I agree with Luigi. A screw softer than the aluminum mount would be too soft.

And if you made the mount out of steel to match the hardness of the screw, it would be a lot heavier.

If you DO want a harder thread, buy a Helicoil kit. When you drill out the old thread, use the Helicoil to go between the screw and the mount material. This way, when you screw things in, they screw into the helicoil.

If you ever strip the Helicoil, you can unscrew it from the hole and replace it.

The only downside is that there needs to be enough room in the metal to support the bigger hole required by the Helicoil.

And have no doubt about the strength. When professional shops find stripped scew holes on cars, this to me is what the BEST ones do to repair it. This way it allows you to keep the same size hole and tread of the original screw rather than having one hole that is bigger tread size than the other.

The kits are not all that expensive, and if you think this will be an on-going problem, the Helicoil will be THE way to solve it.

Regards.