Metallic glass powders from glassy alloys

DETAILED DESCRIPTION OF THE INVENTION Metallic glass alloy powders are prepared according to a process involving first annealing a glassy alloy to an embrittled state and then comminuting the embrittled alloy to a powder.
Glassy alloys suitable for use in the invention process are known products and are disclosed for instance, in Chen and Polk U.
S.
Pat.
No.
3,856,553 issued Dec.
24, 1974.
These alloys can be rapidly quenched from the melt by known procedures to obtain splats or filament (e.
g.
sheets, ribbons, tapes, wires, etc.
) of amorphous metal.
These metallic glasses in sheet, ribbon, tape, splat and wire form can be annealed at a temperature below the glass transition temperature to effect embrittlement.
Heating the metallic glass body to effect embrittlement can be carried out in a suitable annealing furnace.
Such annealing furnaces can be divided into furnaces which operate by a batch process and those operating continuously, and either may be electrically heated or fuel fired.
Gas heated crucible or box furnaces are suitable, but the glassy metal charge should be protected from the furnace gases by a gas-tight crucible or retort.
Electric furnaces with Nichrome or Kanthal resistor elements can be used for temperatures up to 1050.
degree.
C.
which is high enough for embrittlement of most metallic glasses.
Tightly sealed boxes or retorts in which the glassy material is surrounded by inert packs or protective atmospheres can be heated in bell-type or box-type furnaces.
Electric muffle furnaces also require a retort if heated by a Nichrome or Kanthal wire spiral wound on the refractory muffle.
Electric box and muffle furnaces may also be heated by silicon carbide heating elements.
Since these elements burn in air, no gas-tight housing is necessary, but the charge must be contained in a closed retort or box to retain the protective atmosphere or pack.
Continuous furnaces are generally more efficient for the production of embrittled metallic glases.
Several suitable types of horizontal continuous furnaces can be used