The aluminum alloys most frequently used in manufacturing are 2xxx, 6xxx and 7xxx series. 6061 is the one most commonly available. They are all precipitation (age) hardening alloys.
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When these alloys are welded, the heat affected zone becomes solution treated (frequently, if incorrectly, called annealed), making it soft. It can be re-hardened, but because the entire part has not been equally heated and the filler material is not the same as the base material, the hardness will vary. In welded parts, the machinability of the heat affected zone is poor because the material is soft and gummy. Machinability can be greatly improved by boiling the part in water for a couple of hours or longer.
Welding up the holes in your landing gear will soften the area immediately around the hole making it easy to bend. You MAY be able to recover some of the hardness by boiling or heating in an oven at temps up to 350 F., but this will also affect the material not in the HAZ. At some point, over aging begins and the material starts to get softer. I would suggest a non-welding method of plugging the holes, but the strength will never be equal to the material that has not been drilled. Also, if 2024, welding is not recommended, it has a habit of cracking.
precipitation hardening of aluminum alloys | Total Materia
Explore the process of precipitation hardening, a technique for strengthening metal alloys. Discover the historical development of this method, its application in various alloys, and the fundamental steps involved. Learn about the challenges and limitations in understanding and predicting the...
www.totalmateria.com
When these alloys are welded, the heat affected zone becomes solution treated (frequently, if incorrectly, called annealed), making it soft. It can be re-hardened, but because the entire part has not been equally heated and the filler material is not the same as the base material, the hardness will vary. In welded parts, the machinability of the heat affected zone is poor because the material is soft and gummy. Machinability can be greatly improved by boiling the part in water for a couple of hours or longer.
Welding up the holes in your landing gear will soften the area immediately around the hole making it easy to bend. You MAY be able to recover some of the hardness by boiling or heating in an oven at temps up to 350 F., but this will also affect the material not in the HAZ. At some point, over aging begins and the material starts to get softer. I would suggest a non-welding method of plugging the holes, but the strength will never be equal to the material that has not been drilled. Also, if 2024, welding is not recommended, it has a habit of cracking.
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