Posted by Rick Denney on February 05, 2001 at 15:31:45:
In Reply to: Re: Re: Re: Re: Re: Re: Re: thin vs thick metal horns posted by CK on February 05, 2001 at 14:51:41:
Thanks for the references. They describe a process known as "precipitation hardening," which is actually a heat-treatment byproduct as the material cools. The "natural" age-hardening is, in fact, part of the cooling process following heat treatment. For example, one bicycle manufacturer bakes their bicycle frames at 450 degrees for 15 hours, and then allows them to cool very slowly. This is actually intended to de-harden the material after welding, where the welding process has created pockets of brittle material that need to be heat-treated to relax. 450 degrees is what the literature calls "slightly elevated" temperatures, being far below annealing temperatures or those temps required for welding. It can also happen at room temperature over a relatively short period of time as the material reaches equilibrium after having been heated. You are right, this is called age-hardening, but it is hardly a process that will happen over a period of years to normal metals.
The term does not mean the same thing as was used in the post I corrected, which suggested an instrument may exhibit significantly different properties just because it is 50 years old rather than being a month old.
But even though I say that with some certitude, I have this nagging recollection of some process that, maybe, Steve's materials science buddy described about brass aging, that may also cause me to eat my words, at least a little bit. Anyone recall?
Rick "always willing to admit being wrong" Denney