temperatures ranging from 0ºF to 72ºF. After various time delays, the samples were compression tested. An increase in compressive yield strength correlates with an increase in the amount of natural aging. With a 10% yield strength increase from the as-quenched condition as a boundary condition, the amount of time it takes samples at different temperatures to naturally age can be calculated. The 72ºF trial reached the the boundary condition in 25 minutes whereas the 0ºF trial never reached the boundary condition. The 25ºF trial and the 40ºF trial displayed some natural aging, but not as significantly as the 72ºF trial. If a freezer set at 0ºF is used in the forging industry, parts should not crack due to natural aging during stress relief.
Available for download on Monday, June 13, 2022