Plate materials?

[dubious]

I've seen lots of discussion about different plate materials, and how they feel with different types of switches. I have read a few things that confused me and seemed to go against what (little) I know about different materials.

I have read several places that stainless steel plates and more desirable for linear switches, and aluminium is preferred for tactile switches. Many posts I have read say stainless steel is more rigid, and that's why it gives linear switches a nice 'thock.' The flexibility of aluminium has been mentioned as the reason tactile switches are the mechanism of choice with this material.

I'm not trying to start a debate over which plate feels best with which switch (although I find it very interesting) but I have always believedd that steel is a more flexible material than aluminium. My knowledge mostly comes from researching bike frames, where this mode of thinking is pretty common.

In order of stiffness, I always thought it was:
carbon fiber (most stiff) >> aluminium >> steel (less stiff)

Can any material scientists weigh in on this?

[Findecanor]

I am not a materials scientists but I know that it is not easy.
There are different alloys of steel and aluminium - and many of these can be heat-treated to be different "stiffness", which has often been done before you buy it.

The most common aluminium for machining is 6061-T6. The 6061 stands for the alloy (which other metals have been mixed in with aluminium) - it machines well and anodizes well. The T6 part stands for how it has been hardened.
Otherwise, aluminium alloys more common for sheet metal are softer - softer in that they ding more easily.

Steel plates from vintage keyboards I have have been harder to cut, but have often been tougher and more flexible.

Steels with a low carbon content (called "mild steel") are not used that much. Stainless steel can contain carbon, but not as much. With lower carbon content in steel you can't anneal or harden them as much.
Pure aluminium is also rarely used.

[tp4tissue]

carbon fiber = most stiff ?

[dubious]

Thanks for the info Findecanor, and you don't have to be a scientist to weigh in! haha )

I do realize there are different types of alloys, and the end product will always depend on how it's made and what it's made with. I was really just curious about the most common types that are used in keebs, like 6061 alu that you mentioned.

From wikipedia:
"Aluminium alloys typically have an elastic modulus of about 70 GPa, which is about one-third of the elastic modulus of most kinds of steel and steel alloys. Therefore, for a given load, a component or unit made of an aluminium alloy will experience a greater deformation in the elastic regime than a steel part of identical size and shape."
https://en.wikipedia.org/wiki/Aluminium_alloy#Aluminium_alloys_versus_types_of_steel

That makes it sound like aluminium is usually stiffer (i.e. more stiff) than most types of steel, which is the exact opposite of what I've read in most keyboard plate discussions? Again, I know the feels you get from different plates are always based on opinion. I've just seen odd justifications for why switches feel a certain way, and I was hoping we could solve this with some science. 

[dubious]

carbon fiber = most stiff ?

I've always known carbon fiber to be very stiff and rigid for how much it weighs, and that's why it's commonly used in racing. (cars, boats, bikes, snowshoes...)

[Puddsy]

The only real considerations for plate materials should be sound dampening and aesthetics. As far as I can tell it doesn't really affect anything else.

Some have minor pros and cons, but they should be addressed case-by-case.