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In article <BtwExB.Gto@news.cso.uiuc.edu> ritley@uiucmrl.bitnet () writes:
>
>Anyone know what PERMALLOY is commonly used for?  I was lead to believe
>it was used for masks on CRT screens, but I have recently been informed that
>INVAR is more commonly used for this purpose.
PERMALLOY is an old permanent magnet alloy (CRC Handbook has 45
permalloy, 78 permalloy, 4-79 permalloy and 2-81 permalloy's listed).
Basically iron-nickel alloys with high permeability (the number
indicates nickel level, the number in front of the hyphen is Mo).
Invar is very similar, in that it is also iron nickel, but it is the
36% nickel alloy at the TCE minimum.  Fro this reason it is often used
for sealing to glass or ceramics, as there is little or no thermal
coefficient of expansion (TCE) mismatch.  I would have thought that
the ferromagnetic nature of any of these alloys would make them dicey
to use for CRT masks, but the TCE match may force the issue and they
are cheaper than Molybdenum.  My impression is that they have been
largely supplanted by ceramic magnets for permanent magnet
applications.
Steve Axdal
Computing Devices International
app@shamash.cdc.com