Short answer: No.

First I need to point out that tempering means to reduce the strength of a part or material that's too hard and brittle, to get some ductility back, increasing the toughness. So I don't think tempering is the word you want there, you mean heat-treating. Heat treating can (often does) include tempering as part of the cycle, but it's generally used to mean increasing the strength or other desirable properties via one or more heating/cooling cycles. Though it often is just stress-relieving, which doesn't generally increase strength but can improve reliability and dimensional stability. Annealing, which is making something as weak and soft as possible, is technically a heat treatment, but the way "heat treated" is normally used, it means strengthening.

Heat-treating is a vast subject. We're used to hearing that a part is heat-treated, but those two words hide a huge amount of complexity. There is not just one heat-treatment for any given part or material, there are an infinite number of choices the engineer can make, to get desired properties and avoid unwanted compromises.

The heat-treat steps vary widely from one material to the next, and you usually don't know what material a part is made of. Further complications include the fact that a lot of materials used in bikes aren't heat-treatable, or there's no benefit to it. Forged parts gain strength from cold-working, and you'd lose that in a typical heat treat cycle.

One exception, where you do know the material, is the machined-from-billet parts where they tell you it's 7075 T6. In other words when it's already heat-treated and you're not going to get more strength by doing it again.

I'm not going to say I don't use heat-treating; I do. But I'd never attempt to heat-treat a brake caliper that I drilled holes in, which I think is what your question is getting at. Too many unknowns, too little potential upside, and death as a potential downside.

Mark B