Is 'invar' a class of materials, a specific material, or both? From the OP:
> There is, however, a class of metal alloys called Invars (think invariable), that stubbornly refuse to change in size and density over a large range of temperatures.
> There is, however, a class of metal alloys called Invars (think invariable), that stubbornly refuse to change in size and density over a large range of temperatures.
with the addition of cobalt it becomes Kovar, a metal that is common for telescope use or joints where metal bonds to glass.
they're all fairly proprietary and expensive. I've used Invar a lot in the production of heated press platens.