Appeal No. 1997-0538
Application No. 08/262,168
is conducted at a temperature of 2300° F. and argon
pressure of 25 ksi for 4 hours.
The alloy is heat treated to a lamellar or
duplex microstructure comprising predominantly gamma
phase as aquiaxed grains and lamellar colonies, a
minor amount of alpha-two (Ti A1) phase and
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additional uniformly distributed phases that contain
W or Mo or Si, or combinations thereof with one
another and/or with Ti.
The heat treatment is conducted at 1650° to
2400° F. for 1 to 50 hours. A preferred heat
treatment comprises 1850° F. for 50 hours.
The temperature conditions used for the hot isostatic press
and the heat treatment in Larsen appear to be within the
claimed temperature conditions since they are below 1340 to
1400 C which according to page 3, lines 38-40, of Kim, areo
generally considered as the alpha-transus temperature of these
types of alloys. The resulting gamma titanium aluminide
products, like appellants’ gamma titanium aluminide product,
have improved ductility, strength, toughness and creep
resistance. Compare, e.g., Kim, column 2, lines 4-30, and
Larsen, column 3, lines 6-15, with specification, pages 1 and
2.
Given the substantial identity between the claimed gamma
titanium aluminide and the gamma titanium aluminide described
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