Place the welded aluminum in a preheat oven. Heat it to 1000 degrees Fahrenheit for about ten minutes. Use heat-resistant gloves to remove the aluminum from the oven.
Drop the aluminum into a vat of room-temperature water. Leave it in the water for anywhere from a few days to a few weeks. Aluminum needing a greater stabilization of its mechanical properties will need to stay in the water longer. The aluminum will have fairly stable mechanical properties after this treatment. Remove the aluminum from the oven.
Place the aluminum in the oven. Reheat the aluminum to 400 degrees Fahrenheit for up to three hours. This will precipitate the numerous components of the alloy and subsequently strengthen it.