What is the primary strengthening mechanism in high strength “aircraft quality” aluminium alloys?

-and why is it the primary strengthening mechanism?In 7075 aluminium alloy, (about the most common aluminum alloy used in aircraft) is an aluminium alloy, with zinc as the primary alloying element.

7075 aluminum alloy's composition includes zinc, magnesium, copper, and less than half a percent of silicon, iron, manganese, titanium, chromium, and other metals. It is commonly produced in several heat temper grades, 7075-O, 7075-T6, 7075-T651.

The mechanical properties vary with the temper of the metal.



7075-T6 is the most common I work with.



Here's a tech sheet on it from the manufacturer:



http://www.alcoa.com/mill_products/catal鈥?/a>