Welding 6061 weakens it?

Lined up a welder to weld a small bit onto a bike frame right at the 1/4 inch plate where the rear wheel attaches to the frame.
Once welded, does this weaken the frame at this point? I presume that this point of the frame is hardened. No?
Is this idea an Entirely Bad one?
Thanks.
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6061 is an age hardening aluminum. The original frame will (should) be T6 temper (31 kpsi yield), welding it will heat up the HAZ and reduce the strength to T-0 (8 kpsi yield), this will crawl back up to around T-4 temper (13 kpsi yield)just by letting it sit for a month or two. It will never get up to the original T-6 temper without solution treating it.
I hope that you meant you have found someone to weld it for you. Aluminum welding on a safety critical part is not something you do without practice. Whether this is a critical component is up to you.
DaveC wrote:

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