Motorcycle frames “Expiration date“

[SEBASTIANOFA]

hello everyone, do aluminum alloy or steel motorcycle frames change their microstructural characteristics over time even without the vehicle being used? Assuming you have two identical frames, one many years old perfectly preserved and sealed, the other new from the factory, both without work cycles, will they show the same microstructure ? lately some manufacturers also offer carbon frames, do these not suffer from aging even without use?
Thanks

 

[MintJulep]

No.
Yes.
No.

 

[dik]

I understand that with 6061, the strength can marginally impove over time.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[SEBASTIANOFA]

improves up to a certain point and then stops I guess ?

 

[EdStainless]

The structures do not change with time.
And the bulk properties do not change either.
Al does have a much lower fatigue strength and toughness than steel.
While this does not necessarily mean a shorter lifespan it does mean less damage tolerance.
Carbon is fine as long as you know the usage history.
It can be very difficult to detect internal damage in a carbon fiber structure.

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P.E. Metallurgy, consulting work welcomed

 

[SEBASTIANOFA]

Thanks Ed, I read that even at room temperature there are changes in the strength and resistance of the metals, natural age hardening, does this not mean that over time the characteristics of the piece will change? If we think of the daily temperature changes, don't these have an effect?
Is this a temporary change that will then stabilize definitely?

 

[EdStainless]

In nearly all cases involving engineering alloys the changes in properties over time are small compared to the actual properties.
If something was heat treated incorrectly then there might be greater change over time.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[SnTMan]

How about that DC-3?

Regards

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[SEBASTIANOFA]

ok, thus assuming a continuous temperature variation ranging from 0 to 30° which could be the annual one from winter to summer, the microstructural changes will continue indefinitely or for a given temperature range it will only be possible to arrive at a certain type of change and then stabilize ?

 

[3DDave]

The metal structure moves to the lowest energy state available for the temperature; a lower state might be available but would require going over an energy barrier to get there, much like any local minimum energy state might have a neighboring one that is lower, but essentially unreachable. Such processes are why heat treat is required/used.

Still, the concern expressed so far isn't even academic.

I'd recommend any introductory material engineering textbook describing how metal crystals and alloys work rather than trying to gather the 200 pages or so one paragraph at a time. Perhaps "The New Science of Strong Materials: Or Why You Don't Fall through the Floor" as an inexpensive introduction.

Edit: I see this isn't the first time for a similar or an identical concern: long term storage of cars and motorcycles. That's better asked of museum conservators.

A car chassis will fail aging without use?
Aluminum protection needed?
Fatigue corrosion or stress corrosion in car chassis

 

[IRstuff]

Quantum tunneling allows for getting to other energy states without going "over" a barrier

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